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  • [ ♪ Intro ♪ ]

  • After years of searching, there's one place in the solar system where we've managed

  • to find life.

  • Okay, so I'm talking about Earth.

  • But there are other bodies that astronomers suspect could be habitable -- at least for

  • special types of single-celled life forms.

  • Probably not, like, space hippos or anything.

  • Although that would be awesome.

  • One of those bodies is Saturn's moon Enceladus, which almost definitely has an ocean's worth

  • of liquid water underneath its icy surface.

  • Based on what we know about life, we've thought this environment could be habitable,

  • but we haven't known that for sure.

  • But now, we do.

  • According to research published on Tuesday in Nature Communications, Enceladus' environment

  • could totally be habitable for at least one real-world microbe.

  • We don't know the exact conditions in Enceladus' oceans, but astronomers do have some educated guesses.

  • Plumes of water actually shoot into space through cracks at the moon's southern pole,

  • and we've driven the Cassini spacecraft through some of them to figure out what compounds

  • were inside.

  • Besides regular old H2O, there were molecules like carbon dioxide, hydrogen, ammonia, and methane.

  • That last one's especially important, because methane is produced by all kinds of organisms

  • on Earth, including single-celled archaea.

  • So this could be an indicator that there's life on Enceladus, too.

  • But before scientists got ahead of themselves, they had to see if methane-producing organisms

  • could even survive there.

  • That's where this new paper came in.

  • In this study, a team of researchers got together three different, methane-producing species of archaea.

  • Then they cultivated them in an environment we think is similar to Enceladus' southern ocean.

  • Specifically, they looked at the composition of gases, the pressure, and the pH.

  • Some of the gases on Enceladus -- like ammonia -- actually prevent certain species of archaea

  • from growing.

  • So they wanted to see if any of these three could not just survive, but thrive.

  • And one did.

  • It's a little microbe known as Methanothermococcus okinawensis, which is a mouthful.

  • It came from a hydrothermal vent field almost a thousand meters below sea level in the East China Sea.

  • Of course, just because one species could thrive in the lab doesn't mean there are

  • definitely microbes swimming on another world.

  • The researchers caution that methane can also be created through chemical reactions that

  • don't require living organisms.

  • And even if there is life making methane on Enceladus, geologic processes are definitely

  • responsible for at least some of it, too.

  • Still, the fact that we've found one species that could theoretically live there suggests

  • there could also be others.

  • And that strengthens astrobiologists' hope for finding life beyond the rock we call home.

  • Meanwhile, on pretty much the other side of the observable universe, a star went supernova.

  • Well, it actually went supernova about 10 and a half billion years ago.

  • But since light can only travel so fast, we had to wait a while to see it.

  • The good news is, it was totally worth the wait.

  • Thanks to a study published last month in The Astrophysical Journal, we've confirmed

  • this supernova is officially the oldest one ever detected.

  • The cosmic explosion -- memorably dubbed DES16C2nm -- was first captured in 2016 by the Dark Energy Survey.

  • The DES is an international collaboration trying to pin down the science behind dark energy.

  • That's the mysterious phenomenon astronomers believe could be causing the universe's

  • expansion to accelerate.

  • To investigate it, the survey is mapping 300 million galaxies, all billions of light-years away.

  • It isn't specifically looking for supernovas, but when you study that many galaxies, you're

  • bound to find one or two.

  • This one just turned out to be a special bonus -- and not only because of its age.

  • DES16C2nm actually belongs to the rarest class of supernova, known as superluminous supernovas.

  • And as the name implies, they're really bright -- about 100 times brighter than your

  • typical supernova, and even brighter than some galaxies!

  • They were discovered about a decade ago, and since then, we've only managed to identify

  • a handful of them.

  • We're still trying to pin down exactly how they work, but some scientists think they're

  • caused by matter falling onto a newly-formed magnetar.

  • Magnetars are the rapidly spinning, super dense cores of massive stars that went supernova,

  • and they have a magnetic field 100 trillion times stronger than Earth's.

  • And that makes them emit a lot of energy.

  • As that energy interacts with matter falling onto the magnetar, it makes the supernova extra bright.

  • Now that they've spotted one superluminous supernova, astronomers can go back into the

  • DES data to see if they can find more.

  • And future projects, like NASA's Wide-field Infrared Survey Telescope, will also be able

  • to detect ones even more distant.

  • It'll be able to find supernovas from when the universe was less than a billion years old!

  • And this is important because, the more distant superluminous supernovas we can find, the

  • more we can understand how space evolved.

  • Information on these supernovas is few and far between, but as far as we can tell, they

  • seem to explode in more or less the same way -- at least within a specific range of wavelengths.

  • If this is true, we could use these supernovas as distance markers to figure out how far

  • it is to different galaxies, and to figure out the size and even age of the universe.

  • With more research, they could possibly help us answer some of the many questions surrounding

  • the expansion of the universe -- or even dark energy itself.

  • Thanks for watching this episode of SciShow Space, which we couldn't make without our

  • Patreon supporters.

  • A year ago this coming Tuesday, we launched another project that couldn't exist without

  • our patrons: SciShow Psych.

  • As a thank-you to our patrons who made that channel happen, we'll be having a birthday

  • livestream celebration for SciShow Psych on Tuesday, March 6 at 3pm ET.

  • Hank and Brit will be there, as well as some of the crew, and if you're a SciShow patron,

  • we hope you can join us for this hour-long livestream too!

  • Bring your psych questions and your party hats!

  • [ ♪ Outro ♪ ]

[ ♪ Intro ♪ ]

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公式にはエンセラドゥスで生命が生存する可能性がある (It's Official: Life Could Survive on Enceladus)

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    林宜悉 に公開 2021 年 01 月 14 日
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