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1,284 new planet discoveries by Kepler telescope

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« on: May 11, 2016, 08:04:34 pm »

from The Washington Post....

Speaking of Science

NASA's Kepler telescope confirms a record-breaking 1,284 new planets

By RACHEL FELTMAN | 2:50PM EDT - Tuesday, May 10, 2016

This artist's concept depicts select planetary discoveries made to date by NASA's Kepler Space Telescope. — Picture: W. Stenzel/NASA Ames.
This artist's concept depicts select planetary discoveries made to date by NASA's Kepler Space Telescope.
 — Picture: W. Stenzel/NASA Ames.

NASA scientists announced 1,284 new exoplanets at a news conference on Tuesday — candidates found by the Kepler Space Telescope that have now been confirmed with 99 percent certainty. This is the largest dump of new planet discoveries in history, and it more than doubles the count of confirmed planets for the intrepid space telescope.

On Monday, earthlings watched as Mercury passed between our planet and the sun, all three celestial bodies lining up in just the right way for Mercury to appear as a small black dot creeping over our bright host star. That phenomenon — one planet passing in front of its star, from the visual perspective of another planet — is known as a “transit”. And that's how Kepler finds new, alien worlds.

This animation shows how NASA's Kepler Space Telescope has been able to detect
more than a thousand new planets. — Video: NASA's Ames Research Center/YouTube.

Kepler (which is technically broken, but still finds new planets in its second life as “K2”) tracks the subtle dimming of distant stars to detect possible planets that orbit them. It's our best method for detecting exoplanets, even though it can only hunt down worlds that are set up to “transit” from Earth's perspective.

Even though the data collection of the K1 mission is over, scientists are still working on parsing out the primary mission's data. They have to weed out false positives from the thousands of potential planets — star dimming actually caused by mischievous companion stars or other objects:

Graphic: W. Stenzel/NASA Ames.
Graphic: W. Stenzel/NASA Ames.

In a paper published on Tuesday in the Astrophysical Journal, a team led by Princeton University's Timothy Morton presents a new statistical method for calculating the likelihood that a given candidate is, in fact, a planet. Their analysis yielded 1,284 confirmations. Another 1,327 planets from the Kepler catalogue are almost certainly planets, according to the researchers, but these worlds don't reach the 99 percent probability threshold — so more study will be needed to adequately confirm their existence. The other 707 potential worlds are likely nonexistent, according to the analysis.

Of the newly confirmed planets, nine are thought to be rocky planets (like Earth, as opposed to gas giants or tiny worlds made of ice) in the habitable zone — meaning that they're the right distance from their host stars to potentially host liquid water, a necessary ingredient for life as we know it.

“Planet candidates can be thought of like bread crumbs,” Morton said in a statement. “If you drop a few large crumbs on the floor, you can pick them up one by one. But, if you spill a whole bag of tiny crumbs, you're going to need a broom. This statistical analysis is our broom.”

The statistical method could allow scientists to decide which “planets” to set aside as false positives or doggedly pursue as potential sites for alien life using less time and fewer resources.

“They say not to count your chickens before they're hatched, but Tim's numbers allow us to do exactly that,” Natalie Batalha, Kepler mission scientist at NASA's Ames Research Center, said during Tuesday's news conference. “This is going to be very important for Kepler's most valuable planet discoveries, those small planets found orbiting in the habitable zone.”

As of today, NASA knows of 21 exoplanets that it considers likely to be rocky, potentially wet worlds. And based on Kepler data, Batalha said, our galaxy probably has more than 10 billion rocky planets that live in the habitable zones of their stars.

That's a lot of Earths.

Before Kepler, we had no idea of how common these kinds of planets might be. The fact that they seem to be run-of-the-mill is great news in the search for life: The less special we are, the more likely we are to have company somewhere in the galaxy or beyond.

Scientists could further explore the habitability of these worlds by measuring the way their host stars' light changes as it passes through planetary atmospheres. The molecular signatures analyzed using this method could reveal the presence of water and other life-giving molecules, showing us which worlds are closest to Earth on the planetary family tree.

• Rachel Feltman runs The Washington Post's Speaking of Science blog.


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« Reply #1 on: August 25, 2016, 07:47:29 pm »

from The Washington Post....

Scientists say they've found a planet orbiting
Proxima Centauri, our closest neighbor

By RACHEL FELTMAN | 1:00PM EDT - Wednesday, August 24, 2016

Artist's impression of the planet orbiting Proxima Centauri. — Picture: G. Coleman/ESO.
Artist's impression of the planet orbiting Proxima Centauri. — Picture: G. Coleman/ESO.

SCIENTISTS have discovered what they believe to be a new planet, the closest one ever detected outside our solar system. It is a small, rocky planet not unlike our own, orbiting the sun's closest stellar neighbor.

Astronomers have long suspected that the star Proxima Centauri would be home to a planet, but proof had been elusive. Dim red dwarf stars like Proxima have been found to host billions of small, closely orbiting planets throughout the galaxy. Now a study published on Wednesday in the journal Nature provides the best evidence yet for a tantalizingly close target on which to seek alien life.

“It's so inspiring, it's our closest star,” Lisa Kaltenegger, a Cornell astronomer who wasn't involved in the new study, told The Washington Post. “A planet next door. How much more inspiring can it get?”

Located about 4.25 light years from the sun, Proxima is less famous than the Alpha Centauri binary star system it hangs around with. But while Alpha Centauri is made up of two rather sun-like stars, Proxima is actually closer. It used to be that scientists were far more interested in stars like our own sun than in dim little dwarves like Proxima, but the times are changing — these types of stars are far more common in the galaxy, and scientists now believe they might be just as capable of hosting life as more familiar looking suns.

The proposed planet comes to light not long after a would-be-world orbiting Alpha Centauri B was determined to be nothing but a fluke in the data. Scientists know that most stars in the galaxy harbor planets, but we've had difficulty finding our closest companions in the cosmos.

Proxima b will no doubt be dubbed “Earthlike” by many, but let's not jump the gun. Here's what we know: The planet, based on statistical analysis of the behavior of its star, is quite likely to exist. Beyond that, we know very little.

This animation shows what it may be like to travel from our planet to the nearest
Earth-like planet. — Video: European Southern Observatory.

Proxima b orbits its parent star every 11 days. Because of the method used to detect it, we don't actually know how massive the planet candidate is — but we can say with confidence that it's at least 1.3 times as massive as the Earth. It's just over 4 million miles away from its cool, tiny red dwarf of a star (much closer than we are to our own sun), so it is blasted with enough radiation to maintain a balmy surface temperature of around minus 40 degrees Fahrenheit.

Based on what we know about the planets that form around red dwarf stars, it's probably rocky — like Earth, Venus and Mars — and is likely tidally locked, meaning that one face of the planet constantly stares at the sun while the other half is left in darkness.

To call a planet “Earthlike”, scientists have to show that a planet is likely to be rocky and capable of holding liquid water. If Proxima b has an atmosphere — a question unlikely to be answered anytime soon — then it could have a temperature quite close to Earth's, meaning it would at least be capable of maintaining liquid water on its surface.

Even if Proxima b has (or once had) an atmosphere and held water, the evolution of life is far from guaranteed. For one thing, we're working with a sample size of one (the Earth) and have no idea how common the spark of life really is — even on planets that have all the same ingredients as the ones found at home.

Then there's Proxima itself: Known as a flare star, the red devil lashes huge flares of radiation out into space every few hours. Anything that evolved on a nearby planet would have to live deep underground or underwater to survive — unless it evolved some level of protection from radiation that scientists on Earth can scarcely imagine.

Artist's impression of the surface of Proxima b. — Picture: M. Kornmesser/ESO.
Artist's impression of the surface of Proxima b. — Picture: M. Kornmesser/ESO.

The discovery of this planet, be it Earth-like or not, has been a long time coming. Led by Guillem Anglada-Escudé from Queen Mary University of London, 31 scientists from eight different countries spent several months collecting data on Proxima. They were looking to build on previous indications of planetary presence, studying the “wiggle” in the star's light that would be caused by the seesaw gravitational pull between it and an orbiting planet (this is known as the Doppler method). Such a wiggle had been seen before, but the signal wasn't strong enough to prove a planet was there.

Anglada-Escudé and his colleagues applied for several months of observation time on the European Southern Observatory's HARPS (High Accuracy Radial velocity Planet Searcher) spectrograph, allowing them to collect 54 nights worth of data on this telltale stellar wiggle.

“There had previously been claims of other planets, so we had to be really careful here,” Anglada-Escudé said during an embargoed news briefing held by Nature on Tuesday. The data from those 54 nights made a pretty strong case for the presence of a planet, but “it wasn't enough.” The researchers weren't satisfied until they combined their data with the older signals, the ones that hadn't made enough of a case on their own.

“And then the [statistical] significance goes sky high,” he said.

Others agree that while the planet has yet to be confirmed using direct observational methods, the researchers have likely found something special. ESO astronomer Henri Boffin, who previously worked as HARPS's instrument scientist but wasn't involved in the new research, told The Washington Post that Proxima b's signal looked to be about three times as strong as that of Alpha Centauri Bb, the “planet” that turned out to be nothing but noise.

“It is quite amazing that our closest stellar neighbor would harbor a low-mass planet,” Boffin said. “Even if this is not so surprising after all, as it now seems established that the vast majority of stars host at least one planet, it is still nice to have apparently found the closest to us.”

Now the researchers will look for other methods to help confirm the planet's existence and learn about its composition. Direct observation — staring at the planet with a telescope — isn't possible with current technology. The star is just too bright and close to the planet for any telescope to see the latter. There's a small chance — something like 1.5 percent probability — that the planet “transits” in front of its star, or passes in front of the star from the perspective of Earth's telescopes. If that's the case, scientists will be able to study the planet's mass and atmosphere by analyzing the way Proxima's light passes around it.

“That's the first thing we're going to go look for,” John Brown Paul Strachan, a PhD student at Queen Mary University of London who contributed to the study, told The Washington Post. “If it does transit, then that opens a whole field to us, where we might be able to start seeing details about the atmosphere of the planet.”

But Strachan and his colleagues aren't giving up hope of a direct observation in the near future. They believe that instruments like the James Webb Space Telescope, launching in 2018, will allow them to glimpse Proxima b in no time.

If Proxima b proves to be a real planet — and one particularly worthy of study — a visit wouldn't be totally outside the realm of possibility. But even though Proxima is our closest neighbor, it's still awfully far: NASA's New Horizons probe had to travel 3 billion miles to get to Pluto, and took nearly a decade to do so. At around 25 trillion miles away, a trip to Proxima b would be more than 8,000 times as long. At least one well-funded group is trying to develop the technology needed to propel a tiny probe into the Centauri system, but don't hold your breath.

Then again, the detection of an Earthlike atmosphere on Proxima b would provide some excellent motivation.

As Anglada-Escudé said in a statement, “The search for life on Proxima b comes next.”

• Rachel Feltman runs The Washington Post's Speaking of Science blog.


Read more on this topic:

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