Alright everyone, here is one of your most
asked for videos, everything you could want to know about the Trappist system. And I can see why there is so much interest,
it is such a unique system compared to anything else that we know of, an entire solar system
contained well within the distance of Mercury and the Sun. It is one of the closest places to us that
could harbour alien life outside the solar system, it being only 40 light years away
from us. That means we won’t be visiting it anytime
soon, but with improved technology from the James Webb Space Telescope, we will be able
to gain an insight to another solar system like never before. I’m Alex McColgan, and you’re watching
Astrum, and together we will go through the Trappist system, and see why it is so special. Let’s begin at the heart of the Trappist
system, Trappist-1 itself. The ultra-cool red dwarf star, a star which
is just a little bit bigger than Jupiter, but a lot more massive. Red dwarf stars are the most common type of
star in the galaxy. Even our closest neighbour, Proxima Centauri
is a red dwarf, as are 50 of the closest 60 stars to us. Being so cool means they are very long lived,
stellar models suggest they could exist for trillions of years, which is far more than
the current age of the universe. Although there are many known red dwarves
with exoplanets around them, typically red dwarves are dubious candidates to have life. This is because the “goldilocks zone”,
or the distance from the star where water could theoretically pool on the planet’s
surface, is extremely close to the parent star, meaning any exoplanets orbiting in this
zone are likely tidally locked. This means one side to the planet would always
be facing the star, the other side would be in perpetual night. The night side would be cold enough for gases
in the atmosphere to freeze. Also, red dwarf stars are often flare stars,
or stars that can have their brightness increase very rapidly to magnitudes brighter than they
are normally. This is similar in a way to a solar flare
on our Sun, but on a much grander scale. This variation in temperatures and radiation
is not good for life to develop on any planets nearby, or for planets retaining their atmospheres
during a huge flare. Trappist-1 however, while being a red dwarf,
does not flare up as much as its other red dwarf cousins, 30 times less than a typical
red dwarf star, great for the chances that atmospheres exist on the exoplanets around
the star. All the exoplanets are likely to be tidally
locked to the parent star though, something we’ll come on to later. Which leads us on nicely to the planets of
Trappist-1. Trappist-1 has astounded scientists in that
it has 7 known Earth sized planets orbiting it. Optimistically speaking, 6 out of the 7 planets
orbit within the system’s goldilocks zone. These planets are so close together, the furthest
out planet still only orbits at roughly 9 million km away from the star, in comparison
Mercury orbits our star at 58 million km. Let’s go through what we know about each
of Trappist’s exoplanets. It should be noted that our current observations
aren’t going to be perfect and will only improve as time goes on, but this is what
we think at this point in time. Trappist-1 b, the closest planet to the star. It is slightly larger than Earth but with
the same mass, meaning surface gravity would be about 80% of Earths, quite similar to Venus. It is also similar to Venus in that it has
an extremely thick atmosphere potentially full of CO2, meaning that because this planet
only orbits 1.7 million km from the star, it is going to be really hot. A year on Trappist-1 b lasts only 36 hours. This atmosphere could also be rich in water,
and surface pressure is likely to be 10,000 times greater than Earth’s. With such close proximity to the star and
significant greenhouse gases, surface temperature is thought to be between 500-1700c. Not the ideal place for our type of life then. Trappist-1 c is the next planet, orbiting
at 2.4 million km away from the star. At this distance out, it is getting about
2 times the starlight Earth gets from our Sun. It’s size and mass are about 10% more than
Earth, which means it has a very similar gravity to Earth. It is very similar to Trappist-1b in that
scientists believe it to also have a thick water vapour atmosphere, although Trappist-1c’s
is probably less thick. This means its surface temperature is likely
to be hot, but not as high as Trappist-1b. Next is Trappist-1d, only an extra 1 million
km further out than Trappist-1c. One year lasts only 97 hours. Trappist-1d is kind of like a mix between
Earth and Mars, as it is 30% smaller than Earth and only 30% as massive, meaning the
surface gravity is little under half of Earth’s. It is found on the inner part of the goldilocks
zone, meaning at this point in the solar system the surface temperature is now cool enough
for water to pool on the surface. It only receives 4.3% more starlight than
Earth, and combine this with solar flares from the star, it is likely to still be pretty
toasty for our standards. Trappist-1d has been found to have a volatile
layer on the surface, perhaps an ocean, or a thick atmosphere. And this is where oceans and atmospheres become
very important, because as I mentioned, all these planets are tidally locked, meaning
a thin atmosphere or no atmosphere means that one side of the planet would be scorched,
and the dark side would be freezing, much like what happens with Mercury. Venus on the other hand has a thick atmosphere
which circulates the heat around the planet, meaning night or day, it is the same temperature. So, if these Trappist exoplanets, like Trappist-1d,
has only a thin atmosphere or small ocean, the chances are that one side of the planet
would be devoid of anything but rock, and the other side might be covered in ices. There may be a small band of habitability
along the twilight zone, but that would be it. With a large ocean or atmosphere, the planet
might be able to distribute the heat much better, meaning it could be habitable all
over, as much as we understand habitability anyway. This planet may well be an ocean world, with
over 250 times the amount of water more than Earth’s oceans, although other studies have
suggested the atmosphere could also be similar to Venus’. We will get a better understanding from the
James Webb Telescope. Trappist-1e orbits another 1 million km out
again, at 4.4 million km from the star. Its year takes 146 hours, and at this distance
it only gets 60% of the starlight Earth does. Size, mass and gravity are all very Earth
like, and it is probably the only planet in the Trappist-1 system to have a rock-iron
composition like Earth. It also has a compact, hydrogen poor atmosphere
which is good as hydrogen is a strong greenhouse gas, and would make the planet inhospitable
from this distance. With this compact atmosphere, water could
pool on the surface, and the temperature would be very Earth-like if a little cooler, depending
on the albedo of the planet and how much heat the atmosphere retains. All in all, it is considered one of, if not
the most Earth-like exoplanet that we know of, and it is going to be one of the first
targets for the James Webb Telescope to try and detect signs of life. How amazing would it be if it really was a
cousin to Earth only 40 light years away? From Trappist-1f and beyond, we are still
in the goldilocks zone, but it is starting to get much cooler at this distance. Trappist-1f orbits at a distance of 5.8 million
km from the star, and a year takes 220 hours, or roughly 9 days. Its size is very Earth like, although it is
less dense, meaning surface gravity would be about 80% of Earth's. The most recent studies on this planet have
suggested that its low density means it is likely to be 20% water, which at this distance
from the star would cause a massive greenhouse effect, meaning the water would be in a gaseous
form. This is known as a steam world, and it would
probably be no more habitable than the gas or ice giants of our solar system due to the
high pressure and temperature on the surface, likely in the hundreds of degrees Celsius. Trappist-1g is slightly bigger than Earth,
and orbits at 7 million km, taking 12 days to do so. There hasn’t been too much information discovered
about this planet, other than water has again been found on it. This planet is still found in the goldilocks
zone, although right on the far edge, so it is still a candidate for habitability. And lastly, Trappist-1h. It orbits at 9.3 million km, and takes 19
days to do so. It’s the smallest of the known exoplanets
in this system, and also the least dense, meaning its gravity is comparable to our Moon’s. Due to the cool nature of the host star, being
this far out means the planet is likely icy as it does have water. Theoretically, it could also have liquid water
on the surface if it had a hydrogen rich atmosphere to act as a greenhouse gas, but again, little
is known about this planet. So that’s all the planets. Could this system really be habitable? Well it depends on a number of factors, but
what we’ve seen so far is promising. Water has been detected on most, if not all
the planets. The host star is a red dwarf, but not a very
active one. If these exoplanets have strong enough magnetic
fields, they could deflect a lot of the solar wind. If any of them do have magnetic fields, I
can’t imagine how glorious some of the aurora on these planets would look like! They are also all roughly Earth sized, with
similar gravities and densities, not a huge factor for life, but we know it worked here! And lastly, although these planets are tidally
locked, they may still have mechanisms for evenly distributing the heat across the planet. All in all, Trappist-1 is such an interesting
system, and I can’t wait to see what we find out about it in the future. My fingers are crossed, my thumbs are pressed,
and I’m praying that the James Webb Telescope launches successfully in 2021, what it is
going to see in the universe will be astounding, I can guarantee it. Thanks for watching! Well, it’s the holidays, and if you’re
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