NASA’s Planet-Hunting Kepler Telescope

(Source: atomstargazer, via abcstarstuff)

Think Outside the Box to Find Extraterrestrial Life

Our Milky Way galaxy, and the billions of others beyond, is chock-a-block with extra-solar planets, scientists have learned in recent decades. But whether any of them can support life is a far more complex and contentious issue.

Many researchers hold that potentially “habitable” planets have to be rocky and within a limited zone in relation to their central sun—conditions that allow for the continuing presence of liquid water on their surfaces. (See: “Most Earthlike Planets Found Yet: A ‘Breakthrough.’”)

But in a provocative review article published this week in the journal Science, theoretical physicist Sara Seager of the Massachusetts Institute of Technology lays out a case for habitability being potentially more common than generally predicted.

As a pioneer in the study of exoplanet atmospheres, she paints a different picture of what kinds of planets might support life.

“Our basic premise is that to be habitable, a planet has to have liquid water,” Seager said in an interview. “In addition, planets with thin atmospheres are mostly heated by their stars.”

“But what primarily controls surface temperature is the greenhouse effect, what types of gases are in the atmosphere, and how massive a planet’s atmosphere is. That’s what we really have to understand.”

Not Your Usual Planet
With that in mind, Seager describes how large planets ten times farther from their stars than Earth is from the sun could also have liquid water and potentially life if, for instance, they had enough hydrogen gas in their atmospheres.

Hydrogen gas, she said, has a much more powerful greenhouse effect than what’s in our atmosphere. So it could potentially keep a planet’s surface warm with far less radiation from its star.

Relatively dry planets that are close to their suns could also be habitable, Seager said. They need to have less water to create suitable temperatures at their surface because atmospheric moisture is the most effective greenhouse gas of all. (See: “Smallest Exoplanets Found—Each Tinier Than Earth.”)

She described Venus as an example of the dynamic run amok: The close-in planet once had a lot of water, but the presence of so much moisture set off a runaway greenhouse effect that ultimately made the planet unlivable. A drier early Venus, she said, might have evolved into a quite habitable planet.

Planets that aren’t even orbiting stars—the many free-floating planets now known to exist—could support life, she said. They would need heat generated by radioactive or other processes at their cores, as well as the necessary atmospheric gases to keep the warmth in the atmosphere. (See: “‘Orphan Planet’ Spotted, Orbits No Star.”)

“If there is one important lesson from exoplanets,” Seager writes in her Science review, “it is that anything is possible within the laws of physics and chemistry.”

Astronomers have been extraordinarily successful in finding exoplanets in recent years, and have been finding many within what are considered to be classic habitable zones.

Signs of Life
The next step for the researchers is to learn how to identify elements and compounds in the atmospheres that are considered “biosignature gases,” or signs of possible life. This is Seager’s specialty.

On Earth, for instance, the presence of large amounts of atmospheric oxygen is a sure sign of life because it would quickly bond with other elements and disappear if not constantly replenished.

In exoplanet atmospheres other compounds, like ozone and methane, especially in conjunction with oxygen, would be considered signs of possible extraterrestrial life.

James Kasting, an exoplanet expert from Pennsylvania State University, said that Seager’s views on the potential diversity of habitable exoplanets are similar to those held by others in the community. But her emphasis on these planets as targets for future exploration is something of a challenge.

That’s not because of the science involved, but because of long-planned and long-frustrated efforts to have NASA launch an orbiting telescope that could actually image and analyze exoplanet atmospheres.

Eye in the Sky
A past effort to get such an instrument off the ground—called the Terrestrial Planet Finder (TPF)—is extremely unlikely to be funded anytime soon because of its $5 billion-plus price tag.

“The telescope we hope someday will be built has to be designed to look for particular kinds of planets,” Kasting said. “Many of us believe a TPF telescope that looks at planets in more conservatively defined habitable zones is more likely to be successful than those that look for these hydrogen exoplanets or others outside of our best understood areas.”

While a TPF mission is well off in the future, NASA recently approved development of another exoplanet-finding satellite called the Transiting Exoplanet Survey Satellite (TESS).

Scheduled to launch in 2017, TESS will look for exoplanets around 500,000 of the smaller, cooler class M stars that are relatively close to our solar system. In contrast, the Kepler Space Telescope searches for exoplanets in a distant region containing 150,000 stars hundreds of light-years away.

TESS will not be capable of providing significant information about exoplanet atmospheres on its own, but it may be able to do so in conjunction with the James Webb Space Telescope “if we’re lucky,” Seager said. The James Webb Space Telescope is scheduled to go up in 2018.

Seager concludes her journal article by writing that despite obstacles, “the field of exoplanet characterization is on track to understand habitability and to find habitable worlds.”

That doesn’t mean extraterrestrial life necessarily exists, or that any possible future detection will come with 100 percent certainty, she said. But at least we’re getting ever better at looking.

Stay Curious. Watch: Somewhere, Something Incredible Is Waiting To Be Known (Carl Sagan Tribute Series)

Star systems great and small

Upper image: Comparison of blue hypergiant R66 with its disk of dusty material, and our Solar system.

Lower image: The sun-like star 55 Cancri A and 4 members of its planetary system, compared with the brown dwarf Cha 110913-773444 with a hypothetical planetary system (this brown dwarf is known to have a protoplanetary disk).

(Source: invaderxan)

Search Is On for ‘Eyeball Earth’ Alien Planets

Alien worlds resembling giant eyeballs might exist around red dwarf stars, and researchers are now proposing experiments to simulate these distant planets and see how capable they are of supporting life.

Red dwarfs are small, faint stars about one-fifth as massive as the sun and up to 50 times dimmer. They are the most common stars in the galaxy and are thought to make up to 70 percent of the stars in the universe — vast numbers that potentially make them valuable places to look for extraterrestrial life.

Indeed, the latest results from NASA’s Kepler space observatory reveal that at least half of these stars host rocky planets that are half to four times the mass of Earth. [Gallery: A World of Kepler Planets]

Tidally locked ‘eyeball Earths’
When looking for alien life as we know it, scientists typically focus on worlds that have water, since there is life virtually everywhere there is water on Earth. As such, they concentrate on the habitable zone of a star — the area surrounding a star where it is neither too hot nor too cold for liquid water to exist on a planet’s surface.

Since red dwarfs are relatively cool, their habitable zones are often closer than the distance at which Mercury orbits the sun. This makes it relatively easy for astronomers to spot worlds in a red dwarf’s habitable zone — the exoplanets’ orbits are small, meaning they complete them quickly and often, and researchers can in principle readily detect the way these worlds regularly dim the light of these stars.

When a planet orbits a star very closely, the gravitational pull of the star can force the world to become tidally locked with it.

“This means that they always show the same side to their star just as our moon does to the Earth, which means they have one permanent day and one permanent night side,” study lead author Daniel Angerhausen, an astronomer and astrobiologist at Rensselaer Polytechnic Institute, Troy, N.Y., told Astrobiology Magazine.

This scenario of permanent day and permanent light could lead to a striking kind of world — one resembling an eyeball. Its night side would be covered in an icy, frozen shell, while its day side would host a giant ocean of liquid water constantly basking in the warmth of its star. [9 Exoplanets That Could Host Alien Life]

“For me, the eyeballs are just one example of the plethora of crazy things we are finding out there in space,” Angerhausen said. “In the field of exoplanets we find hot Jupiters, highly eccentric planets that light up like comets when they come close in to their host star, or evaporating Mercurys — all of them planets that we don’t have in our solar system and that astronomers did not even dream about 10 or 20 years ago.”

The idea of an eyeball Earth, as such a world is called, was spurred by the detection of an exoplanet called Gliese 581g about 20 light-years away, which may be the first known potentially habitable alien world (although scientists continue to debate whether the planet really exists). Planetary geophysicist Raymond Pierrehumbert of the University of Chicago suggested that if Gliese 581g is real, it could be an eyeball Earth.

“We already have telescopes that detect planets that might be eyeballs,” Angerhausen said.

Given the profound differences between the day and night sides of eyeball Earths, “they are potentially the easiest habitable terrestrial planets to detect and distinguish,” Angerhausen said. However, little is known about precisely how easy they are to detect and how habitable they really are.

“Our proposal will find out how common and stable these eyeballs are,” Angerhausen said.

Modeling eyeball Earths
To learn more about what eyeball Earths might be like, Angerhausen and his colleagues are proposing a project they hope to carry out in Brazil dubbed HABEBEE, short for “Exploring the Habitability of Eyeball-Exo-Earths.” The plan is to for the first time see what a stable eyeball Earth needs to support life.

The scientists first aim to construct a variety of eyeball Earth models that vary in mass, distance from their stars, how much radiation they receive, magnetic field strength and their ice composition and density. By providing general and extreme cases of stable and transient eyeball Earths, they can help predict how well existing and future telescope surveys can detect and characterize them.

An eyeball planet is one of several possible scenarios for planets in a red dwarf’s habitable zone.

“A little bit closer to the star — that is, hotter — they would completely thaw and become water worlds; a little bit further out in the habitable zone — that is, colder — they would become total iceballs just like [Jupiter’s moon] Europa, but with a potential for life under the ice crust,” Angerhausen said. “These planets — water, eyeball or snowball — will most probably be the first habitable planets we will find and be able to characterize remotely. Thats why it is so important to study them now.”

The ocean of an eyeball Earth will likely span a range of temperatures. “It’s probably pretty hot in the center of the eye and then gradually gets colder towards the edge of the ice crust,” Angerhausen said. Still, much remains uncertain — for instance, if the ocean transports heat well, the planet might warm enough all over to turn into a water world without ice, he suggested.

The researchers also plan an expedition to the Antarctic Peninsula to gather specimens of microbes at transition zones between ice and water that might be analogous to oceans on eyeball Earths. The aim is to see what metabolism of life on the alien worlds might be like.

The researchers finally aim to see how well life can survive on eyeball Earths using an existing planetary simulation chamber originally designed to imitate Mars at the Brazilian Astrobiology Laboratory. Antarctic microbe samples can be tested in atmospheric, radiation and other conditions that simulate a number of possible eyeball Earth scenarios. The researchers can test the survival and genetic activity of the microbes to see how well they behave.

“I like the idea of having a few cubic meters of space that mimic another world in a chamber,” Angerhausen said. “It’s like having a probe from a world light years away in a jar.”

Detecting life?
Over the course of their lifetimes, red dwarfs can go from barely to highly active when it comes to dangerous bursts and flares, causing ultraviolet radiation to jump by 100 to 10,000 times normal levels and potentially sterilizing the surface of a nearby planet or even helping to strip off its atmosphere.

To see what harm such radiation might wreak on the habitability of eyeball Earths, the researchers plan to monitor the radiation levels of known red dwarfs over time and investigate previously gathered red dwarf radiation data, knowledge that can help them simulate red dwarfs better.

They also plan on understanding the effects of streams of energetic particles from red dwarfs on the surfaces and atmospheres of eyeball Earths by using the Brazilian National Synchrotron Light Source at Campinas to blast ice with radiation.

“It is not obvious that these planets could be stable for long periods, which we believe is necessary for the origin, maintenance and evolution of life,” said astrobiologist Douglas Galante at the Brazilian Synchrotron Light Source, who organized the Sao Paulo Advanced School of Astrobiology where Angerhausen and his colleagues initiated the HABEBEE proposal.

“Many more studies have to be done, theoretical, experimental and observational, so that we better understand the habitability of these planets,” Galante added.

Upcoming and current telescopes such as NASA’s James Webb Space Telescope might be able to see if planets have eyeball structures. When telescopes improve further, astronomers could look for molecular signs of life on eyeball Earths, researchers said.

“To finally detect life or what we call ‘biomarkers,’ we probably have to wait for next-generation telescopes, such as the 30-meter-class ground-based telescopes that are currently getting built and future space-based platforms such as the Terrestrial Planet Finder,” Angerhausen said. “However, history shows that astronomers are quite creative using current available instruments and telescopes, so maybe one of my colleagues may come up with a new exciting observation strategy that will make it even possible earlier.”

The scientists detailed their findings in the March issue of the journal Astrobiology.

This story was provided by Astrobiology Magazine, a web-based publication sponsored by the NASA astrobiology program.

Kepler Makes Discoveries Inside the Habitable Zone

NASA’s Kepler mission has discovered two new planetary systems that include three super-Earth-size planets in the “habitable zone,” the range of distance from a star where the surface temperature of an orbiting planet might be suitable for liquid water.

The size of Kepler-62f is now measured, but its mass and composition are not. However, based on previous studies of rocky exoplanets similar in size, scientists are able to estimate its mass by association. Scientists do not know whether life could exist on the newfound planets, but their discovery signals we are another step closer to finding a world similar to Earth around a star like our sun.

Duration: 01:06:30

via NASA Television.

(Source: skeptv.net, via skeptv)

Billions of stars. Billions of galaxies. A thousand years just to count all of the stars in our galaxy and then another thousand to count the galaxies in the universe. At TEDYouth 2012, Olivier Guyon examines the possibility of finding other planets within these astronomical numbers, some potentially rife with life.

The Search For Other Earth-like Planets | Olivier Guyon

(Source: youtube.com)

Last Thursday (April 18), Kepler mission scientists announced the discovery of a tantalizing star system named Kepler-62, found with the help of NASA’s exoplanet hunter Kepler. This discovery has prompted a teaming up of Kepler and SETI in the hunt for transmitting extraterrestrials.

At least five worlds are known to be orbiting Kepler-62. Two of the exoplanets, dubbed Kepler-62e and Kepler-62f, are located within the star’s habitable zone with orbital periods of 122 and 267 days, respectively. And it gets even better.

Both planets are very small and may possess rocky surfaces. “e” is 1.6 times the size of Earth and “f” is 1.4 times the size of Earth.

While the 1,200 light-year distance puts a damper on further observations right now, Kepler-62e and f are the smallest worlds detected by Kepler to date that orbit within the habitable zone of their star, allowing liquid water to exist (if it is indeed present), thereby potentially supporting the evolution of life as we know it on their hypothetical rocky surfaces.

That might be all we get to know for now, but Kepler is continuously reducing the uncertainty of hunting for ETIs. As Kepler-62 demonstrates, there are a lot more promising worlds out there to study.

With a Penny4NASA, there’s a chance we can expedite these kinds of discoveries, creating technology to advance the capabilities of Kepler and SETI and learning more than we ever have before.

Read more:
http://astronaut.com/kepler-62-is-a-ripe-seti-target/

(Source: pennyfournasa, via pennyfournasa)

abcstarstuff:

StarStuff episode 624 is now out
Listen to it on the best ABC radio stations across Australia.
On Science 360 Radio in the United States.
On line as audio on demand and as a podcast at:
http://www.abc.net.au/science/starstuff
or as a free download from iTunes

This week’s show…..

Most Earth like planet ever
The most Earth like planet yet discovered has been found by NASA’s Kepler Space Telescope. The discovery is one of two super Earth sized planets, both of which could also be water worlds with global oceans.

Blazar mystery baffles astronomers
Astronomers say they don’t fully understand new data about a distant blazar which appear to be indicating something new about powerful energy jets produced by black holes called quasars. The data comes from a galaxy located half way to the edge of the universe.

Huge ancient stellar factory discovered
The most prolific star factory in the cosmos, a huge starburst galaxy, producing millions of new stars, has been discovered in the early universe. The discovery shows the cosmos already had all the ingredients to produce prodigious amounts of stars when the infant universe was just one-sixteenth of its current age.

First signs of the dark matter particle
Physicists claim they’ve had their first concrete hint of what they believe to be the particle behind dark matter and therefore nearly a quarter of all matter in the universe. Called a “weakly interacting massive particle” or WIMP, it could hold the answer to one of the biggest questions in physics today.

New rocket aces first flight
The Antares rocket, one of two launchers developed with NASA backing to fly cargo to the International Space Station, has blasted off on its first test flight. The Orbital Sciences spacecraft was launched from the new mid-Atlantic commercial spaceport at Wallops Island, Virginia.
.

StarStuff is broadcast weekly on the best ABC Radio stations in Australia,
On the National Science Foundation’s Science 360 Radio across the United States.
As audio on demand and as a free podcast at….
http://www.abc.net.au/science/starstuff

skeptv:

The Hunt For A Second Earth

NASA’s Kepler telescope was launched to find other planets just like earth— and now, scientists think they may have found not just one, but three! Trace shows us where they are in the solar system and why the discovery is so important.

via DNews Channel.

Has Kepler Found Ideal SETI-target Planets?

Mountain View: NASA’s Kepler mission has discovered a new planetary system that is home to five small planets around a slightly smaller star than our Sun. Two of them are super-Earth planets, most likely made of rock or ice mixed with rock, which are located in the habitable zone of their host star. This discovery is providing a target for the SETI search, since if life has thrived on these worlds and reached a point where civilization has developed complex technology, it may be detectable.

When the NASA Kepler mission was launched on March 9, 2007, the Delta II rocket was carrying the hope of a large community of scientists who dedicate their work to studying extra-solar planets, planets in orbit around other stars. The Kepler mission’s main scientific objective is exploration of the structure and diversity of planetary systems. It accomplishes this goal by staring almost constantly at a large field composed of about 150,000 stars to detect small dips in brightness due to the transits of a planet.

Kepler has already been a successful NASA mission with the discovery of 2,740 planet candidates with estimated sizes from Mercury to larger than Jupiter. A fifth of these planet candidates are also called “super-Earths”, a new class of planets, without analog in our solar system, with a radius between 1.25 to 2 times the radius of our planet.

Today, in a scientific article published in Science magazine and through a NASA press conference, the Kepler team announced the discovery of a multiple planet system, composed of 5 Earth-sized and super-Earth planets orbiting a K-type star.

The detection of these planets was indirect since Kepler astronomers observed the attenuation of the host star’s brightness due to the passage of a planet in the line of sight, and not the planets themselves. The authenticity of this multiple planet system was confirmed by a statistical analysis based on previous detections of multiple planets by Kepler.

“By estimating the rate of false-positives due the remote possibility of additional planet-hosting stars in the photometric aperture we have strong confidence that we have discovered two genuine transiting super-Earth planets in the habitable zone of their host star. Such calculations are only possible because of the thousands of additional transiting extrasolar planets that Kepler has discovered” said Jason Rowe, Research Scientist at the Carl Sagan Center of the SETI Institute and co-author of the work

The outermost planet, named Kepler-62f (radius about 1.4 times Earth’s radius and a period of 267 Earth days) is located in the habitable zone of the star, a region around the star where a rocky planet with an atmosphere similar to Earth could host liquid water on its surface. The team expanded the definition of the Habitable Zone by taking into account the evolution of the brightness of the host star. Their calculations suggest that Kepler-62e (radius about 1.6 times Earth’s radius and a period of 122 Earth days) was also in the habitable zone so that liquid water could have existed on its surface, too.

Similar to Venus and Mars that are believed to have lost their surface water 1 billion years and 3.8 billion years ago respectively, before our sun was more luminous, the host star’s habitable zone was broader in the past. The Kepler team’s calculations suggest that Kepler-62e (radius about 1.6 times Earth’s radius and a period of 122 Earth days) is also in the habitable zone so that liquid water could exist on its surface, too.

“These discoveries move us farther down the road to discovering planets similar to Earth. While we don’t know if Kepler-62e and f are rocky or whether they have liquid water pooling on their surfaces, their existence shows that the incidence of small worlds in the habitable zone of sun-like stars is high. Thus we can look forward to the discovery and detailed characterization of Earth’s cousins in the years and decades to come by future missions and telescopes.“ said Jon Jenkins Senior Scientist at the Carl Sagan Center of the SETI Institute and also co-author of the work.

Both Goldilocks planets’ masses remain unknown since they are too small to produce detectable gravitational effects on the host star and between themselves. However, considering a lower upper limit for their mass and the age of the star, estimated to be 7 billion years, the team suggests that both planets are solid and either made of a dry rocky material, like Earth, or a large body of water surrounding a core of iron and rock (a water world).

Kepler discoveries are an amazing opportunity to focus the search for technosignatures conducted at the Center for SETI Research led by Gerry Harp. Kepler provides the detection of exoworlds that could host water on their surfaces and potentially life. Unfortunately, the planets of the Kepler-62 system are too distant (850 light-years from Earth) to be fully characterized, and no direct measurement of their atmospheric composition is possible with current technologies.

“Since December of 2011, the SonATA program to search for extraterrestrial intelligence with the Allen Telescope Array has been focusing on the Kepler exoplanet candidates and especially those planets expected to be within the “Habitable Zone” of their stars. Our surveys improve on previous, generally narrowband SETI by covering the radio frequency range where Earth’s atmosphere is most transparent, including many frequencies never before observed. We expect to complete a meaningful survey of these stars in less than 1 year — be sure to check back soon.” says Gerry Harp, Director of the Center for SETI Research.

image: An artistic view of the system seen from Kepler-62f. The host star is slightly redder than our sun. The smaller exoplanets Kepler-62b (1.3 times Earth’s radius) & Kepler-62c (0.5 times Earth’s radius) are close to the star. Kepler-62d (2 times Earth’s radius) is significantly bigger and closer, Kepler-62e (1.6 times Earth’s radius) & Kepler-62f (1.4 times Earth’s radius) are relatively close to each other and both are sustaining water and rocky surface as suggested by the clouds’ color, water, atmosphere and rocks credit: Danielle Futselaar/SETI Institute

Stay Curious! | About The SETI Institute:

The mission of the SETI Institute is to explore, understand and explain the origin, nature and prevalence of life in the universe. The SETI Institute is a private, nonprofit organization dedicated to scientific research, education and public outreach. Founded in November 1984, the SETI Institute began operations on February 1, 1985. Today it employs over 120 scientists, educators and support staff. Research at the Institute is anchored by three centers. Dr. Gerry Harp is Director of the Center for SETI Research (Dr. Jill Tarter continues as Bernard M. Oliver Chair for SETI). Dr. David Morrison is the Director for the Carl Sagan Center for the Study of Life in the Universe. Edna DeVore leads our Center for Education and Public Outreach.for Education and Public Outreach. SETI Institute website, SETI.org.

jtotheizzoe:

The New York Times has created an interactive feature tallying all of the exoplanets discovered by NASA’s Kepler Telescope. You should really check out the link, because theirs is animated, and much bigger, and completely awesome. 

This comes after news of Kepler’s detection of a new multiplanet system, with not one but two planets in the habitable zone (original research paper). Doesn’t mean that either of them would, could, or should have life, but put a check mark next to criteria #1 for biology.

This brings us to a total of 871 confirmed exoplanets, which is a drop in a drop in a drop in the bucket for how many are estimated to be out there.

Bonus: Find out more about how astrobiologists calculate the odds of extraterrestrial civilizations in this episode of It’s Okay To Be Smart: The Odds of Finding Life and Love.

astronemma:

It’s Time for Next Phase in Search for Alien Life, Scientists Say

With more and more Earth-like alien planets being discovered around the galaxy, humanity should now start planning out the next steps in its hunt for far-flung alien life, researchers say.

On Thursday (April 18), scientists announced the discovery of three more potentially habitable exoplanets — Kepler-62e, Kepler-62f and Kepler-69c — further suggesting that the cosmos is jam-packed with worlds capable of supporting life as we know it.

So the time is right to get the ball rolling beyond mere discovery to the detailed study and characterization of promising alien planets, researchers said — a task that will require new and more powerful instruments. 

“You really want to collect the light from these planets, to figure out — take the data, not just infer —whether or not there’s water, and even signs of life, on these planets,” Lisa Kaltenegger of the Max Planck Institute for Astronomy and the Harvard-Smithsonian Center for Astrophysics, who was part of the team that discovered Kepler-62e and f, said during a press conference Thursday.

As their names suggest, the three newfound planets were discovered by NASA’s prolific Kepler space telescope, which has spotted more than 2,700 potential alien worlds since its March 2009 launch. Just 122 have been confirmed to date, but mission scientists expect more than 90 percent will end up being the real deal.

Read more: [x]

Lisa Kaltenegger | Newly Discovered Exoplanets Kepler-62e and Kepler-62f

Lisa Kaltenegger (Max Planck Institute for Astronomy & Harvard-Smithsonian Center for Astrophysics) on the newly discovered, potentially habitable planets Kepler-62e and Kepler-62f - the best candidates for habitable, earth-like planets we know.

Kepler Team Finds System with Two Potentially Habitable Planets

NOTE: The Kepler spacecraft is able to detect planets that transit or cross the face of their host star. Measuring a transit tells astronomers the size of the planet relative to its star.

image 1: Kepler-62e, in the foreground, is nearer to its star and covered by dense clouds. Closer in orbits a Neptune-size ice giant with another small planet transiting its star. Both habitable-zone planets may be capable of supporting life. credit: David A. Aguilar (CfA)

image 2: Masses and sizes for selected planets. The curves show the mass-radius-relation (average density) for different types of planets: The blue line indicates the loci of planets made mostly (75%) of water, the black line that of planets like our Earth that consist almost exclusively of rock (represented here by the mineral Enstatite, MgSiO3, a member of the pyroxite silicate mineral series that makes up most of the Earth’s mantle), and so on. The measured radii of Kepler-62e and Kepler-62f plus an estimate of their mass places them in a region (blue areas) where it is highly probable for them to be earth-like planets, that is: planets with a solid (if possibly covered in water) surface. Kepler-11f, on the other hand, is a Mini-Neptune, showing clearly that a comparatively low mass does not necessarily make for a solid planet. credit: L. Kaltenegger (MPIA)

image 3: The habitable zone (in which liquid water on a planet’s surface can exist) for different types of stars. The inner planets of our Solar System are shown on top, with Earth and Mars in the habitable zone. Kepler-62 is a notably cooler star, and Kepler-62e and -62f are in its habitable zone. For Kepler-69c, another planet announced today by NASA, the error bars for the star’s radiation are such that it could possibly in the habitable zone as well. Kepler-22b, the smallest planet found in a habitable zone before the recent discoveries, is very likely a Mini-Neptune, and not a solid planet. In what is denoted the empirical habitable zone, liquid water can exist on the surface of a planet if that planet has sufficient cloud cover. In the narrow habitable zone, liquid water can exist on the surface even without the presence of a cloud cover. credit: L. Kaltenegger (MPIA)

image 4: Kepler-62 system. Five planets, two of which are in the Habitable Zone. credit: NASA

The newly discovered planets named Kepler-62e and -f are super-Earths in the habitable zone of a distant sun-like star. The largest planet in the image, Kepler-62f, is farthest from its star and covered by ice. Kepler-62 resides in the constellation Lyra, and is about 1,200 light-years from Earth.

This might be the most exciting exoplanet news yet. An international team of scientists analyzing data from NASA’s Kepler mission has found a planetary system with two small, potentially rocky planets that lie within the habitable zone of their star. The star, Kepler-62, is a bit smaller and cooler than our Sun, and is home to a five-planet system. Two of the worlds, Kepler-62e and Kepler-62f are the smallest exoplanets yet found in a habitable zone, and they might both be covered in water or ice, depending on what kind of atmosphere they might have.

“Imagine looking through a telescope to see another world with life just a few million miles from your own. Or, having the capability to travel between them on a regular basis. I can’t think of a more powerful motivation to become a space-faring society,” said Harvard astronomer Dimitar Sasselov, who is co-author of a new paper describing the discovery.

62e is 1.61 times Earth’s size, circles the star in 122.4 (Earth) days. 62f is 1.4 times the size of Earth, and orbits its star in 267.3 days. Previously, the smallest planet with known radius inside a habitable zone was Kepler-22b, with a radius of 2.4 times that of the Earth.

A third planet in another star system was also announced at a press briefing today. Kepler-69c is 70 percent larger than the size of Earth, and orbits in the habitable zone of a star similar to our Sun. Researchers are uncertain about the composition of Kepler-69c, but astronomer Thomas Barclay from the BAER Institute said its closer orbit of 242 days around a Sun-like star means it is likely more like a super-Venus rather than a super-Earth.

The team says that while the sizes of Kepler 62e and 62f are known, their mass and densities are not. However, every planet found in their size range so far has been rocky, like Earth.

“These planets are unlike anything in our solar system. They have endless oceans,” said lead author Lisa Kaltenegger of the Max Planck Institute for Astronomy and the Harvard Smithsonian Center for Astrophysics. “There may be life there, but could it be technology-based like ours? Life on these worlds would be under water with no easy access to metals, to electricity, or fire for metallurgy. Nonetheless, these worlds will still be beautiful blue planets circling an orange star — and maybe life’s inventiveness to get to a technology stage will surprise us.”

As the warmer of the two worlds, Kepler-62e would have a bit more clouds than Earth according to computer models. More distant Kepler-62f would need the greenhouse effect from plenty of carbon dioxide to warm it enough to host an ocean. Otherwise, it might become an ice-covered snowball.

“Kepler-62e probably has a very cloudy sky and is warm and humid all the way to the polar regions. Kepler-62f would be cooler, but still potentially life-friendly,” said Harvard astronomer and co-author Dimitar Sasselov. “The good news is — the two would exhibit distinctly different colors and make our search for signatures of life easier on such planets in the near future.“

“All of the other interesting planets in the habitable zone were until now discovered by what is known as the radial velocity method,” said Kaltenegger. “This method gives you a lower limit for the planet’s mass, but no information about its radius. This makes it difficult to assess whether or not a planet is rocky, like the Earth. A small radius (less than 2 Earth radii), on the other hand, is a strong indicator that a planet around is indeed rocky – unless we are talking about a planet around a very young star.”

“What makes Kepler-62e and Kepler-62f so exciting is a combination of two factors,” Kaltenegger added. “We know their radius, which indicates that these are indeed rocky planets, and they orbit their star in the habitable zone. That makes them our best candidates for habitable planets out there yet.”

Kaltenegger provides more details on these exoplanets in this video.

Sources: Max Planck Institute for Astronomy, CfA, UniverseToday

ikenbot:

Kepler-62 Has Two Water Worlds Circling in its Habitable Zone

NASA’s Kepler spacecraft has discovered two planets that are the most similar in size to Earth ever found in a star’s habitable zone — the temperate region where water could exist as a liquid.

The finding, reported online today in Science1, demonstrates that Kepler is closing in on its goal of finding a true twin of Earth beyond the Solar System, says theorist Dimitar Sasselov of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, who is a member of the Kepler discovery team.

Both planets orbit the star Kepler-62, which is about two-thirds the size of the Sun and lies about 1,200 light years (368 parsecs) from the Solar System. The outermost planet from the star, Kepler-62f, has a diameter that is 41% larger than Earth’s and takes 267 days to circle its star. The inner planet, Kepler-62e, has a diameter 61% larger than Earth’s and a shorter orbit of 122 days.

Kepler detected the planets by recording the tiny decrease in starlight that occurs when either of them passes in front of their parent star. Astronomers used those measurements to calculate the planets’ relative size compared to that star.

Continue: Worlds Apart