Astronomy and Astrophysics

Nature's Wild Side
Rosalba Perna, University of Colorado

Nature is seldom quiet. Like on Earth, but on a much bigger scale, cosmic explosive phenomena are ubiquitous. In this introductory talk, I will present a brief survey of the most common and dramatic cosmic explosions. In particular, I will discuss how massive stars, of mass larger than about ten times the mass of the Sun, end their life with a giant bang, which we call a "Type II supernova". They shine with the brightness of 10 billion suns. In the aftermath of the event, a compact object is left behind, which can be either a dense pack of neutrons, known as neutron star, or a black hole, an object so dense that not even light can escape its grip. When a massive star is also rapidly rotating, the supernova can be accompanied by an even more dramatic explosive event: an intense flash of gamma rays, known as "Gamma-ray Burst". Gamma-ray bursts are the most powerful explosions ever observed in the Universe. Other cosmic phenomena which yield a brief but intense burst of gamma-rays are mergers of two neutron stars or of a neutron star and a black hole. Among the realm of cosmic explosions some are of a different, thermonuclear origin. These include the so-called "Novae", which are nuclear explosions on the surface of white dwarfs, caused by ignition of nuclear fusion of accreted Hydrogen; if the nuclear burning disrupts the star, it will give rise to an even more dramatic explosive event, known as "Type Ia supernova".

Background Review Article:

Zhang W, Woosley S E and MacFadyen A I, Gamma-ray bursts: nature’s brightest explosions. 2003 Astrophys. J. 586 356.

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Astronomy and Astrophysics

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