91福利

Dance of Death in the Stellar Graveyard

Just like all of us, stars go through a cycle of birth, life and death. In this talk, I will explore our knowledge regarding the afterlife of stars. Most stars end their lives as white dwarves, burnt out stellar embers held up by the pressure of degenerate electrons. Many white dwarfs monotonously fade away, and serve both as laboratories for physics under extreme conditions, as well as cosmic chronometers measuring the age of the Galaxy. However, quite a few of them face a less peaceful future, undergoing various types of interaction and accretion.

If fed by a companion star, a white dwarf may grow in mass up to the Chandrasekhar mass, and explode in type Ia supernova, bright enough to serve as a beacon on cosmological distances. Yet the details of the pathway to these cataclysmic events is far from being understood. Less extreme, but closer to home, are white dwarfs hosting the remnants of planetary systems. Asteroids crossing the tidal disruption radius of their host white dwarf will be shredded into a disc of gas and dust. This circumstellar debris is accreted into the pure hydrogen atmosphere of the white dwarf, and measuring the amounts of contamination provides an accurate chemical fingerprint of the constituents of extra-solar terrestrial material.