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A ‘Super Earth’ that’s potentially habitable… and it might even be raining there

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In a
tantalising first, scientists have discovered water on a planet outside our
solar system that has temperatures suitable for life.

Two research
groups announced this week that they have found water vapor in the atmosphere
of a planet 110 light-years away in the constellation Leo.

This
so-called Super Earth is just the right distance from its star to conceivably
harbour life.

It is the
only exoplanet known so far to have both water and temperatures needed for
life, the University College London team reported in the journal Nature
Astronomy on Wednesday. But lead author Angelos Tsiaras stressed: “This is
definitely not a second Earth”.

Its star and
atmosphere are so different than ours, “Earth-like conditions are not
possible,” Tsiaras said.

“The only
question that we’re trying to ask here, and we’re pushing forward, is the
question of habitability.”

A
Canadian-led team announced similar findings Tuesday. In a paper just submitted
to the Astronomical Journal for publication, these scientists suggest
it might even be raining there.

“This
represents the biggest step yet taken toward our ultimate goal of finding life
on other planets, of proving that we are not alone,” the study’s lead
astronomer, Bjorn Benneke of the University of Montreal, said in a statement.

Discovered
in 2015, the planet known as K2-18b is twice the size of Earth with eight times
the mass. While it is thought to be rocky, no one knows if water’s flowing on
the surface.

Its star, a
red dwarf, is considerably smaller and cooler than our sun, a yellow dwarf, and
its atmosphere is also different than ours.

Nonetheless,
Tsiaras said K2-18b could help determine, “Is the Earth unique?”

The results
are doubly exciting, Tsiaras noted, given this is not only the first Super
Earth with water detected in its atmosphere but the planet also resides within
the habitable zone of its star.

The research
teams used archived data from the Hubble Space Telescope and other spacecraft
to analyse the planet’s atmosphere.

Further
observations are needed to determine whether the planet is indeed a true water
world, using next-generation observatories like Nasa’s James Webb Space
Telescope and the European Space Agency’s Ariel, both due to launch in the
2020s.

Future
telescopes on Earth and in space should help uncover more Super Earths orbiting
red dwarf stars – believed to be the most common planets and stars in our Milky
Way galaxy.

Super Earths
are defined as having a mass greater than Earth but less than gas giants like
Uranus and Neptune; more than 1,260 have been confirmed to date.

While water
already has been identified in the atmospheres of hot gas giants circling other
stars, the latest findings represent the first detection of water vapor in the
atmosphere of another type of exoplanet, Tsiaras said.

A Nasa tally
currently lists more than 4,000 confirmed exoplanets and another 4,000
potential candidates.

Most have
been detected using the transit method, where telescopes watch for a slight,
fleeting dimming of a star’s light as a planet passes in the field of view.

For now,
scientists know K2-18b takes 33 days to orbit its star, so one year there is
one month here. At this distance, temperatures range from minus 73 degrees to
47 degrees Celsius.

The star,
glowing red in the day sky, is believed to bombard the planet with radiation
harsh enough to quickly inflict any human visitors with cancer, although “life
there may have evolved differently” in order to survive, noted the London
team’s Ingo Waldmann.

A sister
planet, meanwhile, orbits closer to the star and is likely too hot to be in the
habitable zone.

The cloud
cover isn’t too thick on K2-18b, otherwise it would have obscured the water
vapor in the atmosphere, according to the scientists.

The surface,
meanwhile, could be wet or dry. The London data suggest water vapor makes up
anywhere between 0.01 per cent and 50 per cent of the atmosphere – “quite a big
range,” Waldmann acknowledged.

Either way,
given the planet’s mass, it would be difficult to walk on the surface.

“Maybe not
quite your vacation destination just yet,” Waldmann joked.

source: Reuters

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