Astrophysicists find five-planet system with most Earth-like exoplanet yet

Apr 18, 2013 by Michele Johnson
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-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)

(Phys.org) —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 Kepler-62 system has five planets; 62b, 62c, 62d, 62e and 62f. The Kepler-69 system has two planets; 69b and 69c. Kepler-62e, 62f and 69c are the super-Earth-sized planets.

Two of the newly discovered planets orbit a star smaller and cooler than the sun. Kepler-62f is only 40 percent larger than Earth, making it the exoplanet closest to the size of our planet known in the habitable zone of another star. Kepler-62f is likely to have a rocky composition. Kepler-62e, orbits on the inner edge of the habitable zone and is roughly 60 percent larger than Earth.

The third planet, Kepler-69c, is 70 percent larger than the size of Earth, and orbits in the habitable zone of a star similar to our sun. Astronomers are uncertain about the composition of Kepler-69c, but its orbit of 242 days around a sun-like star resembles that of our neighboring planet Venus.

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.

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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. Credit: NASA

"The Kepler spacecraft has certainly turned out to be a rock star of science," said John Grunsfeld, associate administrator of the Science Mission Directorate at NASA Headquarters in Washington. "The discovery of these rocky planets in the habitable zone brings us a bit closer to finding a place like home. It is only a matter of time before we know if the galaxy is home to a multitude of planets like Earth, or if we are a rarity."

The Kepler space telescope, which simultaneously and continuously measures the brightness of more than 150,000 stars, is NASA's first mission capable of detecting Earth-size planets around stars like our sun. Orbiting its star every 122 days, Kepler-62e was the first of these habitable zone planets identified. Kepler-62f, with an orbital period of 267 days, was later found by Eric Agol, associate professor of astronomy at the University of Washington and co-author of a paper on the discoveries published in the journal Science.

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.

"The detection and confirmation of planets is an enormously collaborative effort of talent and resources, and requires expertise from across the scientific community to produce these tremendous results," said William Borucki, Kepler science principal investigator at NASA's Ames Research Center at Moffett Field, Calif., and lead author of the Kepler-62 system paper in Science. "Kepler has brought a resurgence of astronomical discoveries and we are making excellent progress toward determining if planets like ours are the exception or the rule."

The diagram compares the planets of the inner solar system to Kepler-69, a two-planet system about 2,700 light-years from Earth in the constellation Cygnus. The two planets of Kepler-69 orbit a star that belongs to the same class as our sun, called G-type. Kepler-69c, is 70 percent larger than the size of Earth, and is the smallest yet found to orbit in the habitable zone of a sun-like star. Astronomers are uncertain about the composition of Kepler-69c, but its orbit of 242 days around a sun-like star resembles that of our neighboring planet Venus. The companion planet, Kepler-69b, is just over twice the size of Earth and whizzes around its star once every 13 days. The artistic concepts of the Kepler-69 planets are the result of scientists and artists collaborating to help imagine the appearance of these distant worlds. The Kepler space telescope, which simultaneously and continuously measures the brightness of more than 150,000 stars, is NASA's first mission capable of detecting Earth-size planets around stars like our sun. Credit: NASA Ames/JPL-Caltech

The two habitable zone worlds orbiting Kepler-62 have three companions in orbits closer to their star, two larger than the size of Earth and one about the size of Mars. Kepler-62b, Kepler-62c and Kepler-62d, orbit every five, 12, and 18 days, respectively, making them very hot and inhospitable for life as we know it.

The five planets of the Kepler-62 system orbit a star classified as a K2 dwarf, measuring just two-thirds the size of the sun and only one-fifth as bright. At seven billion years old, the star is somewhat older than the sun. It is about 1,200 light-years from Earth in the constellation Lyra.

A companion to Kepler-69c, known as Kepler-69b, is more than twice the size of Earth and whizzes around its star every 13 days. The Kepler-69 planets' host star belongs to the same class as our sun, called G-type. It is 93 percent the size of the sun and 80 percent as luminous and is located approximately 2,700 light-years from Earth in the constellation Cygnus.

"We only know of one star that hosts a planet with life, the sun. Finding a planet in the habitable zone around a star like our sun is a significant milestone toward finding truly Earth-like planets," said Thomas Barclay, Kepler scientist at the Bay Area Environmental Research Institute in Sonoma, Calif., and lead author of the Kepler-69 system discovery published in the Astrophysical Journal.

The diagram compares the planets of the inner solar system to Kepler-62, a five-planet system about 1,200 light-years from Earth in the constellation Lyra. The five planets of Kepler-62 orbit a star classified as a K2 dwarf, measuring just two thirds the size of the sun and only one fifth as bright. At seven billion years old, the star is somewhat older than the sun. Much like our solar system, Kepler-62 is home to two habitable zone worlds, Kepler-62f and Kepler-62e. Kepler-62f orbits every 267 days and is only 40 percent larger than Earth, making it the smallest exoplanet known in the habitable zone of another star. The other habitable zone planet, Kepler-62e, orbits every 122 days and is roughly 60 percent larger than Earth. The size of Kepler-62f is known, but its mass and composition are not. However, based on previous exoplanet discoveries of similar size that are rocky, scientists are able to determine its mass by association. The two habitable zone worlds orbiting Kepler-62 have three interior companions, two larger than the size of Earth and one about the size of Mars. Kepler-62b, Kepler-62c and Kepler-62d, orbit every five, 12, and 18 days, respectively, making them very hot and inhospitable for life as we know it. The artistic concepts of the Kepler-62 planets are the result of scientists and artists collaborating to help imagine the appearance of these distant worlds. The Kepler space telescope, which simultaneously and continuously measures the brightness of more than 150,000 stars, is NASA's first mission capable of detecting Earth-size planets around stars like our sun. Credit: NASA Ames/JPL-Caltech

When a planet candidate transits, or passes in front of the star from the spacecraft's vantage point, a percentage of light from the star is blocked. The resulting dip in the brightness of the starlight reveals the transiting planet's size relative to its star. Using the transit method, Kepler has detected 2,740 candidates. Using various analysis techniques, ground telescopes and other space assets, 122 planets have been confirmed.

Early in the mission, the Kepler telescope primarily found large, gaseous giants in very close orbits of their stars. Known as "hot Jupiters," these are easier to detect due to their size and very short orbital periods. Earth would take three years to accomplish the three transits required to be accepted as a planet candidate. As Kepler continues to observe, transit signals of habitable zone planets the size of Earth orbiting stars like the sun will begin to emerge.

Ames is responsible for Kepler's ground system development, mission operations, and science data analysis. NASA's Jet Propulsion Laboratory in Pasadena, Calif., managed Kepler mission development.

Astrophysicists find five-planet system with most Earth-like exoplanet yet
This artist's conception depicts Kepler-62e, a super-Earth-size planet in the habitable zone of a star smaller and cooler than the sun, located about 1,200 light-years from Earth in the constellation Lyra. Kepler-62e orbits it's host star every 122 days and is roughly 60 percent larger than Earth in size. Scientists do not know if Kepler-62e is a waterworld or if it has a solid surface, but its discovery signals another step closer to finding a world similar to Earth. Credit: NASA/Ames/JPL-Caltech

Ball Aerospace & Technologies Corp. in Boulder, Colo., developed the Kepler flight system and supports mission operations with the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder.

The Space Telescope Science Institute in Baltimore archives, hosts and distributes Kepler science data. Kepler is NASA's 10th Discovery Mission and was funded by the agency's Science Mission Directorate.

Explore further: Continents may be a key feature of Super-Earths

More information: "Kepler-62: A Five-Planet System with Planets of 1.4 and 1.6 Earth Radii in the Habitable Zone," by W.J. Borucki et al., Science, 2013. www.sciencemag.org/content/early/2013/04/17/science.1234702.abstract

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Czcibor
1.6 / 5 (7) Apr 18, 2013
Wow!

By occasion: "sun like star" and on 267.3 days orbit receives half of solar radiation... Shouldn't it be rather "much dimmer than Sun"?
thales
1 / 5 (5) Apr 18, 2013
That's amazing! Give it 5 years before there's a movie or TV show along the lines of a Star Trek/Seaquest hybrid.
Lurker2358
3 / 5 (12) Apr 18, 2013
While the sizes of Kepler 62e and 62f are known, Agol said, their mass and densities are not—but every planet found in their size range so far has been rocky, like Earth.


Ok, so assuming it has at least some rock, it should have a magnetic field, though it would be slightly colder than Mars, depending on GHG presence. I assume it's not in any sort of runaway situation, nor is it a hybrid, since they claimed it wasn't like Neptune.

I'm guessing rocky/metal core, water-ice covered, with possible sub-surface lakes.

For example: If it has the average density of water, it's mass would be 2.97e24kg, and it's surface gravity would be, 2.49m/s^2.

If it has the average density of granite, it's mass and surface gravity would be about 3 times that, at about 7.5m/s^2.

If it had Earth-like density the surface gravity would be 13.84m/s^s.

Slightly cold is also better than too hot. You can always make a fire.

I think this is a keeper, though atmosphere is all-important.
210
1 / 5 (8) Apr 18, 2013
While the sizes of Kepler 62e and 62f are known, Agol said, their mass and densities are not—but every planet found in their size range so far has been rocky, like Earth.


Ok, so assuming it has at least some rock, it should have a magnetic field, though it would be slightly colder than Mars, depending on GHG presence..

Definite solar winds, so, it needs an ELECTROmagnetic field and to have that, its needs a sizeable, hot, metal-liquid core, either inner or outer part of the core. Then its genesis become an issue. Earth was made molten by bombardment and we have a great number of 'fragments' left and Jupiter shepherding our continued existence. What protects them and how was their hot core made. AND, no moon...we gain GREAT advantage with having a moon and also having liquid water. MASS, the gravity, we may need MANY generations to get used to it and any life that is used to it would swim right through a persons and not know it hit anything. Oh, bubba, NO GUNS!
word-
210
1 / 5 (6) Apr 18, 2013
Wow!

By occasion: "sun like star" and on 267.3 days orbit receives half of solar radiation... Shouldn't it be rather "much dimmer than Sun"?

Change of chronological reference yes, exposure, no. But I see what you meant to indicate.
Ducklet
1.8 / 5 (10) Apr 18, 2013
It's interesting that Kepler-62 is 7 billion years old, so these planets have had ample time to develop advanced life. In fact, it's 2 billion years older than the Sun, so one can assume the planets are significantly older as well. And if complexity doubles every ~350 million years...
Thadieus
1 / 5 (5) Apr 18, 2013
I believe Planet 62B is really the Planet Melkot. The Melkotian home world. I believe we better proceed with caution! Yellow Alert!
Sonhouse
3.6 / 5 (5) Apr 19, 2013
It's interesting that Kepler-62 is 7 billion years old, so these planets have had ample time to develop advanced life. In fact, it's 2 billion years older than the Sun, so one can assume the planets are significantly older as well. And if complexity doubles every ~350 million years...

It also could be the case that any techno civilization is long gone also. Where will life on Earth be in 3 billion years? Probably fried because our sun is due to run out of hydrogen before then.
SHREEKANT
1 / 5 (9) Apr 19, 2013
I THINK SUPER NOVA, TIME OF FORMATION OF PLANETS, PRESENCE OF ELEMENT IN SUPERNOVA REMNANT, PRESS. & TEMP. AT THE POINT OF PLANET FORMATION, REVOLUTION & ROTATION PERIOD OF THE PLANETS ETC. ARE MORE IMPORTANT THAN MERE SIZE OF SOURCE & PLANET for HABITABLE ZONE
visual
1.4 / 5 (5) Apr 19, 2013
Are these planets detected only because they happen to transit their stars?
There are so many that we detected already... and to think that there might be thousands of times more which are not seen only because they are not aligned just right... wow.
They are definitely much more common than I personally imagined.
Fleetfoot
4.5 / 5 (6) Apr 19, 2013
I THINK ...


If you thought more, people might find your posts interesting enough to read and you wouldn't need to shout.
Fleetfoot
5 / 5 (4) Apr 19, 2013
Are these planets detected only because they happen to transit their stars?
There are so many that we detected already... and to think that there might be thousands of times more which are not seen only because they are not aligned just right... wow.
They are definitely much more common than I personally imagined.


Yes. Based on that argument, current estimates suggest almost every star has planets though binary stars probably have fewer.
antialias_physorg
3.7 / 5 (9) Apr 19, 2013
I would just like for them to stop saying 'Earth-like' planets. It conjurs up all kinds of -unwarranted - assumptions. Especially if the term Earth-like is reused in the article in an entirley different meaning than in the heading.

Ok, so assuming it has at least some rock, it should have a magnetic field

Why would you imagine that? Where's the connection between 'rocky' and 'magnetic field'?
E.g. Mars is rocky and has no mangetic field to speak of (roughly 1/800th the strength of that of Earth and very unevenly distributed). Mercury is also rocky and has a megnetic field of only about 1% the strength of that of Earth

Are these planets detected only because they happen to transit their stars?

There's various ways to detect planets (based on their mass, the mass of their star and their distance to said star or each other) besides a direct transit.
Requiem
2.3 / 5 (6) Apr 19, 2013
Isn't it generally accepted that differentiation and a molten core is the result of radioactive decay of elements within the planet and pressure forces(in lieu of a tidal force situation like Io)?

So Mars and Mercury don't have strong magnetic fields with respect to their mass anymore because they are smaller than the Earth and their cores solidified faster. By extension, something of roughly equal composition to the Earth but larger would be likely to have a magnetic field that lasts longer than Earth's will. Maybe atmospheric insulation plays a major roll in the rate at which energy escapes the system, but I doubt it.
Requiem
1.8 / 5 (5) Apr 19, 2013
(at least on the Earth+ scale)
dogbert
2.3 / 5 (9) Apr 19, 2013
antialias_physorg,
I would just like for them to stop saying 'Earth-like' planets. It conjurs up all kinds of -unwarranted - assumptions.


So would I. Almost every new planet discovery is heralded with the comment "earth like!" when there is no data to indicate that the discovered planet is at all like the earth.
QuixoteJ
2.1 / 5 (7) Apr 19, 2013
Great news! I just wish all the extrasolar planetary discoveries were more mainstream news. The rate at which these things are being discovered is unprecedented! The new estimations of the number of planets out there indicate that planets may be the rule and not the exception... this is an amazing time, and it isn't getting enough mainstream media recongnition.
SleepTech
5 / 5 (1) Apr 19, 2013
antialias_physorg,
I would just like for them to stop saying 'Earth-like' planets. It conjurs up all kinds of -unwarranted - assumptions.


So would I. Almost every new planet discovery is heralded with the comment "earth like!" when there is no data to indicate that the discovered planet is at all like the earth.


I agree. One of the main reasons I became a regular to this site was that, when planets were first being discovered by Kepler, physorg called them "exoplanets" instead of "ALIEN PLANETS!"
Modernmystic
2.5 / 5 (8) Apr 19, 2013
It's nice that the Kepler is finding planets that are possibly more significantly "Earth like" than ever before...but we won't see an "Earth like" planet until we get a lot better resolutions, are able to take reliable spectrographs of the atmospheres etc etc...

Wasn't the terrestrial planet finder supposed to be able to do all of this?
Q-Star
1.7 / 5 (6) Apr 19, 2013
It's nice that the Kepler is finding planets that are possibly more significantly "Earth like" than ever before...but we won't see an "Earth like" planet until we get a lot better resolutions, are able to take reliable spectrographs of the atmospheres etc etc...

Wasn't the terrestrial planet finder supposed to be able to do all of this?


Yes, and shamefully both the TPF and LIS telescopes have suffered from the endless budget wrangling in Washington. (Ditto the the JWST which should have already been in service.)
Lurker2358
1 / 5 (6) Apr 19, 2013
Why would you imagine that? Where's the connection between 'rocky' and 'magnetic field'?
E.g. Mars is rocky and has no mangetic field to speak of (roughly 1/800th the strength of that of Earth and very unevenly distributed). Mercury is also rocky and has a megnetic field of only about 1% the strength of that of Earth


Mars and Mercury are a fraction of the mass of the Earth. Mars clearly had a magnetic field in the past, but when the internal heat dissipated it's field eventually died. That's the prevailing theory found in encyclopedias and documentary anyway.

A planet with more than one Earth mass should be well differentiated, even if it's abnormally low in rock. The metal should have melted out of the rock and concentrated in the core, and this would provide a dynamo for magnetic field.

With other telescopes, scientists may be able to use the wobble method to confirm and to estimate the masses of the planets in the system. This would give 2 lines of evidence anyway...
Lurker2358
1 / 5 (6) Apr 19, 2013
Anyway, A_P, if you have more mass (which can't be verified at the moment, but I can't imagine a realitistic planet could 1.4 Earth radii without at least 1 Earth mass,) then you would have more GPE from during accretion, therefore more initial heat. Also, you would presumably have more radioactive material to produce continued warming and melting in the interior. This is why a 1.4 E. radii planet should have a strong magnetic field. At least that should be true, if we're assuming it's not made of something silly, like pure water.

If it was made of the same exact stuff as Earth, in the exact same ratios, then it should be about 2.744 Earth Masses, and should be covered entirely with water and water-ice, except possibly the tallest mountains, since the oceans should be 40% deeper on average.

Of course, those are assumptions. For all we know, at this point, it could have anywhere from 0 to a couple hundred Earth atmospheres.
Lurker2358
1.4 / 5 (9) Apr 19, 2013
I laugh at how people thing we are just going to easily find some habitable planet around another star, but the same people throw a big fit over a few PPM change in CO2 concentration in Earth atmosphere.

If things really do need to be that fine tuned to find Earth-like life, or to support a decent Earth colony, then you guys may as well stop looking now. You'll never find it.
Gawad
5 / 5 (6) Apr 19, 2013
This is why a 1.4 E. radii planet should have a strong magnetic field.

Ehhhh....It's still really very, very speculative. Right now the only "Earth-like" planet to have a strong magnetic field that we know of is, well, Earth. The planet that is the most Earth-like in terms of raw specs that we know of is Venus, to within a tenth of mass, diameter and gravity (give or take a stone or two) and it has none. In fact, it turns out to be Earth's "evil twin". So it dosen't take that much to throw things off completely. Venus' magnetic fields is a perfect example.

It's theorized that Venus lost its magnetic field a few million years after it lost its water to exessive solar heating. This stopped plate tectonics, which resulted in a homoginization of the tempurature in the mantle and therefore an end to convection. At which point what field(s) there would have been (dispite the planet's lack of rotation) collapsed completely. So even based on "Earth Twins" its a 50-50 sample at best.
GSwift7
3 / 5 (8) Apr 19, 2013
If it was made of the same exact stuff as Earth, in the exact same ratios, then it should be about 2.744 Earth Masses, and should be covered entirely with water and water-ice, except possibly the tallest mountains, since the oceans should be 40% deeper on average


That's all reasonable, but I think you're making a few assumptions. You seem to be implying that plate tectonics are a common feature, for one.
Lurker2358
1 / 5 (6) Apr 20, 2013
Gawad:

Good points. Mass and Size aren't enough to tell us about the magnetic field or lack, after all.

We'll need a team to study this system using the wobble method to figure out what the mass is, but I figure that will take at least 2 or 3 orbits of the 62f in order to sort out it's signature from the other planets, particularly since 62e is actually closer to the star and more massive.

We'll also need spectrometry to figure out what is the composition of the atmosphere. At least if you can get the mass to within a decent margin, get the size to a good margin, and at least figure out the top 1 or 2 atmosphere components, then we'll have a much better idea of what types of theory crafting to do. that will answer questions like, "terrestrial with thick/thin atmosphere?" or "failed gas giant?" and "Is the atmosphere CO2, CH4, or SO2, or N2, or H2, or H2O, etc?" and so on.

Obviously composition totally changes the way we would conceive of the planet.
xel3241
4 / 5 (1) Apr 20, 2013
Lurker, the problem is that we're increasing the amount of CO2 faster than the Earth can deal with it. The current CO2 increase played out over millions of years would have little to no harmful effect on life's development, but the current playout over 200 years certainly will. Certainly extraterrestrial life and intelligence are more common than you believe.

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