Across the universe, galaxies are colliding with each other. Thus the stars themselves typically don’t collide when galaxies merge. That said, the stars in both the Andromeda galaxy and our Milky Way will be affected by the merger. The Andromeda galaxy contains about a trillion stars.

Around 13.8 billion years ago, all the matter in the Universe emerged from a single, minute point, or singularity, in a violent burst. This expanded at an astonishingly high rate and temperature, doubling in size every 10-34 seconds, creating space as it rapidly inflated.

American astronomer Edwin Hubble and others discovered in the 1920s that the Universe is expanding by showing that most galaxies are receding from the Milky Way — and the farther away they are, the faster they are receding. The roughly constant ratio between speed and distance became known as the Hubble constant.

All objects in the universe are constantly falling. You fall to the earth every time you jump. You and the earth are constantly falling around the sun. You, the earth, and the sun are constantly falling around the center of the galaxy.

Stars are not scattered randomly through space, they are gathered together into vast groups known as galaxies. The Sun belongs to a galaxy called the Milky Way. Astronomers estimate there are about 100 thousand million stars in the Milky Way alone. Outside that, there are millions upon millions of other galaxies also!

If the star is large enough, it can go through a series of less-efficient nuclear reactions to produce internal heat. However, eventually these reactions will no longer generate sufficient heat to support the star agains its own gravity and the star will collapse.