Habitable planet near Earth
US astronomers said Wednesday they have discovered an Earth-sized
planet that they think might be habitable, orbiting a nearby star, and
believe there could be many more planets like it in space.
The planet, found by astronomers at the University of California,
Santa Cruz, and the Carnegie Institution of Washington, is orbiting in
the middle of the "habitable zone" of the red dwarf star Gliese 581,
which means it could have water on its surface.
Liquid water and an atmosphere are necessary for a planet to possibly
sustain life, even it it might not be a great place to live, the
scientists said.
The scientists determined that the planet, which they have called
Gliese 581g, has a mass three to four times that of Earth and an orbital
period of just under 37 days.
Its mass indicates that it is probably a rocky planet and has enough
gravity to hold on to an atmosphere, according to Steven Vogt, professor
of astronomy and astrophysics at the University of California, Santa
Cruz, and one of the leaders of the team that discovered the planet.
If Gliese 581g has a rocky composition similar to Earth’s, its
diameter would be about 1.2 to 1.4 times that of the Earth, the
researchers said. The surface gravity would be about the same or
slightly higher than Earth’s, so that a person could easily walk upright
on the planet, Vogt said. Gliese 581g was discovered by scientists
working on the Lick-Carnegie Exoplanet Survey, during 11 years of
observing the red dwarf star Gliese 581, which is only 20 light years
from Earth.
For astronomers, eleven years of observation is considered a short
time and 20 light years, which is roughly 117.5 trillion miles, rather
close. The sun is around eight and a half light minutes from Earth.
“The fact that we were able to detect this planet so quickly and so
nearby tells us that planets like this must be really common,” said
Vogt.
The planet is tidally locked to its star, meaning that one side is
always facing the star and basking in perpetual daylight, and the other
is in perpetual darkness because it faces away from the star.
With surface temperatures decreasing the further one goes toward the
dark side of the planet and increasing as one goes into the light side,
the most habitable part of the new planet would be the line between
darkness and light, which is known as the “terminator”. The researchers
estimate that the average surface temperature of the planet would be
between -24 and 10 degrees Fahrenheit (-31 to -12 degrees Celsius).
But actual temperatures would range from “blazing hot on the side
facing the star to freezing cold on the dark side,” they said.
The findings, which will be published in the Astrophysical Journal
and posted online at arXiv.org, “offer a very compelling case for a
potentially habitable planet,” said Vogt. AFP
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