Hi I’m Alex McColgan, and welcome to Astrum. It’s been a long time coming, and after
a lot of requests, here is everything you could want to know about Jupiter.
Jupiter It is a massive planet. The largest in our
Solar system. It is so massive, it is 1/1000th that of our Sun. That might not sound a lot,
but once you realise the Sun contains 99.86% of all the mass in the solar system, you’ll
realise that Jupiter equals almost the remainder. Its mass is two and a half times that of all
the other planets in the solar system combined. And this brings about an interesting phenomenon,
the barycentre between Jupiter and the Sun is actually above the surface of the Sun,
at 1.068 solar radii from the Sun's centre. What is a barycentre I hear you ask? Well
you see, when we think of an object orbiting another object, we don’t necessarily think
that the smaller object has a gravitational influence on the bigger object. So the definition
of a barycentre is the centre of mass between these two objects. With Jupiter being the
size it is, it doesn’t orbit anywhere close to the centre of the Sun. The orbit in fact
looks more like this, with Jupiter and the Sun rotating around the barycentre. In this
case, the barycentre is above the surface of the Sun. Still don’t believe me? Have a look at this.
I want to give you a really crude representation of what a barycentre is.
So here we have the Sun and Jupiter, and we find that the centre of mass
is much closer to the Sun than it is to Jupiter.
While Jupiter has the greatest mass of any
planet in the solar system, it’s not the densest planet. It is the most massive only
because it is the biggest. If Neptune was the same size as Jupiter, it would be the
most massive. And if Jupiter was the same size as Earth, Earth would be over 4 times
more massive. As it is though, the diameter of Jupiter is 11 times that of Earth, and
its total mass is 318 times more than Earth. As we know, mass affects gravity. This means
that Jupiter has a huge gravity, over twice that of Earth at 2.528g at its surface. The
gravity of Jupiter affects every planet to one degree or another. It is also strong enough
to tear asteroids apart and capture 67 moons at least. Some scientists think that Jupiter
destroyed many celestial objects in the ancient past as well as preventing other planets from
forming. [video] They even predict the gravity of Jupiter is perturbing Mercury’s already
eccentric orbit enough that in a few billion years the tiny planet may either crash into
the Sun or be ejected from the solar system altogether. [end video] At the moment though,
it could be the hero of the inner 4 planets. Without Jupiter acting as a “cosmic vacuum
cleaner”, it wouldn’t be sucking up dangerous objects like long-period comets, or perturbing
their orbit enough or giving them a little kick of energy so that they leave the solar
system altogether. And a question I always had as a child, could
Jupiter become a star? Surely someone just needs to throw a match in seeing as it’s
made of flammable hydrogen. Sadly, current thinking is that Jupiter would actually need
to be roughly 75 times more massive than it is now to be massive enough to be a star,
although its volume isn’t too far off from the smallest known red dwarf.
Jupiter is the 5th planet from the Sun, and it’s 5 times further away from the Sun than
Earth. Even so, it can be the 3rd brightest object in the night sky, after the moon and
Venus. I just want to show how bright that is. Just
using a handy cam, we can see Jupiter quite easily in the night sky. With a maximum apparent
magnitude of -2.94, it can actually cast shadows. As a result of it being so obvious in the
sky, it makes a very nice target for amateur astronomers. One of my subscribers was kind
enough to show what he saw when Jupiter pass by the moon. With good magnification, you
can see its patterns quite clearly. And what makes these patterns? The cloud layer
is only about 50km thick and contains ammonia crystals much like on Saturn, but the colouration
comes from compounds heating up from deep within Jupiter and then rising. These compounds
are known as chromophores, and when they reach the clouds, they interact with the UV light
of the Sun to create these spectacular multi-coloured bands. This is quite the cycle though, and
the face of Jupiter can change dramatically over time. Even if their colours do change,
the actual latitude of these bands remains consistent enough to be given identifying
designations, but they can vary in width over the course of time. Lots of storms and turbulence
occur where the bands meet and it is the reason Jupiter has the very famous great red spot.
This storm is huge. It can easily fit the diameter of Earth within it. It has existed
for as long as we know since it was first discovered in the 17th century. It might very
well be a permanent feature of the planet, but interestingly it has decreased in size
since observations began. The reason for its reddish colour is unknown, and the colour
of the spot can vary greatly – from brick red to almost white. The most recent theory
for its colour is chemical compounds being broken up by the UV light of the Sun, much
in the same way as the process that happens on the rest of the planet. The storm is actually
much higher up in the atmosphere than the surrounding clouds and as a result can interact
with sunlight a lot more. This would explain why its colour can be much stronger than anything
around it. Another storm, known as “Red Spot Jr”, formed when three storms merged
into one, and it has so far passed unscathed by its bigger neighbour and is now quite a
prominent feature of the planet. It could last for another couple of hundreds of years
if it avoids the same fate of a similar storm which passed right through the heart of the
Great Red Spot. So what do we think Jupiter is made of? Well
much like Saturn, under the atmosphere are gaseous, then liquid, then metallic forms
of hydrogen. The further into the planet you go, the greater the pressure becomes. Under
immense pressure, hydrogen acts as a metal. Beneath that is an ice or rocky core. Because
we can’t recreate on Earth the immense pressures Jupiter experiences, we don’t really know
what properties these materials have at the core. Roughly 90% of Jupiter is thought to
be hydrogen, 10% helium, and then trace amounts of methane, ammonia and others.
And yes, you may have noticed on this picture, Jupiter does indeed have rings. Nothing on
the scale of Saturn, but there are 4 planetary rings. The main ring is very thin but bright,
the rest quite wide but exceptionally faint. The main ring is about 6,500km wide, and the
only distinctive feature you can see is what is known as the Metis notch.
Something else of note about Jupiter is its remarkably strong magnetosphere. It is 14
times stronger than Earth’s, due to the planet’s liquid metallic hydrogen centre.
This makes it the strongest magnetosphere of any planet in the solar system, and it’s
beaten only by the Sun’s sunspots. There are a couple of reasons why this is really
interesting. The first being that magnetospheres channel solar wind to the planet’s pole
which produce magnificent aurorae. The second is that the four biggest moons of Jupiter
are protected from this solar wind because they orbit within the magnetosphere. This
implies they don’t need their own strong magnetospheres because Jupiter is doing that
for them. And I’ll just very quickly talk about the
Moons, because I want to save them for a future video. Jupiter has 67 known natural satellites.
51 are under 10km in diameter, but the 4 largest, "Galilean moons", are some of the biggest
in the solar system. They are Io, Europa, Ganymede and Callisto, and they are all interesting
in their own right. Ganymede is actually the biggest moon in the solar system and has a
greater diameter than that of Mercury. We’re almost at the end of this video sadly,
but we’ll finish by talking about the orbit and rotation of Jupiter. Jupiter like I mentioned
before is the 5th planet from the Sun, it’s found on the outskirts of the asteroid belt
and sits in between the orbits of Mars and Saturn. It is 778 million km away from the
Sun on average, or 5.2AU, and completes its orbit every 12 Earth years. The axial tilt
of the planet is small, only 3 degrees. This means it doesn’t experience much change
in seasons, unlike Earth and Mars. And very much like Saturn, its radius at the equator
is greater than at the poles. It rotates very fast, faster than any other planet, completing
a rotation in only 10 hours. But due to it not being solid, it doesn’t rotate the same
speed all over, a rotation at the poles taking 5 minutes longer than at the equator.
And with this final thought, take a look at Jupiter through the infrared. Demonstrating
the immense size and power of this planet, this dot at the bottom of the planet is the
impact of an object from space, which if it had hit Earth, could have spelled the end
of our planet as we know it. We can be glad Jupiter is there, not only for its beauty,
but also because in so many ways it is an asset to our solar system.
Thank you so much for watching this far. Did you learn something today about Jupiter you
never knew before? What other things do you know that I didn’t include in this video?
I would most humbly ask that you share it with friends, family, neighbours and acquaintances
as I put a lot of time into these videos, and if this channel really takes off I would
be able to do it full time and make more of these kinds of videos in the future much faster.
And what would you like to see next on this channel? Post in the comments below, and I’ll
see you next time.