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  • [♪ INTRO]

  • The Sun is a pretty big deal.

  • It affects pretty much everything that happens here on Earth

  • as well as all the other planets in the solar system.

  • But in some ways, we know shockingly little about what the Sun is actually like.

  • Now, that's about to change, thanks to the first results from NASA's Parker Solar Probe.

  • Parker set out for the Sun in August of 2018, and since then,

  • it's been looping around our star in tighter and tighter orbits.

  • So far, it's swung within 24 million kilometers of the Sun's surface,

  • more than twice as close as the orbit of Mercury.

  • And last week, in a set of four papers published in the journal Nature,

  • scientists revealed the results of Parker's first two flybys of the Sun.

  • The spacecraft's goal is to study the Sun's outermost layer, called the corona.

  • The corona is a thin layer of plasma that can reach millions of degrees Celcius.

  • It's also the source of the solar wind,

  • a stream of electrically-charged particles moving outward from the Sun.

  • But we don't know much about the Corona

  • because it's only visible from Earth during a solar eclipse.

  • Now, though, in its first flybys, Parker is already starting to tell us more.

  • For instance, by the time the solar wind reaches Earth,

  • it has a pretty smooth, steady appearance,

  • but Parker's first measurements reveal that's definitely not true when it first gets going.

  • Close to the Sun, the solar wind looks far more turbulent.

  • Its charged particles latch onto the Sun's powerful magnetic field,

  • so as the Sun rotates, the wind gets dragged along for the ride.

  • And because every action has an equal and opposite reaction,

  • the energy it takes to drag the solar wind

  • also permanently slows down the spinning of the Sun itself.

  • I mean, just a little bit, but it's pretty amazing that a bunch of tiny particles

  • can put the brakes on something as big as the Sun!

  • Measuring the details of that process may help astronomers better understand

  • how young stars interact with the disks of gas and dust that surround them,

  • since scientists think that material is strongly connected to the magnetic field.

  • Speaking of which, Parker also showed that

  • the Sun's magnetic field is way more variable than scientists assumed in the past.

  • As it flew past the Sun, Parker repeatedly measured

  • nearly complete 180s in the field's direction.

  • So, instead of pointing away from the Sun like usual,

  • the magnetic field would point almost directly back towards it,

  • for seconds or minutes at a time.

  • Scientists can't detect this from Earth,

  • but this new information may offer clues about

  • the processes that get the solar wind flowing in the first place.

  • Finally, other Parker observations are only hints of what might be coming next.

  • Like, for a long time, astronomers have predicted that

  • dust that drifts too close to the Sun eventually gets vaporized,

  • leaving a dust-free zone around the star.

  • And now, the probe's cameras appear to be

  • detecting less dust floating around in space as it gets closer to the Sun.

  • Which seems to support that prediction.

  • But to be sure that's what is happening,

  • scientists will have to wait for closer approaches.

  • Fortunately, those are coming.

  • Over the next five years, Parker will slowly lower its orbit

  • until it gets within just 6.5 million kilometers of the Sun.

  • In the meantime, the data will keep flowing.

  • Back in September, the probe made its third close approach,

  • so keep your eyes peeled for new findings in the months ahead.

  • We also got new details last week about a new instrument that was installed in April

  • on LIGO, the United States' gravitational wave observatory.

  • LIGO searches for ripples in spacetime, which radiate outward

  • from massive gravitational events like the mergers of black holes.

  • The new instrument is called the quantum vacuum squeezer,

  • and it sounds like it's straight out of Star Trek.

  • To understand what it does, first we need to talk about how LIGO works.

  • LIGO has two L-shaped detectors thousands of kilometers apart:

  • one in Washington State and another in Louisiana.

  • Each one works the same way.

  • The two arms of the L intersect, and there's a set of mirrors where they meet.

  • On either end, a laser shines toward the mirrors.

  • Those mirrors reflect light back toward their source and onto a sensor.

  • If they travel exactly the same distance, they'll cancel each other out.

  • But if a gravitational wave washes over the detector,

  • it physically distorts space and briefly changes the length of the tubes.

  • Because it only distorts space in one direction,

  • it creates a slight difference in length between each arm of the L.

  • That means signals from the lasers won't perfectly cancel each other out.

  • So any time a mismatch is measured at both detectors,

  • it's a potential sign of a gravitational wave.

  • To make sure nothing disrupts the light from the lasers and creates a false signal,

  • the whole system operates in a nearly perfect vacuum.

  • But vacuums are weird things.

  • On the tiniest scales, the effects of quantum mechanics

  • mean that particles like photons are popping in and out of existence all the time.

  • Even in a totally empty space.

  • If some of those extra photons hit the special light sensors,

  • they can add uncertainty to the distance measurement

  • that's at the heart of how LIGO works.

  • Scientists call this effect quantum vacuum noise.

  • And that's where the quantum vacuum squeezer comes in.

  • This noise has two basic qualities: phase and amplitude.

  • Phase affects the timing of when photons arrive at the light sensor,

  • while amplitude describes how many photons there are.

  • A quantum vacuum squeezer is a special instrument made of crystals and mirrors

  • that can basically exchange one kind of quantum fluctuation for the other.

  • In the case of LIGO, variation in phase is more of a problem than variation in amplitude,

  • so the squeezer narrows down the range of possible phases,

  • while allowing amplitude to vary more.

  • Explaining exactly how this device works would probably require a whole series of videos.

  • But the end result is that LIGO is more sensitive to gravitational waves.

  • With the squeezer installed on both detectors, it can detect gravitational waves out to

  • 400 million light-years away, which is about 15% farther than before. Which is a lot!

  • Before the devices were installed in April, LIGO would detect about one gravitational wave a month.

  • Now it's more like one every week.

  • Which is great news, because detectors like LIGO

  • are our only tool for studying gravitational events like the mergers of black holes.

  • And when you think about it, it's really pretty cool

  • that we can only detect some of the universe's biggest events

  • once we know what's going on at the tiniest scales.

  • Thanks for watching this episode of SciShow Space!

  • And if you want to learn more about what LIGO is doing,

  • you might like this video about gravitational waves

  • and how they're changing the future of astronomy.

  • [♪ OUTRO]

[♪ INTRO]

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