Finally! A Low Mass Super-Earth With Some Funky Atmosphere

Article written: 7 Apr , 2017
Updated: 28 Apr , 2017
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In 2015, astronomers discovered an intriguing extrasolar planet located in a star system some 39 light years from Earth. Despite orbiting very close to its parent star, this “Venus-like” planet – known as GJ 1138b – appeared to still be cool enough to have an atmosphere. In short order, a debate ensued as to what kind of atmosphere it might have, whether it was a “dry Venus” or a “wet Venus”.

And now, thanks to the efforts of an international team of researchers, the existence of an atmosphere has been confirmed around GJ 1138b. In addition to settling the debate about the nature of this planet, it also marks the first time that an atmosphere has been detected around a low-mass Super-Earth. On top of that, GJ 1138b is now the farthest Earth-like planet that is known to have an atmosphere.

Led by John Southworth (of Keele University) and Luigi Mancini (of the University of Rome Tor Vergata), the research team included members from the Max Planck Institute for Astronomy (MPIA), the National Institute for Astrophysics (INAF), the University of Cambridge and Stockholm University. Their study, titled “Detection of the atmosphere of the 1.6 Earth mass exoplanet GJ 1132b“, recently appeared in The Astrophysical Journal.

Artist’s impression of the “Venus-like” exoplanet GJ 1132b. Credit: cfa.harvard.edu

Using the GROND imager on the La Silla Observatory’s 2.2m ESO/MPG telescope, the team monitored GJ 1132b in different wavelengths as it transited in front of its parent star. Given the planet’s orbital period (1.6 days), these transits happen quite often, which presented plenty of opportunities to view it pass in front of its star. In so doing, they monitored the star for slight decreases in its brightness.

As Dr. Southworth explained to Universe via email, these observations confirmed the existence of an atmosphere:

“What we did was to measure the amount of dimming at 7 different wavelengths in optical and near-infrared light. At one of these wavelengths (IR) the planet seemed to be slightly bigger. This indicated that the planet has a large atmosphere around it which allows most of the starlight to pass through, but is opaque at one wavelength.”

The team members from the University of Cambridge and the MPIA then conducted simulations to see what this atmosphere’s composition could be. Ultimately, they concluded that it most likely has a thick atmosphere that is rich in water and/or methane – which contradicted recent theories that the planet had a thin and tenuous atmosphere (i.e. a “dry Venus”).

The ESO’s Paranal Observatory, located in the Atacama Desert of Chile. Credit: ESO

It was also the first time that an atmosphere has been confirmed around a planet that is not significantly greater in size and mass to Earth. In the past, astronomers have detected atmospheres around many other exoplanets. But in these cases, the planets were either gas giants or planets that were many times Earth’s size and mass (aka. “Super-Earths”). GJ 1132b, however, is 1.6 times as massive as Earth, and measures 1.4 Earth radii.

In addition, these findings are a significant step in the search for life beyond our Solar System. At present, astronomers seek to determine the chemical composition of a planet’s atmosphere to determine if it could be habitable. Where the right combination of chemical imbalances exist, the presence of living organisms is seen as a possible cause.

By being able to determine that a planet at lower end of the super-Earth scale has an atmosphere, we are one step closer to being able to determine exoplanet habitability. The detection of an atmosphere-bearing planet around an M-type (red dwarf) star is also good news in and of itself. Low-mass red dwarf stars are the most common star in the galaxy, and recent findings have indicated that they might be our best shot for finding habitable worlds.

Besides detecting several terrestrial planets around red dwarf stars in recent years – including seven around a single star (TRAPPIST-1) – there is also research that suggests that these stars are capable of hosting large numbers of planets. At the same time, there have been concerns about whether red dwarfs are too variable and unstable to support habitable worlds.

Artist’s impression of Kepler-1649b, the “Venus-like” world orbiting an M-class star 219 light-years from Earth. Credit: Danielle Futselaar

As Southworth explained, spotting an atmosphere around a planet that closely orbits a red dwarf could help bolster the case for red dwarf habitability:

“One of the big issues has been that very-low-mass stars typically have strong magnetic fields and thus throw out a lot of X-ray and ultraviolet light. These high-energy photons tend to destroy molecules in atmospheres, and might also evaporate them completely. The fact that we have detected an atmosphere around GJ 1132b means that this kind of planet is indeed capable of retaining an atmosphere for billions of years, even whilst being bombarded by the high-energy photons from their host stars.

In the future, GJ 1132b is expected to be a high-priority target for study with the Hubble Space Telescope, the Very Large Telescope (VLT) at the Paranal Observatory in Chile, and next-generation telescopes like the James Webb Space Telescope (scheduled for launch in 2018). Already, observations are being made, and the results are being eagerly anticipated.

I’m sure I’m not the only one who would like to hear what astronomers discover as they set their sights on this nearby star system and it’s Venus-like world! In the meantime, be sure to check out this video about GJ 1132b, courtesy of MIT news:

Further Reading: Max Planck Institute for Astronomy

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7 Responses

  1. Jim Krug says

    Great article, Matt. You have a really strong ability to take what should be some very complex science, and break it down into ways that regular people can understand.

    I really appreciate your work, even if I do not always comment on it. Keep doing what you’re doing. (And WOW- what a discovery!)

    JIm Krug

  2. danR2 says

    “Due to the commonality of flare ups and particle streams, it would be difficult for any planets orbiting them to retain their atmospheres.”

    It would depend on the existence of any Oort cloud, and perhaps any perturbing large-mass planets sending comets into star-grazing orbits. Given the small distance of GJ 1132b to its sun, there would be a huge supply of water, as the planet would intercept lots of them near their perigees. I’ll await further research on the system as to what they find far from it, as well as near.

    • Member

      You’re saying that the presence of an Oort cloud and giant planets would allow for the atmosphere to be replenished by water-bearing comets? Just to clarify?

      • lauro says

        I’m pretty sure that’s what he meant

      • danR2 says

        Yes. That should read ‘perihelion’, not perigee. I tried to find out more about the star, but apparently things are still pretty preliminary.
        An Oort cloud (or Kuiper belt) would normally be pretty stable against stray comets or other objects making regular forays into or around their sun. Massive bodies would be able to throw some of them into highly elliptical orbits, and given the absurdly close orbit of the planet, they might be intercepted at frequent enough intervals to replenish water—and perhaps nitrogenous compounds—to compensate for what is stripped away from the outer atmosphere by flares.

        I’ll have to look into whether red dwarf systems typically evolve such cloud features at all. If not, then it’s a hopeful sign that this red dwarf and/or its class at least, and perhaps many more, are stable concerning frequency and intensity of flares.

      • danR2 says

        Curiously, I have been not only unable to find research evidence for any ex-solar Oort cloud around any star at all

        http://www.researchgate.net/publication/241580212_Revisiting_the_Search_for_Extrasolar_Oort_Clouds

        but our own ‘Oort’ cloud remains a hypothesis, supported only by indirect evidence

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