Voyager 2’s Notes from Interstellar Space | SciShow News

Voyager 2’s Notes from Interstellar Space | SciShow News


[♪ 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 whole “black” part. 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 the “tiniest-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]