Could we live on Proxima b, the latest planet to be found in the habitable zone?
Thursday, 1 September 2016
Q: So we've discovered a planet in the habitable zone. Does this really mean we could live there someday?
A: Dr Nicholas Rattenbury, Department of Physics, University of Auckland says:
The definition of the 'habitable zone' around a star does not suggest necessarily that any planet in the habitable zone will be have all the features that make life on Earth possible.
Apart from being at the right distance from its host star, to have the sort of conditions suitable for surface life such as that we find on Earth, a planet must have an atmosphere, and the nature of that atmosphere is vital.
The planet mustn't be too large or two small. Too large and it would most likely have a thick, dense atmosphere, like gaseous planets Neptune or a Jupiter.
Too small, and it won't have enough mass to hold on to an atmosphere for long enough for life to emerge — Mars in our solar system is smaller than Earth and lost its atmosphere over time, making it impossible for liquid water to remain on the surface.
[T]here hasn't been any detection of an atmosphere on Proxima b.
Proxima b orbits Proxima Centauri – a dwarf star, fainter and dimmer than our own Sun.
[Proxima b] has to orbit close to the star to get the right amount of energy for liquid water to exist.
[T]he planet is likely tidally locked to Proxima Centauri – a situation where the planet presents only one side to the star, that side being forever irradiated by the star with the other side in perpetual night.
Whether or how such a planet could sustain life is uncertain, but as ever, theories exist to make this possible.
Ideally we'd like to see transit observations of the planet – to see if Proxima b passes between us and its host star Proxima Centauri. This would cause a dip in the amount of light we see coming from Proxima Centauri and would give us the radius of the planet.
As it stands, the planet could be even more massive than Jupiter [which could comfortably contain 1300 Earths]. We simply don't know yet.
If we choose to design a space-probe mission to explore other planetary systems, then the Proxima Centauri system no doubt will be top of the list of systems to investigate.