Hi I’m Alex McColgan, and you’re watching
Astrum, and today I am super excited. Why? Because I get to show you the amazing planet
that is Saturn. As far as the planets go, this is my favourite
that 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 insights to these pictures,
as well as explain everything you could want to know about the 6th planet from the Sun. Physical Characteristics
Saturn is big. It’s is a gas giant with an average radius
about nine times that of Earth, making it the second biggest planet in our Solar System. I say average radius though, because its equatorial
and polar radii differ by almost 10%: 60,268 km at the equator, versus 54,364 km from pole
to pole. While only one-eighth the average density
of Earth, 0.687 g/cm3 compared to 5.514 g/cm3, with its larger volume Saturn has the mass
of over 95 Earths. Interestingly, Saturn is the only planet of
the Solar System that is less dense than water—about 30% less. 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. Saturn is called a gas giant, but it is not
entirely made of gas, it’s just got too much mass for that. Especially when we know that it consists primarily
of hydrogen, 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. 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 (right side of image), 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, 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 of Venus for any 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. Atmosphere
Saturn's atmosphere has a banded pattern similar to Jupiter's, but Saturn's bands are much
fainter and are much wider near the equator. And the reason 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 a blistering 1800 km/h. Visible storms are also known to appear on
Saturn, like this one that lasted just under a year in 2011. 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 this storm wasn’t an early rendition
of this great white spot, the next one is expected in 2020. In storms on Saturn, lightning is produced. Cassini has even detected the sound of the
thunder. But while this mean sound weak, the power
of lightning on Saturn is about 1,000 times stronger than on Earth. Poles
Still talking about storms, but moving on to the planet’s poles, we find that each
pole has giant, permanent storms. NASA reported in November 2006 that Cassini
had observed a "hurricane-like" storm locked to the south pole that had a clearly defined
eyewall. Eyewall clouds had not previously been seen
on any planet other than Earth. The ring is similar to the eyewall of a hurricane,
but much larger. The clear air there is warm, like the eye
of hurricane, but on Saturn it is locked to the pole, whereas a hurricane on Earth drifts
around. The north pole is even more unusual. There is a persistent hexagon shaped storm
that rotates with the planet, but it doesn’t change longitude like the rest of the cloud
on the planet. The straight sides of the polar hexagon are
each about 13,800 km (8,600 mi) long, making them larger than the diameter of the Earth. And why does this happen and to such a big
scale? No-one really knows. Nature seems to have a thing for 60 degree
angles though. Giant’s Causeway anyone? But like the south pole, the north pole also
has a vortex, or eye wall. Aurora
While not anywhere near as strong as Jupiter’s, Saturn does have a magnetosphere which is
strong enough to deflect Solar wind from the Sun. And Saturn's magnetosphere, like Earth's,
produces aurorae. Their location and brightness strongly depends
on the Solar wind pressure: the aurorae become 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 into the upper atmosphere. There, they collide with atoms and molecules,
exciting them to higher energies. The atoms and molecules release this added
energy by radiating light at different colours and wavelengths. On Earth, this light is mostly from oxygen
atoms and nitrogen molecules. On Saturn, it is from hydrogen. Rings
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 with a smaller amount of
rocky 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. The first 5 rings, from the closest to the
planet outward are, D ring, which is very faint, C ring, B Ring – which is the brightest
and widest of all the rings, A ring – which is the last of the large bright rings, and
then F ring. The rings extend from 66,000 km to 120,700
km above Saturn's equator are made up mostly 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 toward the outer part of the rings,
than in the inner part. The red in the image indicates sparser ringlets
likely 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 made 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 (about 2 inches) in diameter. Green and blue shades indicate regions where
there are particles of sizes smaller than 5 centimeters (2 inches) and 1 centimeter
(less than one third of an inch), respectively. Overall it’s thought that the particles
in the rings aren’t bigger than 10m, and can be microscopic in size. Using occultations again, scientists observe
the brightness of a star as the rings pass in front of the star. This provides a measurement of the amount
of ring material between the spacecraft and the star which means we can estimate how thick
the rings are. Colors in this image indicate the orientation
of clumps, and brightness indicates the density of ring particles. Yellow is too dense to let starlight through,
and so shows this to be the densest parts of the main rings. The main rings are thought to be as little
as 10m thick, to 1 km thick. Particularly 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. Look at the top of this video, where the B
ring meet the A ring. Zooming in on this structure reveals ridges
and spokes a couple of km tall, their presence 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, which can be seen all in
only a day, can be up to 200km. So I’ve talked about the d, c, b, and a
rings, and also mentioned the F ring. The F ring has a great can also get quite
wonky, and has a perfect example of what is called a shepherd moon, Prometheus, that leaves
a ripple in the ring as it orbits. Once during its 14.7-hour orbit of Saturn,
Prometheus (102 kilometers, or 63 miles across) reaches the point in its elliptical path,
called apoapse, 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. So what comes after the F ring? First, Janus or Epimetheus Ring, G Ring, Pallene
Ring and then the E Ring. Now, this picture is amazing, and I might
do a separate video just on this. But for the sake of time, this bright blue
ring is the E ring, you can just about see the faint Pallene Ring at the top of the picture. The G ring is the next distinct ring, and
again you can just about see the Janus or Epimetheus ring at the top below it. And can you see us? We’re all in this picture too. Here’s Earth and the Moon! So now you know 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 simply we don’t know. We know that some of the moons are responsible
for some of the material there, and we also know that some of the material there is responsible
for some of the moons. Moons
And talking of moons, I’m going to give you a brief run down about those that belong
to Saturn. Again, I plan to do a separate video or videos
about them as there are at least 150, 53 with formal names! They come in all shapes and sizes, and most
uniquely, Saturn’s biggest moon Titan, which is even bigger than Mercury, is the only moon
in the Solar System with a thick atmosphere around it. I’m also going to throw in here that Saturn
has the Death Star orbiting it, biding its time. We call it Mimas. Orbit
Lastly, I’m going to talk about Saturn’s orbit. Now Saturn orbits about 9 to 10 times further
away from the Sun as Earth, and one year on Saturn takes 30 Earth years. Funnily enough, a day on Saturn is different
depending on where you stood (not that you could stand on Saturn). At the equator or at the poles, a day lasts
about 10 hours and 14 minutes. Everywhere else (apart from the poles) 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. Saturn Colours
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. The gas planet's subtle northward gradation
from gold to azure is 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
Cassini, Saturn remains a world of mystery.
