Space & Innovation

New Kepler Mission Cranking Out Exoplanet Finds

The Kepler planet-hunting spacecraft is 'working really well' despite changing its techniques due to mechanical problems.

The Kepler planet-hunting spacecraft is "working really well" despite changing its techniques due to mechanical problems, the lead author of a new study says.

Under a new mission called "K2″, Kepler has found 234 planetary candidates in the first year of searching. That is beyond the expectations of the community, since Kepler cannot point as precisely as it used to due to a reaction wheel (stabilization) problem.

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"The main reason we wrote this paper is that there are way too many planets for us to look at by ourselves," Harvard University's Andrew Vanderburg wrote Discovery News in an e-mail. "We need help from other astronomers to learn all we can about these exciting new planets. So we hope that our paper serves as an invitation to others to start taking a look."

Infographic showing how the K2 mission works. | NASA

Until 2013, Kepler stayed pointed at a spot in the Cygnus constellation, looking for planets passing in front of its stars. That mission appeared to end for good, however, when two of the four reaction wheels on Kepler failed, likely due to age.

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The spacecraft needs a minimum of three reaction wheels to stabilize its position in space. NASA, however, proposed an alternate mission called K2. Simply speaking, Kepler now uses the pressure of the sun to stay stable, but it has to swing its view from time to time to make sure the sun stays out of its viewfinder.

"It turns out that the new method is working almost exactly as well for bright stars as Kepler worked before its malfunction," Vanderburg wrote. "This is not something anyone expected back in 2013 after the mechanical failure. Even the most optimistic estimates of K2′s performance were not that hopeful."

While Kepler isn't finding as many planets today, Vanderburg points out the spacecraft also isn't looking at as many stars. But the stars it is looking at under the new mission tend to be brighter (easier to spot) than the old mission. Bright stars are easier to perform follow-up observations, so this gives an advantage for confirming if the planets spotted are indeed real.

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Among those follow-ups that Vanderburg looked at is the WASP-47 system, which has two gas giant planets orbiting very close to their parent star. The unprecedented "hot Jupiter" find could help astronomers figure out how big planets can live so close to their parent stars, because that's definitely not the case in our own solar system. Another example is WD 1145+017, a white dwarf that may have a planet falling apart nearby due to the star's gravity.

"There are other stars with planets in here that we're observing as well, and hope to study and learn more about in the future," Vanderburg added. "Some particularly exciting research we would like to do is learn about the masses and radii of these planets. This allows us to know what the planets are made of - are they rocky like the Earth, or are they gaseous like Neptune and Jupiter? For some particularly special planets, we might be able to learn about their atmospheres, to find out what gases are present."

The new study is accepted in the Astrophysical Journal Supplement Series and is available in preprint version on Arxiv.

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The Kepler planet-hunting spacecraft is "working really well" despite changing its techniques due to mechanical problems, the lead author of a new study says.

Under a new mission called "K2″, Kepler has found 234 planetary candidates in the first year of searching. That is beyond the expectations of the community, since Kepler cannot point as precisely as it used to due to a reaction wheel (stabilization) problem.

"The main reason we wrote this paper is that there are way too many planets for us to look at by ourselves," Harvard University's Andrew Vanderburg wrote Discovery News inan e-mail. "We need help from other astronomers to learn all we can about these exciting new planets. So we hope that our paper serves as an invitation to others to start taking a look."

Until 2013, Kepler stayed pointed at a spot in the Cygnus constellation, looking for planets passing in front of its stars. That mission appeared to end for good, however, when two of the four reaction wheels on Kepler failed, likely due to age. The spacecraft needs a minimum of three reaction wheels to stabilize its position in space. NASA, however, proposed an alternate mission called K2. Simply speaking, Kepler uses the pressure of the sun to stay stable, but it has to swing its view from time to time to make sure the sun stays out of its viewfinder.

Kepler-452b: The Closest Exoplanet Match to Earth

"It turns out that the new method is working almost exactly as well for bright stars as Kepler worked before its malfunction," Vanderburg wrote. "This is not something anyone expected back in 2013 after the mechanical failure. Even the most optimistic estimates of K2′s performance were not that hopeful."

While Kepler isn't finding as many planets today, Vanderburg points out the spacecraft also isn't looking at as many stars. But the stars it is looking at under the new mission tend to be brighter (easier to spot) than the old mission. Bright stars are easier to perform follow-up observations, so this gives an advantage for confirming if the planets spotted are indeed real.

Among those follow-ups that Vanderburg looked at is the WASP-47 system, which has two gas giant planets orbiting very close to their parent star. The unprecedented "hot Jupiter" find could help astronomers figure out how big planets can live so close to their parent stars, because that's definitely not the case in our own solar system. Another example is WD 1145+017, a white dwarf that may have a planet falling apart nearby due to the star's gravity.

"There are other stars with planets in here that we're observing as well, and hope to study and learn more about in the future," Vanderburg added. "Some particularly exciting research we would like to do is learn about the masses and radii of these planets. This allows us to know what the planets are made of - are they rocky like the Earth, or are they gaseous like Neptune and Jupiter? For some particularly special planets, we might be able to learn about their atmospheres, to find out what gases are present."

The new study is accepted in the Astrophysical Journal Supplement Series and is available in preprint version on Arxiv.

Artist’s impression of WD 1145+017 (white dwarf star, at left) and a planet shedding nearby (center). This is one planetary find by the K2 mission.

Thursday (July 23) was a red letter day for exoplanet astronomers -- it was

the day that marked the announcement of the discovery of Kepler-452b

, an alien world that possesses more Earth-like traits than any exoplanet discovered before it.

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Located around 1,400 light-years away, at first this extrasolar planet may not appear very "Earth-like." For starters, it is approximately 60 percent bigger than Earth and likely 5 times more massive. This means that the surface gravity on Kepler-452b would be twice that of Earth's.

But the world has a 385 day orbit around a very sun-like (G2-class) star, putting it right inside of the habitable zone for that star. Previous exoplanet discoveries have either been too big, too small, or have wide or extremely compact orbits; none have been approximately Earth-sized (and probably rocky) with an orbit within the habitable zone of a sun-like star.

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Shown here are six the small "habitable zone planets" discovered by NASA's Kepler Space Telescope. Each exoplanet orbits their star within the region that allows just the right amount of solar energy to allow water to exist in a liquid state on their surface (assuming they have water and if they even have a "surface"). As you can see, each is wildly different and none are approximately Earth-sized

and

orbit a sun-like star. Kepler-452b, however, ticks all the boxes, making it an intriguing exoplanet for rigorous study.

Kepler-452b has another fascinating characteristic: it's older than Earth. The star it orbits, Kepler-452, is approximately 1.5 billion years older than our sun, indicating that the star system is quite a bit older than our solar system. According to planetary formation theory, planets form soon after their stars are born. This means that Kepler-452b is an older world, likely existing inside its star's habitable zone for 6 billion years.

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If there are life's ingredients* on Kepler-452b's surface, including a bountiful supply of liquid water and a life-supporting atmosphere, life could thrive on this world. Of course, the question of life is pure speculation -- we don't know if there's any water or even an atmosphere -- but it is a tantalizing thought.

*Life "as we know it", in any case.

In this artist's impression, the size of Kepler-452's habitable zone is compared with that of our sun's, with the size of the planet's orbits overlaid. Also, the compact star system surrounding the M-dwarf Kepler-186 is included. As can be seen, the habitable zone surrounding Kepler-186 would fit well within the orbit of Mercury around the sun -- red dwarfs are smaller and cooler than G2-class stars, so their habitable zones will be a lot more compact.

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To date, 1,030 exoplanets have been confirmed by the Kepler mission, but only a dozen less than twice the size of Earth that orbit within their star's habitable zones have been discovered. All of these approximately Earth-sized "habitable" worlds orbit 3 classes of star: G stars (like the sun), K stars and M stars (a.k.a. M-dwarfs).

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G-class stars are hotter and more massive than K-class stars and K-class stars are hotter and larger than M-dwarfs. As the star class becomes cooler, the habitable zone around each shrinks.

Currently, it is not known if Kepler-452b even has a rocky surface -- but planetary models suggest that it should have. If this is the case, the alien world would be a fascinating place, leading Kepler mission scientists to speculate that the exoplanet may have a thick atmosphere and, possibly, active volcanoes. But the big question is whether such a world could host life. Unfortunately we'll have to wait until the next generation of space telescopes to possibly observe Kepler-452b's hypothetical atmosphere. To find life, however, we may never know until we have the ability to send a probe there. Alas, at 1,400 light-years distant, we'll be waiting a long time for that to happen.

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