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  • [♪ INTRO]

  • Fifteen years ago, the Galileo spacecraft plunged into Jupiter's atmosphere,

  • ending its eight-year mission studying the planet and its moons.

  • But that doesn't mean it stopped sharing the system's secrets.

  • As reported in a paper published this week in Nature Astronomy, researchers found something

  • new and surprising hiding in data Galileo captured all the way back in 1997:

  • evidence of water plumes on one of Jupiter's moons, Europa!

  • According to a new computer model, while you were breaking in your Nintendo 64,

  • this spacecraft might've been quietly observing water on another world.

  • If plumes on Europa sounds familiar, it might be because there's another moon with

  • water plumes whose name also starts with an 'E': Enceladus.

  • It orbits Saturn, and we've talked about it here before.

  • Europa is about six times bigger though, around the same size as our Moon, and data suggest

  • it has twice as much water as the Earth does.

  • It's enough for a global, underground ocean,

  • but we've never actually had definitive proof that it's down there.

  • To do that, well, we'd need to find something like plumes.

  • As early as 2012, we had some hints from the Hubble Space Telescope that they might exist,

  • and we've compiled even more evidence over the years.

  • But because all these measurements were done at the very limit of Hubble's sensitivity,

  • their accuracy is debated.

  • To solve this mystery, we need better data, ideally, something closer to the source.

  • Unfortunately, Juno, our spacecraft currently orbiting Jupiter,

  • doesn't have the equipment to study these features.

  • In fact, it was launched before any evidence of plumes had been discovered.

  • So we can't give the local help a side quest.

  • The good news though, is we had our old friend Galileo!

  • Likely inspired by those Hubble discoveries,

  • a team of astronomers recently gave the 20-year-old data another look.

  • And we're glad they did.

  • During its flyby of Europa, Galileo got as close as 206 kilometers from the moon's surface,

  • and it measured changes in Europa's magnetic field strength and distribution of plasma.

  • Now, we think those changes could easily be explained by the presence of a plume,

  • one maybe around 1000 kilometers wide and at least 200 kilometers tall.

  • At least that's what the team's computer models suggest.

  • And if this turns out to be true, it would be a huge bonus for space exploration.

  • After all, it means that if we sent a mission to Europa, we'd be able to sample its oceans

  • without drilling through kilometers of ice.

  • But this is only one model, so we'll need more evidence to be sure.

  • And ultimately, our best chance of confirming Europa's plumes is still sending a craft

  • back to Jupiter that's capable of detecting them.

  • Which, of course, astronomers are already working on.

  • NASA's Europa Clipper mission is slated to launch in the 2020s,

  • and it'll have nine instruments to help study the plumes' composition, like a mass spectrometer.

  • There may also be a lander in the works, if it gets the funding.

  • And an ESA mission dubbed JUICE should launch in 2022.

  • When it reaches Jupiter around 2030, it'll study Europa, as well as two of Jupiter's

  • other moons astronomers believe have some liquid water under their surfaces:

  • Ganymede and Callisto.

  • So, we'll just have to wait and see.

  • Meanwhile, here's some news we had to wait over 13 billion years to see,

  • light from some of the very first stars in the universe.

  • A paper published in Nature this week reports the discovery of stars forming in a

  • distant galaxy as early as 250 million years after the Big Bang,

  • when the universe was only 2% its current age.

  • Using an array of radio telescopes called ALMA, an international team of astronomers

  • was able to analyze the light coming from stars in the galaxy dubbed MACS1149-JD1.

  • Based on how fast the galaxy is moving away from us, they estimated its light to be about

  • 13.3 billion years old; only 500 million years younger than the universe itself.

  • They could make this estimate because the universe is expanding, so galaxies farther

  • away, and therefore older, are moving away from us faster than the ones nearby.

  • And we can detect those speeds based on what the light from these galaxies looks like.

  • Of course, if the galaxy has light, it probably means it has stars, too.

  • And since they couldn't just suddenly pop into existence, it means they have to be even

  • older than 13.3 billion years.

  • The researchers figured out their age by modeling when early bursts of star formation

  • had to have happened in order to make the galaxy's light signature,

  • also called its spectra, match their data.

  • They found there had to be a bunch of stars forming around 300 million years

  • prior to the light we're seeing now.

  • And that means most of the stars themselves, and therefore the galaxy as a whole,

  • was forming only 250 million years after the universe came to be.

  • Besides being cool to know about, this discovery is good news for anyone trying to study the

  • universe's first generation of stars, because it suggests we have the tools to study them.

  • We can figure out exactly when they started forming and what properties they have.

  • And this is especially good news for one future mission: NASA's James Webb Space Telescope,

  • which is designed to study the early universe.

  • So when it finally launches, it looks like it has yet another target to train its sights on.

  • All it has to do now is go to space.

  • Clearly, a lot of astronomy involves waiting.

  • Thanks for watching this episode of SciShow Space!

  • If you can't wait for the next space news episode, it's okay: We have plenty of other

  • stuff for you to learn about, like what would happen if the universe were shaped like a donut.

  • Because this is a thing astronomers think about.

  • [♪ OUTRO]

[♪ INTRO]

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エウロパで水蒸気を検出...20 年前 (We Detected Water Plumes on Europa... 20 Years Ago)

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    林宜悉 に公開 2021 年 01 月 14 日
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