A pale, hazy—or milky—band in the sky can be seen on a very dark night, away from strong lights. This is the Milky Way galaxy. The hazy look is caused by the large number of faraway stars; your eyes cannot differentiate the stars as individual sources of light. Instead, they see only one luminous point-source, so there is no detail visible at all times. The haze also contributes to the illusion of distance because our eyes are used to looking at solid objects rather than distant ones. The Milky Way extends for hundreds of thousands of light-years and contains more than 100 billion stars. It is one of the largest structures in the universe. Although made up of stars, it has no central star or nucleus like our own galaxy, the Andromeda Galaxy. The Milky Way consists of two main parts: a spherical body about 5% of a light-year across called the galactic core, and a large flattened structure around it called the galactic disk. We can see evidence of these components from space with images such as this one from the Hubble Space Telescope. Stars are formed when clouds of gas and dust within galaxies collapse under their own weight forming solar systems with planets. These planets then evolve into worlds with oceans and life as we know it. Our sun will one day join them in death with the possible exception of another planet orbiting it in time.