Hi,I’m Alex McColgan,
大家好 我是Alex McColgan
and you’re watching Astrum,
and today I am super excited.
Because I get to show you the amazing planet.
That is Saturn.
As far as planets go, this is my favourite one which isn’t Earth.
and I think by the end of this video, you may agree with me.
because thanks to the Cassini probe
we have some astonishing imagery
of this beautiful planet.
I’m going to give some insights into these pictures,
as well as explain everything you could want to know
about the 6th planet from the Sun.
A Saturn is big.
It’s a gas giant with an average radius
about nine times that of Earth
making it the senond biggest planet in our solar system.
I say average radius though
because its equatorial and polar radii differ by almost 10%.
The radius is sixty thouand kilometers at the equator.
It is only fifty-four thousand kilometers from pole to pole.
The Saturn is only one-eighths the average density of Earth,
being 0.7 g/cm3
compared to Earth’s (very dense) 5.5 g/cm3
but because Saturn is so much larger,
it has a mass over 95 Earth’s.
Interestingly, Saturn is the only planet of the solar system
that is less dense than water
about 30% less in tight
which means if you’re to have a bath big enough,
it would float.
Saturn is classified as a gas giant
because the part of the planet we see is just gas.
It doesn’t have a surface that we know of,
although it may have a solid core.
But although Saturn is called a gas giant,
it’s not entirely made of gas.
It’s got just too much mass for that.
Especially when we know that it consists primarily of hydrogen,
特别是 我们知道 土星含有大量氢气
which becomes liquid under high pressures.
Saturn has a very hot interior, reaching 11,700 °C at the core
which is twice as hot as the surface of the Sun
and the planet radiates 2.5 times more energy into space than it receives from the sun
but if we look at Saturn through the infrared,
we see Saturn’s glow, represented in brilliant
shades of electric blue, sapphire and mint green.
On the night side, with no sunlight, Saturn’s own thermal radiation lights things up.
This light is generated deep within Saturn,
and works its way upward, eventually escaping into space.
Scientists predict that Saturn’s interior is probably made of a core of iron, nickel, and rock,
科学家们预测 土星内部可能由铁 镍 岩石组成
surrounded by a deep layer of metallic hydrogen,
a middle layer of liquid hydrogen
and liquid helium and an outer gaseous layer.
But seeing as we can’t even land on the
surface,obviouslly,for an extended period of time without being crushed
actually testing this theory for Saturn
where pressures and gravity are huge
is a bit of a ways off
Saturn’s atmosphere has a banded pattern similar to Jupiter’s,
but Saturn’s bands are much fainter and much wider near the equator.
And the reason why Saturn is yellow?
It has ammonia crystals in its upper atmosphere.
But while the surface of Saturn may appear calm,
the planet is actually very active.
The winds on Saturn are the second fastest
among the solar system’s planets, after Neptune’s.
They can be blistering in 1800 km/h.
Visible storms are also known to appear on Saturn,
like this one that lasted just under a year in 2011
2011年 一场可见风暴 持续了近一年时间
Every 30 Earth years,
the planet produces what is called a “Great White spot”
which is a unique but short-lived phenomenon
that occurs once every Saturnian year.
If the storm that we see here
wasn’t the early rendition of Great White Spot
the next one we expect to see is in 2020.
In storms on Saturn, lightning is also produced.
Cassini has even detected the sound of thunder.
But while this may sound weak,
the power of lightning on Saturn is about 1,000 times stronger than that on Earth.
Still talking about storms, but moving on to the planet’s poles,
we find that each pole has giant, permanent storm.
NASA reported in November 2006 that Cassini had observed a hurricane-like storm
2006年11月 NASA报道 卡西尼号探测到了类飓风风暴
located to the south pole that had a clearly defined eyewall.
Eyewall clouds had not previously been seen on any other planet than Earth.
在此之前 除了地球 其它行星从未发现过眼壁
The ring is similar to the eyewall of a hurricane, but much much larger.
The clear air there is warm, like the eyewall of hurricane,
but on Saturn it is locked to the pole,
whereas a hurricane on Earth would drift around.
The north pole is even more unusual.
There is a permanent hexagon-shaped storm
that rotates with the planet
but it doesn’t change longitude like the rest of the clouds on the planet.
The straight sides of the polar hexagon
are each about 13,800 km long,
making them larger than the diameter of the Earth.
And why does this happen and to such a big scale?
Well, no one really knows.
Nature seems to have a thing for 60 degree angles though.
Anyone seen Giant’s Causeway ?
But like the south pole,
the north pole also has an eyewall vortex in its center.
Now, while not anyway near as strong as Jupiter’s,
Saturn does have a magnetosphere
which is strong enough to deflect the solar wind from the sun.
And Saturn’s magnetosphere, much like Earth’s, produces aurorae.
Their location and brightness strongly depend on the solar wind pressure:
the aurora becomes brighter and move closer to the poles
when the Solar wind pressure increases.
The same process produces auroras on both Earth and Saturn.
Electrons stream along the magnetic field lines of the planet into the upper atmosphere.
There, they collide with atoms and molecules,
excite them to higher energies.
The atoms and molecules release this energy
by radiating light at different colors and wavelengths
On Earth, this light is mostly from oxygen atoms and nitrogen molecules.
On Saturn, it is from hydrogen.
Now the rings for me are one of the highlights of the planet.
Saturn has a prominent ring system that consists of
nine continuous main rings,
made mostly of ice particles
and smaller amounts of rock debris and dust.
While they are mainly named after letters of the alphabet,
the naming conventions are still a little confusing,
so bear with me here
Now the first 5 rings, from the closest to the planet outward are, the D ring, which is very faint,
C ring, B Ring which is the brightest and widest of all the rings
the A ring, which is the last of the bright rings, and then the F ring.
The D ring starts from 66,000 km from Saturn’s center
and last to the bright rings’ finish as 140,000 km above Saturn’s center.
These rings are mostly made up of
water ice, with traces of rocks.
If we look in the ultraviolet at a section of the brightest rings,
it shows there is more ice towards the outer part of the rings than in the inner part.
The red in the image represents sparser ringlets made of
dirty and possibly smaller particles,
than in the icier turquoise ringlets.
If we look at a picture representing radio occultation,
we can judge the size of the individual particles
that make up the rings.
Color is used to represent information about ring particle sizes
based on the measured effects of the three radio signals.
shades of red indicate regions where there is a lack of particles
less than 5 centimeters in diameter, so, generally quite big particles.
Green represents particles of sizes smaller than 5 centimeters
and blue represents particles smaller than 1 cm.
Overall, it’s thought that
the particles in the rings aren’t bigger than 10m and can be microscopic in size.
The main rings are thought to be as little as 10 meters thick to 1 kilometer thick.
Particularly in the B rings,
we can see that the rings are not perfectly symmetrical.
During the planet’s equinox, the rings can get a bit wonky.
在土星昼夜平分线上 B 环有点不均匀
Look at the top of this video, where the B ring meets the A ring.
Zooming in on this structure reveals ridges and spokes a couple of kilometers tall.
Their presence is given away by their shadows.
Zooming out again, we can see the scale of
how many spokes there are during this period.
Oscillations happen all the time in the rings though,
perhaps due to the presence of a shepherd moon, or even just naturally.
The differences in these oscillations, which can be seen
all in a day, can be up to 200 kilometers.
So I’ve talked about the D, C, B,
前面我已经谈过D环 C环 B环
and the A rings and also mentioned the F ring.
The F ring can also get a bit wonky,
and has a perfect example of
what is called a shepherd moon.
This one being Prometheus
that leaves a ripple in the ring as it orbits.
Once during its 14.7-hour orbit of Saturn,
Prometheus, which it’s only 63 miles or 102 kilometers across,
reaches the point in its eclipitical path,
where it is farthest away from Saturn and closest to the F ring.
At this point, Prometheus’ gravity is just strong enough
to draw a streamer of material out of the core region of the F ring.
And that’s what caused these ripples which you can see.
So what comes after the F ring?
Well, the first after the F ring,
is Janus or Epimetheus Ring,
then, the G Ring, the Pallene Ring, and then the E Ring.
I know it’s a little bit confusing,
but bear with me and I’ll go through it again.
Now look at this picture, it’s absolutely amazing,
现在 看看这张图片 它是如此惊艳
and I might just do a separate video on this.
But for the sake of time,
this bright blue ring you see on the outside is the E ring,
And just below that you can see the faint Pallene Ring
at the top of the picture.
The G ring is the next distinct ring, and you can just about see
the Janus or Epimetheus ring also at the top but just below it.
And can you see us?
We’re also in this picture.
There, right in the corner, is Earth and its moon.
So now you know a little bit about the rings.
I think you’ll agree they are so interesting in their own right.
Theories abound as to why they are there,
but we simply don’t know.
We know that some of the moons are responsible for some of the material there,
but we also know that some of the material there
is responsible for some of the moons.
And talking of moons, I’m going to give you
a brief rundown about those that belong to Saturn.
Again, I do plan to do a separate video or even videos about them
as there are at least 150 moons and moonlets, 53 with formal names.
They come in all shapes and sizes, and most uniquely,
它们大小不同 形状各异 更独特的是
Saturn’s biggest moon Titan, which is even bigger than Mercury,
土星最大的卫星 提坦 比水星还大
is the only moon in the solar system with a thick atmosphere around it.
I’m also gonna throw in here that Saturn has the Death Star orbiting it,
We call it Mimas.
Lastly, we are coming to the end.
I just got one last thing I want to talk about.
I want to talk about Saturn’s orbit.
Saturn orbits about 9 to 10 times farther away from the Sun than Earth does.
And one year on Saturn can take 30 Earth years.
But funnily enough, a day on Saturn is different depending on
where you stood (not that you could really stand on Saturn).
At the equator or at the poles,
a day lasts about 10 hours and 14 minutes.
Elsewhere, so everywhere apart from the poles near the equator,
a day lasts 10 hours and 38 minutes.
The issue is, because Saturn isn’t solid,
it’s not bound to rotate at the same speed all over.
I just want to leave you with this.
Few sights in the solar system
are more strikingly beautiful than softly hued Saturn
embraced by the shadows of its rings.
And look at this beautiful change from gold to blue.
It’s a striking visual effect that scientists don’t fully understand.
Current thinking says that it may be related to seasonal influences,
tied to the cold temperatures in the northern winter hemisphere.
And despite all that we have learned from the probe Cassini
Saturn remains a world of mystery.
I really appreciate you watching this far,
and if you did find this video interesting
then I’d ask you to please like and share it
as it helps me a lot.
It’s still a small channel and I would love to be able to grow
I plan to do a video for every planet in our solar system.
I’ve already made videos for Mars and Mercury,
and if you enjoy this video,
I’m sure you’d like those ones too,
so you should definitely check those out.
and of course I would continue to keep making videos
about our solar system and beyond,
so really, please subscribe and you won’t miss any of the future things I got to show you.
所以 赶快订阅吧 别错过新的视频哦