Debris disk: Ring around star

Hi,
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 isHeic0821f.jpg 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. Ring Around a StarYou 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. This false-color composite image reveals the orbital motion of the planet Fomalhaut b.
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.

Dragallur
PS: I lost.

Tidal forces: Roche limit

Hi,
thanks to one of my frequent readers I will add short post to tidal forces because I forgot very important thing: Roche limit.

Roche limit is distance from object (star, planet). If satellite (moon) crosses this distance it will be eventually ripped apart (by tidal forces). Important is that for every satellite it is different because every satellite, like man-made has different properties. It is very complicated to know exact Roche limit for anything because there is lot of stuff you must count in.

1)2)
3)4)

On first picture there is planet orbiting sun in save distance and no great tidal forces are disturbing it.

On second planet is coming closer to Roche limit and its shape is disturbed because red side is much closer.

When planet crosses limit is starts to be ripped apart. Stuff nearer (red) starts to fly faster and that is end to our planet.

Dragallur