NEW FOUND PLANET orbits backward

Planets orbit stars in the same direction that the stars rotate. They all do. Except one.

A newfound planet orbits the wrong way, backward compared to the rotation of its host star. Its discoverers think a near-collision may have created the retrograde orbit, as it is called.

The star and its planet, WASP-17, are about 1,000 light-years away. The setup was found by the UK's Wide Area Search for Planets (WASP) project in collaboration with Geneva Observatory. The discovery was announced today but has not yet been published in a journal.

"I would have to say this is one of the strangest planets we know about," said Sara Seager, an astrophysicist at MIT who was not involved in the discovery.

What's going on

A star forms when a cloud of gas and dust collapses. Whatever movement the cloud had becomes intensified as it condenses, determining the rotational direction of the star. How planets form is less certain. They are, however, known to develop out of the leftover, typically disk-shaped mass of gas and dust that swirls around a newborn star, so whatever direction that material is moving, which is the direction of the star's rotation, becomes the direction of the planet's orbit.

WASP-17 likely had a close encounter with a larger planet, and the gravitational interaction acted like a slingshot to put WASP-17 on its odd course, the astronomers figure.

"I think it's extremely exciting. It's fascinating that we can study orbits of planets so far away," Seager told SPACE.com. "There's always theory, but there's nothing like an observation to really prove it."

Cosmic collisions are not uncommon. Earth's moon was made when our planet collided with a Mars-sized object, astronomers think. And earlier this week NASA's Spitzer Space Telescope found evidence of two planets colliding around a distant, young star. Some moons in our solar system are on retrograde orbits, perhaps at least in some cases because they were flying through space alone and then captured; that's thought to be the case with Neptune's large moon Triton.

The find was made by graduate students David Anderson at Keele University and Amaury Triaud of the Geneva Observatory.

Bloated world

WASP-17 is about half the mass of Jupiter but bloated to twice its size. "This planet is only as dense as expanded polystyrene, 70 times less dense than the planet we're standing on," said professor Coel Hellier of Keele University.

The bloated planet can be explained by a highly elliptical orbit, which brings it close to the star and then far away. Like exaggerated tides on Earth, the tidal effects on WASP-17 heat and stretch the planet, the researchers suggest.

The tides are not a daily affair, however. "Instead it's creating a huge amount of friction on the inside of the planet and generating a lot of energy, which might be making the planet big and puffy," Seager said.

WASP-17 is the 17th extrasolar planet found by the WASP project, which monitors hundreds of thousands of stars, watching for small dips in their light when a planet transits in front of them. NASA's Kepler space observatory is using the same technique to search for Earth-like worlds.

Who lives in the eleventh dimension? - PARALLEL UNIVERSES

Five New Planets Found; Hotter Than Molten Lava

Most of the five new planets are much hotter and bigger than any planet in our solar system.

Illustration courtesy William Borucki, NASA

Victoria Jaggard in Washington, D.C.

National Geographic News

January 4, 2010

Five new planets have been found orbiting distant stars—the first confirmed new worlds from NASA's recently launched Kepler space telescope mission, astronomers announced today.

Like many of the more than 400 exoplanets—planets outside our solar system—found to date, the new planets are so-called hot Jupiters. They're about the same mass as Jupiter and orbit very close to their host stars, which makes the planets relatively easy to spot from Earth.

The smallest of the new planets is about the same size as Neptune, though much more massive. All of the planets are hotter than molten lava and could turn gold to goo, according to NASA temperature estimates.

Dubbed Kepler 4b, 5b, 6b, 7b, and 8b, the five new planets range in temperature from 2,000 to 3,000 degrees Fahrenheit (1,090 to 1,650 degrees Celsius), William Borucki, Kepler's principal investigator, said today during a press briefing at the American Astronomical Society's annual meeting in Washington, D.C.

One of the worlds, Kepler 7b, is among the lowest-density planets yet found, with about the same density as Styrofoam, he said. (Related: "'Backward' Planet Has Density of Foam Coffee Cups.")

These planets are "certainly no place to look for life—that will be coming later," with discoveries of Earth-like planets, Borucki said.

Kepler "Working So Well"

Kepler's main goal is to find rocky, Earthlike planets orbiting in stars' habitable zones—the regions in which planets receive enough heat from their stars for liquid water to exist.

While the new finds don't meet those criteria, they do show that the instrument is working as expected—offering "a tantalizing hint at what we can expect in a few years' time," noted Greg Laughlin, an astronomer at the University of California, Santa Cruz.

"It's wonderful to see Kepler working so well."

How to Find New Planets

Kepler looks for extrasolar planets by spying the decrease in starlight as a planet transits, or crosses in front of, its host star, as seen from Earth.

The orbiting telescope, which launched last March, spotted the five new worlds in its first six weeks of operation.

Each planet's existence was later confirmed using a method called radial velocity, which looks for the wobble in a star's orbit caused by the gravitational pull of an orbiting planet.

The radial velocity observations were "a beautiful match" for Kepler's data, Borucki said. "It completely confirms that we really have planets here."

Having both sets of data creates a "truly valuable situation" in planet hunting, UCSC's Laughlin added.

That's because each method does more than just help confirm the other. Each technique provides different types of information, which help build a more complete picture of the alien world.

Radial velocity, for example, gives details about a planet's mass and orbit, while transits can reveal a planet's size relative to its star. This in turn tells astronomers about the planet's density.

Planet-hunting missions such as Kepler have shown us that the densities of exoplanets are all over the map, Laughlin said.

Some of the biggest worlds, for instance, have been found to be unexpectedly "puffed up" by an as-yet unexplained heat source.

Kelper 5b, for instance, is much more massive than Jupiter but is much less dense then water, said mission co-investigator Dimitar Sasselov.

"It's like looking at a football team," Laughlin said. "You might guess that they're all 250 to 300 pounds. But then you find out that some of them are 25 pounds—that would come as a surprise."

Hundreds of Candidates for New Planets

Although Kepler's five new planets are the only ones confirmed by the mission so far, the telescope's first few months of data actually contain hundreds of candidates.

The Kepler mission, expected to last at least three and a half years, will likely announce many more new worlds in coming years as astronomers are able to confirm the planets' existence.

But it will take several Earth years before Kepler scientists can be sure they've seen an Earth-size world in its star's habitable zone, Laughlin said.

That's because a planet orbiting at the right distance from its star will be farther out than a hot Jupiter and so will take much longer to complete an orbit of its star—making transits much rarer.

To be sure you've seen a planet, "you have to watch long enough to see three to four transits," Laughlin said.

Overall, though, the new finds help make it clear that planets with otherwise similar traits can have very different personalities, Laughlin noted.

"It's not a situation of, You've seen one, you've seen them all."

NASA Astronomers Discover Two New Planet

NASA announced that Kepler spacecraft has discovered the first confirmed planetary system with more than one planet "transiting," or crossing in front of, a central star.

The findings, published in Thursday's issue of the journal Science, came from observing about 156,000 stars for seven months as part of a pioneering search for Earth-size planets outside our solar system.

Kepler's ultra-precise camera measures tiny decreases in a star's brightness caused by the orbiting of the planet as it crosses in front of its sun. The size of the planets can be determined by measuring these temporary dips.

Two planets in the newly discovered system, 2,000 light-years away, are the size of Saturn, and a third possible planet is a "super-Earth," 11/2 times the size of our planet. That planet is the size thought to be potentially habitable, but it orbits too close to its star to support life, Washington Post reports.

The planets, now named named Kepler-9b and 9c, were seen transiting the sun-like star called Kepler-9. The announcement comes just days after ESO released data on a planetary system believed to have five orbiting planets, discovered with the HARP ground-based telescope.

Kepler found more than 700 possible planets in its first 43 days, and has discovered five more systems that appear to have more than one transiting planet, TG Daily informs.

Earth-Like Planet Discovered in Libra

Scientists have discovered a new planet in the constellation Libra. The small, rocky planet is special because it appears to have mild temperatures, like Earth. Researchers believe it looks like the first planet outside of our solar system that could be home to liquid water, and maybe even life.

Our solar system has only eight planets — nine if you count Pluto. But outside of our solar system, around other stars, scientists have found dozens and dozens of planets.

"We have discovered more than 100 planets, here in Geneva," says Michel Mayor, a planet hunter at the University of Geneva.

Almost all of these known "extrasolar" planets are giant balls of gas, much like Jupiter or Saturn. Such massive planets are relatively easy to find. They have a gravitational pull that makes their stars wobble, and when scientists see that wobble, they know there is a planet. Small, rocky planets cause less of a wobble, making them harder to find.

Still, Mayor and his colleagues have had some luck using the European Southern Observatory's big telescope at La Silla, Chile. They recently pointed it at a nearby star called Gliese 581, in the constellation Libra.

"It's one of our closest neighbors in the galaxy," Mayor says.

His team has found three planets around this star, and one of them is particularly interesting. They think the planet is a little bigger than Earth, with about five times the Earth's mass. It orbits very close to its star, going all the way around in just 13 days. The planet isn't super hot though, because Gliese 581 is a red dwarf, which is much dimmer and cooler than our sun.

Scientists calculate that average temperatures on the surface of the planet should be around 32 to 104 degrees Fahrenheit. Mayor says that is a friendly environment for liquid water and maybe even life.

"We do not have any reason to believe that life exists on that planet," Mayor concedes. "We can only say that we have the temperature to permit the development of life. I would say it's one very interesting step in a long process going in the direction to having some major discovery related to life in the universe."

A report on the discovery has been submitted to the journal Astronomy and Astrophysics, and other experts agree that it is a significant find. Alan Boss is a planetary scientist at the Carnegie Institution of Washington.

"This seems to be the first discovery of an Earth-like planet," Boss says. "It's not exactly an Earth but it's close enough that I think it does deserve the title of perhaps the first Earth-like planet."

Other small planets discovered in the past have been very hot, or very cold. In many ways, though, this planet is a mystery.

"We do not know what the composition of the planet is," says Boss, explaining that scientists assume it is made of rock and metal like Earth. "We do not know how much water it may or may not have on it."

Boss says we could learn a lot more if scientists launched a space telescope that is specially designed to look at faraway planets. NASA has one in development called the Terrestrial Planet Finder, but it has been delayed indefinitely by budget woes.

"Things like Terrestrial Planet Finder are no longer really in the active NASA plan," Boss says.

Still, some scientists have a mental picture of the place. Todd Henry, an astronomer at Georgia State University, says that if you were standing on this planet and looked up, its sun would appear to be huge — five times bigger than our sun looks to us.

"It's going to look very different in this sort of alien situation that we're in than what we're used to here on Earth," Henry says. "The star itself is actually going to look sort of the color of Mars — sort of a red, ruddy color. But it would be much bigger in the sky than we're used to."

He says the star is also notable because the Geneva team found those two other planets circling it. They are also relatively small planets, which have been harder to find.

"This is starting to look like a solar system we're familiar with," Henry says. "If you were in a spaceship and you sort of flew into this system, this is one of the most interesting ones there is out there now."

But don't count on visiting anytime soon. Even though Gliese 581 is close, compared with other stars, it still would take over 20 years to get there — if we could travel at the speed of light, which we can't do.

6 new planets!

Six New Planets Discovered

ScienceDaily (June 22, 2010) — An international team, including Oxford University scientists, has discovered six diverse new planets, from 'shrunken-Saturns' to 'bloated hot Jupiters', as well a rare brown dwarf with 60 times the mass of Jupiter.

The CoRoT (Convection, Rotation and Transits) space telescope is operated by the French space agency CNES. It discovers planets outside our solar system -- exoplanets -- when they 'transit', that is pass, in front of their stars.

Once CoRoT detects a transit, additional observations are made from the ground, using a number of telescopes all over the world. Although astronomers cannot see the planets directly, they use the space- and ground-based data to measure the sizes, masses, and orbits of these new planets precisely. This is why, among all known exoplanets, those with transits yield the most complete information about planet formation and evolution.

"Each of these planets is interesting in its own right, but what is really fascinating is how diverse they are," said co-investigator Dr. Suzanne Aigrain from Oxford University's Department of Physics. "Planets are intrinsically complex objects, and we have much to learn about them yet."

"Every discovery of an extrasolar planetary system is a new piece in the puzzle of how these systems do form and evolve. The more systems we uncover, the better we can hope to understand the processes at play," said Magali Deleuil, researcher at the Laboratoire d'Astrophysique de Marseille (LAM) and head of the CoRoT exoplanet program.

The six new planets are:

CoRoT-8b: the smallest in this batch: At about 70% of the size and mass of Saturn, CoRoT-8b is moderately small among the previously known transiting exoplanets. Its internal structure should be similar to that of ice giants, like Uranus and Neptune, in the Solar System. It is the smallest planet discovered by the CoRoT team so far after CoRoT-7b, the first transiting Super-Earth.

CoRoT-10b: the eccentric giant: The orbit of CoRoT-10b is so elongated that the planet passes both very close to and very far away from its star. The amount of radiation it receives from the star varies tenfold in intensity, and scientists estimate that its surface temperature may increase from 250 to 600°C, all in the space of 13 Earth-days (the length of the year on CoRoT-10b).

CoRoT-11b: the planet whose star does the twist: CoRoT-11, the host star of CoRoT-11b, rotates around its axis in 40 hours. For comparison, the Sun's rotation period is 26 days. It is particularly difficult to confirm planets around rapidly rotating stars, so this detection is a significant achievement for the CoRoT team.

CoRoT-12b, 13b and 14b: a trio of giants: These three planets all orbit close to their host star but have very different properties. Although CoRoT-13b is smaller than Jupiter, it is twice as dense. This suggests the presence of a massive rocky core inside the planet. With a radius 50% large than Jupiter's (or 16 times larger than the Earth's), CoRoT-12b belongs to the family of `bloated hot Jupiters', whose anomalously large sizes are due to the intense stellar radiation they receive. On the other hand, CoRoT-14b, which is even closer to its parent star, has a size similar to Jupiter's. It is also massive, 7.5 times the mass of Jupiter, which may explain why it is less puffed up. Such very massive and very hot planets are rare, CoRoT-14b is only the second one discovered so far.

CoRoT-15b: the brown dwarf: CoRoT-15b's mass is about 60 times that of Jupiter. This makes it incredibly dense, about 40 times more so than Jupiter. For that reason, it is classified as a brown dwarf, intermediate in nature between planets and stars. Brown dwarfs are much rarer than planets, which makes this discovery all the more exciting.

Dr. Suzanne Aigrain leads a team of UK researchers at the Universities of Oxford, Exeter and St Andrews who participate in the CoRoT exoplanet program. Their research is supported by the Science and Technology Facilities Research Council.

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