Kepler ‘K2’ Finds First Exoplanet, A ‘Super-Earth’, While Surfing Sun’s Pressure Wave For Control

Artist's conception of the Kepler Space Telescope. Credit: NASA/JPL-Caltech

It’s alive! NASA’s Kepler space telescope had to stop planet-hunting during Earth’s northern-hemisphere summer 2013 when a second of its four pointing devices (reaction wheels) failed. But using a new technique that takes advantage of the solar wind, Kepler has found its first exoplanet since the K2 mission was publicly proposed in November 2013.

And despite a loss of pointing precision, Kepler’s find was a smaller planet — a super-Earth! It’s likely a water world or a rocky core shrouded in a thick, Neptune-like atmosphere. Called HIP 116454b, it’s 2.5 times the size of Earth and a whopping 12 times the mass. It circles its dwarf star quickly, every 9.1 days, and is about 180 light-years from Earth.

“Like a phoenix rising from the ashes, Kepler has been reborn and is continuing to make discoveries. Even better, the planet it found is ripe for follow-up studies,” stated lead author Andrew Vanderburg of the Harvard-Smithsonian Center for Astrophysics.

Kepler ferrets out exoplanets from their parent stars while watching for transits — when a world passes across the face of its parent sun. This is easiest to find on huge planets that are orbiting dim stars, such as red dwarfs. The smaller the planet and/or brighter the star, the more difficult it is to view the tiny shadow.

Infographic showing how the Kepler space telescope continued searching for planets despite two busted reaction wheels. Credit: NASA Ames/W Stenzel
Infographic showing how the Kepler space telescope continued searching for planets despite two busted reaction wheels. Credit: NASA Ames/W Stenzel

The telescope needs at least three reaction wheels to point consistently in space, which it did for four years, gazing at the Cygnus constellation. (And there’s still a lot of data to come from that mission, including the follow-up to a bonanza where Kepler detected hundreds of new exoplanets using a new technique for multiple-planet systems.)

But now, Kepler needs an extra hand to do so. Without a mechanic handy to send out to telescope’s orbit around the Sun, scientists decided instead to use sunlight pressure as a sort of “virtual” reaction wheel. The K2 mission underwent several tests and was approved budgetarily in May, through 2016.

The drawback is Kepler needs to change positions every 83 days since the Sun eventually gets in the telescope’s viewfinder; also, there are losses in precision compared to the original mission. The benefit is it can also observe objects such as supernovae and star clusters.

Kepler-62f, an exoplanet that is about 40% larger than Earth. It's located about 1,200 light-years from our solar system in the constellation Lyra. Credit: NASA/Ames/JPL-Caltech
Kepler-62f, an exoplanet that is about 40% larger than Earth. It’s located about 1,200 light-years from our solar system in the constellation Lyra. Credit: NASA/Ames/JPL-Caltech

“Due to Kepler’s reduced pointing capabilities, extracting useful data requires sophisticated computer analysis,” CFA added in a statement. “Vanderburg and his colleagues developed specialized software to correct for spacecraft movements, achieving about half the photometric precision of the original Kepler mission.”

That said, the first nine-day test with K2 yielded one planetary transit that was confirmed with measurements of the star’s “wobble” as the planet tugged on it, using the HARPS-North spectrograph on the Telescopio Nazionale Galileo in the Canary Islands. A small Canadian satellite called MOST (Microvariability and Oscillations of STars) also found transits, albeit weakly.

A paper based on the research will appear in the Astrophysical Journal.

Alien Planet’s Clear Weather Could Show Way To ‘Super-Earth’ Atmospheres

Artist's concdption of a Neptune-sized planet with a clear atmosphere, passing across the face of its star. Credit: NASA/JPL-Caltech

In an encouraging find for habitability researchers, astronomers have detected molecules on the smallest planet ever — a Neptune-sized planet about 120 light-years from Earth. The team behind the discovery says this means the dream of understanding the atmospheres on planets even closer to size of Earth is getting closer.

“The work we are doing now is important for future studies of super-Earths and even smaller planets, because we want to be able to pick out in advance the planets with clear atmospheres that will let us detect molecules,” stated co-author Heather Knutson, of the California Institute of Technology.

This particular world is not life-friendly as we understand it, however. Called HAT-P-11b, it’s not only a gas giant but also a planet that orbits extremely close to its star — making one circle every five days. And unusually among planets of its size that were previously probed by astronomers, it appears to have clear skies.

The team examined the world using the Hubble Space Telescope’s Wide Field Camera 3, looking at the planet as it passed across the face of its star. The team compared the signature of elements observed when the planet was in front of the star and when it was not, and discovered telltale signs of water vapor in its atmosphere.

Artist's conception of what the weather may look like on HAT-P-11b, a Neptune-sized exoplanet. The upper atmosphere (right) appears clear while the lower atmosphere may host clouds. Credit: NASA/JPL-Caltech
Artist’s conception of what the weather may look like on HAT-P-11b, a Neptune-sized exoplanet. The upper atmosphere (right) appears clear while the lower atmosphere may host clouds. Credit: NASA/JPL-Caltech

While other planets outside our solar system are known to have water vapor, the ones previously examined are much larger. Jupiter-sized planets are much easier to examine not only because they are larger, but their atmospheres puff up more (making them more visible from Earth.)

To confirm the water vapor was not a false signal from sunspots on the parent star (which also can contain it), the team used the Kepler and Spitzer space telescopes to confirm the information. (Kepler’s single field of view around the constellation Cygnus, which it had been peering at for about four years, happily included the zone where HAT-P-11b was orbiting.) The infrared information from Spitzer and the visible-light data from Kepler both showed the sunspots were too hot for water vapor.

Further, the discovery shows there were no clouds in the way of the observations — a first for planets of that size. The team also hopes that super-Earths could have clear skies, allowing astronomers to analyze their atmospheres.

“When astronomers go observing at night with telescopes, they say ‘clear skies’ to mean good luck,” stated lead author Jonathan Fraine, of the University of Maryland, College Park. “In this case, we found clear skies on a distant planet. That’s lucky for us because it means clouds didn’t block our view of water molecules.”

The research was published in the journal Nature.

Source: NASA

Gliese 15Ab: The Closest Known Super-Earth?

An artist’s rendering of the newly discovered exoplanet OGLE-2013-BLG-0341LBb (far right) orbiting one star (right) of a binary red dwarf star system, from an Earth-type distance of approximately 0.9 Astronomical Units away. Image Credit: Cheongho Han, Chungbuk National University, Republic of Korea

Our solar neighborhood is rich with planetary systems. Within 20 light-years we’ve detected sizzling gas giants and rocky planets orbiting closer to their host star than Mercury orbits the Sun.

Astronomers have now added one more to the list, and this one — a super-Earth dubbed Gliese 15Ab — ranks as one of the closest known exoplanets, circling its host star only 11.7 light-years away.

Gliese 15 is a binary system, with two cool, dim red dwarfs orbiting each other. Although red dwarfs are the most common type of star in the galaxy, they’re so intrinsically faint that not a single one (including the closest star to the Sun, Proxima Centauri) is visible to the naked eye.

Although Gliese 15A might appear faint from Earth, it is overwhelmingly bright compared to its barely reflective exoplanet. So unfortunately we can’t easily see the exoplanet directly. But it does leave an imprint on its host star. Its small gravitational tug makes Gliese 15A wobble ever so slightly as both orbit a mutual center of mass, known as the barycenter.

The star’s movement is then imprinted on its spectrum. As Gliese 15A moves away from the Earth, its spectral lines stretch to redder wavelengths. But as it moves toward the Earth, its spectral lines compress to shorter wavelengths.

Screen Shot 2014-09-08 at 3.52.34 PM
The radial velocities for Gliese 15Ab. Image Credit: Howard et al.

The change is minute. But the Keck 10-meter telescope, with an extremely high-resolution detector, can see such small changes. And from this tiny wobble, Andrew Howard and colleagues calculated that the planet is 5.35 times the mass of Earth and orbits its star in only 11.44 days, making it a hot super-Earth. And remember, it’s only 11.7 light-years away.

A handful of other planet candidates have been found that are closer, but all — including Gliese 15Ab — have yet to be confirmed by other research teams. In the long run, it may turn out that this hot super-Earth is the closest planet to our pale blue dot. Then again, it may not. That’s how science works.

Nonetheless, Gliese 15Ab might prove to be an exciting target for one of the new planet imagers that came online within the past year.

The findings will be published in the Astrophysical Journal and are available online.

‘Vulnerable’ Earth-Like Planets Could Survive With Friction: Study

Flexible planets: NASA is studying how planets in eccentric orbits flex due to tidal forces. At left is a planet with a thick ice shell, and at right a terrestrial-type planet. Credit: NASA's Goddard Space Flight Center

If you’re a potentially habitable world orbiting in a zone where liquid water can exist — and then a rude gas giant planet happens to disturb your orbit — that could make it difficult or impossible for life to survive.

But even in the newly eccentric state, a new study based on simulations shows that the orbit can be made more circular again quite quickly, taking only a few hundred thousand years to accomplish. The key is the tidal forces the parent star exerts on the planet as it moves in its orbit, flexing the interior and slowing the planet down to a circular orbit.

“We found some unexpected good news for planets in vulnerable orbits,” stated Wade Henning, a University of Maryland scientist who led the work and who is working at NASA’s Goddard Space Flight Center in Maryland. “It turns out these planets will often experience just enough friction to move them out of harm’s way and into safer, more-circular orbits more quickly than previously predicted.

The transition period wouldn’t be pretty, since NASA states the planets “would be driven close to the point of melting” or have a “nearly melted layer” on them. The interior could also host magma oceans, depending on how intense the friction is. But a softer planet flexes more easily, allowing it to generate heat, bleed that energy off into space and gradually settle into a circular orbit. When tidal heating ceases, then life could possibly take hold.

This artists' rendition shows a super-Earth, or low mass exoplanet, orbiting close to its parent star. Credit:  Keck Observatory
This artists’ rendition shows a super-Earth, or low mass exoplanet, orbiting close to its parent star. Credit: Keck Observatory

Another possibility is the eccentric orbit itself may be enough to keep life happy, at least for a while. If the planet is colder and stiffer, and orbiting far from its star, it’s possible the tidal flexing would serve as an energy source for life to survive.

Think of a situation like Europa near Jupiter, where some scientists believe the moon could have a subsurface ocean heated by interactions with the gas giant.

The model covers planets that are between the size of Earth and 2.5 times larger, and future studies will aim to see how layers in the planet change over time.

Source: NASA

New Technique Finds Water in Exoplanet Atmospheres

Artist's concept of a hot Jupiter exoplanet orbiting a star similar to tau Boötes (Image used with permission of David Aguilar, Harvard-Smithsonian Center for Astrophysics)

As more and more exoplanets are identified and confirmed by various observational methods, the still-elusive “holy grail” is the discovery of a truly Earthlike world… one of the hallmarks of which is the presence of liquid water. And while it’s true that water has been identified in the thick atmospheres of “hot Jupiter” exoplanets before, a new technique has now been used to spot its spectral signature in yet another giant world outside our solar system — potentially paving the way for even more such discoveries.

Researchers from Caltech, Penn State University, the Naval Research Laboratory, the University of Arizona, and the Harvard-Smithsonian Center for Astrophysics have teamed up in an NSF-funded project to develop a new way to identify the presence of water in exoplanet atmospheres.

Previous methods relied on specific instances such as when the exoplanets — at this point all “hot Jupiters,” gaseous planets that orbit closely to their host stars — were in the process of transiting their stars as viewed from Earth.

This, unfortunately, is not the case for many extrasolar planets… especially ones that were not (or will not be) discovered by the transiting method used by observatories like Kepler.

Watch: Kepler’s Universe: More Planets in Our Galaxy Than Stars

So the researchers turned to another method of detecting exoplanets: radial velocity, or RV. This technique uses visible light to watch the motion of a star for the ever-so-slight wobble created by the gravitational “tug” of an orbiting planet. Doppler shifts in the star’s light indicate motion one way or another, similar to how the Doppler effect raises and lowers the pitch of a car’s horn as it passes by.

The two Keck 10-meter domes atop Mauna Kea. (Rick Peterson/WMKO)
The two Keck 10-meter domes atop Mauna Kea. (Rick Peterson/WMKO)

But instead of using visible wavelengths, the team dove into the infrared spectrum and, using the Near Infrared Echelle Spectrograph (NIRSPEC) at the W. M. Keck Observatory in Hawaii, determined the orbit of the relatively nearby hot Jupiter tau Boötis b… and in the process used its spectroscopy to identify water molecules in its sky.

“The information we get from the spectrograph is like listening to an orchestra performance; you hear all of the music together, but if you listen carefully, you can pick out a trumpet or a violin or a cello, and you know that those instruments are present,” said Alexandra Lockwood, graduate student at Caltech and first author of the study. “With the telescope, you see all of the light together, but the spectrograph allows you to pick out different pieces; like this wavelength of light means that there is sodium, or this one means that there’s water.”

Previous observations of tau Boötis b with the VLT in Chile had identified carbon monoxide as well as cooler high-altitude temperatures in its atmosphere.

Now, with this proven IR RV technique, the atmospheres of exoplanets that don’t happen to cross in front of their stars from our point of view can also be scrutinized for the presence of water, as well as other interesting compounds.

“We now are applying our effective new infrared technique to several other non-transiting planets orbiting stars near the Sun,” said Chad Bender, a research associate in the Penn State Department of Astronomy and Astrophysics and a co-author of the paper. “These planets are much closer to us than the nearest transiting planets, but largely have been ignored by astronomers because directly measuring their atmospheres with previously existing techniques was difficult or impossible.”

Once the next generation of high-powered telescopes are up and running — like the James Webb Space Telescope, slated to launch in 2018 — even smaller and more distant exoplanets can be observed with the IR method… perhaps helping to make the groundbreaking discovery of a planet like ours.

“While the current state of the technique cannot detect earthlike planets around stars like the Sun, with Keck it should soon be possible to study the atmospheres of the so-called ‘super-Earth’ planets being discovered around nearby low-mass stars, many of which do not transit,” said Caltech professor of cosmochemistry and planetary sciences Geoffrey Blake. “Future telescopes such as the James Webb Space Telescope and the Thirty Meter Telescope (TMT) will enable us to examine much cooler planets that are more distant from their host stars and where liquid water is more likely to exist.”

The findings are described in a paper published in the February 24, 2014 online version of The Astrophysical Journal Letters.

Read more in this Caltech news article by Jessica Stoller-Conrad.

Sources: Caltech and EurekAlert press releases.

Super-Earths Could Be More ‘Superhabitable’ Than Planets Like Ours

Artists impression of a Super-Earth, a class of planet that has many times the mass of Earth, but less than a Uranus or Neptune-sized planet. Credit: NASA/Ames/JPL-Caltech

Alien planets that are slightly bigger than Earth could be more life-friendly than exoplanets closer to our own size, a new study implies. These so-called “super-Earths” that are about two to three times that of our own planet could be “superhabitable” — implying that our own planet is a rare bird indeed when it comes to being good for life.

Bigger rocky planets would have a host of advantages, argue McMaster University’s Rene Heller and Weber State University’s John Armstrong in a paper recently published in Astrobiology. Among them: These worlds would have tectonic activity that takes longer to happen, meaning that the conditions would be more stable for life. Also, a bigger mass implies it’s easier to hang on to a thick atmosphere and to have “enhanced magnetic shielding” to hold a planet’s own against solar flares.

“Our argumentation can be understood as a refutation of the Rare Earth hypothesis. Ward and Brownlee (2000) claimed that the emergence of life required an extremely unlikely interplay of conditions on Earth, and they concluded that complex life would be a very unlikely phenomenon in the Universe,” stated the authors in their paper “Superhabitable Worlds.”

Information about Alpha Centauri Bb. Information about Alpha Centauri Bb. Credit: Planetary Habitability Laboratory/University of Puerto Rico/Arecibo
Information about Alpha Centauri Bb. Information about Alpha Centauri Bb. Credit: Planetary Habitability Laboratory/University of Puerto Rico/Arecibo

“While we agree that the occurrence of another truly Earth-like planet is trivially impossible, we hold that this argument does not constrain the emergence of other inhabited planets. We argue here in the opposite direction and claim that Earth could turn out to be a marginally habitable world. In our view, a variety of processes exists that can make environmental conditions on a planet or moon more benign to life than is the case on Earth.”

As a start, the scientists suggest looking at the Alpha Centauri system, where researchers in 2012 discovered a planet close to Earth’s size that is likely not habitable because it orbits so close to its sun.

The star system, however, is about the right age and has low enough radiation to allow life to occur on a planet or moon that “evolved similarly as it did on Earth”, providing the planet or moon “had the chance to collect water from comets and planetesimals beyond the snowline.” Further, it’s just four light-years from Earth, making it a good target for telescopic observations.

You can read more details of their research in Astrobiology or in preprint version on Arxiv.

Super-Earth’s Probable Water Atmosphere Revealed In Blue Light

Artist's conception of GJ 1214 b passing across its host star, as viewed in blue light. Credit: NAOJ

Playing with the filters on a telescope can show us amazing things. In a recent case, Japanese astronomers looked at the star Gilese 1214 in blue light and watched its “super-Earth” planet (Gliese 1214 b, or GJ 1214 b) passing across the surface from the viewpoint of Earth. The result — a probable detection of water in the planet’s atmosphere.

Observations with the Subaru Telescope using a blue filter revealed the atmosphere does not preferentially scatter any light. If the Rayleigh scattering had been observed, this would have shown hydrogen in the atmosphere, researchers said. (On Earth, Rayleigh scattering of the atmosphere makes the sky blue.)

“When combined with the findings of previous observations in other colors, this new observational result implies that GJ 1214 b is likely to have a water-rich atmosphere,” stated the National Astronomical Observatory of Japan.

This finding confirms work performed in 2010 (where scientists concluded the planet was mainly made of water) and adds on to information in 2012, where infrared measurements with the Hubble Space Telescope revealed a possible steamy waterworld under a thick atmosphere.

The planet is an ideal candidate for exoplanet observations because it is relatively close to Earth (40 light years away) and is about 2.7 times the size of our planet, allowing for possible comparisons between the worlds.

Three images showing the relationship between the atmosphere's composition and the transmitted colors of light. Top: Hydrogen-dominated atmospheres see much of the blue light scattered, meaning that transits become more visible in blue  light than red light. Middle: Atmospheres with less hydrogen scatter blue wavelengths more weakly. Bottom: Cloud-covered planets make it more difficult for light to make its way up through the atmosphere, even if it is dominated by hydrogen. Credit: NAOJ
Three images showing the relationship between the atmosphere’s composition and the transmitted colors of light. Top: Hydrogen-dominated atmospheres see much of the blue light scattered, meaning that transits become more visible in blue light than red light. Middle: Atmospheres with less hydrogen scatter blue wavelengths more weakly. Bottom: Cloud-covered planets make it more difficult for light to make its way up through the atmosphere, even if the atmosphere is dominated by hydrogen.
Credit: NAOJ

There’s still some debate over whether “super-Earths” are closer in nature to Earth or to Uranus or Neptune (each about four times Earth’s diameter), requiring scientists to scrutinize that class of exoplanets to learn more about their properties.

One area under investigation is where the super-Earths form. It is believed that planets arise out of a protoplanetary disk, or cloud of gas, ice and debris that surrounds a young star at the beginning of its life. Hydrogen is a big part of this disk, as well as water ice beyond the “snow line“, or the region in a planetary system where waning heat makes it possible for ice to form.

“Findings about where super-Earths have formed and how they have migrated to their current orbits point to the prediction that hydrogen or water vapor is a major atmospheric component of a super-Earth,” NAOJ stated. “If scientists can determine the major atmospheric component of a super-Earth, they can then infer the planet’s birthplace and formation history.”

The team acknowledges it’s still possible there is hydrogen in GJ 1214 b’s atmosphere, but add their findings do corroborate with past ones suggesting water.

Source: NAOJ

Astronomers Find Tantalizing Hints of a Potentially Habitable Exoplanet

Dwarf star HD 40307 is now thought to host at least 6 exoplanet candidates… one of them well within its habitable zone. (G. Anglada/Celestia)

Located 43 light-years away in the southern constellation Pictor, the orange-colored dwarf star HD 40307 has previously been found to hold three “super-Earth” exoplanets in close orbit. Now, a team of researchers poring over data from ESO’s HARPS planet-hunting instrument are suggesting that there are likely at least six super-Earth exoplanets orbiting HD 40307 — with one of them appearing to be tucked neatly into the star’s water-friendly “Goldilocks” zone.

HARPS (High Accuracy Radial velocity Planet Searcher) on ESO’s La Silla 3.6m telescope is a dedicated exoplanet hunter, able to detect the oh-so-slight wobble of a star caused by the gravitational tug of orbiting planets. Led by Mikko Tuomi of the UK’s University of Hertfordshire Centre for Astrophysics Research, a team of researchers reviewed publicly-available data from HARPS and has identified what seems to be three new exoplanets in the HD 40307 systems. The candidates, designated with the letters e, f, and g, all appear to be “super Earth” worlds… but the last one, HD 40307 g, is what’s getting people excited, as the team has calculated it to be orbiting well within the region where liquid water could exist on its surface — this particular star’s habitable zone.

In addition, HD 40307 g is located far enough away from its star to likely not be tidally locked, according to the team’s paper. This means it wouldn’t have one side subject to constant heat and radiation while its other “far side” remains cold and dark, thus avoiding the intense variations in global climate, weather and winds that would come as a result.

“The star HD 40307, is a perfectly quiet old dwarf star, so there is no reason why such a planet could not sustain an Earth-like climate.”
– Guillem Anglada-Escudé, co-author.

“If the signal corresponding to HD 40307 g is a genuine Doppler signal of planetary origin, this candidate planet might be capable of supporting liquid water on its surface according to the current definition of the liquid water habitable zone around a star and is not likely to suffer from tidal locking.” (Tuomi et al.)

If HD 40307 g is indeed confirmed, it may very well get onto the official short list of potentially habitable worlds outside our Solar System — although those others are quite a bit closer to the mass of our own planet.

UPDATE: HD 40307 g has been added to the Planetary Habitability Laboratory’s Habitable Exoplanets Catalog, maintained by the PHL at the University of Puerto Rico at Arecibo. It’s now in 4th place of top exoplanets of interest based on similarity to Earth. According to Professor Abel Mendez Torres of the PHL, “Average temperatures might be near 9°C (48°F) assuming a similar scaled-up terrestrial atmosphere. It might also experience strong seasonal surface temperature shifts between -17° to 52°C (1.4°  to  126°F) due to its orbital eccentricity. Nevertheless, these extremes are tolerable by most complex life, as we know it.” (Read more here.)

While the other planetary candidates in the HD 40307 system are positioned much more closely to the star, with b, c, d, and e within or at the equivalent orbital distance of Mercury, g appears to be in the star’s liquid-water habitable zone, orbiting at 0.6 AU in an approximately 200-day-long orbit. At this distance the estimated 7-Earth-mass exoplanet receives around 62-67% of the radiation that Earth gets from the Sun.

Representation of the liquid water habitable zone around HD 40307 compared to our Solar System (Tuomi et al., from the team’s paper.)

Although news like this is exciting, as we’re always eagerly anticipating the announcement of a true, terrestrial Earthlike world that could be host to life as we know it, it’s important to remember that HD 40307 g is still a candidate — more observations are needed to not only confirm its existence but also to find out exactly what kind of planet it may be.

“A more detailed characterization of this candidate is very unlikely using ground based studies because it is very unlikely [sic] to transit the star, and a direct imaging mission seems the most promising way of learning more about its possible atmosphere and life-hosting capabilities,” the team reports.

Read: How Well Can Astronomers Study Exoplanet Atmospheres?

Still, just finding potential Earth-sized worlds in a system like HD 40307’s is a big deal for planetary scientists. This system is not like ours, yet somewhat similar planets have still formed… that in itself is a clue to what else may be out there.

“The planetary system around HD 40307 has an architecture radically different from that of the solar system… which indicates that a wide variety of formation histories might allow the emergence of roughly Earth-mass objects in the habitable zones of stars.”

The team’s paper will be published in the journal Astronomy & Astrophysics.

Another researcher on the team, Guillem Anglada-Escudé of Germany’s Universität Göttingen, assembled this tour of the HD 40307 system (not including g) via Celestia.

Inset image: current potentially habitable exoplanets. Credit: PHL @ UPR Arecibo.

Exoplanet Gliese 581g Makes the Top 5

Exoplanet Gliese 581g is back, and “officially” ranking #1 on a list of potentially habitable worlds outside of our solar system thanks to new research from the team that originally announced its discovery in 2010.

Orbiting a star 20 light-years away, the super-Earth is now listed alongside other exoplanets Gliese 667Cc, Kepler-22b, HD85512 and Gliese 581d in the University of Puerto Rico at Arecibo’s Habitable Exoplanets Catalog as good places to look for Earthlike environments… and thus the possibility of life.

First announced in September 2010 by a team led by Steven S. Vogt of UC Santa Cruz, the presence of Gliese 581g was immediately challenged by other astronomers whose data didn’t support its existence. Vogt’s team conducted further analysis of the Gliese system in which it appeared that the orbits of the planets were circular, rather than elliptical, and it was in this type of scenario that a strong signal for Gliese 581g once again appeared.

Read: Could Chance For Life on Gliese 581g Actually Be “100%”?

“This signal has a False Alarm Probability of < 4% and is consistent with a planet of minimum mass 2.2M [Earth masses], orbiting squarely in the star’s Habitable Zone at 0.13 AU, where liquid water on planetary surfaces is a distinct possibility” said Vogt.

And, located near the center of its star’s habitable “Goldilocks” zone and receiving about the same relative amount of light as Earth does, Gliese 581 g isn’t just on the list… it’s now considered the best candidate for being an Earthlike world — knocking previous favorite Gliese 667Cc into second place.

Read: Billions of Habitable Worlds Likely in the Milky Way

The announcement was made on the PHL’s press site earlier today by Professor Abel Méndez, Director of the PHL at UPR Arecibo.

Diagram of the Gliese system. The green area is the habitable zone, where liquid water can exist on a planet’s surface. (PHL @ UPR Arecibo)

“The controversy around Gliese 581g will continue and we decided to include it to our main catalog based on the new significant evidence presented, and until more is known about the architecture of this interesting stellar system”

– Prof. Abel Méndez, UPR Arecibo

Goldilocks And The Habitable Zone – The Increased Place In Space

Artist's impression of a planet orbiting red dwarf GJ1214.


It’s referred to as the “Goldilock’s Zone”, but this area in space isn’t meant for sleepy or hungry bears – it’s the relative area in which life can evolve and sustain. This habitable region has some fairly strict parameters, such as certain star types and rigid distance limits, but new research shows it could be considerably larger than estimated.

In a study done by Manoj Joshi and Robert Haberle, the team considered the relationship which occurs between the radiation for red dwarf stars and a possible planet’s reflective qualities. Known as albedo, this ability to “bounce back” light waves has a great deal to do with surface layers, such as ice and snow. Unlike our G-type Sun, the M-class red dwarf is much cooler and produces energy at longer wavelengths. This means a great deal of the radiation is absorbed – rather than reflected – turning the ice and snow into possible liquid water. And, as we know, water is considered to be a primary requirement for life.

“We knew that red dwarfs emit energy at a different wavelength, and we wanted to find out exactly what that might mean for the albedo of planets orbiting these stars.” explained Dr. Joshi from the National Centre for Atmospheric Science, who carried out the research in collaboration with Robert Haberle from the NASA Ames Research Centre.

What makes this theory even more charming is that M-class stars make up a very substantial portion of our galaxy’s total population – meaning there’s even more possible Goldilock’s Zones yet to be discovered. Considering the lifespan of a red dwarf star also increases the chances – as well as the distance a planet would need to be located for these properties to happen.

“M-stars comprise 80% of main-sequence stars, and so their planetary systems provide the best chance for finding habitable planets, i.e.: those with surface liquid water. We have modelled the broadband albedo or reflectivity of water ice and snow for simulated planetary surfaces orbiting two observed red dwarf stars (or M-stars) using spectrally resolved data of the Earth’s cryosphere.” explains Joshi. “In addition, planets with significant ice and snow cover will have significantly higher surface temperatures for a given stellar flux if the spectral variation of cryospheric albedo is considered, which in turn implies that the outer edge of the habitable zone around M-stars may be 10-30% further away from the parent star than previously thought.”

Have we discovered planets around red dwarf stars? The answer is yes. In order to calculate the effects of radiation and albedo, the team chose to use similar M-class stars, Gliese 436 and GJ 1214, and applied it to a simulated planet with an average surface temperature of 200 K. Why that particular temperature? In this circumstance, it’s the temperature at which one bar of carbon-dioxide condenses – a rough indicator of the outer edge of a habitable zone. It is theorized that anything registering below this temperature is too cold to harbor life.

What the team found was high albedo planets register a higher surface temperature when exposed to longer wavelength radiation. This means ice and snow covered planets could exist much further away from a red dwarf parent star – as much as one third more the distance.

“Previous studies haven’t included such detailed calculations of the different albedo effects of ice and snow.” explains Joshi. “But we were a little surprised how big the effect was.”

Original Story Source: Planet Earth OnLine. Further Reading: Suppression of the Water Ice and Snow Albedo Feedback on Planets Orbiting Red Dwarf Stars and the Subsequent Widening of the Habitable Zone.