Planets can later form in the circumstellar disc.
After about one thousand million years, a sun-like star has reached its stable burning phase. Star formation starts if a cloud exceeds a particular density. During contraction, large clouds break up into several smaller condensations. These rotate, and due to the centrifugal force they form, during this process, a disc made of gas and dust which is normal to the axis of rotation, in the centre of which matter continues to condense and heat up. If the temperature rises to several mil lion degrees, hydrogen nuclei begin to fuse with each other.