There are three types
of planets in our solar system. On the one hand we have rocky worlds like Earth
and Mars have a solid surface on which to put your feet and consist of 'rocks'
(silicates and metals). Then there are gas giants like Jupiter and Saturn, composed
mainly of hydrogen and helium (and actually should be called "Giant
fluid" because most of its interior hydrogen is a liquid or metallic).
Finally we have the ice giants,
Uranus and Neptune, composed of hydrogen and
helium gas giants, but also a lot of "ice" (ice water, ammonia,
methane, etc...). Until a few years ago we thought the rest of the galaxy
stellar system follow a roughly similar pattern. Not so. There are planets out
there totally different to those we know.
First came the
super-Earths, a type of rocky planet that is abundant in the universe.
Depending on its orbit, some super-Earths are believed to have huge lava fields
on the surface, while other global oceans would be covered by water hundreds of
kilometers deep. Then he discovered the minineptune, planets-as the name
suggests, are large balls of ice with a rocky core with a size similar to the
larger super-Earths. A mini Neptune is basically a small ice giant and, in
fact, to this day do not know how to distinguish the super-Earths mini Neptune from
observational data. The mini Neptune is a mystery; hence their study is a
priority. Why it is so interesting to the latest discovery of the Kepler space
telescope, a planet called Kepler-68b and having characteristics make it one of
the super-Earths and mini Neptune.
Kepler-68b is part of a
three-star system whose minimum mass planets have been determined by
terrestrial observations using the radial velocity method (the Kepler telescope
discovers planets by the transit method and can only determine the size of the
worlds discovered). It has a mass of between 6 and 10.3 times that of Earth,
while its radius is 2.3 times that of our planet. With these data we can
calculate its average density, which, with 3.32 grams per cubic centimeter, it
being understood right between the density of the ice giants like Neptune and
the terrestrial planets. Its period-that is, their year-is only 5.4 days, so
that the temperature 'surface' of this world must be very high. Whether
Kepler-68b is actually a dense mini Neptune would be the hottest known so far.
Now, what does
Kepler-68b? With this density should have lots of volatiles (ices and gases),
but also a significant percentage of rock. So, how is its internal structure?
Well this is where things get interesting, because nobody knows. For a mini Neptune,is
too dense, but obviously cannot rule out that it is. But it could also be an
essentially rocky world with a thick atmosphere of hydrogen and helium, or
contain huge amounts of water distributed between the ocean surface and a dense
atmosphere of water vapor. That is, it would be a super-Earth type world ocean,
but why? On the other hand, due to the short distance that separates it from
its star, Kepler-68b may be the remains of a gas giant after losing its outer
layers of hydrogen and helium. Or what is the same; this would be the core of
ice and rock of a gas giant. The only certainty is that there is a world of
carbon.
Moreover Kepler-68 star
system is a compact, similar to Kepler-11 and Kepler-20, a kind of miniature
solar system seems to be very common in the galaxy. The other two planets are
Kepler-68c system (a rocky world with the size of Earth and a period of 9.6
days) and Kepler-68d (a giant Jupiter with the same mass as Jupiter and a
period of 540 days), the latter discovered by the radial velocity method.
Kepler-68b clearly shows the need for theoretical models of the different types
of planets according to their composition. Because what is clear is that the
number of types of planets is much higher than what we thought until recently. The
whole zoos of planets waiting to be discover.
No comments:
Post a Comment