The early universe was a very different place from what we see today. Matter was packed together at temperatures of tens of millions of degrees, hotter than a nuclear explosion, or the interior of a star. As the universe expanded and cooled, matter began to clump together, pulled in by the force of gravity.

Gravity is the force that all objects with mass exert upon one another, pulling the objects closer together. It causes a ball thrown into the air to fall to the earth, and the planets to orbit the sun. The tiny particles that make up matter, such as atoms and subatomic particles, also exert forces on one another.

In fact, the first clumpy galaxies were discovered by examining images of the very distant universe taken by the Hubble Space Telescope. Instead, most galaxies were loosely-structured blobs of stars and gas with a few concentrated “clumps” that glowed brightly with new stars.

A conception of star formation has emerged in which turbulence plays a dual role, both creating overdensities to initiate gravitational contraction or collapse, and countering the effects of gravity in these overdense regions. We discuss formation of both low- and high-mass stars, including ongoing accretion.

Stars form from an accumulation of gas and dust, which collapses due to gravity and starts to form stars. The process of star formation takes around a million years from the time the initial gas cloud starts to collapse until the star is created and shines like the Sun. Without this dust and gas, stars would not form.

Hipparchus is known for the discovery of the first recorded nova (new star). Many of the constellations and star names in use today derive from Greek astronomy. In spite of the apparent immutability of the heavens, Chinese astronomers were aware that new stars could appear.