Placeholder Image

字幕列表 影片播放

  • [ ♪ Intro ]

  • On New Year's Day, the New Horizons spacecraft performed the farthest flyby ever,

  • zooming past an object called MU69.

  • It's a small, frozen rock way past Neptune,

  • and because it's so cold, it likely hasn't changed much in billions of years.

  • So scientists have been hoping it can teach us about the solar system's early conditions.

  • Except, we may have gotten more than we bargained for.

  • For the last few weeks, as the first images of MU69 have trickled in,

  • we've been looking at what we thought was some kind of primordial snowmanbut we were wrong.

  • Last week, NASA released a new picture of MU69,

  • based on images that New Horizons snapped 10 minutes after its closest approach.

  • And after some analysis, astronomers discovered that our beloved snowman

  • is actually more like a pair of lumpy pancakes.

  • We've never seen anything quite like it, and it's throwing astronomers for a loop.

  • And it wasn't simple to get this picture of MU69.

  • At this point in the flyby, New Horizons was looking backward into the solar system,

  • and it saw the rock as nothing but a crescent of light.

  • A lot like with a crescent Moon, the unlit part of its body was completely invisible.

  • And the lit part was so faint that the photos had to have long exposures

  • to collect enough light to see much of anything.

  • But that also meant those images were really blurry,

  • which will happen when you're taking a long-exposure picture while flying by at more than 50,000 kilometers per hour.

  • To form this new image, astronomers stacked a bunch of blurry photos together

  • and processed them to get a sharper image.

  • Then, they traced around the region where background stars were blotted out,

  • which allowed them to outline the shape of MU69.

  • The team found that largest lobe was extremely flat,

  • and the smaller one looked a little more like a walnut.

  • And that kind of throws a wrench in things,

  • because until now, the early data coming in from MU69

  • have mostly confirmed our basic ideas about how the solar system formed.

  • The two lobes, frozen mid-collision, offered pretty solid evidence that, early on,

  • tiny, relatively round planetesimals clumped together to form larger bodies, including the planets.

  • But this flatness thing comes out of left field.

  • We've never seen an object this shape orbiting the Sun.

  • The closest thing to it might be Saturn's moon Atlas.

  • It's flat too, but it formed under completely different circumstances, in the middle of Saturn's rings,

  • so it doesn't help us understand how MU69 came to be.

  • So far, scientists don't have any strong ideas about what might have flattened these rocks.

  • But as more data slowly cross the several billion kilometers between us and New Horizons,

  • we'll continue to learn more.

  • Whatever hypotheses emerge will almost definitely shake up our ideas about the process that made MU69,

  • and the process that likely made Earth.

  • Objects like this can help researchers understand the past and future of our solar system,

  • but astronomers are also interested in a lot more than that.

  • On a much more massive scale, they're also decoding our galaxy's past

  • as a way to understand what's in store for it.

  • We've known since the 1920s that, unlike other galaxies, which are moving away from us,

  • a number of nearby galaxies are moving toward us.

  • They're part of what's called the Local Group and, eventually,

  • the whole thing will merge with other objects to form one massive galaxy.

  • But until now, the details of exactly how and when that will happen have been hard to pin down.

  • Then, last week, astronomers announced in the Astrophysical Journal that they had mapped

  • the motion of our two largest neighbors: the Andromeda and Triangulum galaxies.

  • Along with the Milky Way, they hold most of the mass in the Local Group,

  • and their pasts and futures are intertwined with ours.

  • So studying them has given scientists the clearest picture yet of the Milky Way's fate,

  • and of its eventual collision with Andromeda.

  • The researchers used data from the European Space Agency's Gaia space telescope,

  • which is about 1.5 million kilometers from Earth.

  • Gaia was made to create a 3D map of stars that are mostly in our galaxy.

  • But it's actually powerful enough to peek inside other nearby galaxies, too.

  • For this study, the researchers identified thousands of individual stars in these galaxies,

  • then collected really precise data on their positions and motions, which, by the way,

  • is not easy to do: On the plane of the sky, any movement a few million light-years away is miniscule.

  • But it's worth it.

  • The useful thing about individual stars is that they can give us a detailed look at a galaxy's structure

  • and reveal how stars move around its axis.

  • The scientists were able to use the data to trace the paths of Andromeda and Triangulum

  • for billions of years into the past and future.

  • And they found a few interesting things.

  • For one, it looks like we're actually not poised for a head-on collision with Andromeda,

  • as we used to think.

  • When the two galaxies do have their run-in, it will be more of a shoulder bump,

  • where they hit each other from the side.

  • That doesn't mean it will be pretty though,

  • Andromeda is still headed for us at around 400,000 kilometers per hour,

  • but it won't be the smashup we expected.

  • The new findings also push back the date of that fateful collision to about 4.5 billion years from now.

  • That's around 600 million years later than existing models.

  • These results show that Gaia has lots of potential for exploring beyond the galaxy.

  • And the better we understand these neighbors, the more we can figure out about the structure

  • and evolution of galaxies in general.

  • Astronomy research can often work like a catapult:

  • The farther we go back, the farther we can reach into the future.

  • And from the edges of our solar system to well beyond the Milky Way,

  • astronomers are using that strategy to make sense of the universe.

  • Thanks for watching this episode of SciShow Space News.

  • And a special, spacious thanks to SR Foxley, our Patreon President of Space.

  • Scientists are learning new things about the universe literally every week,

  • and we wouldn't be able to keep up with covering it without your generous support.

  • If you want to help make SciShow high quality and free to everyone who wants it,

  • check out Patreon.com/SciShow.

  • And thank you!

  • [ ♪ Outro ]

[ ♪ Intro ]

字幕與單字

單字即點即查 點擊單字可以查詢單字解釋

B1 中級

MU69是平的,沒有人知道為什麼|科學秀新聞網 (MU69 is Flat, and No One Knows Why | SciShow News)

  • 4 0
    林宜悉 發佈於 2021 年 01 月 14 日
影片單字