Novae
A star showing a sudden large increase in brightness an
then slowly returning to its original state over a few months.
- a nova (plural novas or novae), which mean’new’ in Latin, was the name given by early astronomers to the temporay appearance of a bright star in the sky.
- in fact, a nova is a star that sudden becomes up to a million time brighter than normal and then fades back it original luminosity.
- for a few weeks in 1901 the nova GK Persei outshone every other star in the star except Sirius.
- some novas appear within a few days, while others may take more than one year to return to their former dim state.
- novas are produced by binary stars where one of the pairs is a white dwarf and another is a larger and cooler star.
- the white dwarf’s gravity pulls hydrogen and other stellar material away from its companion star and this material builds up in layers around the surface of the white dwarf.
The white dwarf’s gravity pulls hydrogen.
A massive nuclear explosion.
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- as more material accumulates, the temperature in the lowest layer steadily increase until it reach about 20 millions degrees, at which point the hydrogen ignites into a massive nuclear explosion.
- this explosion blows away the upper layers of material in an expanding spherical cloud of glowing hot gas, and the process starts all over again.
- nove that have only been observed to flare up are known as classical move, while those that have been seen on more than one occasion are known as recurrent nove.
Did you know?
- the material ejected by a nova can travel through space at speeds up to 1,000 miles per hour or 1,500 km per hour.
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