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Seven Earth-sized planets discovered orbiting a nearby star

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An artist’s concept of what it could look like on the surface of one of the exoplanets of TRAPPIST-1.
NASA/JPL-Caltech

Jonti Horner, University of Southern Queensland

An international team of astronomers has found that a nearby star is accompanied by a swarm of at least seven small, rocky worlds. The Conversation

One of the eyecatching claims in the work, published today in Nature, is that in the appropriate circumstances, there is a chance that any (or all) the planets could host the right conditions for liquid water to exist on their surface.

The orbits of several of the planets also appear locked in a delicate dance that could explain how such planetary systems form.

The host of this newly uncovered planetary system is a dim little object called TRAPPIST-1, which lies almost 40 light years from our Sun.

TRAPPIST-1 is so tiny that it only barely counts as a star. It has just 8% of the mass of the Sun and lies right on the boundary between normal stars and brown dwarfs.

TRAPPIST-1 is a tiny ultracool red dwarf, far smaller than the Sun.
ESO

Were this tiny star slightly less massive, it would be too lightweight to fire nuclear fusion in its core, and it would be a failed star.

If TRAPPIST-1 was dropped into our Solar System in the place of the Sun, it would shine in our sky only marginally more brightly than the full Moon. It would be deep red in colour, with a surface temperature of just over 2,200℃.

In this hypothetical scenario, the Solar System would be a lifeless place. Earth’s oceans would freeze, and then our atmosphere would do the same.

To be warm enough to potentially host liquid water, any planets around this dimly glowing ember would have to huddle close and tight.





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