[♪ INTRO]
When it comes to space, it’s easy to imagine the visible things,
like visible matter and light.
But some of the most important processes in the solar system are
invisible phenomena like electric and magnetic fields.
And, thanks to some clever collaborations and up-close observations,
scientists recently announced a couple of big steps forward
in understanding the invisible parts of our solar system.
First up is the granddaddy of the solar system’s electromagnetic environment, the Sun.
Space scientists know quite a bit about the Sun’s magnetic field,
which is responsible for a bunch of phenomena, like sunspots and solar flares.
But it wasn’t until very recently that researchers could
say anything specific about our star’s electric field.
In a paper published this week in The Astrophysical Journal,
scientists have calculated its strength for the very first time,
by getting up close and personal with our star.
The Sun shapes the solar system in a lot of ways,
including through its light, heat, and gravity.
But one of the less obvious ways it affects things is through its solar wind,
a tidal wave of electrically charged particles constantly streaming out of our star.
This wind permeates space and is basically
the background noise to everything that happens in the solar system.
Which is why it’s kind of a problem that scientists
still don’t have a detailed understanding of how it forms.
And one of the biggest unknowns is the role of the Sun’s electric field.
An electric field is the total electric force exerted
by every charged particle in a given area.
And we know that the Sun has one because it has
a lot of charged particles exerting a force on one another.
They’re mostly protons and electrons that result from hydrogen atoms splitting apart.
And all of these particles are superheated because… it’s the Sun.
That heat makes them rush outward toward space, and,
since electrons are way lighter than protons,
they’re more likely to escape the Sun’s gravity.
But all of these separated electrons and protons are still pulling on each other,
which sets up an electric field around the Sun!
This field helps shape the speed and movement of the solar wind,
but even though scientists knew it existed, they didn’t know that much about it.
That’s because, spread across a vast swath of space,
its strength in any one place is pretty weak.
And, by the time the solar wind reaches Earth,
the effects of other processes make it hard to discern even its indirect effects.
So, to measure the field’s impact at all, you’ve got to be right in it.
Fortunately, for the first time, we’ve got a spacecraft close enough
to make those observations: NASA’s Parker Solar Probe.
Parker is currently approaching a distance 10 times closer to the Sun than Earth,
putting it right in the region where the solar wind is being generated.
There, the spacecraft measured the velocities of the electrons around it,
which scientists could then use to estimate the strength of the electric field.
And, to their surprise, Parker revealed that, while the Sun’s electric field
does affect the wind, it doesn’t seem to do so as strongly as they predicted.
So it’s not the main factor pushing the solar wind across the solar system,
and scientists still don’t know what is.
But by ruling out one hypothesis, they’ve opened the door for new,
still-undiscovered processes to lead the way.
After the Sun, the solar system’s next-most powerful
magnetic environment is Jupiter’s.
Like Earth, Jupiter’s magnetic field helps create auroras,
bursts of light emitted as the magnetic field
channels charged particles from space into the atmosphere.
But Jupiter’s auroras aren’t visible to the human eye.
Instead, they shine at ultraviolet, infrared, radio, and even X-ray wavelengths.
And the planet’s X-ray auroras are some of the most intriguing of them all.
These bursts of X-rays seem to be unique to Jupiter, and,
for more than 40 years, scientists have wondered how they form.
Finally, they might have figured it out.
In a paper published last week in the journal Science Advances,
astronomers suggested that these odd auroras form from waves of charged
particles launched into the atmosphere by vibrations in Jupiter’s magnetic field.
Now, researchers had already known for a while that the X-ray auroras were made
by charged oxygen and sulfur atoms emitted by volcanoes on Jupiter’s moon Io.
They could tell because it takes a specific combination of atoms to produce a given
type of aurora, so researchers could identify which atoms were causing these.
The mystery was how these volcanic atoms got
channeled into Jupiter’s atmosphere in the first place.
To look for an answer, the research team combined big-picture observations
made from Earth with small-scale observations made at Jupiter.
To measure Jupiter’s aurora, they used the European Space Agency’s
XMM-Newton, an X-ray telescope that orbits Earth.
Meanwhile, to understand what was happening in Jupiter’s magnetic environment,
they pulled data from NASA’s Juno orbiter, which is currently circling Jupiter.
XMM-Newton observed bursts of X-rays coming from the aurora every 27 minutes.
At the same time, Juno detected massive waves of plasma,
or electrically charged atoms, washing over the spacecraft with a similar frequency.
The source of these waves is unclear, but one possibility is that they’re generated
by interactions between Jupiter’s magnetic field and the solar wind.
As the planet rotates, its field sweeps through space with it,
smacking into the current of the solar wind.
The force of that collision could cause magnetic field lines to bend and compress,
heating up the particles trapped within them and launching a massive wave of plasma.
This wave could include particles that had been blasted into space
by Io’s volcanoes and trapped in the magnetic field lines.
If this hypothesis is correct, each plasma wave would travel back
along the field lines until it strikes Jupiter’s atmosphere,
delivering the oxygen and sulfur atoms that create the aurora.
Space physicists will need more observations to confirm this hypothesis,
but what we know already highlights the dynamic connections
between objects in the solar system.
Aside from being beautiful light shows on Earth, auroras also represent a direct
connection between the Sun, its invisible fields, and all the planets around it.
Another direct connection between Earth and celestial bodies
is how we get things into space.
And that’s by catching a ride on the crawler-transporter!
A specifically made vehicle used to transport million-dollar hopes and dreams
for space exploration to the launch pads.
And we've immortalized it as a pin, featuring a tiny crawler-transporter!
Which is available all month at DFTBA.com/SciShow.
It’s only available in July, so make sure to order yours soon.
In August, we’ll have a whole new pin for you.
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