nova

A nova is a star that temporarily becomes extremely bright and then returns to its original brightness. The plural of nova is novas or novae.

A star is an object in outer space that is basically a big bright ball of gas. The Sun is the only star in our solar system.

The Sun is a medium-sized star in the middle of its life. When a star the size of our Sun or smaller nears the end of its life, it becomes a white dwarf. A white dwarf is small (for a star) and, because of its size, not very bright. However, a white dwarf is very dense, so it has a strong gravitational pull.

In a binary solar system, there are two stars. Sometimes, a white dwarf star in a binary system will pull hydrogen gas from a bigger, neighboring star. Eventually, it may pull so much hydrogen together that it causes an explosion. This explosion causes the white dwarf to become incredibly bright and become what is called a nova.

A nova is temporary. Typically, a white dwarf only stays really bright for several days before returning to its original state. The white dwarf may again start pulling hydrogen from its neighbor and eventually again turn into a nova. Each cycle could take anywhere from a thousand to hundreds of thousands of years.

The first records of the word nova come from around 1680. It comes from the New Latin word novus, meaning “new.” In the past, we thought that a nova was a brand new star.

Now we know that novas are very old stars that are nearing the end of their lives. Why did we think they might be new stars? Because white dwarfs are both small and not very bright, we cannot see them with just our eyes from Earth. However, when it becomes a nova, the white dwarf becomes so bright that we can suddenly see it unaided in our night sky. Past stargazers believed this was a new star being born. As time passed, telescopes helped astronomers discover the existence of white dwarfs and learn what novas really are.

If a large white dwarf or a bigger star accumulates a huge amount of hydrogen, it may create a massive explosion known as a supernova. Unlike a nova, a supernova is the explosion of the star itself and can result in celestial bodies known as neutron stars or even a black hole.

Novas are of great interest to astronomers and researchers studying space.

This white dwarf star, went nova in 2010… @NASAFermi reveals new source of gamma rays. More: http://t.co/RwPBMNSTA8 pic.twitter.com/3ffDZEt3tM

— NASA Goddard Images (@NASAGoddardPix) July 31, 2014

GK Persei is a "classical nova" — an outburst produced by a thermonuclear explosion on the surface of a white dwarf star. (A supernova signals the destruction of an entire star.) This nova briefly appeared as one of the brightest stars in the sky in 1901! https://t.co/4J9UOBZKjh pic.twitter.com/PyXOzLkFVk

— Chandra Observatory (@chandraxray) March 13, 2018

• star
• white dwarf
• hydrogen
• gravity
• nuclear fusion
• explosion
• luminosity
• supernova

True or False?

A nova is a new star that is created when hydrogen gathers together into a big cloud of bright gas.