大家好呀 我是Alex McColgan. 欢迎收看《未知太空》
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.
It is a massive planet.
The largest in our Solar system.
It is so massive,
its mass is 3/1000th that of our sun
that might not seem a lot,
once you realize that 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?
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 toone degree or another.
It is 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.
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, anyway,current thinking is that Jupiter would need to be
roughly 75 times more massive than it is now
to be massive enough to be a star,
尽管它的体积与最小的恒星 红矮星 相差不大
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 you 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 itself 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 though,
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 the sunlight a lot more
This would explain why its colour
can be much stronger than anything else 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?
or 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.
And 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 will 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 futurevideo.
Jupiter has 67 known natural satellites.
51 are under 10km in diameter
but the largest,”the 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 just 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
it completes its orbit from the sun 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,
The 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
将本视频分享给朋友 家人 邻居或者熟人
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
which mean for you a lot more videos
And what would you like to see next on this channel?
Post in the comments below,
and I’ll see you next time.
大家好呀 我是Alex McColgan. 欢迎收看《未知太空》