How we know so much
about planets. That are super far away.
We may have discovered hundreds of exoplanets, but this new
alien world is one of the weirdest yet.
Hello! I’m Terrius, space producer for Discovery News and I
have a confession –
I’m a bit of an exoplanet addict. I’m fascinated by every
exoplanet discovery-- we live in an incredible age where we can see worlds of
all sizes orbiting stars many light-years away.
This is all part of an exciting quest to ultimately track
down a world with similar qualities to Earth. I’m my lifetime I hope that
astronomers will discover a true Earth-like world that we are able to probe its
atmosphere and find possible biosignatures. In other words: finding a world
that could host a life-giving alien biosphere.
The event of finding a truly habitable alien world may be a
long way off, but for now we have missions like
NASA’s Kepler Space Telescope doing mind blowing work detecting small worlds,
big worlds and worlds that are just plain WEIRD. And this latest
exoplanet discovery definitely falls into the
“weird” category.
Kepler-432b is the densest exoplanet discovered to date with a mass of SIX
times that of Jupiter,
but with all that mass jammed into a planet of Jupiter’s
size. But how do you go about measuring the mass of a planet that is nearly
3,000 light-years away?
First detected by NASA’s Kepler space telescope in 2014, the
mission was able to measure the planet’s physical size by gauging how much light
of its host star would dim each time it orbited in front.
These dimming events
are known as “transits” and they can
be used to work out the size and orbital period of distant worlds. But to
measure the planet’s mass, astronomers using two Spanish ground based
observatories measured the slight “wobble”
of the star as that planet orbited. The more massive the planet, the
greater its gravitational effects and the greater the star’s wobble.
This type of observation is known as the “radial velocity” method. When observed
over a long period, a precise measurement of the planet’s mass can be recorded.
By combining data
from transit and radial velocity methods, it’s a fairly simple calculation to
arrive at the planet’s density, combining the mass and size.
And it just so happens that this is one seriously dense
planet. But its density isn’t the only thing that makes Kepler-432b unique
-- it also has one of the most eccentric -- or stretched – orbits of all the
exoplanets discovered to date.
During the 52 day orbit around its star, the world suffers some
extreme seasonal heating. At its furthest orbital point, the exoplanet is a hot
1000 degrees Fahrenheit, but at its closest approach, it bakes to over 1800
degrees.
Its orbit is a clue
as to why we don’t see these kinds of exoplanets very often. Kepler-432b is a
world with an expiration date. Its host star is a huge red giant that is undergoing
its final death throes after running out of hydrogen fuel in its core.
It is predicted to
become so puffed up that its scorching plasma will likely swallow the unfortunate
exoplanet in around 200 million years time. Therefore, Kepler-432b is a planet
of extremes. It’s extremely dense; it has a hellish rollercoaster orbit and it
is destined to be destroyed by a stellar blowtorch in the not-so-distant
future.
Although this is one world certainly not suitable for life
as we know it, it’s yet another reminder about how rich and diverse our galaxy is,
filled with exoplanets that are very different to the planets contained within
our own solar system.
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