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In the world of exoplanets, the easiest to find are the Hot Jupiters
-- large gas giants that orbit super close to their host stars.
For years, those were the only planets beyond
our solar system we could detect.
Even though our technology can now hunt for more
Earth-like worlds, studying Hot Jupiters is still
important for learning about how planetary systems evolve.
So astronomers are still hard at work learning
all they can about these first-gen exoworlds.
And this month in the Astronomical Journal,
they’ve announced that the Hubble Space telescope
has found the first planet with metal gas escaping
its atmosphere -- which offers us further insight
into the planetary life cycle.
The planet in question is known as WASP-121b,
whose discovery was announced back in 2016.
It’s about 20% more massive than Jupiter,
but has nearly twice the diameter, so it’s... puffier.
It’s located about 900 light-years away from us
orbiting an F-type star, one slightly more massive,
hotter, and brighter than our own Sun.
There’s been previous research studying water
in 121b’s atmosphere, but for this study,
astronomers were looking for metals.
They did this by looking at the wavelengths of light
coming from the star that passed through the planet’s
atmosphere during a transit -- those are the times when
the planet passed in front of the star relative to us.
Whatever light’s missing clues us into the elements
that are in the atmosphere.
The team detected ions of magnesium and iron.
Finding metals in Hot Jupiter atmospheres isn’t new,
but they usually hang out in the lower atmosphere as clouds.
For WASP-121b, these metals were not just located
in the atmosphere -- they were also found so far away
from the planet they’re no longer bound to it by gravity.
The planet is shedding metal!
The reason for this is because WASP-121b is so stinkin’ hot.
Its upper atmosphere clocks in at around 2500 degrees Celsius,
10x hotter than any other known exoplanet.
And it gets to that toasty temperature because it’s less than
four million kilometers away from its star, WASP-121a.
The planet’s year is only 1.3 Earth days long!
WASP-121a emits more ultraviolet light than our Sun,
so it’s actually heating up the planet
more than our Sun would.
The magnesium and iron also help heat the planet
because they absorb a lot of UV light.
This heating puffs up the atmosphere,
giving the stuff further away from the core an easier job
of floating off into space.
Basically, the hydrogen and helium in the upper atmosphere
are flying off the planet, taking the magnesium and iron with them.
This is thought to be a standard part of
Hot Jupiter evolution -- they form further out in the solar system,
but migrate inward and lose their outer atmosphere
as they get hotter.
So WASP-121b is a great piece of evidence
in astronomers’ hunt to understand
the formation of gas giants.
But looking at things on an even bigger scale,
a new 3D map of the Milky Way was published last week
in the journal Science, which revealed that
our galaxy is a bit twisted.
It’s hard to figure out how far away stuff is in space.
But one tried and true method since the early 1900s
involves a class of young, bright stars called Cepheids.
Those are stars that are varying in brightness over time,
but their variation is incredibly regular.
In 1912, astronomer Henrietta Swan Leavitt discovered
that the brightness of a Cepheid was directly tied
to the period of its variation.
The brighter the star, the longer it took to vary in brightness.
So by measuring a Cepheid’s period, you know how bright
it’s supposed to be.
By comparing that against how bright it looks
in the night sky, you can determine how far away it is.
There’s a bit more to it, but that’s the gist.
So a team of astronomers based at the
University of Warsaw put together data from
2,431 Cepheids located within our galaxy,
collected by a variety of survey missions,
and determined their location within the Milky Way
relative to the Sun.
And when they plotted these stars in a three-dimensional map,
they discovered that the so-called disk of our galaxy is not flat.
It’s warped, starting at a distance of around
8 kiloparsecs from the galactic center.
The warping becomes steeper at about
10 kiloparsecs out, up the edge of the galaxy at 20.
And our side of the Milky Way is warping in the
opposite direction as what’s happening on the
opposite end of the galaxy.
In other words, if you look at it edge on,
our disk is vaguely s-shaped.
Near the edges, our disk also flares out.
While nearer the center it’s only about 500 light-years thick,
out in the galactic boonies stars can be up to
5000 light-years away from the galactic plane.
This may be due to gravitational interaction
with nearby galaxies, or maybe even dark matter.
We don’t know, yet.
And this isn’t the only evidence that our galaxy is twisted.
This new finding seems to match up with other research,
including a paper published earlier this year.
But having a funky shape doesn’t make us special.
The are other spiral galaxies out there with warped disks
- maybe as many as half of them.
Even our next door neighbor, Andromeda,
isn’t perfectly flat.
Since the Cepheids in this study weren’t distributed evenly
through the Milky Way, our new 3D map of home might
not be 100% accurate.
But it’s a starting point, and more data
should be able to refine it.
And yes, that may make all of that art out there
depicting our galaxy a little bit out of date,
but it’s worth it to actually know more
about our cosmic neighborhood.
Thanks for watching this episode of SciShow Space News.
Hey, if you like space and you like pins,
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And thanks!
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