Astronomy

Do great spot like features favour appear in south hemisphere?

Do great spot like features favour appear in south hemisphere?


We are searching data for your request:

Forums and discussions:
Manuals and reference books:
Data from registers:
Wait the end of the search in all databases.
Upon completion, a link will appear to access the found materials.

As we know, both Jupiter and Neptune have great spot like features in South hemisphere, and Saturn has dragon storm in south hemisphere, is it true that great spot like features appear in South hemisphere more frequently? If so, what is the reason?


Given that we have very few examples, we could not, statistically, draw any significance from any apparent bias. It's also hard to see any theoretical basis for expecting a bias, so my gut feeling would be there probably is no bias.

It's also worth remembering that human observations of these things are essentially a very brief snapshot in a huge period during which we have no idea about what may have been happening. So again the statistical significance of what happens at the moment needs to be carefully considered.


Saturn's Great White Spot phenomenon often occurs in the Northern hemisphere, so it doesn't look like there is any particular preference.


Hubble observations in 1994 revealed that Great Dark Spot on Neptune observed by Voyager 2 had disappeared. In 1998, further observations revealed the formation of a similar dark spot in the planet's northern hemisphere, so at least in the case of Neptune and Saturn (see adrianmcmenamin's answer), both hemispheres are capable of forming such systems.


Great Dark Spot

The Great Dark Spot (also known as GDS-89, for Great Dark Spot, 1989) [1] was one of a series of dark spots on Neptune similar in appearance to Jupiter's Great Red Spot. In 1989, GDS-89 was the first Great Dark Spot on Neptune to be observed by NASA's Voyager 2 spaceprobe. Like Jupiter's spot, Great Dark Spots are anticyclonic storms. However, their interiors are relatively cloud-free, and unlike Jupiter's spot, which has lasted for hundreds of years, their lifetimes appear to be shorter, forming and dissipating once every few years or so. Based on observations taken with Voyager 2 and since then with the Hubble Space Telescope, Neptune appears to spend somewhat more than half its time with a Great Dark Spot.


Do great spot like features favour appear in south hemisphere? - Astronomy

Articles about official constellations and also asterisms, star patterns that aren´t constellations. What they are and where are they? And read about ancient myths and legends telling their exciting s

Andromeda the Chained Princess
Andromeda is in the northern sky eternally chained to her rock. She is one of five constellations described by Ptolemy in the second century that are part of an epic ancient myth. The constellation also contains a quadruple star, a blue snowball, exoplanets and a famous spiral galaxy.

Aquila the Eagle
An ancient eagle straddles the celestial equator. It's the constellation Aquila which has come to us from the Romans who adopted it from the Greeks who adopted from the Babylonians. Located along the Milky Way, Aquila is rich in deep sky objects.

Aries the Golden Ram
Aries was the winged ram from which the Golden Fleece came. Two thousand years ago his constellation marked the spring equinox when the Sun crossed the celestial equator near Beta and Gamma Arietis. The equinox is now in Pisces, but what strange object was discovered in 2007 in Aries?

Auriga the Charioteer
The constellation Auriga represents a charioteer, but he has no chariot. However he does have a she-goat and two kids, as well as a rare ring galaxy and a runaway star. Capella is one of the sky's brightest stars, but it also has some surprises.

Boötes - the Herdsman
This ancient constellation contains black holes as massive as a billion Suns, extrasolar planets and has acquired a meteor shower from an extinct neighbor. Its brightest star, a red giant 25 times the diameter of the Sun, is a sign that spring is here.

Camelopardalis the Giraffe
What do you know about the celestial giraffe Camelopardalis? Probably not much. It has no bright stars. Since it was invented long after the ancient Greeks, it has no folklore. But it has a runaway star, a supernova discovered by a child, and a galaxy from when the Universe was just a toddler.

Cancer the Crab
Cancer the crab scuttles across the late winter sky, well away from its nemesis Hercules. Cancer is a zodiac constellation, the Tropic of Cancer is named for it, and it has existed for over three thousand years. Yet it seems to be a dim and unremarkable constellation. Why all the attention?

Canis Major - the Greater Dog
In a sky full of gods, heroes and wronged women, there are also four dogs. We have Canis Minor and the two dogs of Canes Venatici, but Canis Major is definitely top dog. It's a prominent constellation that has represented a dog from early Greek times.

Canis Minor - the Lesser Dog
Canis Minor is one of Orion's hunting dogs. It trots along behind its master unperturbed by the unicorn (Monoceros), and leaving the hare (Lepus) to the greater dog (Canis Major) to chase. It's a small constellation with not much more to offer than one bright star, but it has a long history.

Cassiopeia the Queen
High in the sky, circling the north celestial pole are the distinctive stars of Cassiopeia, the boastful queen who nearly destroyed her kingdom. The Milky Way runs through the constellation and it's full of star clusters, galaxies and evidence of the life cycles of stars.

Cats in the Sky
There are three constellations named for dogs, but what about cats in the sky? There is astrocat Felicette who went into space and returned safely to Earth, but also constellations of big cats and a pawprint 50 light years across.

Centaurus the Centaur
Half-man, half-horse, Centaurus strides across the southern sky. Its myths and legends go back thousands of years and it's full of marvelous sights. Planets, black holes, an enormous diamond and colliding galaxies are just some of them.

Cepheus the King
An ancient Greek tale of pride and passion is played out across the sky, and involves five constellations, including Cepheus the king. In the constellation Cepheus there are stars being born and stars at the end of their lives, some of which will die in a blaze of glory.

Cetus the Sea Monster
Whale or monster? Benign plankton-eating creature? No, a terrifying colossus, a hybrid with gaping jaws and the powerful scaly coils of a sea serpent. This is the constellation Cetus. The monster fell to the hero Perseus, but the stars and deep sky objects are impressive.

Chamaeleon - the Southern Stellar Lizard
Chamaeleons lived in lands exotic to 16th-century Europeans. Yet although color-changing lizards are fascinating, Chamaeleon the constellation is a small, dim southern sky constellation with no associated mythology. Why does it even exist? Is there anything of interest there?

Coma Berenices – Berenice's Hair
A dazzling queen of ancient Egypt was the inspiration for the constellation Coma Berenices. It's small and dim, but contains the Galactic North Pole and multitudes of galaxies.

Constellation or Asterism
Constellations and asterisms are both patterns of stars. So what is a constellation? And If Saturn is in the constellation Virgo, has it left the Solar System? Why is the Big Dipper an asterism and not a constellation?

Constellations – Facts for Kids
ome of our constellations go back thousands of years. Others were invented when Europeans began to explore the distant seas of the southern hemisphere. But what´s the difference between a constellation, an asterism and a star cluster? And what does the constellation Pyxis represent?

Cosmic 4th of July
What links the USA´s Independence Day holiday, the Crab Nebula and NASA´s Deep Impact spacecraft? What links the American War of Independence with the planet Uranus? And what is the Fireworks Galaxy? Read on to find out.

Cosmic Equines
Horses galloping and flying creatures half human, half horse dark horses invisible but for their silhouettes against the stars behind them. Find out about the cosmic equines that are features of our skies.

Cosmic Father´s Day
What sort of tie would you give a cosmic father? What would you feed him? Where might he find challenging mountaineering, make an astounding golf shot or get up an interstellar soccer game? How can you send a special man a genuinely galactic greeting? Here´s how.

Creepy Crawlies in Space
What was the first Earth creature to go into space? Not a dog, but a fruit fly. Insects and arachnids have been mini-astronauts for over sixty years. They have also inspired the naming of heavenly objects.

Crux - the Southern Cross
Crux is the smallest of the 88 constellations, but it punches above its weight. As Polaris does in the northern hemisphere, in the southern hemisphere the Southern Cross serves as a navigation aid. It's part of the flags of five nations, and its stars also feature widely in traditional lore.

Cygnus the Swan
Seduction and supergiants, a beautiful blue and amber double star, vast explosions, a giant cloud that looks like North America. Where does myth end and astronomy begin? Here is a tour of some of the highlights of the constellation Cygnus the swan.

Delphinus the Dolphin
Delphinus (the Dolphin) sounds like one of the southern sea constellations invented by early European navigators. However it's an ancient northern constellation first catalogued by Ptolemy in the 2nd century. Small and made up of faint stars, its diamond is still easily visible in a clear dark sky.

Dorado the Mahi Mahi
Since the heavenly flying fish (Volans) is intact, its neighboring constellation Dorado must still be hungry. Dorado is a dolphinfish, mahi mahi being the most common type. Mahi mahi pursue flying fish through tropical seas, and you might imagine Dorado chasing Volans through the southern skies.

Draco – the Dragon
An enormous dragon circles the northern celestial pole. It's Draco, the constellation that contains a star that was the pole star at the time of the pharaohs, numerous impressive deep sky objects, and dozens of exoplanets.

Galactic Winter Games
Welcome to the Galactic Winter Games, a starry tribute to Earth´s Winter Olympic Games. It´s a tour of some really cool cosmic sights – as well as some hot ones, such as one of the biggest explosions in the Universe.

Heavenly Aviaries - Bird Constellations
The night sky is full of starry birds. Here is a selection, ranging from the majestic swan to the exotic birds of the southern skies: the peacock, bird of paradise and toucan. There is also an emu whose image appears not in the stars, but in the dark nebulae.

Hydra the Water Snake – Deep Sky Objects
It's not surprising to find plenty of deep-sky objects in such a big constellation as Hydra. Its varied objects include the Ghost of Jupiter, beautiful globules that are over twice the age of the Sun, and a dramatic grand design spiral galaxy known for its titanic explosions.

Hydra the Water Snake – Myths and Stars
What links the biggest constellation in the sky with the flag of Brazil? Why is the star V Hydrae bright red? How did the hero Hercules vanquish a nine-headed monster?

Lacaille's Skies - Sciences
There's a curious set of constellations in the southern skies. They don't represent exotic animals, heroic deeds or the foibles of ancient deities. They're composed of dim and nameless stars. Find out why Abbe Lacaille invented them, and take a quick tour.

Lacaille's skies – Arts
Much of the southern sky wasn't visible to the ancient Mediterranean civilizations. Instead of representing the ancient myths, the constellations were invented long afterwards by European explorers and astronomers. Some of Abbe Lacaille's inventions are tributes to the arts.

Lacerta - the Northern Stellar Lizard
Although the night sky has two lizards, the classical world wasn't enthralled by small reptiles. Both Lacerta and Chamaeleon constellations date from about the 17th century, which is considered modern. Lacerta is home to a fiery dwarf, a puffy planet and one of the most energetic known galaxies.

Leo the Lion
Leo is a Zodiac constellation and its stars have represented a lion for over four thousand years. Leo contains one of the brightest stars in the sky and one of the dimmest, as well as a selection of spiral galaxies loved by amateur astronomers. And why isn't Regulus the star of summer anymore?

Libra the Scales
Lying between Virgo and Scorpius in the zodiac, Libra is an ancient constellation. The stars now represent a weighing scale, as they did four thousand years ago in Babylon. But how did its brightest stars come to have names related to a scorpion's claws?

Lyra the Heavenly Harp
Music of the spheres? Here’s a harp to play it on: Lyra, the harp of Orpheus, that almost brought his beloved back from death. The constellation has one of the sky’s brightest stars, a star that is really four stars, and a colorful donut.

Monoceros the Unicorn
Did you know that there is a unicorn constellation? Certainly Monoceros isn't a classical constellation, and it's almost too faint to see. But it has a lot of interesting stars and other objects in it.

Obsolete Constellations
What happens to constellations when you don't want them anymore? Nothing, physically. They aren't real groups of stars like star clusters are. They're the products of human imagination, and they come and go. Here are half a dozen of my favorite obsolete constellations.

Octans – the Octant
Octans was one of the southern constellations created by 18th-century French astronomer Nicolas-Louis de Lacaille. He used them to fill the gaps in the southern sky map, naming them for tools of the arts and sciences of his day. An octant was a navigation device that preceded the sextant.

Ophiuchus – the Tour
Ophiuchus the Snake Bearer represents the healer Asclepius who was a god of healing in classical times. He was associated with snakes – symbols of wisdom and regeneration – and in the sky he's entwined with Serpens.

Orion the Hunter
The stars of Orion have been part of humanity's mythscape for thousands of years. Seven bright stars outline the hunter's body. One of them is a supergiant nearing the end of its life. Yet just visible to the unaided eye is a vast stellar nursery where the next generation of stars is forming.

Pegasus the Winged Horse
A flying horse on feathered wings - it's the constellation Pegasus. You can spot it by its most noticeable feature, the Great Square of Pegasus, though one star of the square belongs to poor Princess Andromeda. There's also a star in Pegasus very like our Sun with a planet circling it.

Perseus the Hero
Perseus was a first-class hero: demi-god, monster-slayer, maiden-rescuer, founder of Mycenae. When he died the gods put him in the sky. His constellation contains beautiful nebulae, a demon and a singing black hole.

Sagittarius the Archer
In northern hemisphere summer, the ancient zodiac constellation Sagittarius stands low on the southern horizon. It's a special constellation, for when you see Sagittarius, you're looking into the heart of the Milky Way.

Scutum the Shield
Vienna, September 1683. For two months the city had been besieged by an army of the Ottoman Empire, and couldn't hold out much longer. But what does this have to do with astronomy? The link is the constellation Scutum (the Shield).

Serpens and Ophiuchus - Ancient Tales
What is the link between two ancient constellations and modern medicine? According to one myth, how did Ophiuchus end up in the sky? Why would a healer be associated with a snake?

Serpens – a Tour of the Celestial Snake
Snakes were revered in ancient Greece. They represented wisdom, healing and rebirth. The constellation Serpens was included in a 2nd century star catalog, but it's much older than that. Seen through telescopes, it's rich in deep sky objects.

Sextans – the Sextant
Sextans is a southern constellation invented by Johannes Hevelius in the 17th century to represent his astronomical sextant. Its stars are dim, but it's rich in deep sky objects.

Sky of Grand Central Terminal – It´s Backwards
A splendid starry sky crowns the concourse of Manhattan´s Grand Central Terminal. It´s a 1940s reworking of the original that Paul César Helleu designed after consultation with a prominent astronomer. Yet a month after the station opened, a starwise commuter claimed that the sky was backwards.

Star Tales [offsite link]
An updated version of Ian Ridpath´s classic Star Tales about the myths and legends of the night sky is now available online.

Summer Triangle
The Summer Triangle is a stellar treat for northern mid-latitudes summer sky watchers. It graces the sky all night long in summer, and its three bright stars are visible even in urban areas. Under dark skies you can also see the Milky Way within the asterism.

Taurus the Bull
In Greek myth Taurus is Zeus's guise for the seduction of Europa. Yet the bull's red eye still glares at Orion in an enmity created long before the rise of ancient Greece. Today's Taurus is a constellation memorable for its two beautiful star clusters and one of the sky's most amazing objects.

Telescopium and Microscopium
Nicholas-Louis de Lacaille invented over a dozen constellations to fill gaps in the southern sky map. Instead of looking to classical mythology, he celebrated the instruments of the Enlightenment. Two small faint constellations represent extremes of visual aids – the telescope and the microscope.

The Starry Crowns – Corona Australis
A wreath, a crown, a wheel of torment, a boomerang. The constellation Corona Australis has represented them all in different traditions. Its stars are dim, but its stories are vivid.

The Starry Crowns – Corona Borealis
There are two crowns in the sky, the northern and southern ones. Classically, Corona Borealis represents the crown of Ariadne, abandoned heroine of the tale of the Minotaur and the labyrinth. More prosaically, in Australian aboriginal astronomy, it's Womera – the Boomerang, which it resembles.

Triangulum – the Northern Triangle
The sky is full of potential triangles. All you need is three stars that aren't in a line. We have large triangular asterisms – the Summer, Spring, and Winter Triangles. And there are also two triangle constellations. The northern one is Triangulum, and it has a surprisingly long history.

Virgo the Maiden
Virgo is one of the constellations of the zodiac, and its stars have been linked to agricultural goddesses for thousands of years. This area of sky contains thousands of galaxies, dozens of known extrasolar planets, and is where the first quasar was discovered.

Volans Flies the Southern Skies
Volans (the Flying Fish) flees from its predator Dorado (the Mahi Mahi) across the southern sky. They're two of the southern hemisphere constellations that Flemish astronomer Petrus Plancius (1552-1622) created to fill in parts of the sky not visible to northern astronomers.

Vulpecula - the Little Fox
Vulpecula isn't a well known constellation, and its stars are dim. Yet it's interesting. It contains both the first planetary nebula and the first pulsar ever discovered, a handful of exoplanets, and part of the biggest structure in the known Universe.

What Are Constellations
Stories of gods and mortals, love and betrayal, monsters and heroes. They all adorn the night sky in the form of constellations. These star groups have also served as calendars, navigation aids and internationally defined areas of the celestial sphere.

Who Let the Dogs Out?
Someone must have left the door open, because the skies are full of dogs. You can see the dogs of Orion and the hunting dogs of the shepherd Bootes in pursuit of the Great Bear. There is also the Running Dog Nebula and the memory of poor Laika, the first cosmonaut, who perished in space.

Winter Hexagon
From March to May you can see the Spring Triangle in northern skies. In summer the Summer Triangle is most prominent, but may be seen all year round in most of the northern hemisphere. There is also a Winter Triangle. But grandest of all is the Winter Hexagon.

Zodiac Constellations - Quiz
How well do you know the constellations of the zodiac? They are the oldest of the constellations. Here's a little quiz for you to test your knowledge. It's complete with answers and some additional facts about the zodiac constellations.

Links marked with the [offsite link] designation point to websites not associated with BellaOnline.com. BellaOnline.com is not responsible for the material found there.

Content copyright © 2018 by . All rights reserved.
This content was written by . If you wish to use this content in any manner, you need written permission. Contact Mona Evans for details.


Astronomy at a distance: Constellations

First you’ll need to get your bearings. We’ll be guiding you in part by the Cardinal Directions, - North, East, South and West.

If you are facing North, then East is to your right, West is to your left and South is behind you. ‘Due North’ just means ‘nearly-exactly North’. To find North you can use a compass or a compass app on a smartphone. You can also remember where the sun set. At this time of year, in the Northern Hemisphere, this is very close to due West.

Another way is to find the North Star, Polaris. Polaris lies at due North in the sky, and because of its location it does not appear to rotate with the rest of the sky during the night, in fact it appears as though all the other stars are spinning around it. If you have already managed to find The Big Dipper/The Plough, imagine the handle of The Big Dipper to be at the top-left corner of its bowl. You can then find Polaris by following a straight line from the bottom-right corner of the bowl to the top-right corner and beyond until you reach the next brightest star. This star should lie at the tip of the handle of The Little Dipper, another constellation that looks very similar to the Big Dipper, but is smaller and flipped upside down. This star at the tip of The Little Dipper’s handle is Polaris.

Here are some of the constellations that you can pick out in the night sky in the UK at the moment if you were to go outside at around 8-9pm:

    : Also known as The Plough, this is one of the most well-known sights in the sky and is named for its shape: four bright stars make up a bowl and three bright stars make up a handle. The Plough is actually part of a bigger constellation called Ursa Major, ‘The Great Bear’. The Plough makes up the bear’s hindquarters and tail. Find The Plough high in the North-East sky, and see if you can spot the rest of Ursa Major.
  • Another famous constellation is Orion. The Greeks saw Orion as a mighty hunter holding up a shield in front of him and raising a club behind him. One of the most stand out features of Orion is the three bright stars in a straight line which form a belt across his waist. Look out for the red giant star Betelgeuse in his shoulder, it’s one of the brightest stars in the sky and its red colour is plain to see. You can find this constellation a little bit above the horizon in the South-West sky.
  • A much simpler constellation is Cassiopeia. Cassiopeia was named for a beautiful but boastful queen, although this constellation is more recognisable as a bright ‘W’ formed by five stars. Look for the ‘W’ a little above the horizon in the North-West sky.
  • Our next constellation contains the brightest star in the night sky, Sirius. Sirius forms the top-right corner of the constellation Canis Major, ‘The Great Dog’. You should be able to make out the front and hind legs of Canis Major as well as its tail. Look just above the horizon between South and South-West for a bright star, if you find Sirius, you’ve found Canis Major. See if you can make out its body.
  • Our final constellation is Taurus, ‘The Bull’. Six stars form a small head with the red star Aldebaran in one eye and three stars make two long horns pointing up. Also, a single star stretches to the East to form the body. The star that forms the body lies right next to an amazing cluster of bright blue stars called the Pleiades, and you might also spot the planet Venus which is also very nearby. Venus is the brightest point in the sky right now, so it should be readily visible above the horizon towards due West. Find Venus, and both Taurus and the Pleiades will be nearby. The head of Taurus can be found about halfway between the Pleiades and Orion’s shield.

Can you find everything on this list? If you’re having trouble, make sure you've given your eyes time to adapt to the dark.

The Astronomy and Astrophysics group at Warwick is interested in a huge range of scales across the Universe: planetary systems, how they form, live and die stars, stellar binaries and and the exotic physical processes that they allow us to explore as well as the transient events which mark the end of stellar lifetimes and the galaxies stars inhabit across the Universe. The group started in September 2003 and is both an observational and theoretical group. The group makes use of a wide range of ground-based telescopes, such as ESO's Very Large Telescope (VLT) in Chile and the Isaac Newton Group of telescopes (ING) in the Canary Islands, or the Atacama Large Millimetre Array (ALMA), as well as space telescopes such as NASA's Chandra and ESA's XMM-Newton X-ray observatories and the Hubble Space Telescope. The Warwick astro group partners in the four large spectroscopic surveys (DESI, SDSS-V, WEAVE, and 4MOST) that will start operations throughout 2020-2021.

Terms for republishing
The text in this article is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


Contents

The atmosphere of Jupiter is classified into four layers, by increasing altitude: the troposphere, stratosphere, thermosphere and exosphere. Unlike the Earth's atmosphere, Jupiter's lacks a mesosphere. [15] Jupiter does not have a solid surface, and the lowest atmospheric layer, the troposphere, smoothly transitions into the planet's fluid interior. [3] This is a result of having temperatures and the pressures well above those of the critical points for hydrogen and helium, meaning that there is no sharp boundary between gas and liquid phases. Hydrogen becomes a supercritical fluid at a pressure of around 12 bar. [3]

Since the lower boundary of the atmosphere is ill-defined, the pressure level of 10 bars, at an altitude of about 90 km below 1 bar with a temperature of around 340 K, is commonly treated as the base of the troposphere. [4] In scientific literature, the 1 bar pressure level is usually chosen as a zero point for altitudes—a "surface" of Jupiter. [3] As is generally the case, the top atmospheric layer, the exosphere, does not have a specific upper boundary. [16] The density gradually decreases until it smoothly transitions into the planet's interior approximately 5,000 km above the "surface". [17]

The vertical temperature gradients in the Jovian atmosphere are similar to those of the atmosphere of Earth. The temperature of the troposphere decreases with height until it reaches a minimum at the tropopause, [18] which is the boundary between the troposphere and stratosphere. On Jupiter, the tropopause is approximately 50 km above the visible clouds (or 1 bar level), where the pressure and temperature are about 0.1 bar and 110 K. [4] [19] In the stratosphere, the temperatures rise to about 200 K at the transition into the thermosphere, at an altitude and pressure of around 320 km and 1 μbar. [4] In the thermosphere, temperatures continue to rise, eventually reaching 1000 K at about 1000 km, where pressure is about 1 nbar. [20]

Jupiter's troposphere contains a complicated cloud structure. [21] The upper clouds, located in the pressure range 0.6–0.9 bar, are made of ammonia ice. [22] Below these ammonia ice clouds, denser clouds made of ammonium hydrosulfide ((NH4)SH) or ammonium sulfide ((NH4)2S, between 1–2 bar) and water (3–7 bar) are thought to exist. [23] [24] There are no methane clouds as the temperatures are too high for it to condense. [21] The water clouds form the densest layer of clouds and have the strongest influence on the dynamics of the atmosphere. This is a result of the higher condensation heat of water and higher water abundance as compared to the ammonia and hydrogen sulfide (oxygen is a more abundant chemical element than either nitrogen or sulfur). [15] Various tropospheric (at 200–500 mbar) and stratospheric (at 10–100 mbar) haze layers reside above the main cloud layers. [23] [25] The latter are made from condensed heavy polycyclic aromatic hydrocarbons or hydrazine, which are generated in the upper stratosphere (1–100 μbar) from methane under the influence of the solar ultraviolet radiation (UV). [21] The methane abundance relative to molecular hydrogen in the stratosphere is about 10 −4 , [17] while the abundance ratio of other light hydrocarbons, like ethane and acetylene, to molecular hydrogen is about 10 −6 . [17]

Jupiter's thermosphere is located at pressures lower than 1 μbar and demonstrates such phenomena as airglow, polar aurorae and X-ray emissions. [26] Within it lie layers of increased electron and ion density that form the ionosphere. [17] The high temperatures prevalent in the thermosphere (800–1000 K) have not been fully explained yet [20] existing models predict a temperature no higher than about 400 K. [17] They may be caused by absorption of high-energy solar radiation (UV or X-ray), by heating from the charged particles precipitating from the Jovian magnetosphere, or by dissipation of upward-propagating gravity waves. [27] The thermosphere and exosphere at the poles and at low latitudes emit X-rays, which were first observed by the Einstein Observatory in 1983. [28] The energetic particles coming from Jupiter's magnetosphere create bright auroral ovals, which encircle the poles. Unlike their terrestrial analogs, which appear only during magnetic storms, aurorae are permanent features of Jupiter's atmosphere. [28] The thermosphere was the first place outside the Earth where the trihydrogen cation ( H +
3 ) was discovered. [17] This ion emits strongly in the mid-infrared part of the spectrum, at wavelengths between 3 and 5 μm this is the main cooling mechanism of the thermosphere. [26]

Elemental abundances relative to hydrogen
in Jupiter and Sun [2]
Element Sun Jupiter/Sun
He/H 0.0975 0.807 ± 0.02
Ne/H 1.23 × 10 −4 0.10 ± 0.01
Ar/H 3.62 × 10 −6 2.5 ± 0.5
Kr/H 1.61 × 10 −9 2.7 ± 0.5
Xe/H 1.68 × 10 −10 2.6 ± 0.5
C/H 3.62 × 10 −4 2.9 ± 0.5
N/H 1.12 × 10 −4 3.6 ± 0.5 (8 bar)

The composition of Jupiter's atmosphere is similar to that of the planet as a whole. [2] Jupiter's atmosphere is the most comprehensively understood of those of all the gas giants because it was observed directly by the Galileo atmospheric probe when it entered the Jovian atmosphere on December 7, 1995. [29] Other sources of information about Jupiter's atmospheric composition include the Infrared Space Observatory (ISO), [30] the Galileo and Cassini orbiters, [31] and Earth-based observations. [2]

The two main constituents of the Jovian atmosphere are molecular hydrogen ( H
2 ) and helium. [2] The helium abundance is 0.157 ± 0.004 relative to molecular hydrogen by number of molecules, and its mass fraction is 0.234 ± 0.005 , which is slightly lower than the Solar System's primordial value. [2] The reason for this low abundance is not entirely understood, but some of the helium may have condensed into the core of Jupiter. [22] This condensation is likely to be in the form of helium rain: as hydrogen turns into the metallic state at depths of more than 10,000 km, helium separates from it forming droplets which, being denser than the metallic hydrogen, descend towards the core. This can also explain the severe depletion of neon (see Table), an element that easily dissolves in helium droplets and would be transported in them towards the core as well. [32]

The atmosphere contains various simple compounds such as water, methane (CH4), hydrogen sulfide (H2S), ammonia (NH3) and phosphine (PH3). [2] Their abundances in the deep (below 10 bar) troposphere imply that the atmosphere of Jupiter is enriched in the elements carbon, nitrogen, sulfur and possibly oxygen [b] by factor of 2–4 relative to the Sun. [c] [2] The noble gases argon, krypton and xenon also appear in abundance relative to solar levels (see table), while neon is scarcer. [2] Other chemical compounds such as arsine (AsH3) and germane (GeH4) are present only in trace amounts. [2] The upper atmosphere of Jupiter contains small amounts of simple hydrocarbons such as ethane, acetylene, and diacetylene, which form from methane under the influence of the solar ultraviolet radiation and charged particles coming from Jupiter's magnetosphere. [2] The carbon dioxide, carbon monoxide and water present in the upper atmosphere are thought to originate from impacting comets, such as Shoemaker-Levy 9. The water cannot come from the troposphere because the cold tropopause acts like a cold trap, effectively preventing water from rising to the stratosphere (see Vertical structure above). [2]

Earth- and spacecraft-based measurements have led to improved knowledge of the isotopic ratios in Jupiter's atmosphere. As of July 2003, the accepted value for the deuterium abundance is (2.25 ± 0.35) × 10 −5 , [2] which probably represents the primordial value in the protosolar nebula that gave birth to the Solar System. [30] The ratio of nitrogen isotopes in the Jovian atmosphere, 15 N to 14 N, is 2.3 × 10 −3 , a third lower than that in the Earth's atmosphere (3.5 × 10 −3 ). [2] The latter discovery is especially significant since the previous theories of Solar System formation considered the terrestrial value for the ratio of nitrogen isotopes to be primordial. [30]

The visible surface of Jupiter is divided into several bands parallel to the equator. There are two types of bands: lightly colored zones and relatively dark belts. [6] The wider Equatorial Zone (EZ) extends between latitudes of approximately 7°S to 7°N. Above and below the EZ, the North and South Equatorial belts (NEB and SEB) extend to 18°N and 18°S, respectively. Farther from the equator lie the North and South Tropical zones (NtrZ and STrZ). [6] The alternating pattern of belts and zones continues until the polar regions at approximately 50 degrees latitude, where their visible appearance becomes somewhat muted. [33] The basic belt-zone structure probably extends well towards the poles, reaching at least to 80° North or South. [6]

The difference in the appearance between zones and belts is caused by differences in the opacity of the clouds. Ammonia concentration is higher in zones, which leads to the appearance of denser clouds of ammonia ice at higher altitudes, which in turn leads to their lighter color. [18] On the other hand, in belts clouds are thinner and are located at lower altitudes. [18] The upper troposphere is colder in zones and warmer in belts. [6] The exact nature of chemicals that make Jovian zones and bands so colorful is not known, but they may include complicated compounds of sulfur, phosphorus and carbon. [6]

The Jovian bands are bounded by zonal atmospheric flows (winds), called jets. The eastward (prograde) jets are found at the transition from zones to belts (going away from the equator), whereas westward (retrograde) jets mark the transition from belts to zones. [6] Such flow velocity patterns mean that the zonal winds decrease in belts and increase in zones from the equator to the pole. Therefore, wind shear in belts is cyclonic, while in zones it is anticyclonic. [24] The EZ is an exception to this rule, showing a strong eastward (prograde) jet and has a local minimum of the wind speed exactly at the equator. The jet speeds are high on Jupiter, reaching more than 100 m/s. [6] These speeds correspond to ammonia clouds located in the pressure range 0.7–1 bar. The prograde jets are generally more powerful than the retrograde jets. [6] The vertical extent of jets is not known. They decay over two to three scale heights [a] above the clouds, while below the cloud level, winds increase slightly and then remain constant down to at least 22 bar—the maximum operational depth reached by the Galileo Probe. [19]

The origin of Jupiter's banded structure is not completely clear, though it may be similar to that driving the Earth's Hadley cells. The simplest interpretation is that zones are sites of atmospheric upwelling, whereas belts are manifestations of downwelling. [34] When air enriched in ammonia rises in zones, it expands and cools, forming high and dense clouds. In belts, however, the air descends, warming adiabatically as in a convergence zone on Earth, and white ammonia clouds evaporate, revealing lower, darker clouds. The location and width of bands, speed and location of jets on Jupiter are remarkably stable, having changed only slightly between 1980 and 2000. One example of change is a decrease of the speed of the strongest eastward jet located at the boundary between the North Tropical zone and North Temperate belts at 23°N. [7] [34] However bands vary in coloration and intensity over time (see below). These variations were first observed in the early seventeenth century. [35]

Specific bands Edit

The belts and zones that divide Jupiter's atmosphere each have their own names and unique characteristics. They begin below the North and South Polar Regions, which extend from the poles to roughly 40–48° N/S. These bluish-gray regions are usually featureless. [33]

The North North Temperate Region rarely shows more detail than the polar regions, due to limb darkening, foreshortening, and the general diffuseness of features. However, the North-North Temperate Belt (NNTB) is the northernmost distinct belt, though it occasionally disappears. Disturbances tend to be minor and short-lived. The North-North Temperate Zone (NNTZ) is perhaps more prominent, but also generally quiet. Other minor belts and zones in the region are occasionally observed. [36]

The North Temperate Region is part of a latitudinal region easily observable from Earth, and thus has a superb record of observation. [37] It also features the strongest prograde jet stream on the planet—a westerly current that forms the southern boundary of the North Temperate Belt (NTB). [37] The NTB fades roughly once a decade (this was the case during the Voyager encounters), making the North Temperate Zone (NTZ) apparently merge into the North Tropical Zone (NTropZ). [37] Other times, the NTZ is divided by a narrow belt into northern and southern components. [37]

The North Tropical Region is composed of the NTropZ and the North Equatorial Belt (NEB). The NTropZ is generally stable in coloration, changing in tint only in tandem with activity on the NTB's southern jet stream. Like the NTZ, it too is sometimes divided by a narrow band, the NTropB. On rare occasions, the southern NTropZ plays host to "Little Red Spots". As the name suggests, these are northern equivalents of the Great Red Spot. Unlike the GRS, they tend to occur in pairs and are always short-lived, lasting a year on average one was present during the Pioneer 10 encounter. [38]

The NEB is one of the most active belts on the planet. It is characterized by anticyclonic white ovals and cyclonic "barges" (also known as "brown ovals"), with the former usually forming farther north than the latter as in the NTropZ, most of these features are relatively short-lived. Like the South Equatorial Belt (SEB), the NEB has sometimes dramatically faded and "revived". The timescale of these changes is about 25 years. [39]

The Equatorial Region (EZ) is one of the most stable regions of the planet, in latitude and in activity. The northern edge of the EZ hosts spectacular plumes that trail southwest from the NEB, which are bounded by dark, warm (in infrared) features known as festoons (hot spots). [40] Though the southern boundary of the EZ is usually quiescent, observations from the late 19th into the early 20th century show that this pattern was then reversed relative to today. The EZ varies considerably in coloration, from pale to an ochre, or even coppery hue it is occasionally divided by an Equatorial Band (EB). [41] Features in the EZ move roughly 390 km/h relative to the other latitudes. [42] [43]

The South Tropical Region includes the South Equatorial Belt (SEB) and the South Tropical Zone. It is by far the most active region on the planet, as it is home to its strongest retrograde jet stream. The SEB is usually the broadest, darkest belt on Jupiter it is sometimes split by a zone (the SEBZ), and can fade entirely every 3 to 15 years before reappearing in what is known as an SEB Revival cycle. A period of weeks or months following the belt's disappearance, a white spot forms and erupts dark brownish material which is stretched into a new belt by Jupiter's winds. The belt most recently disappeared in May 2010. [44] Another characteristic of the SEB is a long train of cyclonic disturbances following the Great Red Spot. Like the NTropZ, the STropZ is one of the most prominent zones on the planet not only does it contain the GRS, but it is occasionally rent by a South Tropical Disturbance (STropD), a division of the zone that can be very long-lived the most famous one lasted from 1901 to 1939. [45]

The South Temperate Region, or South Temperate Belt (STB), is yet another dark, prominent belt, more so than the NTB until March 2000, its most famous features were the long-lived white ovals BC, DE, and FA, which have since merged to form Oval BA ("Red Jr."). The ovals were part of South Temperate Zone, but they extended into STB partially blocking it. [6] The STB has occasionally faded, apparently due to complex interactions between the white ovals and the GRS. The appearance of the South Temperate Zone (STZ)—the zone in which the white ovals originated—is highly variable. [47]

There are other features on Jupiter that are either temporary or difficult to observe from Earth. The South South Temperate Region is harder to discern even than the NNTR its detail is subtle and can only be studied well by large telescopes or spacecraft. [48] Many zones and belts are more transient in nature and are not always visible. These include the Equatorial band (EB), [49] North Equatorial belt zone (NEBZ, a white zone within the belt) and South Equatorial belt zone (SEBZ). [50] Belts are also occasionally split by a sudden disturbance. When a disturbance divides a normally singular belt or zone, an N or an S is added to indicate whether the component is the northern or southern one e.g., NEB(N) and NEB(S). [51]

Circulation in Jupiter's atmosphere is markedly different from that in the atmosphere of Earth. The interior of Jupiter is fluid and lacks any solid surface. Therefore, convection may occur throughout the planet's outer molecular envelope. As of 2008, a comprehensive theory of the dynamics of the Jovian atmosphere has not been developed. Any such theory needs to explain the following facts: the existence of narrow stable bands and jets that are symmetric relative to Jupiter's equator, the strong prograde jet observed at the equator, the difference between zones and belts, and the origin and persistence of large vortices such as the Great Red Spot. [7]

The theories regarding the dynamics of the Jovian atmosphere can be broadly divided into two classes: shallow and deep. The former hold that the observed circulation is largely confined to a thin outer (weather) layer of the planet, which overlays the stable interior. The latter hypothesis postulates that the observed atmospheric flows are only a surface manifestation of deeply rooted circulation in the outer molecular envelope of Jupiter. [52] As both theories have their own successes and failures, many planetary scientists think that the true theory will include elements of both models. [53]

Shallow models Edit

The first attempts to explain Jovian atmospheric dynamics date back to the 1960s. [52] [54] They were partly based on terrestrial meteorology, which had become well developed by that time. Those shallow models assumed that the jets on Jupiter are driven by small scale turbulence, which is in turn maintained by moist convection in the outer layer of the atmosphere (above the water clouds). [55] [56] The moist convection is a phenomenon related to the condensation and evaporation of water and is one of the major drivers of terrestrial weather. [57] The production of the jets in this model is related to a well-known property of two dimensional turbulence—the so-called inverse cascade, in which small turbulent structures (vortices) merge to form larger ones. [55] The finite size of the planet means that the cascade can not produce structures larger than some characteristic scale, which for Jupiter is called the Rhines scale. Its existence is connected to production of Rossby waves. This process works as follows: when the largest turbulent structures reach a certain size, the energy begins to flow into Rossby waves instead of larger structures, and the inverse cascade stops. [58] Since on the spherical rapidly rotating planet the dispersion relation of the Rossby waves is anisotropic, the Rhines scale in the direction parallel to the equator is larger than in the direction orthogonal to it. [58] The ultimate result of the process described above is production of large scale elongated structures, which are parallel to the equator. The meridional extent of them appears to match the actual width of jets. [55] Therefore, in shallow models vortices actually feed the jets and should disappear by merging into them.

While these weather–layer models can successfully explain the existence of a dozen narrow jets, they have serious problems. [55] A glaring failure of the model is the prograde (super-rotating) equatorial jet: with some rare exceptions shallow models produce a strong retrograde (subrotating) jet, contrary to observations. In addition, the jets tend to be unstable and can disappear over time. [55] Shallow models cannot explain how the observed atmospheric flows on Jupiter violate stability criteria. [59] More elaborated multilayer versions of weather–layer models produce more stable circulation, but many problems persist. [60] Meanwhile, the Galileo Probe found that the winds on Jupiter extend well below the water clouds at 5–7 bar and do not show any evidence of decay down to 22 bar pressure level, which implies that circulation in the Jovian atmosphere may in fact be deep. [19]

Deep models Edit

The deep model was first proposed by Busse in 1976. [61] [62] His model was based on another well-known feature of fluid mechanics, the Taylor–Proudman theorem. It holds that in any fast-rotating barotropic ideal liquid, the flows are organized in a series of cylinders parallel to the rotational axis. The conditions of the theorem are probably met in the fluid Jovian interior. Therefore, the planet's molecular hydrogen mantle may be divided into cylinders, each cylinder having a circulation independent of the others. [63] Those latitudes where the cylinders' outer and inner boundaries intersect with the visible surface of the planet correspond to the jets the cylinders themselves are observed as zones and belts.

The deep model easily explains the strong prograde jet observed at the equator of Jupiter the jets it produces are stable and do not obey the 2D stability criterion. [63] However it has major difficulties it produces a very small number of broad jets, and realistic simulations of 3D flows are not possible as of 2008, meaning that the simplified models used to justify deep circulation may fail to catch important aspects of the fluid dynamics within Jupiter. [63] One model published in 2004 successfully reproduced the Jovian band-jet structure. [53] It assumed that the molecular hydrogen mantle is thinner than in all other models occupying only the outer 10% of Jupiter's radius. In standard models of the Jovian interior, the mantle comprises the outer 20–30%. [64] The driving of deep circulation is another problem. The deep flows can be caused both by shallow forces (moist convection, for instance) or by deep planet-wide convection that transports heat out of the Jovian interior. [55] Which of these mechanisms is more important is not clear yet.

Internal heat Edit

As has been known since 1966, [65] Jupiter radiates much more heat than it receives from the Sun. It is estimated that the ratio of the thermal power emitted by the planet to the thermal power absorbed from the Sun is 1.67 ± 0.09 . The internal heat flux from Jupiter is 5.44 ± 0.43 W/m 2 , whereas the total emitted power is 335 ± 26 petawatts . The latter value is approximately equal to one billionth of the total power radiated by the Sun. This excess heat is mainly the primordial heat from the early phases of Jupiter's formation, but may result in part from the precipitation of helium into the core. [66]

The internal heat may be important for the dynamics of the Jovian atmosphere. While Jupiter has a small obliquity of about 3°, and its poles receive much less solar radiation than its equator, the tropospheric temperatures do not change appreciably from the equator to poles. One explanation is that Jupiter's convective interior acts like a thermostat, releasing more heat near the poles than in the equatorial region. This leads to a uniform temperature in the troposphere. While heat is transported from the equator to the poles mainly via the atmosphere on Earth, on Jupiter deep convection equilibrates heat. The convection in the Jovian interior is thought to be driven mainly by the internal heat. [67]

Vortices Edit

The atmosphere of Jupiter is home to hundreds of vortices—circular rotating structures that, as in the Earth's atmosphere, can be divided into two classes: cyclones and anticyclones. [8] Cyclones rotate in the direction similar to the rotation of the planet (counterclockwise in the northern hemisphere and clockwise in the southern) anticyclones rotate in the reverse direction. However, unlike in the terrestrial atmosphere, anticyclones predominate over cyclones on Jupiter—more than 90% of vortices larger than 2000 km in diameter are anticyclones. [68] The lifetime of Jovian vortices varies from several days to hundreds of years, depending on their size. For instance, the average lifetime of an anticyclone between 1000 and 6000 km in diameter is 1–3 years. [69] Vortices have never been observed in the equatorial region of Jupiter (within 10° of latitude), where they are unstable. [11] As on any rapidly rotating planet, Jupiter's anticyclones are high pressure centers, while cyclones are low pressure. [40]

The anticyclones in Jupiter's atmosphere are always confined within zones, where the wind speed increases in direction from the equator to the poles. [69] They are usually bright and appear as white ovals. [8] They can move in longitude, but stay at approximately the same latitude as they are unable to escape from the confining zone. [11] The wind speeds at their periphery are about 100 m/s. [10] Different anticyclones located in one zone tend to merge when they approach each other. [71] However Jupiter has two anticyclones that are somewhat different from all others. They are the Great Red Spot (GRS) [9] and the Oval BA [10] the latter formed only in 2000. In contrast to white ovals, these structures are red, arguably due to dredging up of red material from the planet's depths. [9] On Jupiter the anticyclones usually form through merges of smaller structures including convective storms (see below), [69] although large ovals can result from the instability of jets. The latter was observed in 1938–1940, when a few white ovals appeared as a result of instability of the southern temperate zone they later merged to form Oval BA. [10] [69]

In contrast to anticyclones, the Jovian cyclones tend to be small, dark and irregular structures. Some of the darker and more regular features are known as brown ovals (or badges). [68] However the existence of a few long–lived large cyclones has been suggested. In addition to compact cyclones, Jupiter has several large irregular filamentary patches, which demonstrate cyclonic rotation. [8] One of them is located to the west of the GRS (in its wake region) in the southern equatorial belt. [72] These patches are called cyclonic regions (CR). The cyclones are always located in the belts and tend to merge when they encounter each other, much like anticyclones. [69]

The deep structure of vortices is not completely clear. They are thought to be relatively thin, as any thickness greater than about 500 km will lead to instability. The large anticyclones are known to extend only a few tens of kilometers above the visible clouds. The early hypothesis that the vortices are deep convective plumes (or convective columns) as of 2008 is not shared by the majority of planetary scientists. [11]

Great Red Spot Edit

The Great Red Spot (GRS) is a persistent anticyclonic storm, 22° south of Jupiter's equator observations from Earth establish a minimum storm lifetime of 350 years. [74] [75] A storm was described as a "permanent spot" by Gian Domenico Cassini after observing the feature in July 1665 with his instrument-maker Eustachio Divini. [76] According to a report by Giovanni Battista Riccioli in 1635, Leander Bandtius, whom Riccioli identified as the Abbot of Dunisburgh who possessed an "extraordinary telescope", observed a large spot that he described as "oval, equaling one seventh of Jupiter's diameter at its longest." According to Riccioli, "these features are seldom able to be seen, and then only by a telescope of exceptional quality and magnification." [77] The Great Spot has been nearly continually observed since the 1870s, however.

The GRS rotates counter-clockwise, with a period of about six Earth days [78] or 14 Jovian days. Its dimensions are 24,000–40,000 km east-to-west and 12,000–14,000 km north-to-south. The spot is large enough to contain two or three planets the size of Earth. At the start of 2004, the Great Red Spot had approximately half the longitudinal extent it had a century ago, when it was 40,000 km in diameter. At the present rate of reduction, it could potentially become circular by 2040, although this is unlikely because of the distortion effect of the neighboring jet streams. [79] It is not known how long the spot will last, or whether the change is a result of normal fluctuations. [80]

According to a study by scientists at the University of California, Berkeley, between 1996 and 2006 the spot lost 15 percent of its diameter along its major axis. Xylar Asay-Davis, who was on the team that conducted the study, noted that the spot is not disappearing because "velocity is a more robust measurement because the clouds associated with the Red Spot are also strongly influenced by numerous other phenomena in the surrounding atmosphere." [81]

Infrared data have long indicated that the Great Red Spot is colder (and thus, higher in altitude) than most of the other clouds on the planet [82] the cloudtops of the GRS are about 8 km above the surrounding clouds. Furthermore, careful tracking of atmospheric features revealed the spot's counterclockwise circulation as far back as 1966 – observations dramatically confirmed by the first time-lapse movies from the Voyager flybys. [83] The spot is spatially confined by a modest eastward jet stream (prograde) to its south and a very strong westward (retrograde) one to its north. [84] Though winds around the edge of the spot peak at about 120 m/s (432 km/h), currents inside it seem stagnant, with little inflow or outflow. [85] The rotation period of the spot has decreased with time, perhaps as a direct result of its steady reduction in size. [86] In 2010, astronomers imaged the GRS in the far infrared (from 8.5 to 24 μm) with a spatial resolution higher than ever before and found that its central, reddest region is warmer than its surroundings by between 3–4 K. The warm airmass is located in the upper troposphere in the pressure range of 200–500 mbar. This warm central spot slowly counter-rotates and may be caused by a weak subsidence of air in the center of GRS. [87]

The Great Red Spot's latitude has been stable for the duration of good observational records, typically varying by about a degree. Its longitude, however, is subject to constant variation. [88] [89] Because Jupiter's visible features do not rotate uniformly at all latitudes, astronomers have defined three different systems for defining the longitude. System II is used for latitudes of more than 10°, and was originally based on the average rotation rate of the Great Red Spot of 9h 55m 42s. [90] [91] Despite this, the spot has 'lapped' the planet in System II at least 10 times since the early 19th century. Its drift rate has changed dramatically over the years and has been linked to the brightness of the South Equatorial Belt, and the presence or absence of a South Tropical Disturbance. [92]

It is not known exactly what causes the Great Red Spot's reddish color. Theories supported by laboratory experiments suppose that the color may be caused by complex organic molecules, red phosphorus, or yet another sulfur compound. The GRS varies greatly in hue, from almost brick-red to pale salmon, or even white. The higher temperature of the reddest central region is the first evidence that the Spot's color is affected by environmental factors. [87] The spot occasionally disappears from the visible spectrum, becoming evident only through the Red Spot Hollow, which is its niche in the South Equatorial Belt (SEB). The visibility of GRS is apparently coupled to the appearance of the SEB when the belt is bright white, the spot tends to be dark, and when it is dark, the spot is usually light. The periods when the spot is dark or light occur at irregular intervals in the 50 years from 1947 to 1997, the spot was darkest in the periods 1961–1966, 1968–1975, 1989–1990, and 1992–1993. [93] In November 2014, an analysis of data from NASA's Cassini mission revealed that the red color is likely a product of simple chemicals being broken apart by solar ultraviolet irradiation in the planet's upper atmosphere. [94] [95] [96]

The Great Red Spot should not be confused with the Great Dark Spot, a feature observed near Jupiter's north pole in 2000 by the Cassini–Huygens spacecraft. [97] A feature in the atmosphere of Neptune was also called the Great Dark Spot. The latter feature, imaged by Voyager 2 in 1989, may have been an atmospheric hole rather than a storm. It was no longer present in 1994, although a similar spot had appeared farther to the north. [98]

Oval BA Edit

Oval BA is a red storm in Jupiter's southern hemisphere similar in form to, though smaller than, the Great Red Spot (it is often affectionately referred to as "Red Spot Jr.", "Red Jr." or "The Little Red Spot"). A feature in the South Temperate Belt, Oval BA was first seen in 2000 after the collision of three small white storms, and has intensified since then. [99]

The formation of the three white oval storms that later merged into Oval BA can be traced to 1939, when the South Temperate Zone was torn by dark features that effectively split the zone into three long sections. Jovian observer Elmer J. Reese labeled the dark sections AB, CD, and EF. The rifts expanded, shrinking the remaining segments of the STZ into the white ovals FA, BC, and DE. [100] Ovals BC and DE merged in 1998, forming Oval BE. Then, in March 2000, BE and FA joined together, forming Oval BA. [99] (see White ovals, below)

Oval BA slowly began to turn red in August 2005. [101] On February 24, 2006, Filipino amateur astronomer Christopher Go discovered the color change, noting that it had reached the same shade as the GRS. [101] As a result, NASA writer Dr. Tony Phillips suggested it be called "Red Spot Jr." or "Red Jr." [102]

In April 2006, a team of astronomers, believing that Oval BA might converge with the GRS that year, observed the storms through the Hubble Space Telescope. [103] The storms pass each other about every two years, but the passings of 2002 and 2004 did not produce anything exciting. Dr. Amy Simon-Miller, of the Goddard Space Flight Center, predicted the storms would have their closest passing on July 4, 2006. [103] On July 20, the two storms were photographed passing each other by the Gemini Observatory without converging. [104]

Why Oval BA turned red is not understood. According to a 2008 study by Dr. Santiago Pérez-Hoyos of the University of the Basque Country, the most likely mechanism is "an upward and inward diffusion of either a colored compound or a coating vapor that may interact later with high energy solar photons at the upper levels of Oval BA." [105] Some believe that small storms (and their corresponding white spots) on Jupiter turn red when the winds become powerful enough to draw certain gases from deeper within the atmosphere which change color when those gases are exposed to sunlight. [106]

Oval BA is getting stronger according to observations made with the Hubble Space Telescope in 2007. The wind speeds have reached 618 km/h about the same as in the Great Red Spot and far stronger than any of the progenitor storms. [107] [108] As of July 2008, its size is about the diameter of Earth—approximately half the size of the Great Red Spot. [105]

Oval BA should not be confused with another major storm on Jupiter, the South Tropical Little Red Spot (LRS) (nicknamed "the Baby Red Spot" by NASA [109] ), which was destroyed by the GRS. [106] The new storm, previously a white spot in Hubble images, turned red in May 2008. The observations were led by Imke de Pater of the University of California, at Berkeley, US. [110] The Baby Red Spot encountered the GRS in late June to early July 2008, and in the course of a collision, the smaller red spot was shredded into pieces. The remnants of the Baby Red Spot first orbited, then were later consumed by the GRS. The last of the remnants with a reddish color to have been identified by astronomers had disappeared by mid-July, and the remaining pieces again collided with the GRS, then finally merged with the bigger storm. The remaining pieces of the Baby Red Spot had completely disappeared by August 2008. [109] During this encounter Oval BA was present nearby, but played no apparent role in destruction of the Baby Red Spot. [109]

Storms and lightning Edit

The storms on Jupiter are similar to thunderstorms on Earth. They reveal themselves via bright clumpy clouds about 1000 km in size, which appear from time to time in the belts' cyclonic regions, especially within the strong westward (retrograde) jets. [112] In contrast to vortices, storms are short-lived phenomena the strongest of them may exist for several months, while the average lifetime is only 3–4 days. [112] They are believed to be due mainly to moist convection within Jupiter's troposphere. Storms are actually tall convective columns (plumes), which bring the wet air from the depths to the upper part of the troposphere, where it condenses in clouds. A typical vertical extent of Jovian storms is about 100 km as they extend from a pressure level of about 5–7 bar, where the base of a hypothetical water cloud layer is located, to as high as 0.2–0.5 bar. [113]

Storms on Jupiter are always associated with lightning. The imaging of the night–side hemisphere of Jupiter by Galileo and Cassini spacecraft revealed regular light flashes in Jovian belts and near the locations of the westward jets, particularly at 51°N, 56°S and 14°S latitudes. [114] On Jupiter lightning strikes are on average a few times more powerful than those on Earth. However, they are less frequent the light power emitted from a given area is similar to that on Earth. [114] A few flashes have been detected in polar regions, making Jupiter the second known planet after Earth to exhibit polar lightning. [115] A Microwave Radiometer (Juno) detected many more in 2018.

Every 15–17 years Jupiter is marked by especially powerful storms. They appear at 23°N latitude, where the strongest eastward jet, that can reach 150 m/s, is located. The last time such an event was observed was in March–June 2007. [113] Two storms appeared in the northern temperate belt 55° apart in longitude. They significantly disturbed the belt. The dark material that was shed by the storms mixed with clouds and changed the belt's color. The storms moved with a speed as high as 170 m/s, slightly faster than the jet itself, hinting at the existence of strong winds deep in the atmosphere. [113] [d]

Circumpolar cyclones Edit

Other notable features of Jupiter are its cyclones near the northern and southern poles of the planet. These are called circumpolar cyclones (CPCs) and they have been observed by the Juno Spacecraft using JunoCam and JIRAM. The cyclones have only been observed for a relatively short time from perijoves 1-15 which is approximately 795 days or two years. The northern pole has eight cyclones moving around a central cyclone (NPC) while the southern pole only has five cyclones around a central cyclone (SPC), with a gap between the first and second cyclones. [116] The cyclones look like the hurricanes on Earth with trailing spiral arms and a denser center, although there are differences between the centers depending on the individual cyclone. Northern CPCs generally maintain their shape and position compared to the southern CPCs and this could be due to the faster wind speeds that are experienced in the south, where the average wind speed around 80 m/s to 90 m/s. Although there is more movement among the southern CPCs they tend to retain the pentagonal structure relative to the pole. It has also been observed that the angular wind velocity increases as the center is approached and radius becomes smaller, except for one cyclone in the north, which may have rotation in the opposite direction. The difference in the number of cyclones in the north compared to the south is due to the size of the cyclones. The southern CPCs tend to be bigger with radii ranging from 5,600 km to 7,000 km while northern CPCs range from 4,000 km to 4,600 km. [117]

The northern cyclones tend to maintain an octagonal structure with the NPC as a center point. Northern cyclones have less data than southern cyclones because of limited illumination in the north-polar winter, making it difficult for JunoCam to obtain accurate measurements of northern CPC positions at each perijove (53 days), but JIRAM is able to collect enough data to understand the northern CPCs. The limited illumination makes it difficult to see the northern central cyclone, but by making four orbits, the NPC can be partially seen and the octagonal structure of the cyclones can be identified. Limited illumination also makes it difficult to view the motion of the cyclones, but early observations show that the NPC is offset from the pole by about 0.5˚ and the CPCs generally maintained their position around the center. Despite data being harder to obtain, it has been observed that the northern CPCs have a drift rate of about 1˚ to 2.5˚ per perijove to the west. The seventh cyclone in the north (n7) drifts a little more than the others and this is due to an anticyclonic white oval (AWO) that pulls it farther from the NPC, which causes the octagonal shape to be slightly distorted.

Current data shows that the SPC shows a positional variation between 1˚ and 2.5˚ in the latitude and stays between 200˚ to 250˚ longitude and has shown evidence of this recurring approximately every 320 days. The southern cyclones tend to behave similarly to the northern ones and maintain the pentagonal structure around the SPC, but there is some individual movement from some of the CPCs. The southern cyclones don't move around the south pole, but their rotation is more steady around the SPC, which is offset from the pole. Short term observation shows that the southern cyclones move approximately 1.5˚ per perijove, which is small compared to the wind speeds of the cyclones and the turbulent atmosphere of Jupiter. The gap between cyclones one and two provides more movement for those specific CPCs, which also causes the other cyclones that are close to move as well, but cyclone four moves less because it is farthest from the gap. The southern cyclones move clockwise individually, but their movement as a pentagonal structure moves counter-clockwise and drifts more toward the west.

The circumpolar cyclones have different morphologies, especially in the north, where cyclones have a "filled" or "chaotic" structure. The inner part of the “chaotic” cyclones have small-scale cloud streaks and flecks. The “filled” cyclones have a sharply-bound, lobate area that is bright white near the edge with a dark inner portion. There are four “filled” cyclones and four “chaotic” cyclones in the north. The southern cyclones all have an extensive fine-scale spiral structure on their outside but they all differ in size and shape. There is very little observation of the cyclones due to low sun angles and a haze that is typically over the atmosphere but what little has been observed shows the cyclones to be a reddish color.

Disturbances Edit

The normal pattern of bands and zones is sometimes disrupted for periods of time. One particular class of disruption are long-lived darkenings of the South Tropical Zone, normally referred to as "South Tropical Disturbances" (STD). The longest lived STD in recorded history was followed from 1901 until 1939, having been first seen by Percy B. Molesworth on February 28, 1901. It took the form of darkening over part of the normally bright South Tropical zone. Several similar disturbances in the South Tropical Zone have been recorded since then. [118]

Hot spots Edit

Some of the most mysterious features in the atmosphere of Jupiter are hot spots. In them, the air is relatively free of clouds and heat can escape from the depths without much absorption. The spots look like bright spots in the infrared images obtained at the wavelength of about 5 μm. [40] They are preferentially located in the belts, although there is a train of prominent hot spots at the northern edge of the Equatorial Zone. The Galileo Probe descended into one of those equatorial spots. Each equatorial spot is associated with a bright cloudy plume located to the west of it and reaching up to 10,000 km in size. [6] Hot spots generally have round shapes, although they do not resemble vortexes. [40]

The origin of hot spots is not clear. They can be either downdrafts, where the descending air is adiabatically heated and dried or, alternatively, they can be a manifestation of planetary scale waves. The latter hypotheses explains the periodical pattern of the equatorial spots. [6] [40]

Early modern astronomers, using small telescopes, recorded the changing appearance of Jupiter's atmosphere. [25] Their descriptive terms—belts and zones, brown spots and red spots, plumes, barges, festoons, and streamers—are still used. [119] Other terms such as vorticity, vertical motion, cloud heights have entered in use later, in the 20th century. [25]

The first observations of the Jovian atmosphere at higher resolution than possible with Earth-based telescopes were taken by the Pioneer 10 and 11 spacecraft. The first truly detailed images of Jupiter's atmosphere were provided by the Voyagers. [25] The two spacecraft were able to image details at a resolution as low as 5 km in size in various spectra, and also able to create "approach movies" of the atmosphere in motion. [25] The Galileo Probe, which suffered an antenna problem, saw less of Jupiter's atmosphere but at a better average resolution and a wider spectral bandwidth. [25]

Today, astronomers have access to a continuous record of Jupiter's atmospheric activity thanks to telescopes such as Hubble Space Telescope. These show that the atmosphere is occasionally wracked by massive disturbances, but that, overall, it is remarkably stable. [25] The vertical motion of Jupiter's atmosphere was largely determined by the identification of trace gases by ground-based telescopes. [25] Spectroscopic studies after the collision of Comet Shoemaker–Levy 9 gave a glimpse of the Jupiter's composition beneath the cloud tops. The presence of diatomic sulfur (S2) and carbon disulfide (CS2) was recorded—the first detection of either in Jupiter, and only the second detection of S2 in any astronomical object— together with other molecules such as ammonia (NH3) and hydrogen sulfide (H2S), while oxygen-bearing molecules such as sulfur dioxide were not detected, to the surprise of astronomers. [120]

The Galileo atmospheric probe, as it plunged into Jupiter, measured the wind, temperature, composition, clouds, and radiation levels down to 22 bar. However, below 1 bar elsewhere on Jupiter there is uncertainty in the quantities. [25]

Great Red Spot studies Edit

The first sighting of the GRS is often credited to Robert Hooke, who described a spot on the planet in May 1664 however, it is likely that Hooke's spot was in the wrong belt altogether (the North Equatorial Belt, versus the current location in the South Equatorial Belt). Much more convincing is Giovanni Cassini's description of a "permanent spot" in the following year. [121] With fluctuations in visibility, Cassini's spot was observed from 1665 to 1713. [122]

A minor mystery concerns a Jovian spot depicted around 1700 on a canvas by Donato Creti, which is exhibited in the Vatican. [123] [124] It is a part of a series of panels in which different (magnified) heavenly bodies serve as backdrops for various Italian scenes, the creation of all of them overseen by the astronomer Eustachio Manfredi for accuracy. Creti's painting is the first known to depict the GRS as red. No Jovian feature was officially described as red before the late 19th century. [124]

The present GRS was first seen only after 1830 and well-studied only after a prominent apparition in 1879. A 118-year gap separates the observations made after 1830 from its 17th-century discovery whether the original spot dissipated and re-formed, whether it faded, or even if the observational record was simply poor are unknown. [93] The older spots had a short observational history and slower motion than that of the modern spot, which make their identity unlikely. [123]

On February 25, 1979, when the Voyager 1 spacecraft was 9.2 million kilometers from Jupiter it transmitted the first detailed image of the Great Red Spot back to Earth. Cloud details as small as 160 km across were visible. The colorful, wavy cloud pattern seen to the west (left) of the GRS is the spot's wake region, where extraordinarily complex and variable cloud motions are observed. [125]

White ovals Edit

The white ovals that were to become Oval BA formed in 1939. They covered almost 90 degrees of longitude shortly after their formation, but contracted rapidly during their first decade their length stabilized at 10 degrees or less after 1965. [126] Although they originated as segments of the STZ, they evolved to become completely embedded in the South Temperate Belt, suggesting that they moved north, "digging" a niche into the STB. [127] Indeed, much like the GRS, their circulations were confined by two opposing jet streams on their northern and southern boundaries, with an eastward jet to their north and a retrograde westward one to the south. [126]

The longitudinal movement of the ovals seemed to be influenced by two factors: Jupiter's position in its orbit (they became faster at aphelion), and their proximity to the GRS (they accelerated when within 50 degrees of the Spot). [128] The overall trend of the white oval drift rate was deceleration, with a decrease by half between 1940 and 1990. [129]

During the Voyager fly-bys, the ovals extended roughly 9000 km from east to west, 5000 km from north to south, and rotated every five days (compared to six for the GRS at the time). [130]


3 Drift Rate and Formation

Between 5 and 6 November, NDS-2018 moved about 47° in 19.07 hr, or 2.46°/hr (270 m/s). This drift rate extrapolates to a location of 308°W on 10 September, while the dark feature is observed at 339°W on that date. The longitude discrepancy could be the result of an error as small as 0.8% in the drift rate measured from the 5 and 6 November data or a small change in drift rate over the

56-day interval between the observations, which is common among giant vortices (Smith et al., 1989 Wong et al., 2018 ). It is difficult to estimate the feature's location under a constant drift rate assumption in prior years, because very small errors in the drift rate can substantially change the extrapolated longitude of the feature over long time periods.

In each year of OPAL data, bright cloud features are seen in the active region at 10–35°N. Ground-based near-infrared observations in the 2017 time period also showed the presence of cloud activity spanning the 25–50°N region (Molter et al., 2019 ). We mark bright features as white arrows in Figure 1 and list the feature longitudes in Table 1. If we assume that these bright clouds mark the same feature from year to year, then we calculate drift rates very close to the 2.46°/hr drift rate measured for the dark spot itself in November 2018. Note that the zonal wind speed at 23°N is 311 m/s, or 2.81°/hr westward (Sromovsky et al., 1993 ), so the dark spot (and potentially the bright cloud features in 2015–2017) is drifting eastward with respect to the winds. In comparison, the Voyager 2 Great Dark Spot was located at 20°S, drifted at 2.73°/hr (Hammel et al., 1995 Smith et al., 1989 ).

Date UTC W. Longitude (deg) Drift rate (deg/hr)a a Drift rate assumes that the listed feature is the same feature as in 2018-11-05 observations
2015-09-18 17.805 11 2.45
2016-10-04 0.558 87 2.46
2017-10-07 7.278 253 2.45
2018-09-10 2.160 339 2.44
2018-11-05 13.548 48
2018-11-06 8.622 95 2.46
  • a Drift rate assumes that the listed feature is the same feature as in 2018-11-05 observations

We hypothesize that the 2016–2017 maps show cloud activity associated with the formation of NDS-2018 before the dark spot itself was visible. Although data sampled at an annual cadence are not sufficient to test this hypothesis, it is still clear that over these years, discrete regions of cloud activity were present on Neptune at the same latitude as NDS-2018, while all other longitudes within this band of activity lacked bright cloud features. The OPAL observations are able to reveal for the first time that enhanced cloud activity presaged the appearance of a dark spot by about 2 years. The SDS-2015 dark vortex may have shared a similar formation process, although it is likely that the onset of the OPAL program's Neptune observations in 2015 was too late to constrain the timing of its origin to within 1 year. The maximum contrast of SDS-2015 was about 6.7% in the F467M filter, and contrast decreased by about 1.7% per year over the 2015–2017 time period (Wong et al., 2018 ). If the 10% contrast of NDS-2018 is representative of the contrast of a freshly formed dark spot, then SDS-2015 could have been about 2 years old when first discovered by OPAL.

SDS-2015 was discovered at 46°S in 2015, drifting to 49°S in 2017, with companion clouds offset to the north by 1–4° (Wong et al., 2018 ). Prior to its discovery, ground-based observations showed bright cloud features in 2014–2015 at latitudes of 35–45°S, while features in 2013 were spread over a wider range of 35–52°S (Hueso et al., 2017 ). Qualitatively, the observations suggest a similar formation process for NDS-2018 and SDS-2015. All previously observed dark spots were seen fully formed, with no record of their formation. SDS-2015 was observed through its demise, however, showing a slow poleward drift and diminishing size over several years (Figure 1 Wong et al., 2018 ).


Spot the Great Cluster in Hercules

Early summer gives us the chance to observe the Milky Way's globular clusters: vast spherical groupings of stars which orbit the center of our galaxy like moths around a flame.

Globular clusters are distinguished from galactic clusters because of their age (very old), size (often a hundred thousand stars or more) and location (above and below the main plane of the Milky Way). They are interesting targets for any sort of optical aid, binoculars or telescopes.

In binoculars, most globular clusters do not resolve into their component stars, but appear as an ill-defined hazy spot. As more telescopic power is concentrated on them, globular clusters gradually resolve into stars. In small telescopes the outer reaches of the cluster start to reveal stars in larger telescopes more and more stars are revealed. In a really large Dobsonian telescope, the true nature of globular clusters is resolved: countless tiny stars all the way from the stragglers at the outside edges to the concentrated brilliance at the cluster's core.

While galaxies often disappoint beginners because of their lack of detail in a telescope, a globular cluster seen in an amateur telescope of moderate aperture (8 to 12 inches) is actually more beautiful visually than in any photograph, because the human eye can encompass the whole range of stellar densities.

Where to look

The largest and richest globular cluster in the Northern Hemisphere is perfectly placed for observation on these warm evenings of early summer: directly overhead. Go out to a dark location around 11 p.m. this week and lie down on your back (a blanket or lawn chair will be more comfortable).

If your feet are pointing south, you should see pretty much what's in this chart. The three bright stars (Vega, Deneb, and Altair) of the summer triangle will be to your left, and Arcturus will be to your right. Right in between are four stars of medium brightness which form a keystone shape: these are the body of Hercules.

With binoculars take a look just below the star in the upper right of the keystone, a third of the way to the star at the lower right of the keystone. You should see a faint fuzzy spot: this is the Great Cluster in Hercules.

What you can see

Once you've located the Great Cluster, wait an hour until it moves away from the zenith. Now you should be able to point your telescope at it (hard to do when it's directly overhead.) If your telescope is 4 inches (100 mm) aperture or smaller you will see a glowing patch of light. If your telescope is larger, you will begin to resolve the cluster into stars. In a telescope of 8 inches (200 mm) or larger it is an object of great beauty, like a gigantic swarm of fireflies.

If you're at a really dark site and can see the Milky Way &ndash many urban and suburban residents have never seen this milky swath of light that is quite noticeable under dark, rural skies &ndash notice how far the Hercules Cluster is from the main band of the Milky Way. This main band represents the center of the galaxy and the primary spiral arms, which combined hold the vast majority of our galaxy's stars.

Although globular clusters are part of the Milky Way, they orbit independently around the core of the Milky Way, but not in the plane where the majority of the galaxy's stars lie. There are more than a hundred globular clusters associated with the Milky Way, but they all lie well above or below the plane of the galaxy itself.

The Hercules Cluster was the 13th object catalogued by Charles Messier in his catalog of objects which he thought could be mistaken for comets. Therefore it is often called Messier 13 or M13 for short.


Cancer’s famous Beehive star cluster.

Cancer makes up for its lackluster stars by having within its boundaries one of the sky’s brightest star clusters, the Beehive cluster, also known as M44. Another name for the Beehive is Praesepe (Latin for “manger“).

In a dark sky, the Beehive looks like a tiny faint cloud to the unaided eye. As seen through ordinary binoculars, this nebulous patch of haze instantly turns into a sparkling city of stars. It is an open cluster, one of the nearest to our solar system. The Beehive is thought to contain a larger star population than most other nearby clusters.

The Beehive’s stars appear to be similar in age and proper motion to stars of the V-shaped Hyades open star cluster. It’s possible the two clusters were born from two parts of a single vast cloud of gas and dust in space.

The sun shines directly overhead at noon, as seen from those located along the Tropic of Cancer, at the Northern Hemisphere’s summer solstice. Image via solsticebahamas.com.

Significance of constellation Cancer. Cancer’s stature as a constellation of the zodiac has remained steadfast over the millennia. Over two thousand years ago, the sun shone in front of the constellation Cancer during the Northern Hemisphere’s summer solstice. That’s not the case today, however. Today, the sun resides in front of the constellation Taurus when the summer solstice sun reaches its northernmost point for the year on or near June 21.

Nonetheless, Cancer still seems to symbolize the height and glory of the summer sun. To this day, we say the sun shines over the Tropic of Cancer – not the “tropic of Taurus” – on the June solstice. That’s in spite of the fact that the sun in our time passes in front of the constellation Cancer from about July 21 until August 10.

Nowadays, the sun doesn’t enter the constellation Cancer until about a month after the Northern Hemisphere’s summer solstice.

Hercules attacked by Karkinos (bottom) and the Lernaean Hydra, under the aid of Athena. White-ground ancient Greek Attic lekythos, ca. 500-475 B.C. Louvre Museum, Paris.


Image: Jupiter's great red spot viewed by Voyager I

Credit: NASA's Goddard Space Flight Center

At about 89,000 miles in diameter, Jupiter could swallow 1,000 Earths. It is the largest planet in the solar system and perhaps the most majestic. Vibrant bands of clouds carried by winds that can exceed 400 mph continuously circle the planet's atmosphere.

Such winds sustain spinning anticyclones like the Great Red Spot—a raging storm three and a half times the size of Earth located in Jupiter's southern hemisphere. In January and February 1979, NASA's Voyager 1 spacecraft zoomed toward Jupiter, capturing hundreds of images during its approach, including this close-up of swirling clouds around Jupiter's Great Red Spot.

This image was assembled from three black and white negatives. The observations revealed many unique features of the planet that are still being explored to this day.


‘Triple Vision’ Image Of Jupiter Shows What’s Beneath Its Clouds

The largest planet in our Solar System, Jupiter, is our own ‘failed star.’

Although it gravitationally undergoes self-compression, it’s too light to initiate nuclear fusion.

Jupiter’s enormous core temperatures — 24,000 °C (43,000 °F) — contrast with its icy cloud-tops: -145 °C (-234 °F).

The familiar bands, spots, and turbulence are superficial, optical features.

However, other wavelengths can reveal processes beneath Jupiter’s clouds.

Infrared light showcases the thickness of the clouds, planet-wide.

The strongest infrared signals indicate the thinnest clouds, allowing warmer, deeper Jovian regions to shine.

Meanwhile, ultraviolet light gets absorbed by chromophore particles, absent in white spots but present in red ones.

Dark infrared regions, including the Great Red Spot (and “Red Spot Jr.”), possess thick clouds.

However, tiny infrared “dots” indicate downdrafts, creating convection and enabling Jovian lightning storms.

Visible cloud breaks in Jupiter’s bands appear hot, allowing infrared emission through.

The atmosphere is thinnest just above the equator, excepting a snake-like streak of thick, opaque clouds.

Three interactive visualizers allow interactive multiwavelength comparisons between features.

Combined with NASA’s Juno mission, scientists hope to explain Jupiter’s evolving Great Red Spot.

Mostly Mute Monday tells an astronomical story in images, visuals, and no more than 200 words. Talk less smile more.