NASA's recent discovery of Kepler-186f, the first habitable Earth-sized planet is big news in humankind's long search for extraterrestrial life.
A universe full of exoplanets: Thanks
to the Kepler Space Telescope, which was launched in 2009 to hunt
planets across the universe, we've managed to find around 1800 exoplanets so far, many of which have been discovered in just the last year or so.
Image Credit: NASA
Kepler has
had so much success because it's the first piece of space technology
that is remarkably adept at detecting tiny changes in light coming from
distant stars. The small, periodic dimming of a stars light is the
classic smoking gun which scientists use to find exoplanets.
Image Credit: NASA
The
long-held Holy Grail for planet hunters has been to find a world which
is the Earth's "twin" and therefore thought to be capable of supporting
life.
Kepler has
advanced this cause amazingly so far, managing to find many planets that
are a similar size to our Earth. In fact, thanks to Kepler, we now know
that the Earth-sized planets are actually quite common in our galaxy.
Image Credit: NASA
The bad
news? Most of the Earth-sized planets found so far are either too hot or
too cold to support life. For instance Kepler-20e, the first Earth-sized planet discovered, has an extremely small 6-day orbit, making planet's surface temperature is an inhospitable 1,400 degrees.
Image Credit: NASA
On the other
hand, the Kepler telescope has also discovered many planets within the
"habitable zone" of star systems. This is the region where planets may
be at the correct temperature to support liquid water. However, many of
these planets such as Kepler-22b, thefirst habitable-zone exoplanet discovered,
are several times the size of Earth. Unfortunately, these "Super-Earth"
sized planets are unlikely to be rocky like our home, and are probably
composed of liquid or gaseous outer shells.
Image Credit: NASA
Our first exoplanetary relative: Kepler-186f is the first exoplanet discovered that
is both the right size and distance from its own sun, making it the
best candidate for supporting life so far. That's exciting news.
Image Credit: National Geographic
The size of
Kepler-186f, which is within 10% of Earth's, is particularly
encouraging. Although scientists don't have direct evidence of the
planet's composition, observations and models of other exoplanets
suggest that planets similar in dimensions to the Earth are most likely
to have a rocky composition. This can be seen with similar planets
within our own system such a Venus or Mars.
Image Credit: NASA
We've
actually found exoplanets in habitable zones that are as small as 1.5
times the size of Earth before, but the models predict that the chances
of a rocky planet increase significantly the closer you get to the
Earth's size, making Kepler-186f the most exciting exoplanet discovery
to date.
What's next? Right
size, right distance. Great news, but these characteristics alone don't
guarantee that a planet is habitable. There's other crucial information
that we need before we can be confident in launching future
space-probes on long journeys to strange star systems in search of life.
One of the
most important things that we need to know is what the atmospheres of
exoplanets such as Kepler-186f are composed of. The atmosphere plays a
crucial role in habitability in many ways such as protecting the surface
from solar radiation, and by regulating the planet's temperature. Its
significance can be seen in a planet like Venus, which is a similar size
to Earth and orbits within the habitable zone, but has a
greenhouse-filled atmosphere that renders it far too hot to support
life.
So how can
we find out more about the atmosphere of exoplanets? Well, in 2018 we're
sending an exciting new telescope into space that can do just that.
It's called the James Webb Space Telescope, and its mirrors are an impressive 7 times larger than those of the venerable Hubble Space Telescope.
Image Credit: NASA
The
telescope will help decode planetary atmosphere by observing changes in
light when a planet passes in front of a star. When this happens, the
light changes because certain wavelengths are absorbed by
the chemicals in an exoplanet's atmosphere. The gaps that appear in the
spectra of the star's light are therefore a cosmic fingerprint that can
reveal just what the atmosphere is made of. Because this absorption
effect isn't particularly strong, it will take a powerful telescope
capable of seeing in infrared like the James Webb to observe them.
Image Credit: NASA
So does this
mean that we can confirm that Kepler-186f is actually habitable soon?
Sadly that seems unlikely, even with the James Webb. The Kepler-186
system is 500 light-years from Earth. This means that the light from its
star is too dim to gather the detailed light signatures needed to
decipher further details about the exoplanet.
But we're sending up another piece of high tech space equipment that could help. The Transiting Exoplanet Survey Satellite (TESS)
will be launched in 2017 to conduct an all-sky survey to find
exoplanets in our solar neighborhood. The stars that TESS will scan are
30 to 100 times brighter than those surveyed by the Kepler satellite, so
we'll be able to quickly learn more about an exoplanet's composition
soon after it's first discovered. With its wide-field cameras, TESS will
cover an area of the sky 400 times larger than Kepler.
Image Credit: MIT
Because
Kepler has shown that Earth-sized planets are relatively common, it's
expected that Kepler-186f is just the tip of the iceberg, and we'll soon
find hundreds more similarly sized planets orbiting the habitable zones
of stars. Future space missions will allow us to find out a lot more
about these planets than just their locations, and may even help us to
directly detect the bio-signatures of life, such as the presence of water, oxygen, or even photosynthesis, on other planets.
Image Credit: Harvard
And just like that, our place in the universe may suddenly appear to be little less lonely.
source: http://www.policymic.com/
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