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A Relatively Nearby Earth-Sized Planet

Given my abiding interest in red dwarf stars and the planets that circle them, I always keep an eye on what’s happening with the MEarth project. Two arrays of robotically controlled telescopes are involved in MEarth (pronounced ‘mirth’), one at the Fred Lawrence Whipple Observatory on Mt. Hopkins (AZ), the other a cluster of eight at the Cerro Tololo Inter-American Observatory in Chile. Both these arrays are controlled from MEarth’s offices in Cambridge (MA). MEarth is all about observing nearby M-dwarfs in the hunt for Earth-class planets.

My fascination in these stars is simply a result of the numbers. We’ve learned that M-dwarfs comprise as much as 80 percent of the stars in the Milky Way. Earth is not, in other words, orbiting the most common type of star out there. We also know that M-dwarfs host planets. If we learn that conditions on such worlds can support life, then we’ve dramatically expanded the search space for astrobiology. The prospect of a living world, probably tidally locked to its star, conjures images strange and wonderful, a world where shadows are permanent and half of the planet is an ice-covered waste, as Stephen Baxter recently portrayed in a planet called ‘Per Ardua’ that circles Proxima Centauri in his novel Ultima (Roc, 2015).

The latest news from MEarth comes out of MEarth-South, whose 40-centimeter instruments have detected an interesting light curve around the star GJ 1132, finding a dip of approximately 0.3 percent in the starlight. The signal, confirmed by other instruments in Chile, flags a planet that is roughly 1.2 times the size of the Earth, in a tight 1.6-day orbit. Given the star’s radius and the amount of light it blocks, researchers led by Zachory Berta-Thompson (MIT) calculate this is a planet with about 1.6 times Earth’s mass, a world that may well be rocky.

MIT-GJ1132b-01_0

Image: In this artist’s rendering of GJ 1132b, a rocky exoplanet very similar to Earth in size and mass, circles a red dwarf star. GJ 1132b is relatively cool (about 226 degrees C) and could potentially host an atmosphere. At a distance of only 39 light-years, it will be a prime target for additional study with Hubble and future observatories like the Giant Magellan Telescope. Credit: Dana Berry.

The world is probably tidally locked. And life on GJ 1132b looks to be unlikely, given an estimated average temperature of 500 K (226 degrees Celsius). Says Berta-Thompson:

“The temperature of the planet is about as hot as your oven will go, so it’s like burnt-cookie hot. It’s too hot to be habitable — there’s no way there’s liquid water on the surface. But it is a lot cooler than the other rocky planets that we know of.”

That’s a useful fact because while surface conditions appear inimical to life, the planet is cool enough to retain a substantial atmosphere. GJ 1132 is a mere 39 light years from Earth, making it the closest Earth-sized exoplanet yet discovered. Recently we’ve been discussing the next generation of space telescopes, and now we find a world that will surely be a target for scrutiny, especially by the James Webb Space Telescope, which should be able to analyze the chemical constituents of the planet’s atmosphere and even detect the patterns of its winds.

“If we find this pretty hot planet has managed to hang onto its atmosphere over the billions of years it’s been around, that bodes well for the long-term goal of studying cooler planets that could have life,” adds Berta-Thompson. “We finally have a target to point our telescopes at, and [can] dig much deeper into the workings of a rocky exoplanet, and what makes it tick.”

Berta-Thompson points out that some 500 star systems are known to be closer to us than GJ 1132, and instruments like TESS (Transiting Exoplanet Survey Satellite) and CHEOPS (Characterizing Exoplanets Satellite), both scheduled for launch in 2017, will help us study many more targets. Learning how to analyze the atmospheres of nearby worlds is critical for our investigations into exoplanetary life. Planets like GJ 1132b will be useful in refining our tools as we begin to turn them to worlds with better prospects for living things.

The paper is Berta-Thompson et al., “A rocky planet transiting a nearby low-mass star,” Nature 527 (12 November 2015), 204–207 (abstract).

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Comments on this entry are closed.

  • Alex Tolley November 11, 2015, 14:36

    If the planet is tidally locked, shouldn’t the surface temperatures be very different depending on location? If the planet has retained some sort of atmosphere despite the temperature, doesn’t that mean that either it is being replenished, or that there is a potential cold sink to maintain that atmosphere in a cycle? In this particular case, are we talking about a planet like a tidally locked Venus?

  • Andrew LePage November 11, 2015, 16:42

    The announcement of the discovery of a Venus-like planet, GJ 1132b, “only” 39 light years away has generated a lot of excitement. But this find is just the tip of the iceberg. Based on a statistical analysis of initial finds from NASA’s Kepler mission, it is estimated that there could be 135 billion “Venus analogs” in our galaxy alone. In fact, it is likely that there are more Venus-like worlds than Earth-like worlds out there.

    http://www.drewexmachina.com/2014/09/15/abundance-of-venus-analogs/

  • Dave Moore November 11, 2015, 21:03

    There have been quite a few papers recently speculating on the effect of the stellar wind, stellar flares and the long luminous phase of M stars on Earth mass planets in their habitable zone. Finding whether this planet has an atmosphere, will go a long way to answering some of these questions. It is therefor an important discovery.

    I also wager, you will find similar mass planets in approximately 3.2, 6.4 and 13 day orbits.

  • kamal ali November 11, 2015, 21:24

    Would there be a temperate zone on this planet near the terminator? Also, I believe there were some studies characterizing the parameters under which the atmosphere would not freeze out on the far side. I wonder though whether the temperature even at the terminator may be too hot? There may be a region behind the terminator where the temperature allows liquid water on the surface, but there is no sunlight!

  • Eniac November 11, 2015, 22:21

    … – there’s no way there’s liquid water on the surface

    This strikes me as wrong. According to the phase diagram of water, at 226 degrees Celsius liquid water exists at pressures above 30 bar, which is less than the atmospheric pressure at Venus. So, if it is really 226 degrees Celsius, liquid water is not only possible, but arguably likely, because the greater mass should allow a denser atmosphere and more retained hydrogen than either Earth or Venus.

  • Michael November 12, 2015, 3:17

    I doubt that this world has any water at all as from the diagram you can see that the pre-main sequence stage has a high luminosity for a great length of time.
    https://upload.wikimedia.org/wikipedia/commons/3/39/PMS_evolution_tracks.png

    Not only is there a long higher luminosity stage but high UV as well to break water down, although the gravity of the world is quite high it must have got scorching hot for a length of time. This planet is most likely is a super Venus type world with a hot crushing CO2 atmosphere.

  • Antonio November 12, 2015, 3:36

    CHEOPS is scheduled for launch in 2018, not 2017: http://www.esa.int/spaceinimages/Images/2015/11/Cheops_entering_acoustic_chamber

    Surely there will be rocky planets around nearer M-dwarfs.

  • Harry R Ray November 12, 2015, 10:21

    The really big question should be: Is there an even SMALLER(i.e.,UNDETECTABLE by MEarth) planet transiting Gliese1132 in its habitable zone(from 15 to 30 day orbital periods)? Spitzer observed Gliese1214 for a month and found nothing. Undaunted, the Spitzer team will probably try the same thing here. As far as the atmousphere of Gliese 1132b goes, I predict that Hubble will find a flat spectrum(indicating either thick haze, or a 100% high altitude cloud cover) exactly the same as that of Gliese 1214b.

  • Harry R Ray November 12, 2015, 10:23

    Regarding my above comment; I expect Spitzer to COMPLETE these observations BEFORE TESS is launched!

  • ljk November 13, 2015, 9:33

    THIS news item is rather significant in terms of the chances for life elsewhere:

    http://www.abc.net.au/news/2015-11-13/origin-of-earths-water-found-in-ancient-rocks/6935928

    And a related news item about early Earth and its relation to life elsewhere:

    http://phys.org/news/2015-11-pale-orange-dot-early-earth.html

  • ljk November 13, 2015, 13:19

    Reality always is stranger and more interesting than fiction, especially when it comes to alien planets, which we have only just begun to explore:

    http://www.dailygalaxy.com/my_weblog/2015/11/first-alien-planet-weather-system-discovered-and-mapped-5400-mph-winds.html

  • ljk November 16, 2015, 14:55
  • ljk November 18, 2015, 10:01

    High doses of solar radiation from its red dwarf sun may make this supposedly Earthish planet not so Earthlike:

    http://phys.org/news/2015-11-blasts-earth-like-planet-uninhabitable.html

  • ljk November 18, 2015, 10:32

    With an entire galaxy/Universe presumably at our disposal with all of their incredible potentials, why are we searching for another copy?

    https://aeon.co/opinions/in-space-there-really-might-be-no-place-like-home

    “We take off into the cosmos, ready for anything: for solitude, for hardship, for exhaustion, death. Modesty forbids us to say so, but there are times when we think pretty well of ourselves. And yet, if we examine it more closely, our enthusiasm turns out to be all a sham. We don’t want to conquer the cosmos, we simply want to extend the boundaries of Earth to the frontiers of the cosmos. For us, such and such a planet is as arid as the Sahara, another as frozen as the North Pole, yet another as lush as the Amazon basin. We are humanitarian and chivalrous; we don’t want to enslave other races, we simply want to bequeath them our values and take over their heritage in exchange. We think of ourselves as the Knights of the Holy Contact. This is another lie. We are only seeking Man. We have no need of other worlds. A single world, our own, suffices us; but we can’t accept it for what it is. We are searching for an ideal image of our own world: we go in quest of a planet, a civilization superior to our own but developed on the basis of a prototype of our primeval past. At the same time, there is something inside us which we don’t like to face up to, from which we try to protect ourselves, but which nevertheless remains, since we don’t leave Earth in a state of primal innocence. We arrive here as we are in reality, and when the page is turned and that reality is revealed to us – that part of our reality which we would prefer to pass over in silence – then we don’t like it anymore.”

    ― Stanisław Lem, Solaris

  • Christopher Phoenix November 18, 2015, 22:25

    Fascinating development, Paul, I look forward to seeing what wonderful things we discover when the next generation of space telescopes launch.

    I think I spotted one typo you’ll probably want to correct, though.

    Planets like GJ 1132b will be useful in refining our tools as we begin to turn them to worlds with more condign prospects for living things.

    Condign?

    Amusingly enough, I found that “condign” is an adjective describing a punishment as appropriate or fitting to the crime. Hopefully future space colonists will not find their new homes to be condign.

    Penal space colonies have been featured in a number of science fiction stories, ranging from Jack Vance’s “The Kragen” to the Riddick movies. Sending criminals to live out their lives on harsh colonial planets or exiling incorrigible prisoners to maximum-security prisons located on uninhabitable worlds (making escape almost impossible) mirrors events of our own history. Particularly, the rotting prison ships and exile of prisoners to Australia in the British empire.

    But it seems to me likely that space communities will be less tolerant of criminals than terrestrials, depending on the exact nature of their crimes. Everyone within a fragile space habitat depends on each other. And everyone aboard consumes a fraction of the oxygen, food, and water which must be provided artificially. All the same, where people fly in space, there will be people flying in space who don’t always follow the rules.

    As for sending prisoners to penal colonies around other stars, that isn’t likely to happen until space travel is as routine and cheap as it is in many SF stories. Still makes for good stories, though!

  • Paul Gilster November 19, 2015, 9:42

    Ouch! Can’t believe I misused ‘condign’ that way — now changed in the text. Thanks for spotting the error! I remember the Vance story, by the way. Great writer, Jack Vance.

  • Christopher Phoenix November 19, 2015, 23:06

    Well, “condign” is a new addition to my vocabulary so I can’t hold it against you. Glad I helped out!

    Yes, Jack Vance was a good writer! I’ll have to seek out some more of his stories. I read “The Kragen” in the collection The Great SF Stories: 1964 , along with Norman Spinrad’s “Outward Bound”. I’ve been hunting around to find all the portrayals of slower-than-light starships in early SF, and I find that a lot of stories dealing with STL starships lead on to the invention of FTL, like the lightsails in Cordwainer Smith’s fiction.

    “Outward Bound” is exactly this kind of story, though I personally think the utterly fictitious hyperdrive in the story is much less interesting than the portrayal of nomadic life in a STL trading ship. It’s interesting to think about what our interstellar future might be like if FTL travel turns out to be impossible forever.