For years, NASA has been working
on an amazing telescope.
It’s called the James Webb Space Telescope,
or JWST, and at one point,
it was intended to launch in 2007.
We’ve been talking about this project
since SciShow started, because James Webb
could transform our understanding of the universe.
But honestly, being a fan of this telescope
is sometimes hard work.
After years of seeing it fail tests and get
things can feel discouraging.
Today, though, I have some good news!
Last week, after more than a decade of delays,
the two halves of the telescope have
finally been joined together.
Although it won’t do identical work,
James Webb is the successor to
the Hubble Space Telescope, which will likely
stop working in the mid-2020s.
And once Webb launches,
it will be charged with a full complement
Using infrared light, it will study
the composition of exoplanets,
probe the oldest galaxies we can see,
and maybe even answer our questions
about what the universe is made of.
But before it can do any of that,
it needs to launch.
And before it can launch,
it needs to be fully tested.
Until recently, Webb’s two main halves
were tested separately.
But now, we can test them together.
One half consists of the telescope itself.
That’s the part with gold-coated mirrors
and a suite of instruments.
The other half has the spacecraft,
which will steer the telescope,
along with the giant, five-layer sunshield
that will block light from the Sun, Earth,
Blocking this light will help keep the telescope
— which is a must, since heat is
a major source of infrared radiation.
So, if it’s not cold enough,
an infrared telescope’s own heat
can overwhelm its instruments
while it’s trying to monitor distant, dim
The sunshield will solve a lot of that problem,
but the telescope will also have a bit of
to keep some of its instruments extra chilly.
Of course, just because the telescope
is mostly-assembled doesn’t mean
it’s ready for launch.
Engineers still have to connect
the electronics between the two halves,
and after that, they have to test them all
They’ll have to make sure they wired
everything correctly and that the equipment
will survive deployment and the vacuum of
That means there’s still room for error.
But hopefully, things will go well,
and the telescope will finally launch in March
Thankfully, even if Webb doesn’t launch
for a while,
there’s plenty of other work to do in astronomy.
For example, researchers are still
hunting for the first solid evidence of
an exomoon — a moon orbiting
a planet outside the solar system.
Moons are usually much smaller
than their planets, so even when we find
an exomoon candidate, it’s tricky to
isolate the signal and confirm
that it’s actually there.
One team of astronomers thinks
there’s a way around this, though.
Their paper has been accepted for
publication in The Astrophysical Journal.
And in it, they propose you can find
certain exomoons by studying their planet’s
And using this method,
they’ve even found an especially exciting
This paper focuses on a type of planet
called hot Jupiters.
These are gas giants that orbit
so close to their stars that their year
could be as little as a few days on Earth.
Until recently, there wasn’t much evidence
that a moon could exist in a stable orbit
around a planet like this.
So the first thing these scientists did
was use math to confirm moons could live there.
And next, they proposed a way
we could identify them.
Drawing on earlier research,
they suggested you could find some
exomoons by looking for certain gases
in their planets’ atmospheres.
This idea is actually based on
what researchers see with Jupiter
and its third-largest moon, Io.
Io has hundreds of active volcanoes
that spew out lava, sulfur-based gases,
and other elements — like sodium and potassium.
And some of those compounds get incorporated
into Jupiter’s upper atmosphere.
Because at least in our solar system,
elements like sodium and potassium
aren’t normally found in
the upper atmospheres of gas giants.
They only seem to get there through
external sources — like volcanic moons.
So, these astronomers hypothesized
that if you detect either sodium
or potassium around a hot Jupiter,
it could have a moon like Io.
This basic idea isn’t new,
but these researchers were among
the first to see if it applied to hot Jupiters.
And as it turns out, it might.
In their study, they looked at data
from 14 of these planets,
all of which had sodium or potassium
signatures in their upper atmosphere.
Then, they ran analyses and identified
one that seems most likely to have a moon.
It’s called WASP-49b,
and is located 550 light-years away.
If this finding is validated,
it would be the first confirmed exomoon.
But even if it’s not, this method is still
a really creative way of studying objects
that are super far from Earth.
It combines the familiar things
that are close to us with alien worlds
hundreds of light-years from here!
At this point, it’s unclear if this technique
could be used to find moons like ours
around planets like Earth.
But hey: Maybe we’ll need even more
creative methods to do that.
There’s a lot to explore in space —
which is part of the reason science fiction
is so fun.
You get to think about what would happen if,
say, a bunch of alien robots called Carl
suddenly appeared on Earth.
Okay, let me explain.
About a year ago, Hank, who co-hosts
this channel with me and started SciShow
and does lots of cool things,
released a book that he worked on forever
called An Absolutely Remarkable Thing.
And that book is now available in paperback,
which is just so much more cozy to hold!
So if space, robots, social media,
or just the general state of humanity are
you’re interested in… you can pick up
of An Absolutely Remarkable Thing
wherever you like to get your books.