In 1986, in a flyby shooting, the Voyager 2 space probe took some of our first photos of Uranus. The planet looked blue-green and featureless, a planetary pokerface. In the decades since, we’ve learned that Uranus does have weather, visible as variations in color on the surface, and new photos from by the Keck II telescope in Hawaii (above) reveal the ice giant’s meteorology in more detail than ever before. The scalloped pattern near the equator is a ring of clouds; the busy, blue-flecked cap at the right end—the planet’s North Pole—are storms.
For sunny weather, try another planet: this one gets sunlight hundreds times weaker than we do on Earth, and the temperature of its upper atmosphere drops as low as -371 F, making it the coldest planet in the solar system.
Image via Lawrence Sromovsky, Pat Fry, Heidi Hammel, Imke de Pater/University of Wisconsin
What’s the News: Jupiter’s moon Io is more volcanically active than any other object in our solar system, releasing 30 times more heat than Earth through volcanism. It’s thought that Jupiter’s gravity pulls so hard on the moon and causes so much friction that the resulting thermal energy melts a huge amount of underground rock, feeding Io’s 400 active volcanoes.
For years, astronomers have debated whether Io’s spewing lava comes from isolated pockets of magma or a layer that spans the entire moon. Astronomers have now peered into Io’s interior for the first time, discovering that it has a global sea of magma roughly 30 miles thick. “It turns out Io was continually giving off a ‘sounding signal’ in Jupiter’s … magnetic field that matched what would be expected from molten or partially molten rocks deep beneath the surface,” lead researcher Krishan Khurana told Wired. Read More
What’s the News: NASA’s considering launching a boat from Earth, hurling it 746 million miles through space, and plopping it onto one of the minus-290 degrees Fahrenheit methane oceans of Titan. This mission to Saturn’s largest moon would the first of its kind to probe an alien ocean and—depending on the weather conditions—could be the first spacecraft to witness extraterrestrial rain. If the proposed mission beats out two other finalists, it could launch within the next five years. “Titan is an endpoint [in] exploring … the limits to life in our solar system,” project leader Ellen Stofan told New Scientist. “We’re going to be looking for patterns in abundances of compounds to look for evidence for more complex or interesting reactions.”
What’s the News: Astronomers have known for many years that Saturn’s moon Titan sports lakes of liquid methane. And in the past couple years, scientists have suggested that it also has an underground ocean composed of water and ammonia. Now, based on past observations by NASA’s Cassini spacecraft, astronomers are saying that Titan’s rotation indeed points to an underground sea—and where there’s water, there may also be life. “Our analysis strengthens the possibility that Titan has a subsurface ocean, but it does not prove it undoubtedly,” researcher Rose-Marie Baland told Astrobiology Magazine. “So there is still work to do.”
What’s the News: Looking at images of odd undulations in the rings of Saturn and Jupiter, astronomers have discovered that comets are to blame. The finding means that a planet’s rings act as a historical record of passing comets, possibly leading to a better understanding of comet populations. “We now know that collisions into the rings are very common—a few times per decade for Jupiter and a few times per century for Saturn,” Mark Showalter, from the SETI Institute in Mountain View, California, told the Daily Mail. “Now scientists know that the rings record these impacts like grooves in a vinyl record, and we can play back their history later.”
Young. Old. Scalding hot. Icy cold. Terrestrial midgets. Gas giants. As the cavalcade of planets spotted beyond our solar system continues to grow, we get to see worlds of all sorts—and we get to speculate on the staggering number of exoplanets that might inhabit just our own galaxy.
Today’s first piece of otherworldly news involves baby exoplanets. Astronomer Christian Thalmann says his team may have spotted planets in the process of forming around three different stars, the first time scientists have spotted the process in action.
An infant star forms from a collapsing cloud of dust and gas and gathers a dense, flat disk of material that rotates with the star like a record album. The material in the disk will eventually clump up into nascent planets. Theoretical models of planet formation predicted that those protoplanets should suck up more gas and dust with their gravity, clearing a wide gap in the otherwise solid disk. [Wired]
Peering at young stars like T Chamaeleontis (T Cha) LkCa15 and AB Auriga, Thalmann and colleagues saw those telltale gaps in the dusty rings (their study is forthcoming in the Astrophysical Journal Letters). The stars are much like our own sun, so these pictures of infant solar systems could resemble what our own looked like as a baby. But though the stars are nearby in cosmic terms—T Cha lies just 350 light years away—the gaps are faint enough that it’s difficult to tell for certain if newly forming planets, and not the influence of binary stars or other objects, are creating them.
If Thalmann’s team is right, catching the birth of new worlds would be a great scientific coup. Our galaxy, however, isn’t exactly hurting for planets.
A new sight appeared on Saturn earlier this month: A massive, swirling storm with a tail that cuts across the gas giant. Amateur astronomer Anthony Wesley, who was the first to spot the Earth-sized scar on Jupiter last summer, took the first pictures of this storm. And then on Christmas Eve the Cassini spacecraft beamed home its own ravishing images.
The spacecraft took images of the planet on December 24th, returning — as usual — jaw-dropping pictures of Saturn showing the storm. This image, taken with a blue filter, shows the storm clearly. The main spot is huge, about 6,000 km (3600 miles) across — half the size of Earth! Including the tail streaming off to the right, the whole system is over 60,000 km (36,000 miles) long.
There’s an added bonus in these images: the shadow of the rings on the planet’s clouds is obvious, but the rings are nearly invisible! You can just make out the rings as a thin line going horizontally across Saturn in the first image. These pictures were snapped when Cassini was almost directly above the rings, which are so thin they vanish when seen edge-on. Actually, that works out well as otherwise they might interfere with the view of the storm in these shots.
For more details, check out the rest of Phil’s post at Bad Astronomy.
80beats: By Demolishing a Moon, Saturn May Have Created Its Rings
80beats: Mysterious Smash on Jupiter Leaves an Earth-Sized Scar
Bad Astronomy: Saturn rages from a billion kilometers away
Saturn’s moon Titan has lakes on its surface and a thick atmosphere, but there’s one more way this cold, distant world is like the Earth: It appears to have volcanoes—though they’re a little chillier than Eyjafjallajökull.
Scientists have long suspected and presented some evidence that Titan could have these features, and this week at the American Geophysical Union meet-up, researchers presented a finding from the Cassini spacecraft that they say is the best evidence yet of a Titanic volcano.
“We finally have some proof that Titan is an active world,” said geophysicist Randolph Kirk of the U.S. Geological Survey, who presented the findings. [NPR]
Into the great unknown, into the wild blue yonder, past the second star on the right and straight on till morning: That’s where NASA’s Voyager 1 is heading. The remarkable spacecraft was launched 33 years ago, and it’s now reaching the edge of our solar system. Within a few years, NASA says, it will enter interstellar space.
Phil Plait reports on how researchers realized they’d reached a milestone in Voyager 1’s journey:
Over all those years, there has been one constant in the Voyager flight: the solar wind blowing past it. This stream of subatomic particles leaves the Sun at hundreds of kilometers per second, much faster than Voyager. But now, after 33 years, that has changed: at 17 billion kilometers (10.6 billion miles) from the Sun, the spacecraft has reached the point where the solar wind has slowed to a stop. Literally, the wind is no longer at Voyager’s back.
Read the rest of his post at Bad Astronomy.
80beats: The Edge of the Solar System Is a Weird and Erratic Place
80beats: Near the Edge of the Solar System, Voyager 2 Finds Magnetic Fluff
80beats: NASA Spacecraft Will Soon Map the Solar System’s Distant Edge
80beats: Voyager 2 Hits the Edge of the Solar System—and Writes Home
Saturn and its moons may owe their distinctive looks to a legacy of destruction.
First, the magnificent rings of the sixth planet: Although astronomers have gazed at the rings for centuries, experts are still debating exactly how these loops formed. Now a new study in the journal Nature proposes that the rings are the leftovers of a large moon that was torn asunder when Saturn’s gravity reeled it in four and a half billion years ago. Lead researcher Robin Canup says this theory explains both how the rings got there, and why they’re made of nearly solid ice.
In the new study, Canup calculated that a moon the size of Titan — Saturn’s largest at some 5,000 kilometers across — would begin to separate into layers as it migrated inward. Saturn’s tidal pull would cause much of the moon’s ice to melt and then refreeze as an outer mantle. As the moon spiraled into the planet, Canup’s calculations show, the icy layer would be stripped off to form the rings. [Science News]
That layered removal is the key to Canup’s explanation, which we covered briefly when she first presented the idea at a meeting in October. Other explanations for the rings’ formation include a comet crashing into a moon, or Saturn pulling in a moon and causing it to shatter all at once. Those events would create a cascade of small objects that Saturn’s gravity could have coalesced into rings, but it would seem that they would have created much rockier rings. In reality, Saturn’s are 95 percent ice.