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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.
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