Page 35 ee8086 astronomy stars galaxies cosmology page

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: ology Page 36 How How do we find black holes? How do we find black holes? Black hole emits no light very difficult to detect! difficult to detect! Cygnus But a black hole can influence its surroundings in it a way that reveals its presence presence Astronomers It contains an extreme luminous star > 19Msun. contains an extreme luminous star 19M deduced from Doppler shift that this star orbits an unseen companion with mass >15Msun. >15M exceeds the neutron star limit of 3Msun cannot be a neutron star That Infer from its effect on its companion in X-ray binaries. EE8086 EE8086 – Astronomy: Stars, Galaxies & Cosmology X-1 (binary system) was the first good candidate A black hole is the only object that can be so massive & yet small enough to be invisible Page 37 Page 38 EE8086 – Astronomy: Stars, Galaxies & Cosmology Gamma Ray Bursts (GRB) Black Holes Merger: Source of Gravity Wave Cosmic -rays observed above our atmosphere since 1960s. our atmosphere since 1960s. satellites detected strong bursts, which occurs few minutes daily which occurs a few minutes daily hard to focus, pass through telescopes unable to determine direction to determine direction Afterglows of GRBs detected at other wavelengths since 1997. 1997 GRB afterglow in a distant galaxy (HST) pinpoint their sources to distant galaxies Its total luminosity would briefly exceed the combined luminosity of a million galaxies. It is difficult to explain this high luminosity EE8086 EE8086 – Astronomy: Stars, Galaxies & Cosmology Page 39 EE8086 – Astronomy: Stars, Galaxies & Cosmology Page 40 Gamma Gamma Ray Bursts (GRB) They must be among the most powerful explosions in the universe, probably signifying the formation of black holes. BEST THEORY : Hypernovae, gigantic supernovae of yp very massive stars (rapidly rotating core) forming black holes. others possibly from the mergers of neutron stars and black holes black holes. Short burst type thought to be catastrophic collisions of 2 orbiting stellar objects in a binary system. EE8086 EE8086 – Astronomy: Stars, Galaxies & Cosmology Page 41...
View Full Document

Ask a homework question - tutors are online