Naked Eye Gamma Burst Observed
The star source was 7.5 billion light-years away from Earth, but from what we can determine the burst was oriented so that it was aimed almost precisely in our direction. This means that the star died nearly 7.4 billion years ago (because the gamma rays moved at essentially light speed). This is nearly 3 billion years before our own Sun even formed and halfway back to the Big Bang itself!
GRBs are the most luminous explosions in the universe, typically happening when a star runs out of fuel and collapses into a black hole or neutron star. The exact mechanism that causes the energy to be released in these powerful jets is not entirely understood, though.
This NASA video demonstrates the imagery from Swift as it observed the burst. Also, this NASA animation of the gamma ray burst is quite fascinating to watch and shows how astronomers think the star erupted, in a "narrow, ultrafast jet" of plasma shooting through the star, "followed by a wider, less energetic jet." These are demonstrated in the graphic below.
"It's this wide jet that Swift usually sees from other bursts," Racusin explained. "Maybe every gamma-ray burst contains a narrow jet, too, but astronomers miss them because we don't see them head-on."
This artist's concept shows the "naked-eye" GRB close up.
Observations suggest material shot outward in
a two-component jet (white and green beams).
NASA/Swift/Mary Pat Hrybyk-Keith and John Jones
Related Articles:
- NASA press release- "Naked-Eye" Gamma Ray Burst Was Aimed Squarely at Earth
- FOX News - Black Hole's "Birth Scream" Heard Across the Universe
- Nature - GRB 080319B: fit to burst (Editor's Summary)
- Nature - Broadband observations of the naked-eye gamma-ray burst GRB 080319B (abstract free - full paper requires subscription or payment)
- Nature - see also Jonathan Grindlay's "News and Views" essay Gamma-ray bursts: Light on the distant Universe (payment required)
Comments
Fascinating! Do you (or someone around) know how fast the “narrow, ultrafast jet” actually is? The reason I’m asking is that if plasma is shot out almost directly towards us, the Doppler blue-shift (countering the cosmological redshift at that distance) must probably be significant.
Burt
I’m curious about your comment: the burst was oriented so that it was aimed almost precisely in our direction….
Can you elaborate?
The NASA press release says that the probable reason for its brightness was that the narrow jet happened to be pointed more or less directly at us.
“The team believes the jet directed toward Earth contained an ultra-fast component just 0.4 of a degree across. This core resided within a slightly less energetic jet about 20 times wider.
“It’s this wide jet that Swift usually sees from other bursts,” Racusin explained. “Maybe every gamma-ray burst contains a narrow jet, too, but astronomers miss them because we don’t see them head-on.”
Such an alignment occurs by chance only about once a decade, so a GRB 080319B is a rare catch.”
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