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  • [♪ INTRO]

  • Sending a spacecraft to explore far-off places in the solar system is cool.

  • But you know what's even cooler?

  • Sending spacecraft to explore outside the solar system.

  • It's new terrain for human-made objects, and we've only done it twice.

  • But in a series of papers published this week in the journal Nature Astronomy,

  • scientists shared the first results from Voyager 2,

  • the second spacecraft to break out of the solar system,

  • so we're starting to learn more about what's out there.

  • In 1977, NASA launched the twin Voyager spacecrafts on a daring mission to explore the outer solar system.

  • Both flew by Jupiter and Saturn a few years later, but then, as Voyager 2 headed for Uranus and Neptune,

  • Voyager 1 veered away from the planets and toward interstellar space.

  • Back in 2012, it became the first artificial object to cross the heliopause.

  • That's the boundary where the Sun's solar wind plows into the gas and dust of interstellar space.

  • It's on the order of hundreds of thousands of kilometers thick,

  • and it's one way astronomers define the edge of the solar system.

  • Voyager 1 made all sorts of measurements about what that boundary area was like,

  • but it was hard for scientists to figure out how much those measurements said about the entire heliopause

  • as opposed to that one spot where it crossed.

  • That's what made it such a big deal when NASA announced last November

  • that Voyager 2 had also reached the heliopause.

  • Now, a year later, researchers have started to compare what the two Voyagers saw.

  • Voyager 2 has been able to collect even more data than its sibling

  • because its instruments are in better condition.

  • The new data tells us that both missions crossed the heliopause at about the same distance:

  • just over 18 billion kilometers for Voyager 1 and just under that for Voyager 2.

  • That's an important datapoint because scientists debate how spherical the heliosphere,

  • or area of the Sun's influence, is.

  • At least at these two locations, it seems pretty symmetric.

  • But, Voyager 2 found the boundary layer at the heliopause to be much thinner.

  • That might be because the Sun's activity is currently near a minimum,

  • compared to the solar maximum that happened around the time Voyager 1 flew through.

  • So maybe there was less of a buffer between the solar system and interstellar space

  • when the second probe passed through.

  • Or maybe it suggests something more fundamental about the structure of the heliosphere.

  • After all, the two probes did spot some differences that aren't easily explained by the Sun's activity.

  • Like, Voyager 1 found patches where plasma from interstellar space was leaking through,

  • something Voyager 2 didn't see at all.

  • It turns out two data points is a heck of a lot better than one, but also still not that many.

  • To really understand what's going on, we are going to need more spacecraft to study different locations.

  • But that's a 40-year journey, so I wouldn't hold your breath just yet.

  • In the meantime, let's look out past Voyager to a record-setting black hole.

  • The most common black holes astronomers find are usually five to fifteen times more massive than the Sun,

  • while so-called supermassive ones can be literally billions of times more massive than that.

  • But those aren't the only black holes out there.

  • Physics suggests that stellar-mass black holes can be as little as half the size we're used to seeing.

  • The only problem is these little ones can be tricky to observe.

  • They're just tiny little black holes.

  • They're black holes!

  • It's hard to see them!

  • Small black holes pull in less material than bigger ones and, if they're not feasting on anything,

  • black holes emit basically nothing.

  • Hence the wholeblackpart.

  • But a paper published last week in the journal Science suggests a new way to find these little runts.

  • And, as is often the case with black holes, scientists went looking for their effect on stuff around them.

  • See, many stars in the galaxy are binary, meaning they're paired with another object

  • and orbit a shared center of mass.

  • If their orbit is aligned just right, we can see these stars move toward and away from the Earth

  • as they circle that center of mass.

  • That forward and backward motion causes their light to alternate between a little-too-red

  • and a little-too-blue as their light waves get stretched and compressed.

  • If they know the mass of the big star and the time it takes to orbit,

  • astronomers can work out how much the second object must weigh.

  • Then, it's time to pull out the telescope.

  • If the second object should weigh as much as a star but there's no star in sight,

  • there's a good chance it's a black hole.

  • Astronomers in this recent study went through an archive of old observations,

  • looking for giant stars that seemed to be changing color in this predictable pattern.

  • Then they narrowed down the search to stars that seemed to be orbiting invisible companions,

  • and they discovered what may be the smallest known black hole.

  • It most likely weighs just 3.3 times the mass of the Sun

  • and it could be as little as 2.6 times the mass of the Sun.

  • If so, that would put it just a hair over the theoretical limit of around 2.5.

  • Basically it's just a little baby black hole.

  • It is more massive than our entire solar system, but still.

  • Even better, the method scientists used to make this discovery

  • gives us a whole new way to look for tiny black holes in our galaxy!

  • Now, when I said record-setting black hole, you probably didn't think I meant thetiniest-ever.”

  • And I'm sure I'll be back soon with more of the biggest, baddest stuff in the universe.

  • But for now it's good to give a win to the little guys.

  • Thanks for watching this episode of SciShow Space, produced by us here at Complexly.

  • We produce over a dozen shows, including Ours Poetica,

  • which is a co-production between Complexly, The Poetry Foundation, and poet Paige Lewis.

  • Ours Poetica brings you a new poem three times per week, read by poets and writers and artists,

  • and sometimes unexpected, yet familiar, voices, like my own.

  • I got to do one for Halloween, and so of course I chose The Raven by Edgar Alan Poe .

  • It's really fun to read and it sounds like it's a creepy poem

  • but actually it's just about how grief is inescapable.

  • So, really just bring you up there.

  • There's a link in the description.

  • [♪ OUTRO]

[♪ INTRO]

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旅行者2號的星際空間筆記|科學秀新聞網 - Powered by Discuz! (Voyager 2’s Notes from Interstellar Space | SciShow News)

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    林宜悉 發佈於 2021 年 01 月 14 日
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