tagged w/ planetary science
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Los Angeles Times...
NASA spacecraft offers detailed views of Saturn's Great White Spot
The Great White Spot, which occurs about once every 30 Earth years, is a windy, towering cloud of ammonia and water spewing out super jolts of thunder and lightning. The storm is about 10,000 times stronger than those on Earth.
PHOTO: An image of Saturn taken by NASA spacecraft Cassini shows the Great White Spot in the planet's northern hemisphere. (NASA / July 7, 2011)
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By Daniela Hernandez, Los Angeles Times
July 6, 2011, 6:27 p.m.
Saturn's Great White Spot, a recurring storm on that planet that has intrigued scientists since it was first observed in 1876, is a windy, towering cloud of ammonia and water spewing out super jolts of thunder and lightning. Now astronomers and NASA's Cassini spacecraft, which has been orbiting Saturn since 2004, have captured the most detailed views to date of the phenomenon.
The luminous storm, which may be the gaseous planet's main mechanism for dissipating heat, occurs about once every Saturnian year, the equivalent of about 30 Earth years. The storms, however, do not follow a precise schedule. The latest round, the most intense on record, was first noticed by ground-based professional and amateur astronomers as a bright speck on Saturn's northern hemisphere on Dec. 5, about nine years before schedule. The previous storm occurred in 1990.
Their observations coincided with Cassini's detection of a deluge of radio waves emitted by Saturn. These radio waves are a signature of lightning and can be used as a measure of its strength.
During the days that followed, that small blemish, moving westward about 65 mph, grew to a size nearly equal to the diameter of the Earth. Two months later, the behemoth had blanketed the entire planet, spanning more than 180,000 miles.
"It turned into a very spectacular storm, with so many [lightning flashes] we couldn't resolve individual ones," said Donald Gurnett, a physicist at the University of Iowa and a contributing author of one of two reports published Wednesday in the journal Nature.
This massive eruption of lightning is caused when heat and water vapor rise from deep within Saturn's atmosphere up to its troposphere, the region of the atmosphere where weather occurs. When that water vapor cools and condenses, it releases heat and, under the right conditions, produces lightning.
The lightning on Saturn originates deep inside the planet's atmosphere, where vapors are at higher pressure. That makes the lightning very intense.
The images and measurements gave scientists new insight into the shape of the current Great White Spot. As water vapor and ammonia were pushed to the troposphere by vertical currents, some of the materials were dragged by eastern winds, creating the storm's characteristic "head" and straggling "tail," both of which are visible from Earth.
First author Agustin Sanchez-Lavega, a planetary scientist at the University of the Basque Country in Bilbao, Spain, and his colleagues were able to estimate that the storm's head, where most of the lightning was concentrated, extended about 160 miles below the cloud tops. Because the sun doesn't shine there, this suggests that the planet's internal heat helps the storms to form, the scientists wrote.
Great White Spots are 10 times larger than normal storms on Saturn and are about 10,000 times stronger than those on Earth. They occur seasonally due to changes in how much sunlight reaches Saturn. Scientists still don't fully understand the interplay between solar energy and Saturn's internal stores in generating these storms.Los Angeles Times...
NASA spacecraft offers detailed views of Saturn's Great... more
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This astonishing video takes environmental innovation to its outer limits: you’ll need to be pretty imaginative to find a way to invest in the ideas it explores
The eye-opening Stanford University talk by NASA titan Chris McKay, is called ‘Biologically Reversible Exploration’This astonishing video takes environmental innovation to its outer limits:... more
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A New Planet — from Beyond the Galaxy
Read more: http://www.time.com/time/health/article/0,8599,2032054,00.html#ixzz15hGdcBa9
By Michael D. Lemonick Thursday, Nov. 18, 2010
Picture: This artist's impression shows HIP 13044 b, an exoplanet orbiting a star that entered our galaxy, the Milky Way, from another galaxy.
AFP / Getty Images
Read more: http://www.time.com/time/health/article/0,8599,2032054,00.html#ixzz15hH2S4xq
Billions of years before the Sun was born, the Milky Way galaxy flicked out its gravitational tongue and slurped down a tiny neighboring galaxy that had ventured too close. The evidence for that ancient act of cosmic cannibalism is the still-digesting remains of the meal: a handful of relatively nearby stars known as the Helmi Stream, whose weird orbits — above and below the plain of the galaxy — are a tipoff to their weird origin.
Now one of those stars has a second claim to fame. HIP 13044, as it's unglamorously known, has a planet whirling around it — the first planet ever found from outside the Milky Way. Aside from its extra-galactic origin, the planet itself, found with a medium-size telescope at the European Southern Observatory in Chile, and described in a new paper in Science, isn't especially remarkable. It's a bit bigger than Jupiter and orbits its parent star in about 16 days — a "year" so short it would once have been considered impossible for so giant a planet, until multiple discoveries of many similar worlds proved such a revolution rate to be pretty common. (See pictures of the labor of space exploration.)
It's the star itself that makes the discovery of a planet surprising, for a couple of reasons. For one thing, its age — perhaps 7 or 8 billion years — means that while HIP 13044 was once much like the Sun, it's gone through a dramatic change of life. As it burned through its supply of hydrogen, the star would have swelled to become a so-called red giant, tens, or even hundreds of times its original size. When that happens to our Sun billions of years from now, Earth will probably be destroyed. Indeed, there's some circumstantial evidence that HIP 13044 may have gulped down a few planets itself, says the paper's lead author Johny Setiawan, of Germany's Max Planck Institute for Astronomy, in Heidelberg. "The star is a fast rotator," he says, "and theory predicts that if a star swallows a planet its rotation rate should increase."
But the new planet, called HIP 13044b, survived the cataclysm. That's probably because the Jupiter-size world originally occupied a Jupiter-like orbit, much farther from its star than Earth is from the Sun. It spiraled in to its present orbit only after HIP 13044 shrank back to a more dignified size — another common stage of life for stars, which return to their original dimensions when they start burning the helium in their core. A tiny handful of planets have been seen orbiting stars that are currently red giants, but this is the first to be found in the next chapter of a star's life. (See pictures of Russia's cosmonaut training center.)
The other thing that makes the star unusual is its composition. The Sun is mostly hydrogen and helium, but it also has significant traces of heavier elements like oxygen, carbon and iron, a quality astronomers call "metallicity" despite the non–metallic nature of some of those elements.
"In the Milky Way," says Setiawan, "the more metals a star has, the more likely it is to have planets." The reason for that is simple: both stars and planets coalesce out of the same vast pool of dust and gas. The higher the metallicity, the bigger the supply of building material and the likelier that some will be left over to form planets.
Dwarf galaxies like the one in which HIP 13044 was born, however — and like the two dozen or so that still orbit the Milky Way — have stars that are notably metal-poor. It was unclear until now whether that meant they'd also be planet-poor. The fact that Setiawan and his colleague Rainer Klement, also of the Max Planck Institute, found one so easily suggests this isn't the case. "Either they were incredibly lucky," says Eric Ford, a planet-searcher at the University of Florida, "or planets aren't uncommon around stars like these."
Whatever the answer, HIP 13044b is clearly a very different world from any we've seen before, one that — without the aid of celestial metals — formed in a very different way. And that in turn suggests that the field of planetary science, which seemed so tidy and settled as recently as the 1990s, is still full of surprises.A New Planet — from Beyond the Galaxy
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Toward the end of September, the sun will turn a spotlight on the asteroid Juno, giving that bulky lump of rock a rare featured cameo in the night sky. Those who get out to a dark, unpolluted sky will be able to spot the asteroid's silvery glint near the planet Uranus with a pair of binoculars.Toward the end of September, the sun will turn a spotlight on the asteroid Juno,... more
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It is a historic mission to another world. It marks a dramatic end to the human race’s initial reconnaissance of the eight planets of our Solar System, and the beginning of detailed study of Mercury.It is a historic mission to another world. It marks a dramatic end to the human... more
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