Stellar Death, Page 3

Stellar Death, Page 3: [Previous Page] [Next Page] [Class Notes] Textbook pages 258 - 270

SUPERNOVAE !!

single star

In February, 1987, a supernova went off in the Large Magellanic Cloud, called: Supernova 1987A. 1987A was the first SN of the year, 1987, hence it was labeled 'A'.

Today, astronomers search for SN in far away galaxies, such as M 51. Hundreds are detected each year (list here). SN1987A is unique because it was nearby (the last naked eye Supernova was in 1604) and and the star that exploded had been previously studied (it was a massive blue supergiant). This confirmed that indeed, massive stars DO explode.

Supernova Remnants

The Big Bang produced very little material besides hydrogen and helium, yet we know that most of our planet is composed of other elements. These other elements were produced inside stars (up to Iron) and during supernova explosions (heavier elements beyond Fe), and were disbursed into the interstellar medium by supernova remnants. Eventually, the remnants cool and collapse to form interstellar clouds from which new stars and planets can be formed.

Supernova from low mass stars
Low mass stars do not become supernova directly. They quietly evolve into planetary nebula and then finally white dwarfs. However, white dwarfs, if allowed to accumulate mass beyond about 1.4 Solar masses, the object will collapse under its own gravity and disintegrate (burn its H/He core up). This releases all that nuclear fusion fuel at once, producing a Type Ia supernova. How might a white dwarf gain mass? In a close stellar binary. Supernova which come from high mass stars are called Type II supernova.