What is a nebula?

A nebula is a giant cloud of dust, gas, and plasma in space. Some nebulae (more than one nebula) arise from gas and dust ejected by the explosion of a dying star, such as a supernova. Other nebulae are areas where new stars begin to form. For this reason, some nebulae are called "stellar nurseries".

These towers of cosmic dust and gas form part of the Eagle Nebula. These so-called Pillars of Creation are part of an active star forming region within the nebula. Credit amp; Copyright: NASA, ESA and the Hubble Heritage Team (STScI/AURA)

How are stars formed in a nebula?

Nebulae are made up of dust and gases, mostly hydrogen and helium. Dust and gases are very scattered in the nebula, but gravity can gradually begin to pull clumps of dust and gas together. As these lumps get bigger and bigger, their gravity gets stronger and stronger.

This landscape of "mountains" and "valleys" strewn with glittering stars is actually the boundary of a nearby young star-forming region called NGC 3324 in the Carina Nebula. This infrared image from NASA's James Webb Space Telescope shows for the first time previously unseen star-forming regions. Credit amp; Copyright: NASA, ESA, CSA, and STScI

Eventually the clump of dust and gas becomes so large that it collapses under its own gravity. The collapse causes the material at the center of the cloud to heat up, and this hot core is the beginning of a star.

Where are the nebulae?

Nebulae exist in the space between stars, also known as interstellar space. The closest known nebula to Earth is called the Helix Nebula (NGC 7293). It is the remnant of a dying star, possibly similar to the Sun. It is located approximately 700 light years from Earth. This means that even if you could travel at the speed of light, it would still take you 700 years to get there!

This infrared image from NASA's Spitzer Space Telescope shows the Helix Nebula, a cosmic star often photographed by amateur astronomers for its vibrant colors and eerie resemblance to a giant eye. The nebula, located about 700 light-years away in the constellation Aquarius, belongs to a class of objects called planetary nebulae.

How do we know what nebulae look like?

Astronomers use very powerful telescopes to take pictures of distant nebulae. Space telescopes such as NASA's Spitzer Space Telescope and the Hubble Space Telescope have taken many images of distant nebulae.

Some examples of nebulae:
• 1. Wreath Nebula
• 2. Witch Head Nebula
• 3. Cone Nebula
• 4 The Omega Nebula
• 5 Eagle Nebula
• 6 Orion Nebula
• 7. Rosette Nebula
• 8 Carina Nebula
• 9 Crab Nebula
• 10 Andromeda Galaxy (Andromeda Nebula)