Nova facts for kids
A nova is a huge explosion that happens on a special kind of star called a white dwarf. This explosion makes the star suddenly become much, much brighter! Imagine a tiny, dense star suddenly shining thousands of times brighter than our Sun. That's a nova!
Novae are different from supernovae. Supernovae are even bigger explosions that destroy a star completely. Novae happen on the surface of a white dwarf star that is part of a two-star system. This means two stars are orbiting each other.
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How a Nova Happens
When two stars are very close, the white dwarf can pull gas from its partner star. This gas is mostly hydrogen. It slowly builds up on the white dwarf's surface.
As more and more hydrogen collects, it gets hotter and hotter. When enough gas piles up, it reaches a critical temperature. This causes a sudden, powerful fusion reaction. It's like a giant hydrogen bomb going off on the star's surface!
Even though it's a huge explosion, a nova doesn't destroy the white dwarf. It only blows away a small amount of material. This material shoots out into space very fast. It can travel at thousands of kilometers per second! The star also gets much brighter, shining up to 100,000 times brighter than our Sun. Scientists have even found that novae can release high-energy gamma-rays.
Can a Star Have More Than One Nova?
Yes, a white dwarf star can have many novae over time. This happens as it keeps pulling hydrogen from its partner star. For example, a star called RS Ophiuchi has exploded six times! It had novae in 1898, 1933, 1958, 1967, 1985, and 2006.
However, if a white dwarf keeps gaining mass, it could eventually become too heavy. If it reaches a certain limit, called the Chandrasekhar limit, it could explode as a much bigger Type Ia supernova. This kind of supernova would destroy the white dwarf.
Seeing Novae from Earth
Sometimes, a nova is bright enough and close enough for us to see it without a telescope. One of the brightest recent examples was Nova Cygni 1975. This nova appeared on August 29, 1975. It was in the constellation Cygnus, near the bright star Deneb. It became almost as bright as Deneb!
Other bright novae include V1280 Scorpii in 2007 and Nova Delphini 2013. Nova Centauri 2013 was discovered on December 2, 2013. It was the brightest nova of this century, shining very brightly in the sky.
Astronomers believe that about 30 to 60 novae happen in our own Milky Way galaxy each year. However, we only discover about 10 of them. This is because many are hidden by dust or are too far away to see easily. We also see many novae in other nearby galaxies, like the Andromeda Galaxy.
Images for kids
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Nova Eridani 2009 (about magnitude 8.4)
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GK Persei: The Nova of 1901
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A nova in the Andromeda Galaxy
See also
In Spanish: Nova para niños
