By Bethan Evans, Gwen Jackson,
Siobhan Waters and Amy Folkard –
the astronomers of Year 9, LGGS
Gilese 1214b
The reason we chose Gilese 1214b is because it is perfect for human
existence. It has a suitable:
- Gravity score
- Atmosphere
- Density / terrain
- Goldilocks zone
We also had to consider other things before making our decision, such as:
- How to detect an Exoplanet
- The effect on the body
- Other aspects we need to know about Gliese 1214b
- What if the planet is already inhabited?
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Now that we know what an exoplanet is, the next problem is
to find one. This is a very difficult process, seeing as planets
do not emit any light of their own. So we cannot look for one
simply by looking through a telescope, partly because they
are so far away and partly because of the fact that, unlike
stars, they do not emit light, they only reflect it so are just
about invisible because it is impossible for even out most
powerful telescopes to differentiate between the light of a
star and the light reflected by a planet.
We have many different methods of detecting
exoplanets. For example, the Optical Gravitational
Lensing Experiment group (OGLE) are
experimenting with one type of detecting planets
which takes the theory behind its method from
Einstein’s General Theory of Relativity. Einstein said
that massive objects in space can bend light on its
way to Earth. This is just one way of detecting
massive exoplanets.
The Transit Method uses the moments during which a
planet passes directly between its star and our Earth. It is
the most successful way of finding a planet yet found, and
has helped to discover most of the planets which we have
found so far. For example, Gilese 1214B was found using
this method, so we know that it has been practical in
finding the exo-planet which is most important to us in
this investigation.
An example of transits closer to home is the transit
of Venus which happened in the summer of 2012.
This was one of the few transits of Venus which we
will be able to see – they happen in pairs, and the
next won’t happen until 2117! An extreme
example of a transit is a solar eclipse. This happens
when the moon passes directly between the Earth
and the Sun and completely blocks the Sun’s light.
Obviously the transits which we are trying to detect are nowhere
near as obvious as the closer-to-home transits. In fact, trying to look
for a planet using the transit method is like trying to detect a fly
flying in front of a lamppost by looking at the light it blocks out –
when standing a kilometre away! The only way we can tell that they
are there is by looking for regular dips in the light emitted by the
star that they orbit. We can use the size of these dips and the
amount of time between them to help estimate the size and orbit
length of the planet we have detected. If they appear enough times,
at constant intervals and sizes, then we can assume that we have
found a new planet.
We set up an experiment to investigate the transit
method for ourselves. This experiment used
polystyrene balls as planets and a light bulb for a
star, and showed us the ideas behind the transit
method.
We ended up with four different graphs telling us
about the transit method, which will be explained
in the next few slides.
Graph 1 – Smaller Planet, Middle Distance from the
Planet, 5 second Intervals.
The dips in the amount are quite big, because as it is further away, the
planet blocks out more light. Also, their frequency is smaller than when
the planet was closer to the star.
Graph 2 – Smaller Planet, Close to the Light Source, 2
second Intervals
This time the dips are smaller because the planet is close to the light
source, and more regular because the intervals were smaller.
Graph 3 – Bigger Planet, Middle Distance from Light
Source, 5 second Intervals
On this graph, the dips are very big compared to the other graphs. This is
because the planet is big and far away.
Graph 4 – Bigger Planet, Close to Light Source, 1 second
Intervals
Altogether from this experiment we can find out that the bigger the
planet, the bigger the dips in the amount of light. Also if it is far away
from its star then it will often block out more light than if it is closer.
Calculating the Habitable Zone of
Gilese 1214
Inner Boundary
Outer Boundary
We then compared this to the semi-major axis of the planet in
question. The semi-major axis of a planet is a way of
measuring how far a planet is from its star so that this
measurement is fair. The semi-major axis of Gilese 1214b is
0.0143, which is between the two values worked out above –
which means that Gilese 1214b is within the Habitable Zone!
We can work out a planet’s atmosphere using what is
called a spectroscope. These instruments are used by
astronomers to help figure out which chemicals can be
found within a planet’s atmosphere, using the light which
passes through it. For example, the Earth’s atmosphere
contains a lot of nitrogen, and enough oxygen for we
humans to survive, as well as other elements. Without this
atmosphere the Earth would be unable to sustain life.
The spectroscope relies on the fact that white light
can be split up into a whole spectrum of rainbow
colours. For example, a rainbow as we see it in the
sky is made when raindrops split up the sun’s ‘white
light’ into the visible spectrum.
Certain elements which can be found in a planet’s
atmosphere absorb certain colours of light. For
example, you would be able to tell if sulphur is in a
planet’s atmosphere because it absorbs a certain
type of yellow light. Each element has its own
specific type of light, which is very useful for
detecting them in a planet’s atmosphere.
So when we look at the spectrum of light which is
passing through an exoplanet’s atmosphere, we
can see tiny scratches where there are types of
light being blocked. These can also be transferred
to graphs, which show dips in the light which is
passing through a planet’s atmosphere.
This is called
ATMOSPHERIC
DISTORTION
We have used this method to work out that the atmosphere of
Gilese 1214b would be suitable for life, which means that we are
one step closer to having a planet which we could live on.
Without a suitable atmosphere, a planet would be completely
unsuitable for life. Our Earth’s atmosphere currently protects us
from harmful sunrays, makes sure that water on Earth is kept on
Earth and generally makes the planet suitable for life.
Venus, however, has an extremely dense atmosphere which
would crush anyone who tried to go there, and Mars has little to
no atmosphere, meaning that all water on Mars would not be
sustained.
So both of these planets, which are quite like Earth, would be
unsuitable for life, and atmosphere plays a big part in this.
Gravity is vital to survival on an
exoplanet. If there is too much gravity we
will be flattened against the surface but if
there is too little we will float. We can
work out the Gravity Score with the
formula: Gravity Score = mass/radius
squared. The Gravity Score of Gliese
1214B is 0.9133140836.
Density is very important when you are trying
to find out if a planet can support life. If it is
not dense enough your will fall through it but
if it is too dense you won’t be able to walk on
it. To find out how dense Gliese 1214B was,
we used the method Mass/Volume = Density.
The density of our own planet, Earth, is 5.5
g/cm3. Gliese 1214B’s density is 1870 kg/cm3.
If we get to Gliese 1214b and find out that it is already
inhabited by aliens, what would be the protocol?
Well you would have to approach them with respect
and gifts, to try and make peace with them so we can
live together. As Gliese 1214b is so much like earth and
human can survive on it, hopefully the aliens should be
just like us. This means they may have enough
intelligence so that we can communicate with each
other successfully. We could share our knowledge with
each other, to widen our knowledge of the universe.
Even though we are evacuating everyone (hopefully)
we still might not be able to bring all of our traditions
and agriculture with us.
… so as a solution we will bring with us many things to remind us
of our old ways and so we can teach the aliens as well.