How Astronomers Will Find Whether Life Can Exist on Proxima b

Tuesday, 30 August 2016 - 5:29PM
Astrobiology
Tuesday, 30 August 2016 - 5:29PM
How Astronomers Will Find Whether Life Can Exist on Proxima b
Last week, astronomers discovered a potentially Earth-like planet orbiting Proxima Centauri, a red dwarf in our closest star system. Considering how little we know about it, the planet is a very promising candidate for life, but there are several pieces of information we need in order to actually determine whether it's habitable. First on the list: whether it has an atmosphere.

The planet, dubbed "Proxima b," is rocky, Earth-sized, and close enough to its comparatively cold star that it could have Earth-like temperatures. However, as a result of its proximity to its star, the planet is exposed to 400 times the number of x-ray fluxes as Earth, which may have wiped out any atmosphere long ago.

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"It is controversial whether or not life can exist in low mass star systems like Proxima Centauri," Harvard astronomer Avi Loeb told Gizmodo. "Some people have argued that such planets cannot have an atmosphere."
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However, there's a chance that volcanic activity could have restored the atmosphere, particularly if that planet has strong, insulating magnetic fields. If that's the case, then observations from the James Webb space telescope might be able to determine whether the planet has an atmosphere, a key requirement for life. According to a new study, the JWST can detect the planet's temperature, which will be essential to making that determination.

Since Proxima b is so close to its star, it is almost certainly tidally locked, meaning that one side permanently faces the sun, creating a "day" side and a "night" side. Loeb and his colleague, Harvard astronomer Laura Kreidberg, determined that the heat from the "day" side would be redistributed to the "night" if there is an atmosphere or ocean. As a result, the JWST can determine whether the planet has an atmosphere by measuring the difference in temperature between the "day" side and "night" side. 

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"The newly detected Earth-mass planet in the habitable zone of Proxima Centauri could potentially host life - if it has an atmosphere that supports surface liquid water," the researchers wrote in their paper, submitted to Astrophysical Journal Letters. "We conclude that JWST observations have the potential to put the first constraints on the possibility of life around the nearest star to the Solar System.
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If the planet is found to have an atmosphere, then we would need to discover what composes it, which the JWST most likely can't detect. For that, we'll need to wait for the Extremely Large Telescope, expected to be unveiled in the 2020s, or perhaps the next advancement in telescope technology.

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"The important thing is that in a couple of years, we should be able to start learning about the atmosphere [of Proxima b]," Loeb said. "If there is one, it's quite likely there'd be a call for a special mission to study just this planet."
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