We now have a brand-new exoplanet to investigate someday in search of
possible life.
Astronomers have discovered a very uncommon Earth-sized world that is only
31 light-years away and is circling its star at a distance that should
support life as we know it. If the exoplanet itself possesses the ideal
circumstances for the development of life, that is.
Although we don't now have access to that information, the planet Earth
stands out as a viable option for a future search for biosignatures on
neighboring, Earth-mass exoplanets.
The constraints of our existing technology hinder the hunt for exoplanets,
or extrasolar planets, or those outside of our Solar System. Without a
doubt, such technology is incredible, but our main methods for locating
exoplanets are much more effective at locating huge planets than small
ones.
They rely on indirect signals, or the influence an exoplanet has on its
host star, which is why. The radial velocity method detects minute changes
in light wavelength as the star is very, very slightly moved around on the
spot by the gravitational interaction with the exoplanet, while the transit
method detects the very faint, regular dips in starlight as an exoplanet
orbits between us and its star.
Therefore, while there are more than 5,200 verified exoplanets as of this
writing, less than 1.5% of them have masses that are less than two
Earths.
And of those, only a dozen are circling their stars at a distance where
temperatures are suitable for liquid water to exist on the surface without
being too hot or too cold.
The first stage in determining whether or not a world is livable for life
is determining where it is located within this so-called habitable zone. And
it is this that a group of astronomers from the Max Planck Institute for
Astronomy (MPIA) in Germany, under the direction of Diana Kossakowski, have
found in the neighborhood of the red dwarf star Wolf 1069.
Wolf 1069b is the name of the recently found exoplanet, which has a mass
1.36 times that of Earth.
"We found a distinct, low-amplitude signal of what looks to be a planet of
about Earth mass when we evaluated the data of the star Wolf 1069,"
Kossakowski said.
It travels one-fifteenth of the distance between the Earth and the Sun
every 15.6 days as it circles the star.
Wolf 1069 is a red dwarf, which is much smaller and colder than the Sun. If
Wolf 1069 were a star like the Sun, that would unquestionably be too hot for
habitability. This indicates that their habitable zones are far
closer to the star
than the
habitable zone
of our Solar System, which only
stretches from Venus to Mars.
Despite being 15 times further from its star than Earth is from the Sun,
Wolf 1069b only receives around 65% of the radiation that Earth does from
the Sun.
A Wolf 1069b that is barren and stony, comparable to Mercury, should be
roughly -23 degrees Celsius at this altitude (-9.4 degrees Fahrenheit).
That's far too cold for liquid water, yet water would vaporize even in the
absence of an atmosphere.
Obviously, there is a lot more to habitability than simply being close
enough to a star.
It would need to be a good, thick atmosphere in order to trap heat and
raise the average temperature. The average temperature of Mars, which
possesses an atmosphere, is
-65 degrees Celsius.
In addition, the atmosphere of the red planet is quite thin, which is
assumed to be a result of the absence of Earth's protective global magnetic
field. (Venus doesn't produce a magnetic field internally either; instead,
it interacts with the solar wind to
produce an exterior one.
It has to do with Venus.
Rotating, convecting, and conducting fluids within the planet's core
produce a magnetic field by converting kinetic energy into magnetic energy.
This phenomenon is known as an internally generated global magnetic field.
Additionally, Wolf 1069b could possess one of these.
According to astronomer Remo Burn
of the MPIA, "our computer models reveal that roughly 5% of all emerging
planetary systems around low-mass stars, such as Wolf 1069, end up with a
single observable planet."
The models also show a period of violent interactions with planetary
embryos that occasionally result in catastrophic collisions when the
planetary system is being built.
These interactions would heat the young planet, indicating that Wolf
1069b's core is still molten, just like the core of the Earth, and may
therefore be producing a magnetic field.
Just one more issue remains. You know how the Moon always faces the same
direction toward Earth? When a body is in tight orbit with a more massive
one, gravitational "brakes" are applied to slow down its spin. This is known
as tidal locking.
The majority of potentially habitable red dwarf exoplanets are tidally
locked because the habitable zone of red dwarf stars is so close to the
star. Accordingly, one side is always in the daytime while the other is
always in the night.
However, not all is lost. According to research, such worlds can still
support life, especially in the vicinity of the terminator—the boundary
between day and night. However, a computed temperature map of Wolf 1069b
indicates that the area directly facing the star is most likely to contain
liquid water.
We will, regrettably, have to wait to learn more: Since Wolf 1069b doesn't
pass in front of us as it orbits its star, there isn't yet a technique to
check if it has an atmosphere.
Kossakowski predicts
that we will have to wait a another ten years for this.
Though it's important that we build our facilities since the majority of
the nearby, potentially livable planets are only discovered through the
radial velocity approach.
The research has been published in
Astronomy & Astrophysics.
