Back again. Last time we were with big fat Saturn with all the moons. This time we’re going to finish off the proper planets and then we can be nearly done with all this. The proper planets do not include Pluto. It genuinely isn’t really a proper planet
765 million miles after Iapetus is:
Uranus (the planet with the name) is sometimes called an ice giant, along with Neptune, because it is full up of different ices and it has the coldest atmospheric temperature of the planets at -224.2°C. However, because it is massive, the middle is a hot sea of water, ammonia and methane and possibly because it is crazy pressurised the methane might break up into carbon that turns into diamonds that sink and melt and form a bottom ocean of liquid diamond with diamond-bergs floating on it. Uranus has a bunch of rings but it’s not Saturn so who cares.
81 thousand miles after Uranus is:
Miranda is a moon that is all smashed up. It has ridges and valleys running in different directions all over it, as well as craters and faults, that can be miles high. There are lots of detailed photos of Miranda only because Voyager 2 had to swing around Uranus in order to get to Neptune and Miranda happened to be nearby. The surface is nuts because of geological activity and squashing and stretching around between Uranus and moons and possibly because a big thing hit it and it exploded and then reformed itself.
38 thousand miles after Miranda is:
This is a cool picture of Ariel in front of Uranus. Ariel is the brightest moon of Uranus and it has big crisscrossing valleys with smooth bottoms that are up to six miles deep. Because they have smooth bottoms they were most likely made by moving liquid, which would have to have been ammonia, methane or carbon monoxide because of coldness. Ariel is absorbent, possibly because tonnes of mini-meteorites hit it and worked up a fine tilth.
46 thousand miles after Ariel is:
A rocky icy block just like all the other moons around here, Umbriel is very dark though. The darkest of the Uranian moons. I failed to depict that. I also failed to depict the Wunda crater, which is very bright. No one knows why the moon is very dark with a very bright ring.
106 thousand miles after Umbriel is:
This one is big and grey. It also has a bunch of long troughs in it, demonstrating that Titania is still tectonically active. The sun facing sides of the trough are white from going frosty in the sun.
91 thousand miles after Titania is:
Oberon is the most cratered major moon around Uranus. Strikes emit a bright ejecta, as on callisto, that make it quite pretty. Some craters have stuff in the bottom of them that no one knows what it is. There is a four mile high mountain on the horizon in the bottom left of this picture.
Below is an amazing video of Uranus and moons as seen by Hubble Telescope. Uranus really is as tilted as shown, it basically rolls around the sun. The video has no sound so below it I’ve put the track I was listening to when I watched it. It went pretty cool with it.
1 billion miles after Oberon is:
One billion miles. Four and a half billion miles from the sun means the sun is pretty small here. The methane in Neptune’s atmosphere absorbs red light and makes the planet look super blue and it has lovely little white clouds drifting on the top at 832 miles per second. There are titanic storms that last years. The structure is the same as Uranus really, with the diamond sea and diamond-bergs and everything. It must be a horrendous place, these big planets are crazy unknowable balls of chemistry.
220 thousand miles after Neptune is:
Triton orbits Neptune the opposite direction to the way Neptune spins. It is the only moon in the solar system that does this so it is thought that Neptune sucked it in from the Kuiper belt. The strange orbit will eventually cause Triton to break up or crash into Neptune. It is the only substantial moon that Neptune has. Triton is -235°C and it has volcanoes. Liquid nitrogen, dust and methane erupt from beneath the surface when they are heated by the sun (!) and the nitrogen condenses and settles down on the surface and makes it shiny. The surface is a dramatic mix of volcanic plains, fissures, ridges, ice caps and cantaloupe melon terrain.
That’s it. We’ve run out of planets. But there is still more solar system and there are still more round things, especially everybody’s second favourite round thing. So we’ll get back together for one last little explore in a bit.