Astronomy

Why is there no hurricane on the Sun?

Why is there no hurricane on the Sun?


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I was reading about gigantic storms on giant gas planets, the great red spot on Jupiter and hexagon on Saturn to name a few, how about our Sun which is consist of plasma(hot gas which have some of their electrons stripped) why don't we see any big hurricane?


We see sunspots, which are giant, planet-sized storms on the surface of the Sun. There are however many differences between sunspots, the Great Red Spot on Jupiter, and tropical cyclones (e.g., hurricanes) on the Earth. Tropical cyclones are low pressure systems fueled by evaporation of warm ocean water and sustained by the Earth's somewhat rapid rotation rate. The Great Red Spot is a high pressure system that is sustained by Jupiter's quite rapid rotation rate. Sunspots are low temperature systems fueled by the Sun's magnetic field and carried along by the Sun's rather low rotation rate.


In addition to the answer above, spiraling storms like hurricanes or the great red spot, are quite orderly and require the right conditions and energy transfer. The great red spot keeps relatively consistent latitude and it's been there for centuries, so it's obviously stable and ordered, though it may be shrinking. The cause of the great red spot isn't known, but efficient heat transfer of Jupiter's vast internal heat, and the principal of hot internal gas rising and cool surface gas falling and Jupiter's very strong Coriolis effect likely helped create and maintain it.

For hurricanes on Earth, a few specific things to happen. There needs to be an energy source to sustain them, which is why they only form over warm oceans, mostly during the summer and fall seasons when oceans are warmest. The rapid evaporation of warm ocean water feeds the hurricane and the condensation of that evaporated water vapor in the upper atmosphere, drives the low pressure system. The spiral is the most efficient form of heat transfer and of light air rising/warm air falling. The high speed surface winds increase the evaporation rate over the ocean, so once the spiral forms and stabilizes, it's self sustaining, until it drifts over colder water or land. Hurricanes are orderly with very efficient heat transfer and ordered layers of rising and falling air.

Over 90% of tropical depressions don't become hurricanes. Generally speaking, a perpendicular direction between the cool air above and the warm air below is required to get the spiraling wind started. That's partly why the IPCC has previously predicted a possible decrease in hurricane formation, because the formative conditions need to be just right and a more turbulent upper atmosphere might decrease hurricane formation even though the warmer oceans works in the opposite direction. All this was footnoted with some uncertainty and predicting changes in wind direction is tricky, so it shouldn't be held against the IPCC. The point is, Hurricanes need the right balance. They don't form easily, though once formed they tend to stabilize and grow, until they drift off the warm ocean water that feeds them.

Air is also quite light, and the heat energy transfer of water's phase change is significant enough to create the 100 plus mph winds in an orderly spiral. On both Jupiter and Earth the right conditions are met for large, high wind speed, spiral storm formation. Like Earth, Jupiter also has clouds and rain, both water and ammonia, which likely assist in it's heat transfer by phase change (though I'm nowhere near smart enough to say how much that contributes regarding Jupiter's red spot, on Earth the phase change of water is essential for hurricane formation. Without abundant warm surface water - no hurricane.

The sun, by comparison, is all plasma. There's no phase change that efficiently increases the transition of heat and energy, though there are probably variations in ionization, but I'll get to that later. The Sun's surface is also quite chaotic and it has magnetic storms, making the neat birth of a spiral storm by perpendicular wind gusts one above the other, less likely.

Magnetic storms are twisted and I don't want to say that nothing spirals or twists on the surface of the sun, because that's not true. But the magnetic storms on the surface of the sun aren't like the neat and tidy cone shaped spirals of hurricanes. They reach well above the sun's atmosphere, not in the atmosphere, and the shape is different.

Finally, the material that makes up the Sun's transition region or "atmosphere" isn't good for hurricane formation. To quote from Wikipedia:

Below, most of the helium is not fully ionized, so that it radiates energy very effectively; above, it becomes fully ionized. This has a profound effect on the equilibrium temperature (see below).

Below, the material is opaque to the particular colors associated with spectral lines, so that most spectral lines formed below the transition region are absorption lines in infrared, visible light, and near ultraviolet, while most lines formed at or above the transition region are emission lines in the far ultraviolet (FUV) and X-rays. This makes radiative transfer of energy within the transition region very complicated.

Below, gas pressure and fluid dynamics usually dominate the motion and shape of structures; above, magnetic forces dominate the motion and shape of structures, giving rise to different simplifications of magnetohydrodynamics.

The transition region itself is not well studied in part because of the computational cost,…

Hurricanes could theoretically form as a result of fluid dynamics, but the rapid rate that partially ionized helium radiates heat makes the formation of large circulating structures, which are basically engines of convection, impractical and unnecessary. There's no need for efficient convection when the energy transfer is very efficient by radiation.

The Sun's atmosphere isn't like the atmosphere of the Earth and in the upper layers of Jupiter where the atmosphere is fairly effective and holding onto it's heat (We wouldn't have warm and cold fronts if it wasn't). Those regions of warm and cold air that mostly maintain their temperature drive the convective process. You need jets of warm and cold air to flow past each other in a hurricane. The Sun's efficient radiation of partially ionized helium works against that principal.

There's also a relatively low Coriolis effect on the surface of the sun, which assists with the formation of hurricanes.

In short, the conditions are not at all right. The Sun's turbulence, it's relatively low rotation rate, no phase-change to feed the system and it's partially ionized helium in it's lower "atmosphere", all work against the formation of spiraling, cone shaped, high speed wind systems.

On Brown dwarfs with much cooler surface temperatures, hurricanes might be entirely possible. The math behind atmospheric convection mechanisms is complicated, so this is more of a general explanation but the Sun isn't a good candidate for hurricanes on many levels.


Astronomy Calendar of Celestial Events for Calendar Year 2021

This astronomy calendar of celestial events contains dates for notable celestial events including moon phases, meteor showers, eclipses, oppositions, conjunctions, and other interesting events. Most of the astronomical events on this calendar can be seen with unaided eye, although some may require a good pair of binoculars for best viewing. Many of the events and dates that appear here were obtained from the U.S. Naval Observatory, The Old Farmer's Almanac., and the American Meteor Society. Events on the calendar are organized by date and each is identified with an astronomy icon as outlined below. Please note that all dates and times are given in Coordinated Universal Time (UTC) must be converted to your local date and time. You can use the UTC clock widget below to figure out how many hours to add or subtract for your local time.

January 2, 3 - Quadrantids Meteor Shower. The Quadrantids is an above average shower, with up to 40 meteors per hour at its peak. It is thought to be produced by dust grains left behind by an extinct comet known as 2003 EH1, which was discovered in 2003. The shower runs annually from January 1-5. It peaks this year on the night of the 2nd and morning of the 3rd. The waning gibbous moon will block out most of the faintest meteors this year. But if you are patient, you should still be able to catch a few good ones. Best viewing will be from a dark location after midnight. Meteors will radiate from the constellation Bootes, but can appear anywhere in the sky.

January 13 - New Moon. The Moon will located on the same side of the Earth as the Sun and will not be visible in the night sky. This phase occurs at 05:02 UTC. This is the best time of the month to observe faint objects such as galaxies and star clusters because there is no moonlight to interfere.

January 24 - Mercury at Greatest Eastern Elongation. The planet Mercury reaches greatest eastern elongation of 18.6 degrees from the Sun. This is the best time to view Mercury since it will be at its highest point above the horizon in the evening sky. Look for the planet low in the western sky just after sunset.

January 28 - Full Moon. The Moon will be located on the opposite side of the Earth as the Sun and its face will be will be fully illuminated. This phase occurs at 19:18 UTC. This full moon was known by early Native American tribes as the Wolf Moon because this was the time of year when hungry wolf packs howled outside their camps. This moon has also been know as the Old Moon and the Moon After Yule.

February 11 - New Moon. The Moon will located on the same side of the Earth as the Sun and will not be visible in the night sky. This phase occurs at 19:08 UTC. This is the best time of the month to observe faint objects such as galaxies and star clusters because there is no moonlight to interfere.

February 27 - Full Moon. The Moon will be located on the opposite side of the Earth as the Sun and its face will be will be fully illuminated. This phase occurs at 08:19 UTC. This full moon was known by early Native American tribes as the Snow Moon because the heaviest snows usually fell during this time of the year. Since hunting is difficult, this moon has also been known by some tribes as the Hunger Moon, since the harsh weather made hunting difficult.

March 6 - Mercury at Greatest Western Elongation. The planet Mercury reaches greatest western elongation of 27.3 degrees from the Sun. This is the best time to view Mercury since it will be at its highest point above the horizon in the morning sky. Look for the planet low in the eastern sky just before sunrise.

March 13 - New Moon. The Moon will located on the same side of the Earth as the Sun and will not be visible in the night sky. This phase occurs at 10:23 UTC. This is the best time of the month to observe faint objects such as galaxies and star clusters because there is no moonlight to interfere.

March 20 - March Equinox. The March equinox occurs at 09:27 UTC. The Sun will shine directly on the equator and there will be nearly equal amounts of day and night throughout the world. This is also the first day of spring (vernal equinox) in the Northern Hemisphere and the first day of fall (autumnal equinox) in the Southern Hemisphere.

March 28 - Full Moon. The Moon will be located on the opposite side of the Earth as the Sun and its face will be will be fully illuminated. This phase occurs at 18:49 UTC. This full moon was known by early Native American tribes as the Worm Moon because this was the time of year when the ground would begin to soften and the earthworms would reappear. This moon has also been known as the Crow Moon, the Crust Moon, the Sap Moon, and the Lenten Moon.

April 12 - New Moon. The Moon will located on the same side of the Earth as the Sun and will not be visible in the night sky. This phase occurs at 02:32 UTC. This is the best time of the month to observe faint objects such as galaxies and star clusters because there is no moonlight to interfere.

April 22, 23 - Lyrids Meteor Shower. The Lyrids is an average shower, usually producing about 20 meteors per hour at its peak. It is produced by dust particles left behind by comet C/1861 G1 Thatcher, which was discovered in 1861. The shower runs annually from April 16-25. It peaks this year on the night of the night of the 22nd and morning of the 23rd. These meteors can sometimes produce bright dust trails that last for several seconds. The nearly full moon will be a problem this year. Its glare will block out all but the brightest meteors. But if you are patient you may still be able to catch a few good ones. Best viewing will be from a dark location after midnight. Meteors will radiate from the constellation Lyra, but can appear anywhere in the sky.

April 27 - Full Moon, Supermoon. The Moon will be located on the opposite side of the Earth as the Sun and its face will be will be fully illuminated. This phase occurs at 03:33 UTC. This full moon was known by early Native American tribes as the Pink Moon because it marked the appearance of the moss pink, or wild ground phlox, which is one of the first spring flowers. This moon has also been known as the Sprouting Grass Moon, the Growing Moon, and the Egg Moon. Many coastal tribes called it the Fish Moon because this was the time that the shad swam upstream to spawn. This is also the first of three supermoons for 2021. The Moon will be near its closest approach to the Earth and may look slightly larger and brighter than usual.

May 6, 7 - Eta Aquarids Meteor Shower. The Eta Aquarids is an above average shower, capable of producing up to 60 meteors per hour at its peak. Most of the activity is seen in the Southern Hemisphere. In the Northern Hemisphere, the rate can reach about 30 meteors per hour. It is produced by dust particles left behind by comet Halley, which has been observed since ancient times. The shower runs annually from April 19 to May 28. It peaks this year on the night of May 6 and the morning of the May 7. The second quarter moon will block out some of the faintest meteors this year. But if you are patient, you should still should be able to catch quite a few good ones. Best viewing will be from a dark location after midnight. Meteors will radiate from the constellation Aquarius, but can appear anywhere in the sky.

May 11 - New Moon. The Moon will located on the same side of the Earth as the Sun and will not be visible in the night sky. This phase occurs at 19:01 UTC. This is the best time of the month to observe faint objects such as galaxies and star clusters because there is no moonlight to interfere.

May 17 - Mercury at Greatest Eastern Elongation. The planet Mercury reaches greatest eastern elongation of 22 degrees from the Sun. This is the best time to view Mercury since it will be at its highest point above the horizon in the evening sky. Look for the planet low in the western sky just after sunset.

May 26 - Full Moon, Supermoon. The Moon will be located on the opposite side of the Earth as the Sun and its face will be will be fully illuminated. This phase occurs at 11:14 UTC. This full moon was known by early Native American tribes as the Flower Moon because this was the time of year when spring flowers appeared in abundance. This moon has also been known as the Corn Planting Moon and the Milk Moon. This is also the second of three supermoons for 2021. The Moon will be near its closest approach to the Earth and may look slightly larger and brighter than usual.

May 26 - Total Lunar Eclipse. A total lunar eclipse occurs when the Moon passes completely through the Earth's dark shadow, or umbra. During this type of eclipse, the Moon will gradually get darker and then take on a rusty or blood red color. The eclipse will be visible throughout the Pacific Ocean and parts of eastern Asia, Japan, Australia, and western North America. (NASA Map and Eclipse Information)

June 10 - New Moon. The Moon will located on the same side of the Earth as the Sun and will not be visible in the night sky. This phase occurs at 10:54 UTC. This is the best time of the month to observe faint objects such as galaxies and star clusters because there is no moonlight to interfere.

June 10 - Annular Solar Eclipse. An annular solar eclipse occurs when the Moon is too far away from the Earth to completely cover the Sun. This results in a ring of light around the darkened Moon. The Sun's corona is not visible during an annular eclipse. The path of this eclipse will be confined to extreme eastern Russia, the Arctic Ocean, western Greenland, and Canada. A partial eclipse will be visible in the northeastern United States, Europe, and most of Russia. (NASA Map and Eclipse Information) (NASA Interactive Google Map)

June 21 - June Solstice. The June solstice occurs at 03:21 UTC. The North Pole of the earth will be tilted toward the Sun, which will have reached its northernmost position in the sky and will be directly over the Tropic of Cancer at 23.44 degrees north latitude. This is the first day of summer (summer solstice) in the Northern Hemisphere and the first day of winter (winter solstice) in the Southern Hemisphere.

June 24 - Full Moon, Supermoon. The Moon will be located on the opposite side of the Earth as the Sun and its face will be will be fully illuminated. This phase occurs at 18:40 UTC. This full moon was known by early Native American tribes as the Strawberry Moon because it signaled the time of year to gather ripening fruit. It also coincides with the peak of the strawberry harvesting season. This moon has also been known as the Rose Moon and the Honey Moon. This is also the last of three supermoons for 2021. The Moon will be near its closest approach to the Earth and may look slightly larger and brighter than usual.

July 4 - Mercury at Greatest Western Elongation. The planet Mercury reaches greatest western elongation of 21.6 degrees from the Sun. This is the best time to view Mercury since it will be at its highest point above the horizon in the morning sky. Look for the planet low in the eastern sky just before sunrise.

July 10 - New Moon. The Moon will located on the same side of the Earth as the Sun and will not be visible in the night sky. This phase occurs at 01:17 UTC. This is the best time of the month to observe faint objects such as galaxies and star clusters because there is no moonlight to interfere.

July 24 - Full Moon. The Moon will be located on the opposite side of the Earth as the Sun and its face will be will be fully illuminated. This phase occurs at 02:37 UTC. This full moon was known by early Native American tribes as the Buck Moon because the male buck deer would begin to grow their new antlers at this time of year. This moon has also been known as the Thunder Moon and the Hay Moon.

July 28, 29 - Delta Aquarids Meteor Shower. The Delta Aquarids is an average shower that can produce up to 20 meteors per hour at its peak. It is produced by debris left behind by comets Marsden and Kracht. The shower runs annually from July 12 to August 23. It peaks this year on the night of July 28 and morning of July 29. The nearly full moon will be a problem this year. It's glare will block block most of the faintest meteors. But if you are patient, you should still be able to catch a few good ones. Best viewing will be from a dark location after midnight. Meteors will radiate from the constellation Aquarius, but can appear anywhere in the sky.

August 2 - Saturn at Opposition. The ringed planet will be at its closest approach to Earth and its face will be fully illuminated by the Sun. It will be brighter than any other time of the year and will be visible all night long. This is the best time to view and photograph Saturn and its moons. A medium-sized or larger telescope will allow you to see Saturn's rings and a few of its brightest moons.

August 8 - New Moon. The Moon will located on the same side of the Earth as the Sun and will not be visible in the night sky. This phase occurs at 13:51 UTC. This is the best time of the month to observe faint objects such as galaxies and star clusters because there is no moonlight to interfere.

August 12, 13 - Perseids Meteor Shower. The Perseids is one of the best meteor showers to observe, producing up to 60 meteors per hour at its peak. It is produced by comet Swift-Tuttle, which was discovered in 1862. The Perseids are famous for producing a large number of bright meteors. The shower runs annually from July 17 to August 24. It peaks this year on the night of August 12 and the morning of August 13. The waxing crescent moon will set early in the evening, leaving dark skies for what should be an excellent show. Best viewing will be from a dark location after midnight. Meteors will radiate from the constellation Perseus, but can appear anywhere in the sky.

August 19 - Jupiter at Opposition. The giant planet will be at its closest approach to Earth and its face will be fully illuminated by the Sun. It will be brighter than any other time of the year and will be visible all night long. This is the best time to view and photograph Jupiter and its moons. A medium-sized telescope should be able to show you some of the details in Jupiter's cloud bands. A good pair of binoculars should allow you to see Jupiter's four largest moons, appearing as bright dots on either side of the planet.

August 22 - Full Moon, Blue Moon. The Moon will be located on the opposite side of the Earth as the Sun and its face will be will be fully illuminated. This phase occurs at 12:02 UTC. This full moon was known by early Native American tribes as the Sturgeon Moon because the large sturgeon fish of the Great Lakes and other major lakes were more easily caught at this time of year. This moon has also been known as the Green Corn Moon and the Grain Moon. Since this is the third of four full moons in this season, it is known as a blue moon. This rare calendar event only happens once every few years, giving rise to the term, “once in a blue moon.” There are normally only three full moons in each season of the year. But since full moons occur every 29.53 days, occasionally a season will contain 4 full moons. The extra full moon of the season is known as a blue moon. Blue moons occur on average once every 2.7 years.

September 7 - New Moon. The Moon will located on the same side of the Earth as the Sun and will not be visible in the night sky. This phase occurs at 00:52 UTC. This is the best time of the month to observe faint objects such as galaxies and star clusters because there is no moonlight to interfere.

September 14 - Neptune at Opposition. The blue giant planet will be at its closest approach to Earth and its face will be fully illuminated by the Sun. It will be brighter than any other time of the year and will be visible all night long. This is the best time to view and photograph Neptune. Due to its extreme distance from Earth, it will only appear as a tiny blue dot in all but the most powerful telescopes.

September 14 - Mercury at Greatest Eastern Elongation. The planet Mercury reaches greatest eastern elongation of 26.8 degrees from the Sun. This is the best time to view Mercury since it will be at its highest point above the horizon in the evening sky. Look for the planet low in the western sky just after sunset.

September 20 - Full Moon. The Moon will be located on the opposite side of the Earth as the Sun and its face will be will be fully illuminated. This phase occurs at 23:54 UTC. This full moon was known by early Native American tribes as the Corn Moon because the corn is harvested around this time of year. This moon is also known as the Harvest Moon. The Harvest Moon is the full moon that occurs closest to the September equinox each year.

September 22 - September Equinox. The September equinox occurs at 19:11 UTC. The Sun will shine directly on the equator and there will be nearly equal amounts of day and night throughout the world. This is also the first day of fall (autumnal equinox) in the Northern Hemisphere and the first day of spring (vernal equinox) in the Southern Hemisphere.

October 6 - New Moon. The Moon will located on the same side of the Earth as the Sun and will not be visible in the night sky. This phase occurs at 11:05 UTC. This is the best time of the month to observe faint objects such as galaxies and star clusters because there is no moonlight to interfere.

October 7 - Draconids Meteor Shower. The Draconids is a minor meteor shower producing only about 10 meteors per hour. It is produced by dust grains left behind by comet 21P Giacobini-Zinner, which was first discovered in 1900. The Draconids is an unusual shower in that the best viewing is in the early evening instead of early morning like most other showers. The shower runs annually from October 6-10 and peaks this year on the the night of the 7th. This year, the nearly new moon will leave dark skies for what should be an excellent show. Best viewing will be in the early evening from a dark location far away from city lights. Meteors will radiate from the constellation Draco, but can appear anywhere in the sky.

October 20 - Full Moon. The Moon will be located on the opposite side of the Earth as the Sun and its face will be will be fully illuminated. This phase occurs at 14:57 UTC. This full moon was known by early Native American tribes as the Hunters Moon because at this time of year the leaves are falling and the game is fat and ready to hunt. This moon has also been known as the Travel Moon and the Blood Moon.

October 21, 22 - Orionids Meteor Shower. The Orionids is an average shower producing up to 20 meteors per hour at its peak. It is produced by dust grains left behind by comet Halley, which has been known and observed since ancient times. The shower runs annually from October 2 to November 7. It peaks this year on the night of October 21 and the morning of October 22. The full moon will be a problem this year for the Orionids. Its glare will block out all but the brightest meteors. But if you are patient, you should still be able to catch a few good ones. Best viewing will be from a dark location after midnight. Meteors will radiate from the constellation Orion, but can appear anywhere in the sky.

October 25 - Mercury at Greatest Western Elongation. The planet Mercury reaches greatest western elongation of 18.4 degrees from the Sun. This is the best time to view Mercury since it will be at its highest point above the horizon in the morning sky. Look for the planet low in the eastern sky just before sunrise.

October 29 - Venus at Greatest Eastern Elongation. The planet Venus reaches greatest eastern elongation of 47 degrees from the Sun. This is the best time to view Venus since it will be at its highest point above the horizon in the evening sky. Look for the bright planet in the western sky after sunset.

November 4 - New Moon. The Moon will located on the same side of the Earth as the Sun and will not be visible in the night sky. This phase occurs at 21:15 UTC. This is the best time of the month to observe faint objects such as galaxies and star clusters because there is no moonlight to interfere.

November 4, 5 - Taurids Meteor Shower. The Taurids is a long-running minor meteor shower producing only about 5-10 meteors per hour. It is unusual in that it consists of two separate streams. The first is produced by dust grains left behind by Asteroid 2004 TG10. The second stream is produced by debris left behind by Comet 2P Encke. The shower runs annually from September 7 to December 10. It peaks this year on the the night of November 4. The new moon will leave dark skies this year for what should be an excellent show. Best viewing will be just after midnight from a dark location far away from city lights. Meteors will radiate from the constellation Taurus, but can appear anywhere in the sky.

November 5 - Uranus at Opposition. The blue-green planet will be at its closest approach to Earth and its face will be fully illuminated by the Sun. It will be brighter than any other time of the year and will be visible all night long. This is the best time to view Uranus. Due to its distance, it will only appear as a tiny blue-green dot in all but the most powerful telescopes.

November 17, 18 - Leonids Meteor Shower. The Leonids is an average shower, producing up to 15 meteors per hour at its peak. This shower is unique in that it has a cyclonic peak about every 33 years where hundreds of meteors per hour can be seen. That last of these occurred in 2001. The Leonids is produced by dust grains left behind by comet Tempel-Tuttle, which was discovered in 1865. The shower runs annually from November 6-30. It peaks this year on the night of the 17th and morning of the 18th. Unfortunately the nearly full moon will dominate the sky this year, blocking all but the brightest meteors. But if you are patient, you should still be able to catch a few good ones. Best viewing will be from a dark location after midnight. Meteors will radiate from the constellation Leo, but can appear anywhere in the sky.

November 19 - Full Moon. The Moon will be located on the opposite side of the Earth as the Sun and its face will be will be fully illuminated. This phase occurs at 08:59 UTC. This full moon was known by early Native American tribes as the Beaver Moon because this was the time of year to set the beaver traps before the swamps and rivers froze. It has also been known as the Frosty Moon and the Dark Moon.

November 19 - Partial Lunar Eclipse. A partial lunar eclipse occurs when the Moon passes through the Earth's partial shadow, or penumbra, and only a portion of it passes through the darkest shadow, or umbra. During this type of eclipse a part of the Moon will darken as it moves through the Earth's shadow. The eclipse will be visible throughout most of eastern Russia, Japan, the Pacific Ocean, North America, Mexico, Central America, and parts of western South America. (NASA Map and Eclipse Information)

December 4 - New Moon. The Moon will located on the same side of the Earth as the Sun and will not be visible in the night sky. This phase occurs at 07:44 UTC. This is the best time of the month to observe faint objects such as galaxies and star clusters because there is no moonlight to interfere.

December 4 - Total Solar Eclipse. A total solar eclipse occurs when the moon completely blocks the Sun, revealing the Sun's beautiful outer atmosphere known as the corona. The path of totality will for this eclipse will be limited to Antarctica and the southern Atlantic Ocean. A partial eclipse will bee visible throughout much of South Africa. (NASA Map and Eclipse Information) (Interactive NASA Google)

December 13, 14 - Geminids Meteor Shower. The Geminids is the king of the meteor showers. It is considered by many to be the best shower in the heavens, producing up to 120 multicolored meteors per hour at its peak. It is produced by debris left behind by an asteroid known as 3200 Phaethon, which was discovered in 1982. The shower runs annually from December 7-17. It peaks this year on the night of the 13th and morning of the 14th. The waxing gibbous moon will block out most of the fainter meteors this year. But the Geminids are so numerous and bright that this could still be a good show. Best viewing will be from a dark location after midnight. Meteors will radiate from the constellation Gemini, but can appear anywhere in the sky.

December 19 - Full Moon. The Moon will be located on the opposite side of the Earth as the Sun and its face will be will be fully illuminated. This phase occurs at 04:37 UTC. This full moon was known by early Native American tribes as the Cold Moon because this is the time of year when the cold winter air settles in and the nights become long and dark. This moon has also been known as the Long Nights Moon and the Moon Before Yule.

December 21 - December Solstice. The December solstice occurs at 15:50 UTC. The South Pole of the earth will be tilted toward the Sun, which will have reached its southernmost position in the sky and will be directly over the Tropic of Capricorn at 23.44 degrees south latitude. This is the first day of winter (winter solstice) in the Northern Hemisphere and the first day of summer (summer solstice) in the Southern Hemisphere.

December 21, 22 - Ursids Meteor Shower. The Ursids is a minor meteor shower producing about 5-10 meteors per hour. It is produced by dust grains left behind by comet Tuttle, which was first discovered in 1790. The shower runs annually from December 17-25. It peaks this year on the the night of the 21st and morning of the 22nd. The nearly full moon will be a problem this year, blocking all but the brightest meteors. But if you are patient enough, you may still be able to catch a few good ones. Best viewing will be just after midnight from a dark location far away from city lights. Meteors will radiate from the constellation Ursa Minor, but can appear anywhere in the sky.


Why is there no hurricane on the Sun? - Astronomy

I am a 8th grade student and I was wondering why there are active volcanoes on Jupiter's moon Io.

The volcanic activity on Io is mostly caused by the pull of Jupiter on Io. Just like Earth's moon gravitationally attracts the oceans, causing tides, Jupiter pulls on Io. Because the pull of gravity is dependent upon the distance between masses, Jupiter pulls more on the side of Io that is closer to it than on the farther side, stretching Io out to a sort of egg-shape. Io's orbit is elliptical, so sometimes it is closer to Jupiter than others. Its elliptical orbit is further perturbed by Europa and Ganymede, two of Jupiter's other large moons. Because of this, Io's surface bulges up and down by as much as 100 meters. These tidal forces provide the energy that fuels Io's volcanos. For more information on Io, check out these webpages:

This page was last updated on July 18, 2015.

About the Author

Cathy Jordan

Cathy got her Bachelors degree from Cornell in May 2003 and her Masters of Education in May 2005. She did research studying the wind patterns on Jupiter while at Cornell. She is now an 8th grade Earth Sciences teacher in Natick, MA.


Why is there no hurricane on the Sun? - Astronomy

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James McCanney's Nonsense

Miscellaneous Wrongnesses From McCanney

Comets emit X-rays, indicating they are not cold.

McCanney claims in that book (on page 1!) that he predicted that comets would give off X-rays, and also that the side of the comet facing the Sun would be the source of these X-rays. This has to do with his claim that comets are plasma balls, electrically coupled with the Sun. Amazingly, years later, it was found that not only do comets give off X-rays, but they comes from the sunward side! Could McCanney have been right?

Nope. Well, his prediction was correct, but for the wrong reason. For a prediction to be counted as a success, it has to be exclusive that is, no other theory could account for it. The problem is, there are plenty of ways a comet could give off X-rays, even though it's cold. For one, comets get smacked by the high-energy particles from the Sun's solar wind. Ice, when hit like that, fluoresces that is, gives off light. At those energies, the light given off is in the form of X-rays. So naturally, the part of the comet facing the Sun is where the X-rays come from.

McCanney is very derisive in his book about this. He says: "Let's get serious. x-rays coming from a docile little snow ball?" But think about it: when you go to the dentist, she isn't heating the X-ray machine to a million degrees to get it to give off X-rays! Those machines work by accelerating electrons to high speeds and slamming them into metals. When the electrons hit the metal, they slow down and emit X-rays in the process. So there are other processes which generate X-rays besides temperature, despite what he is saying there. Ironically, his own process is not thermal either, so why is he so derisive of cold comets giving off X-rays? Oh yeah: it's because he's wrong.

Comet tails cause drag, slowing a comet down and circularizing their orbits.

This is another key part of his theory: since planets orbit the Sun in fairly circular orbits, and comets tend to orbit in extremely elongated ellipses, there must be some method to change a comet orbit into a circle, since he says comets form planets.

To accomplish this he invents a force called "tail drag", and goes through many gyrations to demonstrate it. However, I don't need to go into any details debunking his details, because as I already showed, the tail of a comet is from stuff coming off the nucleus, not stuff coming in. Once the particle leaves the nucleus and becomes part of the tail, it cannot affect the nucleus. So there is no way his tail drag idea can work, because his other ideas about comet tails are so wrong.

Not that this has stopped him from making silly claims using this silly idea.

"Tail drag" changed the orbit of comet Hale-Bopp in 1996

Hale-Bopp was a magnificent comet that became easy to see with the unaided eye back in 1997. It was one of the most well-studied comets of all time. It underwent something a little unusual, though: its orbital shape changed! McCanney, of course, has an "explanation" of this: tail drag (explained in the section above).

From McCanney's book "Planet-X, Comets & Earth Changes", page 52:

The huge comet Hale-Bopp had its orbit reduced from 4200 years to 2650 years in one passage of the Sun. The dirty snowball "jetting concept" could not account for this amazing change in orbit.

Here, McCanney is being incredibly deceptive. The only thing he says that's correct in that statement is that Hale-Bopp's orbit did in fact change. But he is very misleading in the way he says it. First, no credible scientist claims that jets (literally, jets of matter emitted from the comet as solid ice warms up and turns to gas, acting like a little rocket) are what reduced Hale-Bopp's orbit. He might as well say the theory of genetics cannot explain the change either! They simply have nothing to do with each other. Second, it had nothing to do with its passing the Sun. In fact, the change occurred long before it was anywhere near the Sun, when it was still way out in the solar system.

What did happen is that in April 1996, the comet passed less than 72 million miles from Jupiter. That may sound like a long way, but Jupiter is a really massive planet. The long reach of mighty Jupiter's gravity is what bent Hale-Bopp's orbit, not any magical tail drag as claimed by McCanney.

I found this out pretty easily, by doing something most pseudoscientists never do: I asked someone. I posted the question to the Minor Planets Mailing List, which is a mailing list comprised of people who actually go out and do real astronomy (as opposed to people like McCanney, who just make stuff up about it). I received a dozen emails within minutes (!) letting me know what happened to Hale-Bopp back in 1996. I then used some software to plot where Hale-Bopp was in 1996, and the answer was pretty clear: getting so close to Jupiter bent the orbit of the comet, changing the period from more than 4000 years to less than 3000. Simple as that. McCanney is wrong again.

Meteorites formed under pressure

News flash! McCanney gets something right!

Too bad it's for the wrong reason.

On his internet broadcast on several ocassions (for example, on July 1, 2004), he has claimed that mainstream science is wrong about comets because the structure of meteorites clearly indicates they were formed under pressure. But then he says this is all according to his theories. However (hold on to your hats!) he is quite wrong, in both cases.

Meteorites are chunks of space debris that have hit the ground. When in space they are called meteoroids, and while burning in our atmosphere they are meteors. Some are metallic, some are stony. I happen to collect meteorites I have several metallic ones on my bookshelf (the picture shows one of my specimens, actually). Some of these metallic meteorites are quite beautiful. If you slice one and then etch it with a mild acid, a gorgeous pattern can be seen, called a Widmanstatten pattern. It's literally a crystal pattern formed by the metal as it cooled. This indicates that the metal cooled very slowly. Quick cooling obliterates the pattern.

A blob of molten metal a mile across would cool far too quickly to make this pattern. Scientists think that metallic meteorites are actually from the cores of large asteroids! If an asteroid gets big enough as it forms, then the metals in it fall to the center because they are heavy. The core becomes metallic. If the asteroid suffers a big collision, it can shatter. These shards can then fall to Earth, and become the metallic meteorites like the ones on my bookshelf.

So McCanney is right! But wait! Is he really?

Nope. He is trying to say that meteorites come from comets. However, the vast majority of meteorites that hit the Earth are not from comets, because comet material is too fragile it burns up completely. Look at meteor showers those are due to material coming from comets, and those meteors never make it all the way to the ground. The vast majority of meteorites come from asteroids, not comets.

So he's right that meteorites formed under pressure (inside the core of an asteroid), but he's completely wrong in saying this fits with his theory.

The Sun's energy is not produced in its core, but on its surface.

Here is one of those claims that when I read it, I actually said, out loud, "Huh?" This claim is so weird, so out there, that it's almost Hoaglandian in its scope.

According to the standard models of the Sun, the heat and pressure in the Sun is so great that in the core, hydrogen atoms (really just their nuclei) are smashed together. It's a complicated process, but the end result is that they fuse together, forming a helium nucleus. This is called nuclear fusion. In the process, a little bit of heat is let out. But it happens so much in the Sun's core that the total heat generated is enormous! Enough to heat the core to 15 million Celsius, and produce the vast energy of our nearest star.

But not according to McCanney. He claims in his book (in many places page 69 as an example) that there is fusion, but it happens on the surface of the Sun. This is in part what creates his so-called "solar capacitor" (an idea I already trashed here). In fact, again on page 69, he says this is what solves the long-standing "neutrino problem". He also claims the Sun gets cooler as you go deeper, not hotter as you'd expect in the standard model.

Let's look at that neutrino problem. Basically, the equations of nuclear fusion in the Sun predict that a subatomic particle called a neutrino should be created. They are hard to detect, but when the technology finally caught up with theory, only 1/3 rd the number of expected neutrinos were found. Where were the other 2/3 rd of the neutrinos? Hence the problem, which for years was quite a headache for astronomers.

According to McCanney (again, page 69) the lack of neutrinos was because the fusion was happening on the Sun's surface. Since the Sun's surface isn't nearly as hot as the core, the fusion must be happening much slower than predicted (in the same way, I suppose, that one match produces less heat than three will).

But there's a problem. Well, for McCanney, at least. Recently, the neutrino problem was solved. According to theory, there are three types of neutrinos. What if we were only detecting one kind? Sure enough, once again when the technology caught up, it was determined that this is exactly what was happening! The kind of neutrino created in the solar furnace was created in numbers as predicted, but on route to the Earth changed their "flavor". Since we could only detect the one kind, we didn't see the other two kinds, and the number was only 1/3 rd that of the original prediction. This problem is now solved (and I suspect it may earn someone a Nobel Prize someday too).

So McCanney is wrong yet again. And it gets worse for him, too.

Geologists study earthquakes because they can tell us about the interior of the Earth by the way the waves travel. The same is true for the Sun. A new discipline, called helioseismology, studies the effect of waves as they travel through the Sun. By doing this, solar astronomers have been able to map out the interior of the Sun in the same way that seismologists have mapped out the interior of the earth.

This technique has been very successful. So successful, in fact, that scientists have been able to map out the far side of the Sun! And when the far side rotates into view, they have been able to confirm their results, and therefore their method. In other words, this technique works. However, the technique means that the standard model of the solar interior must be correct (which in turn means the Sun does get hotter as you go deeper, not cooler as McCanney claims).

So, in fact, we understand the structure of the Sun pretty well. And, too bad for McCanney, fusion occurs in the core, not the surface. McCanney is wrong again.

Hurricane production is tied in with the "solar capacitor".

Part of McCanney's theory states that electricity flows like a circuit in the solar system. I've already shown this to be completely wrong. But on page 69 of his book, he says that the flow of electricity occurs ". in the direction from the Sun where Earth would be in the month of August, the month of maximum auroras and hurricane activity" (emphasis mine).

I am not exactly sure what he means by this, because it makes no sense. But he goes on for many pages thereafter saying that hurricane activity is tied to his theory.

The standard theory of hurricanes is that water is warmed up in the summer. It heats the air, and, coupled with the Earth's rotation, creates cyclones.

Which theory is correct? If you said McCanney's, then please read the name of my website ten times out loud.

Both theories make a prediction. McCanney's predicts hurricane activity peaks in the summer. Standard theory does too. for local summer. See where I'm going with this? McCanney would predict hurricanes peak only in August, because the force behind hurricanes is tied with the Sun, and not the seasons. That is summer, all right. in the northern hemisphere. But summer in the southern hemisphere is opposite the northern! So the prediction is clear: southern hurricanes (technically, typhoons) should peak in August, too. The standard model says they should peak is austral summer, in February or so.

Guess what? The peak of the number of cyclones in the southern hemisphere is in February, six months offset from the northern peak. The plot here shows just that red is northern hurricanes, and blue southern. You can clearly see that August has a minimal number of cyclones in the south, the opposite of what McCanney's theory predicts (clicking on that image will take you to a great page about hurricanes and typhoons).

Just to head him off at the pass, too, I predict he'll be saying that this year should have a larger than average number of hurricanes due to the influence of Planet X. But, the folks at NOAA have predicted the same thing based on past hurricane trends. Needless to say, they don't use Planet X in their predictive method. So his claiming this is meaningless. Since 1995, we've been in a period of above-average activity anyway.

Oh, and one more thing: he said that auroral activity peaks in August. Bzzzzzt. Actually, the most activity is in October, February, and March. Surprise! McCanney is wrong again.

The Apollo Moon landings were faked.

I had to save this one for last. I mean, c'mon! Even McCanney couldn't claim this!

Wow. Simply, wow. I guess Planet X and his other theories aren't silly enough, he buys into the silliest of them all! I won't bother saying anything else here I'll just send you to my Moon Hoax debunking page, as well as the brilliant website Clavius, and specifically the radiation page.


The strange storms on Jupiter

At the south pole of Jupiter lurks a striking sight—even for a gas giant planet covered in colorful bands that sports a red spot larger than the earth. Down near the south pole of the planet, mostly hidden from the prying eyes of humans, is a collection of swirling storms arranged in an unusually geometric pattern.

Since they were first spotted by NASA's Juno space probe in 2019, the storms have presented something of a mystery to scientists. The storms are analogous to hurricanes on Earth. However, on our planet, hurricanes do not gather themselves at the poles and twirl around each other in the shape of a pentagon or hexagon, as do Jupiter's curious storms.

Now, a research team working in the lab of Andy Ingersoll, Caltech professor of planetary science, has discovered why Jupiter's storms behave so strangely. They did so using math derived from a proof written by Lord Kelvin, a British mathematical physicist and engineer, nearly 150 years ago.

Ingersoll, who was a member of the Juno team, says Jupiter's storms are remarkably similar to the ones that lash the East Coast of the United States every summer and fall, just on a much larger scale.

"If you went below the cloud tops, you would probably find liquid water rain drops, hail, and snow," he says. "The winds would be hurricane-force winds. Hurricanes on Earth are a good analog of the individual vortices within these arrangements we see on Jupiter, but there is nothing so stunningly beautiful here."

As on Earth, Jupiter's storms tend to form closer to the equator and then drift toward the poles. However, Earth's hurricanes and typhoons dissipate before they venture too far from the equator. Jupiter's just keep going until they reach the poles.

"The difference is that on the earth hurricanes run out of warm water and they run into continents," Ingersoll says. Jupiter has no land, "so there's much less friction because there's nothing to rub against. There's just more gas under the clouds. Jupiter also has heat left over from its formation that is comparable to the heat it gets from the sun, so the temperature difference between its equator and its poles is not as great as it is on Earth."

However, Ingersoll says, this explanation still does not account for the behavior of the storms once they reach Jupiter's south pole, which is unusual even compared to other gas giants. Saturn, which is also a gas giant, has one enormous storm at each of its poles, rather than a geometrically arranged collection of storms.

The answer to the mystery of why Jupiter has these geometric formations and other planets do not, Ingersoll and his colleagues discovered, could be found in the past, specifically in work conducted in 1878 by Alfred Mayer, an American physicist, and Lord Kelvin. Mayer had placed floating circular magnets in a pool of water and observed that they would spontaneously arrange themselves into geometric configurations, similar to those seen on Jupiter, with shapes that depended on the number of magnets. Kelvin used Mayer's observations to develop a mathematical model to explain the magnets' behavior.

"Back in the 19th century, people were thinking about how spinning pieces of fluid would arrange themselves into polygons," Ingersoll says. "Although there were lots of laboratory studies of these fluid polygons, no one had thought of applying that to a planetary surface."

To do so, the research team used a set of equations known as the shallow-water equations to build a computer model of what might be happening on Jupiter, and began to run simulations.

"We wanted to explore the combination of parameters that makes these cyclones stable," says Cheng Li (Phd '17), lead author and 51 Pegasi b postdoctoral fellow at UC Berkeley. "There are established theories that predict that cyclones tend to merge at the pole due to the rotation of the planet and that's what we found in the initial trial runs."

Eventually, however, the team found that a Jupiter-like stable geometric arrangement of storms would form if the storms were each surrounded by a ring of winds that turned in the opposite direction from the spinning storms, or a so-called anticyclonic ring. The presence of anticyclonic rings causes the storms to repel each other, rather than merge.

Storms gathered at the south pole of Jupiter, as imaged by the Juno probe. Credit: NASA-JPL/Caltech

Ingersoll says the research could help scientists better understand how weather on Earth behaves.

"Other planets provide a much wider range of behaviors than what you see on Earth," he says, "so you study the weather on other planets in order to stress-test your theories."

The paper, titled, "Modeling the Stability of Polygonal Patterns of Vortices at the Poles of Jupiter as Revealed by the Juno Spacecraft," appears in the September 8 Issue of the Proceedings of the National Academy of Sciences.


Beyond the two cultures: rethinking science and the humanities

Cross-disciplinary cooperation is needed to save civilization.

  • There is a great disconnect between the sciences and the humanities.
  • Solutions to most of our real-world problems need both ways of knowing.
  • Moving beyond the two-culture divide is an essential step to ensure our project of civilization.

For the past five years, I ran the Institute for Cross-Disciplinary Engagement at Dartmouth, an initiative sponsored by the John Templeton Foundation. Our mission has been to find ways to bring scientists and humanists together, often in public venues or — after Covid-19 — online, to discuss questions that transcend the narrow confines of a single discipline.

It turns out that these questions are at the very center of the much needed and urgent conversation about our collective future. While the complexity of the problems we face asks for a multi-cultural integration of different ways of knowing, the tools at hand are scarce and mostly ineffective. We need to rethink and learn how to collaborate productively across disciplinary cultures.


Introduction to Planetary Science and Astronomy Course

Want to take an introductory planetary science and astronomy class? Watch 14 lectures by Planetary Society chief scientist Dr. Bruce Betts recorded for his 2017 Physics 195: Introduction to Planetary Science and Astronomy course at California State University Dominguez Hills. We no longer officially offer this course but if you started it before August 2020 you can complete it and earn your certificate of achievement by 31 December 2020.

Class syllabus

The syllabus contains textbook information and a list of assignments.

Certificate of achievement

Take a quiz to earn your certificate of achievement. Every class includes a special Random Space Fact that you'll need to recognize later for the quiz, so pay attention!

All courses

Take more free online courses from The Planetary Society! Learn how to be a better space advocate and defend our planet from dangerous asteroids.

Intro Astronomy 2017. Class 1: Tour of the Solar System Take a tour of the Solar System in class 1 of Dr. Bruce Betts' online Introductory Planetary Science and Astronomy course at California State University Dominguez Hills.

Intro Astronomy 2017. Class 2: How We Explore Space Lecture 2 of Dr. Bruce Betts' online Introductory Planetary Science and Astronomy course covers easy things to see in the night sky without a telescope, and the electromagnetic spectrum (from gamma rays to visible to radio waves) -- what it is, and how and why we use different wavelength regions to explore planets and even learn their compositions. The class begins with guest Mat Kaplan, Media Producer for The Planetary Society and Bruce and Mat record a What's Up segment for Planetary Radio. Recorded at California State University Dominguez Hills.

Intro Astronomy 2017. Class 3: Telescopes, Eclipses, and the Moon Lecture 3 of Dr. Bruce Betts' online Introductory Planetary Science and Astronomy course covers optical, radio, and space telescopes, eclipses, and an introduction to the Moon including lunar tides, phases and impact cratering. Recorded at California State University Dominguez Hills.

Intro Astronomy 2017. Class 4: Moon, Mercury, Venus-Earth-Mars Atmospheres Lecture 4 of Dr. Bruce Betts' online Introductory Planetary Science and Astronomy course covers the Moon, Mercury (characteristics, geology, core, exploration, water ice at poles), the Terrestrial Planet Atmospheres/Triad Planets -- a comparison of Venus, Earth, and Mars and why their atmospheres are so different, including discussions of the habitable zone, greenhouse effect, temperature systems (Kelvins, Celsius, Fahrenheit), and the carbon cycle. Recorded at California State University Dominguez Hills.

Intro Astronomy 2017. Class 5: Venus & Mars Lecture 6 of Dr. Bruce Betts' 2017 online Introductory Planetary Science and Astronomy course covers Venus (characteristics, geologic evolution, exploration, surface landers, exploration), and Mars (characteristics, many types of geologic features, poles, exploration spacecraft). Recorded at California State University Dominguez Hills.

Intro Astronomy 2017. Class 6: Mars Lecture 6 of Dr. Bruce Betts' 2016 online Introductory Planetary Science and Astronomy course continues exploring Mars including its atmosphere, spacecraft landing and surface operations, and its moons Phobos and Deimos. Recorded at California State University Dominguez Hills.

Intro Astronomy 2017. Class 7: Asteroids and the Asteroid Threat Lecture 7 of Dr. Bruce Betts' 2017 online Introductory Planetary Science and Astronomy course covers asteroids and the near Earth asteroid threat to Earth (including statistics, past impacts, and information on the Chelyabinsk fireball). Recorded at California State University Dominguez Hills.

Intro Astronomy 2017. Class 8: Jupiter and Saturn Lecture 8 of Dr. Bruce Betts' 2017 online Introductory Planetary Science and Astronomy course covers Jupiter, the Galilean Satellites (Io, Europa, Ganymede, Callisto), and introduces the Saturnian System. Recorded at California State University Dominguez Hills.

Intro Astronomy 2017. Class 9: Saturn and Uranus Lecture 9 of Dr. Bruce Betts' 2017 online Introductory Planetary Science and Astronomy course covers the Saturnian System including atmosphere, interior, rings, and moons and introduces the Uranian system. Recorded at California State University Dominguez Hills.

Intro Astronomy 2017. Class 10: Neptune and Trans Neptunian Objects including Pluto and KBOs Lecture 10 of Dr. Bruce Betts' 2017 online Introductory Planetary Science and Astronomy course covers the Neptune System, Transneptunian Objects (TNOs) including the Pluto System and Kuiper Belt Objects, and also covers the solar wind, aurorae, and the heliosphere. Recorded at California State University Dominguez Hills.

Intro Astronomy 2017. Class 11: The Outer Solar System Lecture 11 of Dr. Bruce Betts' 2017 online Introductory Planetary Science and Astronomy course covers the heliosphere, Oort Cloud, light pressure, solar sails, solar effects, comets, origin of solar system, and the laws of planetary motion. Recorded at California State University Dominguez Hills.

Intro Astronomy 2017. Class 12: Exoplanets, the Sun, and Solar Physics Lecture 12 of Dr. Bruce Betts' 2017 online Introductory Planetary Science and Astronomy course covers exoplanets (planets around other stars) including discovery techniques, current knowledge and characteristics, and multi-planet systems. Lecture 12 also covers the Sun and solar physics. Recorded at California State University Dominguez Hills.

Intro Astronomy 2017. Class 13: The Sun (cont.) and Stars Lecture 13 of Dr. Bruce Betts' 2017 online Introductory Planetary Science and Astronomy course continues exploring the Sun (physical characteristics, zones, solar cycle, sunspots, flares, coronal mass ejections, fusion, etc.) and covers stars and stellar evolution (star types and colors, evolution, HR Diagrams, birth and death phases, white dwarfs, neutron stars, black holes). Recorded at California State University Dominguez Hills.

Intro Astronomy 2017. Class 14: Galaxies, the Universe, Life Lecture 14 of Dr. Bruce Betts' 2017 online Introductory Planetary Science and Astronomy course covers galaxies (our place in the Milky Way, types of galaxies, Hubble Deep Field), the Universe (determining distances, expansion of the universe, Big Bang theory and evolution of the universe, WMAP and Planck results, dark matter, dark energy, neutrinos), and life in the universe (Earth life requirements, astrobiology, SETI). Recorded at California State University Dominguez Hills.

Become A Member

When you become a member, you join our mission to increase discoveries in our solar system and beyond, elevate the search for life outside our planet, and decrease the risk of Earth being hit by an asteroid.


Who is Michael Fish?

Michael Fish was born in Eastbourne, Sussex, in 1938 and studied at City University in London. He joined the Met Office in 1962 and started doing broadcasting for BBC Radio nine years later even though he wasn't actually working for the corporation.

He began weather forecasting for the broadcaster in 1974 and for 30 years he was a familiar face on BBC Weather news, gracing viewers with his chequered two-piece suits in varying shades of beige.

The married dad-of-two who is also an author and keen actor, was awarded an MBE in 2014, for services to broadcasting.

During his final forecast before he retired in 2004, his colleague Ian McCaskill called him the "the last of the true weathermen you will ever see".


11.3 Atmospheres of the Giant Planets

The atmosphere s of the jovian planets are the parts we can observe or measure directly. Since these planets have no solid surfaces, their atmospheres are more representative of their general compositions than is the case with the terrestrial planets. These atmospheres also present us with some of the most dramatic examples of weather patterns in the solar system. As we will see, storms on these planets can grow bigger than the entire planet Earth.

Atmospheric Composition

When sunlight reflects from the atmospheres of the giant planets, the atmospheric gases leave their “fingerprints” in the spectrum of light. Spectroscopic observations of the jovian planets began in the nineteenth century, but for a long time, astronomers were not able to interpret the spectra they observed. As late as the 1930s, the most prominent features photographed in these spectra remained unidentified. Then better spectra revealed the presence of molecules of methane (CH4) and ammonia (NH3) in the atmospheres of Jupiter and Saturn.

At first astronomers thought that methane and ammonia might be the main constituents of these atmospheres, but now we know that hydrogen and helium are actually the dominant gases. The confusion arose because neither hydrogen nor helium possesses easily detected spectral features in the visible spectrum. It was not until the Voyager spacecraft measured the far-infrared spectra of Jupiter and Saturn that a reliable abundance for the elusive helium could be found.

The compositions of the two atmospheres are generally similar, except that on Saturn there is less helium as the result of the precipitation of helium that contributes to Saturn’s internal energy source. The most precise measurements of composition were made on Jupiter by the Galileo entry probe in 1995 as a result, we know the abundances of some elements in the jovian atmosphere even better than we know those in the Sun.

Voyagers in Astronomy

James Van Allen: Several Planets under His Belt

The career of physicist James Van Allen spanned the birth and growth of the space age, and he played a major role in its development. Born in Iowa in 1914, Van Allen received his PhD from the University of Iowa. He then worked for several research institutions and served in the Navy during World War II.

After the war, Van Allen (Figure 11.9) was appointed Professor of Physics at the University of Iowa. He and his collaborators began using rockets to explore cosmic radiation in Earth’s outer atmosphere. To reach extremely high altitudes, Van Allen designed a technique in which a balloon lifts and then launches a small rocket (the rocket is nicknamed “the rockoon”).

Over dinner one night in 1950, Van Allen and several colleagues came up with the idea of the International Geophysical Year (IGY), an opportunity for scientists around the world to coordinate their investigations of the physics of Earth, especially research done at high altitudes. In 1955, the United States and the Soviet Union each committed themselves to launching an Earth-orbiting satellite during IGY, a competition that began what came to be known as the space race. The IGY (stretched to 18 months) took place between July 1957 and December 1958.

The Soviet Union won the first lap of the race by launching Sputnik 1 in October 1957. The US government spurred its scientists and engineers to even greater efforts to get something into space to maintain the country’s prestige. However, the primary US satellite program, Vanguard, ran into difficulties: each of its early launches crashed or exploded. Simultaneously, a second team of rocket engineers and scientists had quietly been working on a military launch vehicle called Jupiter-C. Van Allen spearheaded the design of the instruments aboard a small satellite that this vehicle would carry. On January 31, 1958, Van Allen’s Explorer 1 became the first US satellite in space.

Unlike Sputnik, Explorer 1 was equipped to make scientific measurements of high-energy charged particles above the atmosphere. Van Allen and his team discovered a belt of highly charged particles surrounding Earth, and these belts now bear his name. This first scientific discovery of the space program made Van Allen’s name known around the world.

Van Allen and his colleagues continued to measure the magnetic and particle environment around planets with increasingly sophisticated spacecraft, including Pioneers 10 and 11, which made exploratory surveys of the environments of Jupiter and Saturn. Some scientists refer to the charged-particle zones around those planets as Van Allen belt s as well. (Once, when Van Allen was giving a lecture at the University of Arizona, the graduate students in planetary science asked him if he would leave his belt at the school. It is now proudly displayed as the university’s “Van Allen belt.”)

Van Allen was a strong supporter of space science and an eloquent senior spokesperson for the American scientific community, warning NASA not to put all its efforts into human spaceflight, but to also use robotic spacecraft as productive tools for space exploration.

Clouds and Atmospheric Structure

The clouds of Jupiter (Figure 11.10) are among the most spectacular sights in the solar system, much beloved by makers of science-fiction films. They range in color from white to orange to red to brown, swirling and twisting in a constantly changing kaleidoscope of patterns. Saturn shows similar but much more subdued cloud activity instead of vivid colors, its clouds have a nearly uniform butterscotch hue (Figure 11.11).

Different gases freeze at different temperatures. At the temperatures and pressures of the upper atmospheres of Jupiter and Saturn, methane remains a gas, but ammonia can condense and freeze. (Similarly, water vapor condenses high in Earth’s atmosphere to produce clouds of ice crystals.) The primary clouds that we see around these planets, whether from a spacecraft or through a telescope, are composed of frozen ammonia crystals. The ammonia clouds mark the upper edge of the planets’ tropospheres above that is the stratosphere, the coldest part of the atmosphere. (These layers were initially defined in Earth as a Planet.)

The diagrams in Figure 11.12 show the structure and clouds in the atmospheres of all four jovian planets. On both Jupiter and Saturn, the temperature near the cloud tops is about 140 K (only a little cooler than the polar caps of Mars). On Jupiter, this cloud level is at a pressure of about 0.1 bar (one tenth the atmospheric pressure at the surface of Earth), but on Saturn it occurs lower in the atmosphere, at about 1 bar. Because the ammonia clouds lie so much deeper on Saturn, they are more difficult to see, and the overall appearance of the planet is much blander than is Jupiter’s appearance.

Within the tropospheres of these planets, the temperature and pressure both increase with depth. Through breaks in the ammonia clouds, we can see tantalizing glimpses of other cloud layers that can form in these deeper regions of the atmosphere—regions that were sampled directly for Jupiter by the Galileo probe that fell into the planet.

As it descended to a pressure of 5 bars, the probe should have passed into a region of frozen water clouds, then below that into clouds of liquid water droplets, perhaps similar to the common clouds of the terrestrial troposphere. At least this is what scientists expected. But the probe saw no water clouds, and it measured a surprisingly low abundance of water vapor in the atmosphere. It soon became clear to the Galileo scientists that the probe happened to descend through an unusually dry, cloud-free region of the atmosphere—a giant downdraft of cool, dry gas. Andrew Ingersoll of Caltech, a member of the Galileo team, called this entry site the “desert” of Jupiter. It’s a pity that the probe did not enter a more representative region, but that’s the luck of the cosmic draw. The probe continued to make measurements to a pressure of 22 bars but found no other cloud layers before its instruments stopped working. It also detected lightning storms, but only at great distances, further suggesting that the probe itself was in a region of clear weather.

Above the visible ammonia clouds in Jupiter ’s atmosphere, we find the clear stratosphere, which reaches a minimum temperature near 120 K. At still higher altitudes, temperatures rise again, just as they do in the upper atmosphere of Earth, because here the molecules absorb ultraviolet light from the Sun. The cloud colors are due to impurities, the product of chemical reactions among the atmospheric gases in a process we call photochemistry . In Jupiter’s upper atmosphere, photochemical reactions create a variety of fairly complex compounds of hydrogen and carbon that form a thin layer of smog far above the visible clouds. We show this smog as a fuzzy orange region in Figure 11.12 however, this thin layer does not block our view of the clouds beneath it.

The visible atmosphere of Saturn is composed of approximately 75% hydrogen and 25% helium, with trace amounts of methane, ethane, propane, and other hydrocarbons. The overall structure is similar to that of Jupiter. Temperatures are somewhat colder, however, and the atmosphere is more extended due to Saturn’s lower surface gravity. Thus, the layers are stretched out over a longer distance, as you can see in Figure 11.12. Overall, though, the same atmospheric regions, condensation cloud, and photochemical reactions that we see on Jupiter should be present on Saturn (Figure 11.13).

Saturn has one anomalous cloud structure that has mystified scientists: a hexagonal wave pattern around the north pole, shown in Figure 11.14. The six sides of the hexagon are each longer than the diameter of Earth. Winds are also extremely high on Saturn, with speeds of up to 1800 kilometers per hour measured near the equator.

Link to Learning

See images of Saturn’s hexagon with exaggerated color in this brief NASA video.

Unlike Jupiter and Saturn, Uranus is almost entirely featureless as seen at wavelengths that range from the ultraviolet to the infrared (see its rather boring image in Figure 11.1). Calculations indicate that the basic atmospheric structure of Uranus should resemble that of Jupiter and Saturn, although its upper clouds (at the 1-bar pressure level) are composed of methane rather than ammonia. However, the absence of an internal heat source suppresses up-and-down movement and leads to a very stable atmosphere with little visible structure.

Neptune differs from Uranus in its appearance, although their basic atmospheric temperatures are similar. The upper clouds are composed of methane, which forms a thin cloud layer near the top of the troposphere at a temperature of 70 K and a pressure of 1.5 bars. Most the atmosphere above this level is clear and transparent, with less haze than is found on Uranus. The scattering of sunlight by gas molecules lends Neptune a pale blue color similar to that of Earth’s atmosphere (Figure 11.15). Another cloud layer, perhaps composed of hydrogen sulfide ice particles, exists below the methane clouds at a pressure of 3 bars.

Unlike Uranus, Neptune has an atmosphere in which convection currents —vertical drafts of gas—emanate from the interior, powered by the planet’s internal heat source. These currents carry warm gas above the 1.5-bar cloud level, forming additional clouds at elevations about 75 kilometers higher. These high-altitude clouds form bright white patterns against the blue planet beneath. Voyager photographed distinct shadows on the methane cloud tops, permitting the altitudes of the high clouds to be calculated. Figure 11.16 is a remarkable close-up of Neptune’s outer layers that could never have been obtained from Earth.

Winds and Weather

The atmosphere s of the jovian planets have many regions of high pressure (where there is more air) and low pressure (where there is less). Just as it does on Earth, air flows between these regions, setting up wind patterns that are then distorted by the rotation of the planet. By observing the changing cloud patterns on the jovian planets, we can measure wind speeds and track the circulation of their atmospheres.

The atmospheric motions we see on these planets are fundamentally different from those on the terrestrial planets. The giants spin faster, and their rapid rotation tends to smear out of the circulation into horizontal (east-west) patterns parallel to the equator. In addition, there is no solid surface below the atmosphere against which the circulation patterns can rub and lose energy (which is how tropical storms on Earth ultimately die out when they come over land).

As we have seen, on all the giants except Uranus, heat from the inside contributes about as much energy to the atmosphere as sunlight from the outside. This means that deep convection currents of rising hot air and falling cooler air circulate throughout the atmospheres of the planets in the vertical direction.

The main features of Jupiter ’s visible clouds (see Figure 11.2 and Figure 11.10, for example) are alternating dark and light bands that stretch around the planet parallel to the equator. These bands are semi-permanent features, although they shift in intensity and position from year to year. Consistent with the small tilt of Jupiter’s axis, the pattern does not change with the seasons.

More fundamental than these bands are underlying east-west wind patterns in the atmosphere, which do not appear to change at all, even over many decades. These are illustrated in Figure 11.17, which indicates how strong the winds are at each latitude for the giant planets. At Jupiter’s equator, a jet stream flows eastward with a speed of about 90 meters per second (300 kilometers per hour), similar to the speed of jet streams in Earth’s upper atmosphere. At higher latitudes there are alternating east- and west-moving streams, with each hemisphere an almost perfect mirror image of the other. Saturn shows a similar pattern, but with a much stronger equatorial jet stream, as we noted earlier.

The light zones on Jupiter are regions of upwelling air capped by white ammonia cirrus clouds. They apparently represent the tops of upward-moving convection currents. 2 The darker belts are regions where the cooler atmosphere moves downward, completing the convection cycle they are darker because fewer ammonia clouds mean we can see deeper into the atmosphere, perhaps down to a region of ammonium hydrosulfide (NH4SH) clouds. The Galileo probe sampled one of the clearest of these dry downdrafts.

In spite of the strange seasons induced by the 98° tilt of its axis, Uranus ’ basic circulation is parallel with its equator, as is the case on Jupiter and Saturn. The mass of the atmosphere and its capacity to store heat are so great that the alternating 42-year periods of sunlight and darkness have little effect. In fact, Voyager measurements show that the atmospheric temperature is even a few degrees higher on the dark winter side than on the hemisphere facing the Sun. This is another indication that the behavior of such giant planet atmospheres is a complex problem that we do not fully understand.

Neptune ’s weather is characterized by strong east-west winds generally similar to those observed on Jupiter and Saturn. The highest wind speeds near its equator reach 2100 kilometers per hour, even higher than the peak winds on Saturn. The Neptune equatorial jet stream actually approaches supersonic speeds (faster than the speed of sound in Neptune’s air).

Giant Storms on Giant Planets

Superimposed on the regular atmospheric circulation patterns we have just described are many local disturbances—weather systems or storms, to borrow the term we use on Earth. The most prominent of these are large, oval-shaped, high-pressure regions on both Jupiter (Figure 11.18) and Neptune.

The largest and most famous of Jupiter’s storms is the Great Red Spot , a reddish oval in the southern hemisphere that changes slowly it was 25,000 kilometers long when Voyager arrived in 1979, but it had shrunk to 20,000 kilometers by the end of the Galileo mission in 2000 (Figure 11.19). The giant storm has persisted in Jupiter’s atmosphere ever since astronomers were first able to observe it after the invention of the telescope, more than 300 years ago. However, it has continued to shrink, raising speculation that we may see its end within a few decades.

In addition to its longevity, the Red Spot differs from terrestrial storms in being a high-pressure region on our planet, such storms are regions of lower pressure. The Red Spot’s counterclockwise rotation has a period of six days. Three similar but smaller disturbances (about as big as Earth) formed on Jupiter in the 1930s. They look like white ovals, and one can be seen clearly below and to the right of the Great Red Spot in Figure 11.19. In 1998, the Galileo spacecraft watched as two of these ovals collided and merged into one.

We don’t know what causes the Great Red Spot or the white ovals, but we do have an idea how they can last so long once they form. On Earth, the lifetime of a large oceanic hurricane or typhoon is typically a few weeks, or even less when it moves over the continents and encounters friction with the land. Jupiter has no solid surface to slow down an atmospheric disturbance furthermore, the sheer size of the disturbances lends them stability. We can calculate that on a planet with no solid surface, the lifetime of anything as large as the Red Spot should be measured in centuries, while lifetimes for the white ovals should be measured in decades, which is pretty much what we have observed.

Despite Neptune ’s smaller size and different cloud composition, Voyager showed that it had an atmospheric feature surprisingly similar to Jupiter’s Great Red Spot. Neptune’s Great Dark Spot was nearly 10,000 kilometers long (Figure 11.15). On both planets, the giant storms formed at latitude 20° S, had the same shape, and took up about the same fraction of the planet’s diameter. The Great Dark Spot rotated with a period of 17 days, versus about 6 days for the Great Red Spot. When the Hubble Space Telescope examined Neptune in the mid-1990s, however, astronomers could find no trace of the Great Dark Spot on their images.

Although many of the details of the weather on the jovian planets are not yet understood, it is clear that if you are a fan of dramatic weather, these worlds are the place to look. We study the features in these atmospheres not only for what they have to teach us about conditions in the jovian planets, but also because we hope they can help us understand the weather on Earth just a bit better.

Example 11.1

Storms and Winds

Solution

Check Your Learning

Answer:

For the Great Red Spot of Jupiter, the circumference (2πR) is about 63,000 km. Six d equals 144 h, suggesting a speed of about 436 km/h. This is much faster than wind speeds on Earth.

Footnotes

    Recall from earlier chapters that convection is a process in which liquids, heated from underneath, have regions where hot material rises and cooler material descends. You can see convection at work if you heat oatmeal on a stovetop or watch miso soup boil.

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    June nights mean return of rare 'electric blue clouds'

    June features the shortest nights of the entire year north of the equator, but the biggest astronomy event of the month will unfold after the sun has climbed above the horizon over part of the globe.

    This is also one of the only months during which rare noctilucent clouds, which float 50 miles above the Earth's surface, can be seen from the Northern Hemisphere. This is significantly higher than many other clouds or the altitude at which airplanes fly.

    Noctilucent clouds, also known as night clouds, are seen from the village of Negnevichi, 140 kilometers (87 miles) west of Minsk, Belarus, late Tuesday, July 21, 2020. Noctilucent clouds are thin and forming high above the Earth at heights of 70-90 kilometres, so they can only be seen at twilight, shining after the sunset. (AP Photo/Sergei Grits)

    Noctilucent clouds are sometimes called "electric blue clouds" due to their color and the way that they shimmer in the sky after sunset or before sunrise. These unique clouds can only be seen in the far Northern Hemisphere in the weeks surrounding the June solstice due to the angle of the sunlight entering the atmosphere.

    "These clouds actually form around particles left behind by meteors," AccuWeather Astronomy Blogger Dave Samuhel said. "Super cold water droplets freeze on the meteor debris and form ice. These clouds are made purely of ice."

    There is no specific date to look for these clouds, but there are several dates to mark on the June calendar so that you don't miss the top three astronomy events of the month:

    1. "Ring of Fire" Solar Eclipse
    When:
    June 10

    A little over two weeks after the sun, Earth and moon aligned to create a lunar eclipse, the three celestial objects will align again, but in a different order, to create a solar eclipse.

    As the sun rises on Thursday, June 10, the moon will begin to block out the sun over part of the northeastern United States and eastern Canada. Onlookers in cities such as Boston, Montreal and Quebec City may briefly be able to see a partial solar eclipse.

    Most of Europe will also be able to see a partial solar eclipse around midday, local time.

    Proper eye protection is necessary to see this event as looking directly at the sun can lead to serious, permanent eye damage, even if part of it is blocked by the moon. This includes a solar filter or specially made eclipse glasses.

    The upcoming eclipse will be an annular solar eclipse, sometimes called a "Ring of Fire" eclipse, as it takes place when the moon is farther away from the Earth than normal, meaning that it is not quite big enough to block out the entirety of the sun.

    This is different from a total solar eclipse when the moon blocks out the entire sun, causing day to turn to night for a few fleeting moments.

    However, the only areas that will be able to see the ring of fire in the sky are the unpopulated areas of northern Canada, northwestern Greenland and far eastern Russia.

    An annular solar eclipse is seen formed over the sky of Myanmar's ancient historic city of Bagan Friday, Jan. 15, 2010. (AP Photo/Khin Maung Win)

    Another solar eclipse is set to unfold on Dec. 4, but will not be witnessed by many humans as it will only be visible from Antarctica.

    2. June Solstice
    When:
    June 20, 11:32 p.m. EDT

    Summer officially kicks off in June, but the date that marks the start of the new season depends on the definition.

    Forecasters often use meteorological seasons, three-month periods that are the same year in and year out, with meteorological summer always starting on June 1 and ending on Aug. 31.

    This is different than astronomical summer, which varies year to year depending on the precise time of the June solstice and the September equinox. This year, astronomical summer starts on June 20 at 11:32 p.m. EDT and ends on Sept. 22 at 3:21 p.m. EDT.

    During the June solstice, the sun's most direct rays are shining directly on the Tropic of Cancer, making it the longest day of the entire year for the Northern Hemisphere.

    Summer is also the longest season of the entire year, lasting 93 days, 15 hours and 49 minutes, according to TimeAndDate.com.

    After the June solstice, the days in the Northern Hemisphere will slowly but surely get shorter while the days gradually grow longer in the Southern Hemisphere until the December equinox on Dec. 21.

    3. Final supermoon of 2021
    When:
    June 24-25

    The third and final supermoon of 2021 is set to rise just one night before the final weekend of June, illuminating the night for summer activities such as campfires and sleeping under the stars.

    April featured the first of the trio of supermoons, followed by another in May that also coincided with a total lunar eclipse. An encore of the lunar eclipse is not in the offing this month, but the moon will still appear slightly bigger and brighter than other full moons throughout the balance of the year.

    The supermoon is seen setting behind the San Jacinto Mountains early Thursday morning, May 27, 2021, near Palm Springs, Calif. (AP Photo/Cliff Schiappa)

    Even when it's not a supermoon, June's full moon is often called the Strawberry Moon as it is the time of year to gather ripe strawberries, The Old Farmer's Almanac reports.

    Other nicknames for June's full moon include the Hot Moon, the Blooming Moon and the Green Corn Moon.