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  • [INTRO ♪]

  • 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 postponed,

  • 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 of missions.

  • 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, and Moon.

  • Blocking this light will help keep the telescope cold

  • 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 objects.

  • The sunshield will solve a lot of that problem,

  • but the telescope will also have a bit of cold helium

  • 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 together.

  • They'll have to make sure they wired

  • everything correctly and that the equipment

  • will survive deployment and the vacuum of space.

  • That means there's still room for error.

  • But hopefully, things will go well,

  • and the telescope will finally launch in March 2021.

  • 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 chemistry.

  • And using this method,

  • they've even found an especially exciting candidate!

  • 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 elementslike sodium and potassium.

  • And some of those compounds get incorporated

  • into Jupiter's upper atmosphere.

  • That's important.

  • 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 sourceslike 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 things

  • you're interested inyou can pick up the paperback

  • of An Absolutely Remarkable Thing

  • wherever you like to get your books.

  • [OUTRO ♪]

[INTRO ♪]

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