How are galaxies, stars, and planets formed? In what order are they typically formed?
1 Answer
Mar 9, 2016
According to the latest evidence for the Big Bang, it appears that galaxies formed first and then stars and associated planets some time later.
Explanation:
The overall general sequence seems to be:
- The Big Bang starts 13.7 billion years ago
- elementary particles, atoms and the 4 forces form - about 300,000 years later
- galaxies form shortly thereafter - about 13 billion years ago.
- 1st generation stars start to form - some time between 13 to 7 billion years ago. Some stars may have formed solar systems at this time.
- 1st generation stars may have lived out their lives, formed Red Giant stars and collapsed sending matter into the universe or 1st gen starts went supernova generating new elements and scattering them into space.
- the remains of these 1st gen stars (mostly hydrogen and helium, plus smaller amounts of all other elements) formed nebulae and eventually by gravity, start to collapse inward and rotate.
- most of the hydrogen and helium collapse into the centre and eventually ignites nuclear fusion and a 2nd gen star forms - like our sun.
- at the same time the sun is forming the remaining matter is collapsing into the solar system planets, including our own Earth. So, the sun and Earth form roughly at the same time by the same processes.
