Name: なぜ私たちは太陽の極を一度しか見たことがないのか (Why We've Only Ever Seen the Sun's Poles Once)
Uploaded: 2021-01-14T10:30:24.000Z
Duration: 4 min 53 s
Description: VoiceTubeの動画で発音を聞きながら英語表現を覚えよう！学べる英語：

転換語

Even though we've spent decades exploring the solar system,

分詞構句

we've really only done it in two dimensions, generally speaking.

Since the planets are all on the same plane, called the ecliptic,

we haven't needed to go way above or below the solar system.

Everything we need to study is sitting nice and cozy in that plane.

From the ecliptic, it's almost impossible to study the area around the poles of the Sun,

which, like the rest of our star, we're super interested in learning about.

That is where the Ulysses mission came in.

In 1990, NASA and the European Space Agency launched the first real orbiter to go

out of the ecliptic, and it gathered tons of solar data for about eighteen years.

It revolutionized our understanding of our star,

but there's a reason we haven't sent another one yet.

Out-of-ecliptic missions… are kind of a pain.

All the planets orbit in the same plane because they formed from the same

And getting out of that plane is really difficult.

When you launch something from a moving body inside the ecliptic, like the Earth,

your probe will automatically start traveling in a direction that keeps it inside that plane.

To get out, you have to cancel all that motion and move

basically perpendicular to where you started.

It's hard, and none of our rockets can pull it off right from launch.

But Ulysses made it happen, thanks to some cool engineering.

Usually, when we launch something that's gotta go

pretty far, pretty fast, we use a gravity assist.

Basically, you get close to a large body, like a planet,

then use its gravity to slingshot yourself along a new path with a higher speed.

And that's true for out-of-ecliptic missions like Ulysses, too.

After leaving Earth, Ulysses went to Jupiter, which, as the most massive planet, can impart

a huge amount of acceleration to anything that gets close enough.

It flew up over Jupiter's poles, then let the planet's

gravity sweep it over and back under itself.

That got Ulysses going perpendicular to the ecliptic,

and flying back toward the point where it started, essentially going backward!

Then, it started its big loop around the Sun.

Getting Ulysses out of that plane allowed it to study the Sun from a different angle,

including its magnetosphere, composition, and solar winds.

It also carried instruments to study dust in the solar system and ones to look beyond

the Sun at cosmic rays that come from really energetic sources, like black holes.

Over almost two decades, Ulysses made nearly

three full passes over the Sun, and it taught us a lot.

Like, more than a thousand articles worth of stuff!

For one, Ulysses's unique perspective allowed us to make the first

3D survey of our star's magnetosphere and composition.

It also took the first direct measurements of interstellar dust and showed that

tons of it is flooding into the solar system; up to thirty times more than we thought.

And because Ulysses was active for so long, it managed to gather data over about one and

a half solar cycles, which meant it could even see how the Sun changed over time.

Every six-ish years, the Sun is either super active,

with lots of flares and sunspots, or pretty quiet.

And Ulysses showed that things like the solar wind, the flow of charged particles from the star,

actually change depending on its activity level.

It found that the solar winds are getting weaker in general, too!

We think that coincides with a natural reduction in the Sun's magnetic activity,

but we don't know just how, or if and when that trend will stop.

Either way, understanding these changes is super important to us on Earth,

because the solar winds can damage electronics on the

International Space Station and in satellites.

Which we need to tweet! And, you know, call 911 sometimes.

Because of Ulysses's discovery, we're better able to predict the behavior of the

solar winds, so we're better able to protect astronauts in space

And looking much farther from home, Ulysses was also a

player in confirming the existence of magnetars.

These are a type of neutron star with super strong magnetic fields, which emit

big doses of gamma radiation... kinda whenever they feel like it.

Along with a few other satellites, Ulysses snagged observations of only the fourth confirmed

magnetar in 1998, one that was even brighter than the others.

The magnetar hypothesis had just started to become accepted,

so these measurements were really valuable to researchers.

And the list of Ulysses's discoveries goes on from there.

The mission ended in 2008, and there are now mountains of papers and books

So even though getting out of the ecliptic was tricky, it was definitely worth it.

So worth it that we're gonna launch another one!

Today, the ESA and NASA are working on another out-of-ecliptic mission called Solar Orbiter.

It'll launch in 2020 and orbit at an inclination of 25 to 34°,

which isn't as dramatic as Ulysses but will still give us more exciting, 3D data about the Sun!

For now, though, scientists are still pouring over that data from the first mission.

So we'll have plenty to keep us busy until then.

Thanks for watching this episode of SciShow Space!

If you want to keep up with the latest space news, including future missions like Solar Orbiter,

you can go to youtube.com/scishowspace and subscribe.

We release brand-new news episodes every Friday!

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なぜ私たちは太陽の極を一度しか見たことがないのか (Why We've Only Ever Seen the Sun's Poles Once)

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