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by Robby Berman
November 04,
2020
from
BigThink Website
Kepler-186f illustration
Credit: NASA Ames/JPL-Caltech/T. Pyle
A new
study from NASA and the SETI Institute
comes up with an
exciting number
of potentially
life-supporting planets.
-
A
study analyzes data from the Kepler Space Telescope and
the European Space Agency's GAIA survey to estimate the
number of habitable planets.
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There may be 30 such planets in our own galactic
neighborhood.
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The
new estimate may help inform future research and
missions.
Throughout its
nine-year tour of duty that concluded in 2018, NASA's
Kepler Space Telescope produced a massive amount of
observational data.
Scientists are
still going through it all.
Among its revelations were
now-confirmed 2,800 exoplanets, with thousands more still being
analyzed.
A new study of
its data suggests that there may be as many as 300 million
inhabitable planets in our galaxy...
It finds that several of
these could be relatively close by, within 30 light years from
here.
Co-author
Jeff Coughlin stated in a
SETI press release that,
"this is
the first time that all of the pieces have been put together
to provide a reliable measurement of the number of
potentially habitable planets in the galaxy."
(We
previously wrote about a specially designed calculator that
determined there could be exactly
36 contactable civilizations.)
The research (The
Occurrence of Rocky Habitable Zone Planets Around Solar-Like
Stars from Kepler Data), a
collaboration between NASA,
SETI, and other
organizations, was published in The Astronomical Journal.
What the study finds
Illustration of Kepler-7
Credit: SETI
The team that produced the new report was led by Steve Bryson of
NASA's Ames Research Center in California.
The authors of the study
looked for stars that are similar in size, age, and temperature to
our Sun, between 4,527 to 6,027°C.
These stars are
either G dwarfs,
or slightly smaller and more plentiful K dwarfs.
Next, they looked for
planets orbiting such stars that ranged in size from 0.5 to 1.5
times the size of Earth on the assumption that they were most likely
to be rocky planets like ours.
A big factor affecting habitability is the
ability to support
surface water.
Earlier estimates of habitable planets have focused
primarily on an exoplanet's distance from its sun, the so-called
"habitable zone."
The new research also
takes into consideration the amount of light the planet receives
from its sun as a factor in the likelihood of water.
The authors of the study
supplemented the Kepler data with spectroscopic measurements from
the European Space Agency's
GAIA survey of a billion stars in the
Milky Way.
The stars can be dim enough that their habitable zones are close,
causing
any exoplanets there to be tidally locked, which means the
same side always faces their sun.
This makes the stripping
off of their atmospheres more likely.
One of the unknowns is
the degree to which a planet's atmosphere impacts its ability to
retain water, though, and for the current research, the authors
presumed that atmosphere has a minimal effect on the likelihood of
surface water.
Taking all this into consideration, the research,
"estimate with 95%
confidence that, on average, the nearest HZ planet around G and
K dwarfs is ~6 pc away, and there are ~4 HZ rocky planets around
G and K dwarfs within 10 pc of the Sun."
(pc
is the abbreviation for
parsec)
The study offers both a
conservative estimate of the number of habitable exoplanets orbiting
their stars - 0.37 to 0.60 planets per star - and a more optimistic
one: 0.58 to 0.88 per star.
More than half of
galaxy's suitable stars may have habitable planets...
Refining a
search
On a basic level, Coughlin notes, the study means,
"we're one step
closer on the long road to finding out if we're alone in the
cosmos."
The research may also
prove useful in targeting future study and missions.
Says Michelle Kunimoto
of the Transiting Exoplanet Survey Satellite (TESS) group at MIT in
Cambridge, Massachusetts,
"Knowing how common
different kinds of planets are is extremely valuable for the
design of upcoming exoplanet-finding missions."
She adds that,
"surveys aimed at
small, potentially habitable planets around Sun-like stars will
depend on results like these to maximize their chance of
success."
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