A nebula is a cloud of gas and dust in space. It is often the birthplace of stars.

There are four main types of nebulae: emission nebulae, reflection nebulae, dark nebulae, and planetary nebulae.

The Tarantula Nebula is the largest nebula in the Milky Way. It is located in the constellation of Dorado.

The Orion Nebula is the closest nebula to Earth. It is located in the constellation of Orion.

The Orion Nebula is the most famous nebula. It is located in the constellation of Orion and is visible to the naked eye.

The large-scale structure of the universe is made up of galaxies, clusters of galaxies, and superclusters of galaxies.

The Sloan Great Wall is the largest structure in the universe. It is a filament of galaxies that is over 1 billion light-years long.

The fate of the universe is still unknown. Scientists are still studying the universe to try to determine what will happen to it in the future.

The cosmic microwave background is the leftover radiation from the Big Bang. It is the oldest light in the universe.

The Hubble constant is the rate at which the universe is expanding. It is named after Edwin Hubble, who first discovered that the universe is expanding.

The age of the universe is estimated to be 13.8 billion years. This is based on measurements of the cosmic microwave background and the Hubble constant.

The shape of the universe is thought to be flat. This means that the universe is infinite in size.

The future of the universe is still unknown. Scientists are still studying the universe to try to determine what will happen to it in the future.

Hydrogen is the most abundant element in the universe. It makes up about 75% of the mass of the universe.

Helium is the second most abundant element in the universe. It makes up about 25% of the mass of the universe.