Have you ever thought about how LUCKY we are with the placement of the planet that we live
on? The Earth is within a range of the sun that we don’t get too much of the harmful
radiation from it but close enough that it keeps our planet warm enough for life to flourish.
But most of the planets that astronomers have discovered out in outer space are, unlike
our planet, inhospitable and devoid of life as we know it.
They have discovered planets made of solid ice and these types of planets are not very
rare here because the vast majority of space is a cold vacuum.
Astronomers have also found planets made of solid diamonds and others that are full of
toxic chemicals.
There is also a type of planet that has been found that are birthed very close to their
stars. This close proximity to a massive, hot ball of plasma makes the surfaces of these
planets oppressively hot.
One planet that was recently discovered orbiting a giant star called KELT 9. KELT 9 is a star
that is over two times larger than our own sun and burns almost twice as hot.
It is a blue star that burns hotter than ten THOUSAND degrees kelvin which is over seventeen
thousand degrees fahrenheit while our sun only burns around ten thousand degrees fahrenheit
at its hottest.
This star is also still relatively young within the time scale of stars. It is only three
hundred million years old and has much more of its life remaining.
But the features of KELT 9 are not what interests astronomers the most about this star. That
interest is directed towards one of the planets that orbits it.
Using the Kilodegree Extremely Little Telescope, which is also known as KELT, astronomers found
the planet now known as KELT 9 b. They detected this planet by measuring the amount of light
this star was giving out and noticed a small dimming effect in that light as a planet moved
in front of it.
This star and planet are about six hundred and seventy light years away. Isn’t it incredible
that astronomers can pick up on such a small change from that great of a distance using
today’s telescopes?
KELT 9 b is a gas giant, like Jupiter. This planet is almost two point eight times bigger
than Jupiter but only half as dense which makes KELT 9 b a MASSIVE gas giant.
But its size, density, and its make up is not what made astronomers interested in KELT
9 b at first. It orbits its star extremely closely making the surface of the planet hotter
than the majority of stars in our universe.
KELT 9 b orbits its star closely and quickly with one year only lasting thirty six hours.
This means that it experiences all four seasons in that short time making each season last
for only nine hours. Down on the surface, KELT 9 b is EXTREMELY
hot, it can reach daytime temperatures around four THOUSAND six hundred degrees Kelvin which
is equal to seven thousand eight hundred degrees fahrenheit. To put that into perspective the
COOLEST stars only burn at two thousand five hundred degrees Kelvin which is just over
four thousand degrees fahrenheit.
When astronomers compared the surface temperatures to the stars in the observable universe they
found that KELT 9 b is hotter than eighty percent of all the stars.
Our sun is one of those twenty percent of stars that burn hotter than KELT 9 b with
its temperatures soaring to over five THOUSAND seven hundred and fifty degrees Kelvin which
is nearly ten thousand degrees fahrenheit.
But how can a planet be hotter than the majority of stars in our universe and what has caused
this planet to grow to be this incredibly hot?
It turns out that astronomers found that there are a few reasons for KELT-9 b’s sweltering
surface temperatures. One of these reasons for the scorching daytime temperatures is
purely based on the distance that it orbits its star.
Think about the planet closest to our sun, Mercury. Which is one of the hottest planets
in our solar system purely because of its proximity to our sun. With its day time temperatures
maxing out at almost eight times the hottest temperatures we have measured on Earth. The
surface on Mercury can reach temperatures of over eight-hundred degrees fahrenheit which
is still extremely hot even if it is much cooler than KELT 9 b.
But KELT 9 b orbits its star much closer than Mercury does, in fact it orbits TEN times
closer. This means that KELT 9 b is being blasted with light from its star constantly.
This light strikes the surface and heats up its atmosphere to a great degree. But if only
factors of this planet are causing it to heat up, the surface would not reach temperatures
that it does.
So there must be something else that contributes to the extreme temperatures that astronomers
see on KELT 9 b. Not only does KELT 9 b orbit extremely close
to its star, it also is locked in a tidal orbit with it.
An object in a tidal orbit will rotate at a rate so that as it orbits around the star,
the side that faces the star is always the same. This is the same type of orbit that
our Moon has with the Earth. If you look at the moon on a clear night, you will always
see the same side of it.
This means that KELT 9 b has a side of it that is permanently day and a side of the
planet that is permanently night. The day time side of the planet is receiving all of
the heat from the star without having a break to dissipate some of that heat out into space.
So far that is two factors concerning KELT 9 b that leads to its ridiculously hot temperatures.
But there is one other factor that adds to hot temperatures on the surface.
KELT 9 is a star larger than our sun and similarly to our sun it doesn’t only emit visible
light. There are other forms of light that this star produces in the form of radiation
that KELT 9 b is exposed to.
Like all stars in our universe, KELT 9 undergoes nuclear fusion in its core producing enormous
amounts of energy and blasting light out in all directions around it. This light includes
many different wavelengths including visible and ultraviolet light. So not only is KELT-9
b being bombarded with heat from its star but it also is getting blasted with ultraviolet
light.
It is this ultraviolet, or UV, light that causes this gaseous giant to increase in heat
even more and is slowly evaporating the surface. Astronomers were able to discover all of this
information about KELT-9 b and what makes it so hot using data gathered from the shadow
as it orbits around its star. The instruments that they are using now were not built with
the intent to study the atmosphere and properties of different planets in the universe.
But tools that are more tuned for this use have been in the minds of scientists for some
time. And as the hunt for more exoplanets and the need to know more about them grows,
new instruments that can probe deeper into these planets will be built.
Extreme planets exist out in the cosmos and trying to find and identify as many as possible
is the dream of many astronomers. As they delve deeper into the corner of our universe
astronomers keep finding objects that are more unbelievable than the last.
The more that we learn about the universe, the more it shows us that there is still much
more out there yet to be discovered and that we can’t always predict what is going to
be found.
Join us again to discover more marvelous things about the universe all around.
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