It seems like every couple of weeks the news headlines announce a new
“Earth-size” planet, making it look as if leaving earth and inhabiting
another planet is just around the corner.
But actually, we are far from that!
In this video, we are going to talk about a planetary system that
made the world go crazy back when it first came out with how many
Earth-size planets it contains.
We are talking about the planetary system “TRAPPIST-1”!
The story goes back to the year 1999 and begins with a star 40 light
years away in the constellation “Aquarius”, the star was discovered by
the astronomer “John Gizis” with the help of his colleagues.
They gave the star the hideous long name; “2MASS J23062928-0502285”!!!!!
The star was identified as an “ultra-cool” M-type dwarf star, that’s a type
of star, which as their name suggests, holds a very low temperature that
goes below 2700 °K (4400 °F).
You might think that’s still very hot, but believe me, for a star, that’s ”ultra-cool”,
much cooler than our sun’s surface temperature for example, that goes
to nearly 6000 °K ( 10000°F).
The star is very dim in the night sky, stargazers can not see it with the
naked eye, and in comparison to our sun, the star “2MASS
J23062928-0502285” is a dwarf star, with only 11% of the sun’s
diameter which makes it just a little bit bigger than Jupiter, and it’s also
much redder in colour than the sun.
And because of its small size, the star consumes fuel much slower than our own
sun, that’s why when we look at its age, we find it twice as old as
the sun.
Scientists have estimated the star’s age to range between
5.4 and 9.8 billion years, while our sun is only 4 and a half billion
old.
The story progresses ‘till we reach the year 2008 when the construction
to build a new telescope called “TRAPPIST” was approved, the name is
a short for the “TRAnsiting Planets and PlanetesImals Small Telescope”
and it’s a telescope funded by Belgian Fund for Scientific Research and
the Liège University in Belgium.
The “TRAPPIST” telescope consists of 2 robotics telescopes, one located in the “La
Silla Observatory” in Chile and the other in the “Oukaïmeden Observatory”
in Morocco.
The main purpose of building this telescope was to
study bodies outside the solar system, such as exoplanets and comets and
asteroids and other small bodies.
Now, we flash forward again to the year 2016 when astronomer “Michaël
Gillon”, alongside NASA astronomer “Susan M. Lederer” found 3
Earth-sized exoplanets around the star “2MASS J23062928-0502285”,
and in honor of the “TRAPPIST” telescope, astronomers gave the star a
newer neat and fancy name: “TRAPPIST-1”.
More observations in the following year using the NASA’s “Spitzer Space
Telescope” and other telescopes have discovered that the star
“TRAPPIST-1” actually hosts 7 Earth-sized exoplanets, not just 3!
And all 7 planets orbit the host star at a distance
closer than Mercury is to our Sun, that’s so ridiculously close that if
you were to stand on one planet, you’d be able to see the others as moons
in the sky and even visually bigger than our Moon!
Another thing astronomers noticed was how the planets may be tidally
locked to their host star just like how the moon is tidally locked to the
Earth.
Being “tidally locked” means that a body orbits its host with only
one face always facing the host.
In the case of the planetary system “TRAPPIST-1”, all the planets in the
system may have one face facing the star at all times, leading to
permanent day time on one side and permanent night time on another
side, which in turn causes extreme temperature change and weather
patterns.
The discovery marked the first time ever for astronomers to spot THAT
MANY Earth-sized exoplanets around a single star!
Further observations and simulations have confirmed that the first
6 of the exoplanets may be rocky ones, and the last planet could be of
icy nature.
The discovery also marked for the first time 3 planets (“TRAPPIST-1e”
“TRAPPIST-1f” and “TRAPPIST-1g”) in the same planetary system
within the habitable zone.
See, Finding an Earth-size planet is not merely enough for it to be able to host life
as we know it, the planet needs to fall within what astronomers call
“the habitable zone” and also clear some criteria about its atmosphere.
The habitable zone is the zone that is not so far away nor so near to a
star, and at which a planet could orbit with just the right temperature for
life to evolve and for water to exist on it.
For example, the habitable zone of our solar system covers only planet Earth
where liquid water is found, and everywhere else in the solar system there
are either water vapor or ice.
Even though chances are higher within the habitable zone, scientists
think it is also possible for liquid water to exist on all of the first 6 planets
because the temperature of the host star -remember “Ultra-cool”- is not
as hot as the sun to vaporise water on nearby planets.
Now, do scientists know anything about these planets’ composition or
size or how they look like?
Well, they have a vague idea!
We said earlier that the first 6 planets might be rocky and the last one
might be icy, now we’re going to discuss the scientific data of each of the
7 planets, and what astronomers know so far regarding their similarities
to Earth.
We begin with “TRAPPIST-1b”, the “Super Earth” type planet with a
radius equals 1.086 times the radius of the Earth, and a mass equals
0.85 times the mass of the Earth, it’s also the closest planet to its host
star with orbital period equals 1.5 Earth days.
Scientists also believe “TRAPPIST-1b” might have a thick atmosphere.
The second planet in order is “TRAPPIST-1c” and is also a “Super
Earth” type planet with a radius equals 1.056 times the radius of the
Earth, and a mass equals 1.38 times the mass of the Earth, it has an
orbital period equals 2.4 Earth days, and scientists believe it has a
lighter atmosphere than “TRAPPIST-1b”.
“TRAPPIST-1d” is the third planet in order and is a “Terrestrial” type
planet with a radius equals 0.41 times the radius of the Earth, and a
mass equals 0.41 times the mass of the Earth, it has an orbital period
equals 4 Earth days.
Scientists think “TRAPPIST-1d” to be the lightest
one amongst all 7 planets with only 30% of Earth’s mass!
“TRAPPIST-1d” gets roughly the same illumination from its host star as
the Earth gets from the sun.
Regarding its atmosphere though, scientists do not yet know its nature whether it’s
a large atmosphere or an ocean-like, or with a thin ice layer covering
it.
“TRAPPIST-1e” is the first of the planets in the habitable zone, and is
also a “Terrestrial” type planet with a radius equals 0.918 times the
radius of the Earth, and a mass equals 0.62 times the mass of the Earth,
it has an orbital period equals 6.1 Earth days.
Scientists think “TRAPPIST-1e” is just slightly denser than planet Earth
which means it may have a denser iron core as well, in fact, denser than
any of the planets in the whole of “TRAPPIST-1” planetary system, not
just Earth.
Scientists also suggest that “TRAPPIST-1e” has a light atmosphere just
like “TRAPPIST-1c”, and that it’s the most similar planet to Earth in
terms of size and density and the amount of radiation it gets from its host
star, but it does get a little bit less illumination from its host star than
Earth.
“TRAPPIST-1f” is the 2nd planet in the habitable zone, and is a “Super
Earth” type planet with a radius equals 1.045 times the radius of the
Earth, and a mass equals 0.68 times the mass of the Earth, it has an
orbital period equals 9.2 Earth days.
“TRAPPIST-1g” is the 3rd and final planet in the habitable zone of the
“TRAPPIST-1” planetary system, it’s a “Super Earth” type planet with a
radius equals 1.127 times the radius of the Earth, and a mass equals
1.34 times the mass of the Earth, it has an orbital period equals 12.4
Earth days.
“TRAPPIST-1h” is the final and farthest planet around its host star, and
it’s a “Terrestrial” type planet with a radius equals 0.752 times the radius
of the Earth, and a mass equals 0.331 times the mass of the Earth, it
has an orbital period equals 18.8 Earth days.
Did you notice how the farthest planet in the “TRAPPIST-1” planetary
system orbits its host star much faster than mercury orbits the sun!?
Mercury takes about 88 days to orbit the sun while “TRAPPIST-1h” takes
about 19 days!
That gives you an idea of how small and compact the
exoplanets in the “TRAPPIST-1” planetary system are.
Regarding the surface nature of the farthest three “TRAPPIST-1f”,
“TRAPPIST-1g” and “TRAPPIST-1h”, scientists believe they’re far
enough from the host star that they might have frozen water on their
surfaces.
Scientists are able to paint these looks of “TRAPPIST-1” exoplanets
thanks to what is called “The Transit Method” which is one of multiple
methods used to detect exoplanets.
In the transit method, astronomers look for planets that come in front of (Transit)
their host star, and when that happens, astronomers notice a dim in
the star’s light announcing the existence of a planet (or more) orbiting around
it.
Further analysis done on the data from this method results in obtaining
the radius and the mass of the planets which then scientists use to
calculate the density pretty straight forward, and then they can determine
other important factors in the planets’ looks.
We should not also forget the effort of visualization scientists, those are
the people who combine science and art for the public to be able to “see”
an artist's conception of what a world 40 light years away (and more)
could look like.
Visualization scientists transform data and numbers into
art and graphics that not only benefit the public, but also paint a picture
for the scientists to be able to imagine what their data means.
You can enjoy the 3-D artists’ conception of the “TRAPPIST-1” planetary
system and other systems and exoplanets through the web and app
version of the programm “Eyes on Exoplanets” made available for free
by NASA.
The program illustrates how it looks like to observe exoplanets
up close as if you’re right in front of them.
You can download the program through the NASA link in the description
box.
(link: https://eyes.nasa.gov/eyes-on-exoplanets.html)
So, after all these observations and analysis going back more than 20
years, can we consider “TRAPPIST-1” planets as our main destination
for Earth 2.0?
Well, not quite yet, because more information is needed
regarding the planets’ atmospheres, and new telescopes in the future
will aid in obtaining this information.
For example, now astronomers are waiting for the “James Webb Space
Telescope” which is planned to launch in March of the year 2021, if it
didn’t get delayed because of the Corona virus Pandemic.
The telescope is a cooperation between the American space
agency “NASA” and the European space agency “ESA” and the Canadian
space Agency “CSA”.
The “James Webb Space Telescope” is designed to look for faint
infrared radiation from far away objects like exoplanets and stars, which
is exactly the kind of radiation astronomers are looking for when studying
the “TRAPPIST-1” planetary system.
The “James Webb Space Telescope” will be able to provide more
precise observations of faint planetary systems like “TRAPPIST-1” which
in turn will aid in knowing whether or not “TRAPPIST-1” exoplanets
have atmospheres, and their compositions, if they exist.
When looking into information on the atmosphere of planets in the
“TRAPPIST-1” planetary system, astronomers are looking for the same
chemical compositions that support life here on Earth, like methane and
oxygen and water vapor as well, we will definitely stay tuned for
astronomers to find them.