star with three Earth size planets found

[dragon]

And the finds keep on coming. Only 150 light years away

Scientists have discovered a new star with three nearly Earth-sized planets—one of which may have temperatures moderate enough for liquid water—and maybe even life—to exist.

NASA’s Kepler Space Telescope was able to find the star, EPIC 201367065—a cool red M-dwarf about half the size and mass of our own sun, despite being hobbled by the loss of critical guidance systems, .

At a distance of 150 light-years, it ranks among the top 10 nearest stars known to have transiting planets. The star’s proximity means it is bright enough for astronomers to study the planets’ atmospheres, to determine whether they are like Earth’s—and possibly conducive to life.

“A thin atmosphere made of nitrogen and oxygen has allowed life to thrive on Earth. But nature is full of surprises,” says Ian Crossfield, an astronomer at University of Arizona who led the study. “Many exoplanets discovered by the Kepler mission are enveloped by thick, hydrogen-rich atmospheres that are probably incompatible with life as we know it.”
Rocky like Earth

The three planets are 2.1, 1.7, and 1.5 times the size of Earth. The smallest and outermost planet, at 1.5 Earth radii, orbits far enough from its host star that it receives levels of light from its star similar to those received by Earth from the sun, says Erik Petigura, a graduate student at University of California, Berkeley.

Petigura discovered the planets January 6 while conducting a computer analysis of the Kepler data NASA has made available to astronomers. In order from farthest to closest to their star, the three planets receive 10.5, 3.2, and 1.4 times the light intensity of Earth.

“Most planets we have found to date are scorched. This system is the closest star with lukewarm transiting planets,” Petigura says. “There is a very real possibility that the outermost planet is rocky like Earth, which means this planet could have the right temperature to support liquid water oceans.”

Extrasolar planets are discovered by the hundreds these days, although many astronomers are left wondering if any of the newfound worlds are really like Earth, says Andrew Howard, an astronomer at University of Hawaii. The newly discovered planetary system will help resolve this question.

“We’ve learned in the past year that planets the size and temperature of Earth are common in our Milky Way galaxy,” he says. “We also discovered some Earth-size planets that appear to be made of the same materials as our Earth, mostly rock and iron.”


After Petigura found the planets in the Kepler light curves, researchers quickly employed telescopes in Chile, Hawaii, and California to characterize the star’s mass, radius, temperature, and age.

Two of the telescopes involved—the Automated Planet Finder on Mount Hamilton near San Jose, California, and the Keck Telescope on Mauna Kea, Hawaii—are University of California facilities.

The next step will be observations with other telescopes, including the Hubble Space Telescope, to take the spectroscopic fingerprint of the molecules in the planetary atmospheres. If these warm, nearly Earth-size planets have puffy, hydrogen-rich atmospheres, Hubble will see the telltale signal, Petigura says.

The discovery, submitted to Astrophysical Journal, is all the more remarkable, he says, because the Kepler telescope lost two reaction wheels that kept it pointing at a fixed spot in space.

Kepler was reborn in 2014 as “K2″ with a clever strategy of pointing the telescope in the plane of Earth’s orbit, the ecliptic, to stabilize the spacecraft. Kepler is now back to mining the cosmos for planets by searching for eclipses or “transits,” as planets pass in front of their host stars and periodically block some of the starlight.

“This discovery proves that K2, despite being somewhat compromised, can still find exciting and scientifically compelling planets,” Petigura says. “This ingenious new use of Kepler is a testament to the ingenuity of the scientists and engineers at NASA. This discovery shows that Kepler can still do great science.”

Kepler sees only a small fraction of the planetary systems in its gaze: only those with orbital planes aligned edge-on to our view from Earth. Planets with large orbital tilts are missed by Kepler. A census of Kepler planets the team conducted in 2013 corrected statistically for these random orbital orientations and concluded that one in five sunlike stars in the Milky Way galaxy has Earth-size planets in the habitable zone. Accounting for other types of stars as well, there may be 40 billion such planets galaxy-wide.

The original Kepler mission found thousands of small planets, but most of them were too faint and far away to assess their density and composition and thus determine whether they were high-density, rocky planets like Earth or puffy, low-density planets like Uranus and Neptune.

Because the star EPIC-201 is nearby, these mass measurements are possible. The host star, an M-dwarf, is less intrinsically bright than the sun, which means that its planets can reside close to the host-star and still enjoy lukewarm temperatures.

The system most like that of EPIC-201 is Kepler-138, an M-dwarf star with three planets of similar size, though none are in the habitable zone, Howard says.

NASA and the National Science Foundation funded the research.

link

[Borgholio]

That's really not all that far away. I imagine that's close enough for us to image with a sufficiently large telescope.

[Flameblade]

That's really not all that far away. I imagine that's close enough for us to image with a sufficiently large telescope.

It really isn't, thanks to the inverse-square law.

[Borgholio]

Isn't what, very far or close enough to image? Because if it's the latter, then I'm afraid you're mistaken. They've already directly imaged huge planets at distances of 450+ lightyears with existing telescopes. Smaller planets farther away from the star will be more difficult certainly, but not impossible...especially if they ever getting around to launching something the size of the cancelled Terrestrial Planet Finder.

[SpottedKitty]

That's really not all that far away. I imagine that's close enough for us to image with a sufficiently large telescope.

I'll be (pleasantly) surprised if we ever get an actual image of an extrasolar planet much better than our pre-Hubble best view of Pluto — i.e. a small blob — no matter how good the technology gets. All we can "see" right now is the very slight dimming of a star that happens when a planet passes in front of it. Even looking at the very closest stars, the orbits of any planets will be tiny and lost in the star's glare. That's the diameter of the planet's orbit I'm talking about, not the size of the planet itself. Space is just too big to let us see something as tiny as a planet from way over here, unless someone makes a few technological breakthroughs that bend or rewrite a few laws of physics.

Incidentally, this is the only reliable technique that has any hope of detecting not-too-much-bigger-than-Earth planets. The original technique that found the first planets depended on detecting the star wobbling back and forth as one or more planets goes round it. It's easier and more reliable than the other method, but what it can't do is find anything small; most of the first planets detected are probably gas giants much bigger than Jupiter, a surprising number of them in sun-grazing orbits. (These are the "Hot Jupiters" some news reports have mentioned.)

One possible idea I've heard discussed now and then is to examine the light from the star and see if we can detect any light that's passed through the edge of a planet's atmosphere. That would at least allow us to work out the chemical makeup of the atmosphere — for instance, oxygen or water (and not much methane or ammonia) would be dead giveaways for the presence of life. Again, though, the technology isn't quite there yet to do this. Ask again in 50 or 100 years.

Of course, there's always the easy solution... go there and look.

[Borgholio]

Here is a list of all directly-imaged planets so far:

http://en.wikipedia.org/wiki/List_of_di ... exoplanets

They are all indeed nothing more than round blobs at this distance, but the important point is that they have all been directly observed and photographed with a telescope. For an Earth-sized planet that is 1 or 2 AU from the star, we would need something the size of the TPF to directly image it. We certainly wouldn't be able to view the surface, but we could at least measure it's temperature and get a spectrographic analysis of the atmosphere which could tell us if there's life or not.

[SpottedKitty]

<blink> Well, it looks like I'm a bit behind the times, I didn't know about this. Interesting. Thanks for the link.

They're all big gas giants, though, in pretty wide orbits. (I just noticed those numbers in the first two columns, the units are the mass and radius of Jupiter. They're really big.)

[Borgholio]

They're really big

Yeah no kidding. Some actually fall into the realm of Brown Dwarf Companion instead of planet. Still, you gotta start somewhere. The techniques used to photograph such titanic planets will work just fine with tiny Earths so long as you have a sensitive enough telescope and a bit of patience.

[Guardsman Bass]

Not so sure on the habitability of red dwarf-orbiting planets, either in this solar system or in general. Even the smallest planet in this system is at the 1.5 Earth radius size, which in simulations seems to be the boundary between "rocky planet" and "gas dwarf".

And with red dwarfs, you get the volatility in luminosity and flares, tidal heating and locking, and the star potentially pushing any planets currently in its habitable zone into runaway greenhouse effects during the first billion or so years when it's much brighter than it will eventually be.

[Borgholio]

Well they wouldn't be a paradise like our world that's for certain, but even if tidally locked there would still be a band along the terminator where temperatures could support our kind of life.

[Guardsman Bass]

The locking isn't what really concerns me. If it was just that, then a planet with enough atmosphere and surface water could carry heat around sufficiently enough so that the planet could be habitable. It's the other stuff, especially the early extra young star luminosity and the luminosity changes (as the wikipedia article points out, red dwarf stars can have some pretty dramatic reductions in light in heavy sunspot times).

[Borgholio]

True, but wouldn't those changes diminish as the star aged? A red dwarf can live 10 times as long as our own sun, so that ought to be plenty of time to settle down, stabilize, and warm up the planet enough for some kind of pond scum to evolve.

[Zeropoint]

I can't decide whether it would be more exciting to find an exoplanet with life as we know it, or with life as we don't know it.

[Purple]

I'll take what I can meet in person in my lifetime.

[Bedlam]

I can't decide whether it would be more exciting to find an exoplanet with life as we know it, or with life as we don't know it.

The latter would be very very hard to prove.

[Iroscato]

I have to say, I appreciate all the science articles you keep linking to dragon. They always make for fascinating reading, so thank you