Planetas 1.0 - La caída de Plutón

It's June at last and I have time to shoot a proper video.
As promised, the first video on planets.
It will be split into two parts: in this first one we will deal with the planets of the Solar System.
In the second one, I will talk about the possibility of extraterrestrial life and about the moons of other planets
The first obvious question is: how many planets are there?
Well, it is often forgotten that there are many planets, a bazillion of them.
As far as I know, more than 200 have been discovered.
We forget planets are not exclusive to the Solar System.
There are also plenty of Extrasolar Planets.
Some planets don't even orbit around a star -they are lost in the vastness of space.
But of course, by "planets" we usually mean "the planets of the Solar System"
-the most renowned, the ones of which we have the most data, and, just because of that, ultimately the most interesting planets.
And those are the ones I will talk about today.
If you have been paying attention to the news as of late, you will know Pluto is no longer considered a planet,
so now we only have 8 left, which are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
I can't believe I got it right on the first take...
YEAH!
However, you may also know that throughout history the number of planets has varied.
Pluto's example is the most infamous: it was a planet until 2006, but no longer.
For example, in Ancient Greece they had a different list: Mercury, Venus, Mars, Jupiter, Saturn, the Sun and the Moon.
This is a poor classification because, first and foremost, it does not include Earth,
and secondly, because it mixes a bunch of different things with nothing in common
-the Sun, with the Moon, with the planets.
Basically, the Greeks considered that anything that moved through the sky and was bright enough was a planet.
With the development of the telescope and the heliocentric theory,
it was concluded that a "planet" was whatever orbited around the Sun.
But this view is too broad.
As years passed, and as better telescopes developed,
new worlds were included in the "planet" category.
So far so good: we have the 9 typical planets.
But, as you know, after 2006 Pluto was no longer considered a planet.
Why?
To start with, it is a matter of size.
Indeed, ladies and gentlemen: size matters.
... at least in astrophysics.
In other aspects of your lives... well, that is a tale for another time.
The thing is, Pluto is smaller than many moons of the Solar System.
Ours included: Pluto is smaller than the Moon.
So calling it a "planet" was going too far.
Another reason for the demotion of Pluto is that science rarely uses a whole group name for just one object.
To understand this I will have to tell you the story of another "planet": Ceres.
Ceres was discovered in the 19th Century and it is a world between Mars and Jupiter,
between which there is a great gap where nothing had been found before.
The delighted astronomers gave it a name and put it in the "planet" category.
But soon they found another planet not far from Ceres, and they named it Palas.
And then... a third, Juno. And Juno was followed by a forth planet: Vesta.
They were all between Mars and Jupiter, and were nothing like the rest of the planets,
but looked similar to each other.
As time went by, astronomers started to discover hundreds of objects with the size of Ceres, Juno or Vesta.
They had nothing to do with the rest of the planets and they were so many it was impossible to consider them all "planets."
So what happened? When there were enough of them, a new group was created: Asteroids.
Here were included worlds such as Ceres, Juno, Palas or Vesta.
All of these asteroids orbit inside the so-called Asteroid Belt,
between Mars and Jupiter.
It is what separates the first four planets from the last four.
Well, something similar happened to Pluto:
until recently, scientists had the Ceres problem.
As Pluto was the only "rare" object around, they didn't want to create a new group for it alone.
But in time came the discovery of new objects, planets, worlds -whatever you wanna call them.
They look similar to Pluto: very different from the rest of the planets and orbiting the same area.
And when enough Pluto lookalikes and neighbours where discovered,
they were given the name of "Dwarf Planets", a cateogory in which Pluto was also included.
And so Pluto is off the list and only eight remain.
Let's start with Mercury, the first planet of the Solar System, the closest to the Sun.
As an interesting fact we can say Mercury is one of the densest planets of the Solar System,
even though it is very small,
because it is mainly composed of metals,
and that's just why it has a magnetosphere -that is, it has a North Pole and a South Pole.
One of the Mercury-exclusive phenomena is the so-called "Double Dawn":
the Sun rises, but then stops and slips back into the morning horizon, and then it rises again to do the normal sky route.
And the same happens to the rest of the planets that can be seen from Mercury.
The next planet is Venus.
It has a similar size to Earth, hence why they have been called "siblings".
However, the atmosphere of Venus is very different to that of the Earth.
Athmosperic pressure is ninenty times greater, and it has a great deal of greenhouse gases,
so temperatures in the surface can get up to 900ºF.
An interesting fact: Venus is the only planet rotating clockwise
-that is, it spins in the opposite direction to the rest of the planets of the Solar System,
which means the Sun rises in the West and sets in the East, contrary to how it happens in planet Earth.
I won't tell you about Earth because it merits its own video, and I will deal with most of it in the next video.
I also won't talk too much about Mars because, as in the past, we recently sent a probe there...
Well, NASA did anyway...
And they have discovered so many interesting things that it also merits its own video.
On Mars I will only make a note that, contrary to popular thinking,
it is a very cold planet: temperatures vary from lows of -125ºF to highs of up to 23ºF.
Leaving Earth and Mars aside, and planning to deal with them later,
let's take on the Gas Giants.
The first is Jupiter
-an enormous ball of gas and the biggest planet of the solar system.
Its mass doubles the combined mass of the rest of the planets of the Solar System.
It is defined by its famous surface storms.
For example, there is the very scary "Great Red Spot",
which has existed for at least 300 years with winds as fast as 300mph.
Another of Jupiter's famous features is its great number of moons or satellites.
It has 63 satellites.
The next planet is Saturn: very similar to Jupiter, a bit smaller but still a Gas Giant.
Its most defining feature is its rings.
It has the only perceptible ring system from Earth, and it is composed of 60 feet in diameter fragments.
These orbit around Saturn, forming that ring structure visible with a telescope.
Now there are only two planets left in the Solar System:
Uranus and Neptune, which look very much alike.
Uranus is a very cold planet: it is a frozen dessert. Its temperatures go as low as -380ºF.
Although not as spectacular as others, Uranus has a ring-system.
An interesting fact:
its axis of rotation is so tilted that Uranus is almost into the plane of its revolution about the Sun.
This means that its North and South Poles are where the Equator of a planet normally is.
And lastly there is Neptune, a Uranus lookalike.
What are its main features? Its gigantic storms, very similar to Jupiter's.
Until 1994, there was a storm called "The Great Dark Spot", which had the size of planet Earth.
There, winds went up to 1200mph.
And then there is poor Pluto, which has not been a planet since 2006...
It is the outcast among the planets of the Solar System.
And here ends the video on planets.
In the next one I will talk to you about some of the planets in detail
-to start with, I will comment on Earth and Mars, and touch upon some of the aforementioned moons
and the possibility of extraterrestrial life.
I will talk to you about moons of Jupiter such as Europa,
about which I can give you a little sneak peek: it has an underground frozen ocean.
It has so much oxygen that it can support not only micro-organic life,
but also much more complex forms of life.
Scientists bet that, if there is life elsewhere in the Solar System, it is in Europa.
I hoped you enjoyed this and learnt something.
If you have any complaints, doubts, suggestions, praise... leave them in the comments and I'll try to answer to them all.
That's it. So long!