Planetary Accretion:
In astrophysics, accretion is the accumulation
of particles into a massive object by gravitationally attracting more
matter, typically gaseous matter, in an accretion disk. Most astronomical objects, such as galaxies, stars, and planets, are formed by accretion processes.
The Earth formed about four and a half billion years ago by this process. Collisions in giant disc-shaped clouds of material formed and Gravity slowly gathered this material of gas and dust together into clumps
that became asteroids and smaller early planets called planetesimals.
We can see small scale Examples and Evidence of Accretion preformed through experiment on the International Space Station: Click Here & Here
Another demonstration of Planetary Accretion.
Via: YouTube
For Evidence of Planetary Accretion and Accretion Disks in our Universe, we can look at the actual images and measurements provided to us by the Hubble Space Telescope. Here are some examples below...
This was taken by the NASA Hubble Space Telescope. It shows the protoplanetary disc surrounding the young star HL Tauri. These observations reveal substructures within the disc that have never been seen before and even show the possible positions of planets forming in the dark patches within the system.
This is AU Microscopii (AU Mic) a small star located 32.3 light-years (9.9 parsecs) away – about 8 times as far as the closest star after the Sun.
These images of AU Microscopii have been taken by the Hubble space telescope. Each image is a year or more apart and gives us a visual timeline shot of the debris disk around the star.
These images of AU Microscopii have been taken by the Hubble space telescope. Each image is a year or more apart and gives us a visual timeline shot of the debris disk around the star.
These two sets of images, taken by the Hubble telescope, are two different stars, HD 141943 and HD 191089.
(The top images are infrared images of the ones below.)
Again, we can see the debris disks around each star.
Belts of dust or debris have been detected around many other stars in our Universe, Here's an incomplete list below...
Further examples will be added later...
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