Placeholder Image

字幕列表 影片播放

  • SciShow Space is supported by Brilliant.org.

  • [♩INTRO]

  • We've got another discovery to add to the growing list of surprises

  • astronomers have uncovered about the early universe recently.

  • In a paper published last week in the journal Nature,

  • an international group of researchers announced

  • that they'd found a pair of galaxies from the first billion years of the universe.

  • And they're almost impossibly big for their age.

  • The first galaxies started forming a few hundred million years

  • after the Big Bang, and for the most part,

  • we assumed they were fairly small, irregularly shaped collections

  • of a few billion stars, similar to modern dwarf galaxies.

  • Those small galaxies would then act as building blocks,

  • merging together over the next billion or so years

  • to form the much larger galaxies we're used to seeing.

  • Problem is, the pair of galaxies the researchers describe in their paper,

  • which is from about 780 million years after the Big Bang,

  • doesn't really fit that description.

  • Looking so far back in time is difficult

  • because everything is really far away and incredibly dim.

  • To study this pair, the team used the ALMA observatory in Chile

  • to take advantage of an effect called gravitational lensing.

  • That's where the gravitational pull of a large galaxy

  • between us and the object of interest warps that object's light,

  • making it look brighter.

  • Unfortunately, the lensing also heavily distorts the image,

  • so the researchers needed to use computer modeling

  • to calculate things like how far away it is and how much mass it has.

  • Turns out … a lot.

  • They found that the larger of the two galaxies

  • has a mass of gas and dust over 270 billion times the mass of our Sun

  • about 3-5 times as much as the Milky Way.

  • That makes it the most massive object ever detected

  • from the first 950 million years or so of the universe's history.

  • The other galaxy is much smaller, coming in at just 35 billion solar masses,

  • but for its time, it's actually pretty impressive in size, too.

  • But both are nothing

  • compared to the amount of dark matter they're embedded in,

  • which the team estimated to be a few trillion solar masses.

  • Dark matter makes up nearly 85% of all the matter in the universe.

  • It doesn't interact with light at all,

  • which is why it's been so hard to figure out what it's made of.

  • But we know it's there

  • based on how its gravitational pull affects the regular matter we can see.

  • While the dark matter around this pair is roughly equivalent

  • to the amount of dark matter in and around our own galaxy,

  • astronomers have found that early galaxies

  • tend to have much less dark matter relative to their size.

  • It would be more like finding a modern galaxy

  • with 10,000 trillion solar masses of dark matter,

  • instead of just a few trillion.

  • That's how extreme this is.

  • All together, these galaxies and their dark matter

  • almost break the current models astronomers have for early galaxy formation.

  • Like, the math still technically works, butbarely.

  • And that's not all -- we're also seeing the two galaxies right before they merge.

  • Their centers are as close together

  • as our solar system is from the center of the Milky Way.

  • So this pair of galaxies is super weird.

  • And it'll be interesting to see how scientists use the data

  • from this new discovery in future research on how and when

  • galaxies started forming in the early universe.

  • Closer to home, NASA announced last week that the Opportunity rover

  • has officially made it through the worst of its eighth Martian winter.

  • But a planet-wide dust storm might be on the horizon.

  • Unlike the radioactively-powered Curiosity rover,

  • Opportunity relies on solar power to keep running,

  • and sunlight comes at a premium during the winter.

  • Since the rover is in Mars's southern hemisphere,

  • the mission team has to position it on angled ground so its solar panels

  • are tilted northward, toward the Sun.

  • That might not sound like a big deal,

  • but Opportunity's twin Spirit failed to survive their fourth Martian winter

  • back in 2009 because two of its wheels broke

  • and it couldn't maneuver itself into a position

  • where it could capture enough light to keep running.

  • And during the very next winter,

  • Opportunity found itself stuck in one spot for 19 weeks

  • because there were no places within driving distance

  • that could provide the necessary tilt.

  • It's in a much better location now, though

  • inside the western edge of what's known as Endurance Crater,

  • where there's plenty of angled ground.

  • But the tilt of its solar panels isn't the only thing

  • Opportunity has to worry about to get enough light during the winter months.

  • Dust is another main obstacle

  • both the particles that get kicked up into Mars's thin atmosphere during storms,

  • and those that settle on the rover's solar panels.

  • Continent-sized storms happen every year or so,

  • and because there's so little water in the atmosphere,

  • the dust can hang around in the air for weeks.

  • In July 2007, a planet-wide dust storm forced Opportunity

  • to shut down all non-vital systems when the surrounding dust blocked

  • 99% of direct sunlight and it lost 80% of its power output.

  • It took six weeks for the rover to get back to work.

  • Mars hasn't had a planet-wide storm like that since

  • Opportunity's brush with death a decade ago.

  • But the average length of time between those giant storms

  • is 3 Martian years, or 5.5 Earth years.

  • That doesn't necessarily mean you can expect a massive storm

  • every 3 years, but atmospheric scientists aren't sure why it's been so long

  • since the last one.

  • Some think the next one might happen in 2018,

  • as Mars's orbit takes it closer to both the Sun

  • and the solar system's center of gravity.

  • Even if we do get another planet-wide storm next year,

  • the mission team is optimistic.

  • Back in the Martian autumn,

  • Opportunity's panels were the second dustiest they'd ever been.

  • But they've gotten much cleaner since then thanks to some wind.

  • At most, Opportunity might have to put its exploration on hold

  • for a bit while it waits for more wind and sunlight.

  • Not bad for an almost 14-year-old rover

  • that was only supposed to run for 90 days.

  • Like with that almost impossibly large pair of galaxies,

  • sometimes life in space is all about defying the odds.

  • The main reason we've been able to learn about those galaxies

  • or anything else from the early universe

  • is Hubble's Law, which lets you take advantage

  • of the fact that light travels at a constant speed

  • to calculate an ancient galaxy's distance and age.

  • SciShow's sponsor, Brilliant, helped rekindle my understanding

  • of Hubble's law with an interactive lesson in their Astronomy unit.

  • So in this first one, you're standing on a bike path beside a train,

  • and you're facing a train that's going perpendicular to you.

  • The train goes along at 40 mph,

  • they leave the station every 10 minutes and travel in the same direction.

  • So, how many trains go past in an hour.

  • So, six.

  • Now you're finally riding your bike at 20 mph in the same direction as the train,

  • so that halves your answer, and you get three.

  • Going the other way, you get more, because you're going opposite

  • the direction of the train, so you're going to see more trains.

  • So, nine.

  • I got that right!

  • What a cool way to look at this.

  • If you are biking away from the source of a green light

  • and you pedal quickly enough.

  • Like, you'd have to go really, really fast

  • What would happen to the light?

  • When I was biking away from the train, I was seeing the trains less frequently.

  • So I would be seeing the waves of the green light less frequently,

  • so the waves would be longer in between, so that would be red light.

  • AH!

  • I got it!

  • So that was a fun one and I'm going to keep playing it.

  • But I don't want to tell you all the answers

  • and I don't want you to start seeing when I get them wrong

  • So you should go check them out too!

  • And the first 200 people to sign up at https://brilliant.org/scishowspace

  • will get 20% off their annual subscription

  • and support SciShow Space.

  • So, thank you!

  • [♩OUTRO]

SciShow Space is supported by Brilliant.org.

字幕與單字

影片操作 你可以在這邊進行「影片」的調整,以及「字幕」的顯示

B1 中級

一對巨大得令人髮指的古星系 (A Ridiculously Huge Pair of Ancient Galaxies)

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