After days of keeping us in suspense about a new discovery, NASA let the cat out of the bag, in the early hours of yesterday morning. The TRAPPIST optic robotic telescope, located in Chile, recently identified a dwarf star, about forty light years distant from Earth, that is host to seven planets around about the same size as Earth.
Come on now, you didn’t think NASA was going to announce that an alien civilisation had been found, did you? This is still a significant discovery though.
Particularly as three of the seven bodies orbiting TRAPPIST-1 — the star also takes its name from the Belgian operated telescope — are within its star system’s so-called Goldilocks, or habitable zone. This is an area around a star capable of supporting life, that is neither too hot, nor too cold.
It is this bit that is especially of interest, as it means these planets may harbour water in liquid form, and, as a result, potentially life of some sort. And that is obviously an exciting prospect. But talk that we may one day be able to emigrate there is well wide of the mark, to say the least.
There’s a big difference between a planet that is earth-like, and one exactly like Earth. Such bodies are called an Earth twin, or Earth analog. For example, Proxima b, an exoplanet within the habitable zone around Proxima Centauri, the nearest star to the Sun, is considered to be earth-like, as it is a rocky, or terrestrial planet.
It might have some sort of atmosphere, and possibly there could be liquid water on its surface. But Proxima b may be far from habitable, at least as far as humans are concerned. As Proxima Centauri is a red dwarf star, which are relatively cool, Proxima b would need to be quite close to the star, to be within the habitable zone.
With that sort of proximity however, Proxima b would be tidally locked, meaning the planet’s rotational period matches the time it takes to orbit the star. The result here is only one side of the planet would ever face the star.
Therefore, the day side of Proxima b would be quite warm, whereas the night side would be extremely cold. The only spots that might be conducive to life, would be near the day-night terminator. Red dwarf stars themselves pose problems for any planets they host. For instance, they are prone to emitting powerful flares, which may have the effect of sterilising nearby planets.
Not so earth-like, after all. So while some form of life may manage to eke out an existence there, the environment would hardly be suitable for human occupation. The same conditions could well apply to the planets within the Goldilocks zone of TRAPPIST-1, given it too is a relatively cool dwarf star.
I think we might be waiting a long time indeed for news that a planet as habitable as Earth is found. In the meantime we should give thought to taking greater care of our own Earth. Clearly we’re not going to be rocketing off anywhere else in any hurry.
Originally published Friday 24 February 2017, with subsequent revisions, updates to lapsed URLs, etc.