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Climate analysis checks for most livable exoplanets

TRAPPIST-1 planets
This illustration shows the seven Earth-size planets of TRAPPIST-1, an exoplanet system about 39 light-years away. The image shows the relative sizes of planets b through h, from left to right, but does not represent their orbits to scale. (NASA / JPL-Caltech Illustration)

If you had to pick a place to set up shop amid the seven planets in the TRAPPIST-1 star system, 39 light-years from Earth, the fourth rock from that alien sun is the best place to start.

That Earth-sized world, known as TRAPPIST-1 e, came out on top in a recent round of exoplanetary climate modeling, detailed in a paper published Nov. 1 by the Astrophysical Journal.

Not that anyone’s planning on setting up shop there soon: Unless there’s a breakthrough that allows us to travel at a significant fraction of the speed of light, it would take hundreds of thousands of years to get to TRAPPIST-1. But the climate modeling methods developed for the TRAPPIST-1 system could help scientists decide which planets to target first with telescopes capable of analyzing alien atmospheres.

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Hubble keeps hope alive for alien oceans

Red dwarf planet
This artist’s impression shows how the surface of a planet orbiting a red dwarf star may appear. The planet is in the habitable zone, so liquid water exists. (CFA Illustration / M. Weiss)

Do some of the Earth-sized planets around a dwarf star called TRAPPIST-1, just 40 light-years away, have liquid water? Newly reported findings from the Hubble Space Telescope give astrobiologists continued cause for hope.

The seven TRAPPIST-1 planets created a sensation in February because they’re the biggest assemblage of Earth-scale worlds known to exist in a single planetary system. What’s more, three of the planets – known by the letters e, f and g – are in an orbital region where scientists say water could exist in liquid form.

That’s thought to be a key condition for life as we know it, which is why the region is known as TRAPPIST-1’s “habitable zone.”

But is the water really there? To get at that question, astronomers used Hubble to study the amount of ultraviolet radiation received by the planets, and what that might be doing to their atmospheres.

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Astronomers track TRAPPIST-1’s 7th planet

TRAPPIST-1h planet
An artist’s conception shows the planet TRAPPIST-1h. (NASA / JPL-Caltech)

An international research team led by a University of Washington astronomer has worked out the intricate dance of seven planets circling an ultracool dwarf star known as TRAPPIST-1, nailing down the coordinates of the outermost world in the process.

The astronomers found that all seven exoplanets follow stable orbits thanks to a regular pattern of gravitational interactions, known as orbital resonance. And they determined conclusively that the seventh planet, called TRAPPIST-1h, is too cold for life – although it was could have been warmer in its ancient past.

The calculations, laid out today in the journal Nature Astronomy, will go down as another success story for the planet-hunting process.

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