What is a nova

What is a nova?

 

A nova is a star that suddenly shines a thousand times brighter than usual and then usually fades back to insignificant brightness. The name Nova comes from the fact that early astronomers thought such objects were new stars. Novas are relatively rare, and no two novas behave exactly the same. Of course, we are not dealing with "new" stars with these celestial bodies. Stars, glowing gas spheres millions of kilometers in diameter, do not arise and fade overnight. These stars were there a long time ago, and only a special kind of process stimulated them to suddenly increase their brightness and fade.

In 1967, for example, the English amateur astronomer George Alcock discovered a nova in the small constellation dolphin with a maximum brightness of the order of magnitude 4. Then its brightness fluctuated around magnitude 5 for five months and then declined very slowly. Five years later, the Nova had size class 8.Nova Aquila, on the other hand, discovered in 1918, reached the brightness of Sirius with -1.4 in a few days and fell to size class 5 within four months.

What causes a nova is not entirely clear. Apparently, it is about a huge eruption in the outer layers of a star, which causes it to light up and hurl an expanding envelope of gas into space. Such gas envelopes have been observed directly in some cases. Sometimes this phenomenon is repeated several times in a star. One then speaks of a recurring nova.

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