9 May 2013: New Moon
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Transcript of 9 May 2013: New Moon
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9 May 2013: New Moon
Image: May 2012 annular eclipse, Monument Valley AZ
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GRB 130427
4 hour long burst seen by Fermi
z=0.34
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AST101
The Biggest Explosions Since the Big Bang
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1967: A Mystery Unfolds
Vela 5b
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A Century of Gamma Ray Bursts, R. Nemiroff, 1994
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Clues
• Large energy release
• Fast energy release
• Only high energy photons seen
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Possibilities Include…• Asteroids or comets falling onto neutron stars• neutron starquakes• neutron star novae• stellar flares• black holes• white holes• active galactic nuclei• collisions of cosmic strings• strange matter• supernovae
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More Clues
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More Clues
Isotropic distribution on the sky:
• They can be faint and close (within a few hundred light years).
• They can be associated with the halo of the galaxy.
• They can be bright and very far away.
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Isotropy
High degree of isotropy means
• They can not originate in the Galaxy
• They must be cosmological
• Energies exceed 1051 ergs
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The Problem
• Gamma rays do not focus well• Localization by timing• 5-10 degree positions
Compton Gamma Ray Observatory
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The Solution
Beppo-SAX: Satellite per Astronomia X (1996-2002)
Combined burst detector with X-ray imager
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z=0.8
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Irregular galaxy, z=3.4
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GRB 980425 coincident with sn 1998 bwgalaxy is ESO 184-G82, distance = 100 MLy
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GRB 011121 optical decay
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What are the GRBs?
• Peculiar type Ic supernovae (collapse of a massive star)
• Collisions/mergers between neutron stars
• There is about 1/day in the universe, or 1/200 Myr/galaxy
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What are the GRBs?
• And… some are terrestrial – probably associated with lightning and/or the red sprites and blue jets.
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Why the GRBs are Important
• They are the brightest things in the universe
• They are standard candles for the youngest, most distant parts of the universe
• They can be deadly