with this post I am answering to one comment posted about three weeks ago on Roche limit.
Could there be rings around sun?
Yes they are called Debris disks. Debris disk is created from nebula which is surrounding young star. This nebula is full of gas and dust. Either all this stuff is pushed away by radiation or planetesimals are created.
Planetesimals are huge rocks, (more than one kilometer across). They do not need Brownian motion anymore to grow because they have enough strong gravity to pull other rocks, and at some point they can be enough large to be planets.
When those planetesimals collide they left dust and rock behind them. This is what is called debris disk. It is not created by Roche limit as normal planetary ring is and I did not find anything about rings around star that are made by Roche but if I do I will definitely post it here.
This dust in debris disk is usually very small: 1-100 micrometers.
Our sun has this debris disk and you have probably heard about it, it is the Kuiper belt.
There is other example of debris disk and it is around very bright star called Fomalhaut. You can see it on the right top. This star has debris disk which is moved by 1.4 billion miles (roughly 2.24 billion kilometers) to left. It is probably because of huge planet. The dark spot around star (pic. on the left and bot.) is just effect of blocking the light from Fomalhaut so we can see all the debris reflecting photons.
Fomalhaut has at least one planet and this one is called Fomalhaut B. On wiki, I am pretty sure there is mistake in one sentence since they are saying that it is star.
You can easily find Fomalhaut on Celestia, I will write about that program probably next time.
because I was in Finland I could not write anything but today, I am returning with monstrous post! About…. The Game!
Probably you have never heard of it but it is the most played game in the world because everybody is playing it.
It is mind game which you will lose when you think about it, so you and me and other readers just lost because I wrote this sentence!
Now all of us have thirty minutes before we can play again.
Nobody is really sure how and when was this game created. One story says that two guys had to wait through night on train station and they were trying not to think about the train so they finally made this.
There are no official rules, actually there are versions in which you will play in the moment when you are not thinking about it or that there is only one way to win and it is hearing the pope, prime minister of England or queen saying that they won/lost.
There are two strategies either not thinking about game or thinking about it as often as possible, so you can say to others that you just lost.
two months after Apollo 7 NASA launched next mission: Apollo 8. It was December 21st of 1968 when Borman, Lovell and Anders sat in Saturn V rocket. Uniqueness of this crew is that captain (Borman) was not the most experienced member because Lovell was already on two missions while Borman only on one.
This mission skipped some other plans of NASA right to testing all modules n the orbit around Moon. This was because of such a little time for finishing main mission, landing on Moon with men.
Even that there was such a sudden change in program, Borman and his crew spent 7 hours on simulator for each hour of the flight.
Mission was 6 days long. It was going without problems, they used three stages of fuel so they got up on Earth´s orbit and then for two and half an hour they were checking if everything is going well. They were also rotating rocket so they could take some pictures of Earth, they were first human who saw whole Earth.
Since they crossed radiation belt they received about 1.6 miligray (Maybe I will talk about that next time) while normal dose on Earth per year is 2-3 mGy.
Through whole flight spacecraft had to be rotating because without atmosphere heat shield would crack because of high temperatures (200 °C) and on the other side it would be freezing (-100 °C).
Because crew had some sleep problems Borman after few hours of sleep woke ill and then he was vomiting. It was very difficult to clean it up because of no gravity and he wanted not everybody to know.
After orbiting the moon and collecting data they made re-entry (most dangerous part of flight) to Earth´s atmosphere as is shown on the picture.