OM DENNE EPISODE
Transcript: Consider a binary pair where the more massive star has expanded to fill its Roche lobe, and the smaller star is a white dwarf of nearly 1.4 solar masses. As the massive star dumps hydrogen onto the white dwarf the gas is compressed, rapidly heated, and it ignites nuclear reactions that blow off a shell of gas. The resulting emission is called a nova. This process is cyclic because gas can then accumulate again, and on a time scale ranging from a hundred to ten thousand years a new cycle of gas flow, compression, ignition, and blowing off occurs. It’s not exactly periodic, but the flaring up of a star in a nova event is spectacular because the brightness can increase by several orders of magnitude. Roughly thirty to fifty novae are seen per year among the several hundred million stars in the Milky Way galaxy. Nova stands for new stars; these are some of the most prominent events in recorded history in astronomy.
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SØG BLANDT TIDLIGERE EPISODER
Søg efter gamle afsnit af 17. Galactic Mass Distribution and Galaxy Structure.
ANDRE EPISODE I DENNE PODCAST
Transcript: It’s a great challenge to determine the true incidence of binary and multiple star systems. The nearest stars are well observed, but it’s a very small sample. As we go to more distant stars a faint companion might not be detectable. Spectroscopic binaries are biased towards small sep…
Transcript: How does mass transfer occur in a close binary pair? The Roche surface or lobes define the region of space where gas is bound to one or both stars. If either star becomes a giant the outer layers swell to fill the lobe, and the teardrop shape becomes the actual surface of the star. I…
Transcript: Most binary stars orbit slowly with a large distance between the two stars. However, a small fraction of binary systems are in close, tight, rapid orbits. In this situation mass transfer can occur from one star to the other. The system of two co-orbiting stars is surrounded by two te…
Transcript: Consider a binary system where a giant or a supergiant star is in orbit around a white dwarf and where a mass transfer between the lobes pushes the white dwarf over the Chandrasekhar limit. At this point the white dwarf collapses catastrophically to form either a neutron star or a blac…
Ansvarsfraskrivelse: Podcasten og kunstværket, der er indlejret på denne side, er fra Dr. Christopher D. Impey, Professor, Astronomy, som tilhører dens ejer og ikke er tilknyttet eller godkendt af Listen Notes, Inc.
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