Gamma ray bursts (GRBs) have been routinely observed by orbiting observatories, such as NASA’s Fermi and Swift spacecraft, and astronomers are planning on using them as cosmic flashbulbs to probe the details of the early Universe. The researchers published their findings in the journal Nature today.
GRBs are seen almost daily, and are thought to signal the collapse of a star’s core into a black hole, which triggers a cataclysmic explosion. The light from such an explosion can shine all across the observable Universe, through time as well because some of these explosions happened early in the 13-billion year history of the Universe. Last week, at a Fermi/Swift conference in Munich, Germany, astronomers discussed how they could use GRBs to chart the chemical evolution of the cosmos.
Volker Bromm, an astronomer at the University of Texas at Austin, says that GRBs might carry information about the composition of the first stars that were birthed in the Universe, only a couple of hundred million years after the Big Bang.
Faint galaxies, quasars, and other extremely distant objects emit GRBs. GRBs are brighter than distant galaxies, making them easier to find. A spectrograph can split them up into their constituent wavelengths to reveal chemical absorption lines.
GRBs are unpredictable and brief, lasting only a couple of seconds at the highest energies. They are followed by lingering afterglows that can be measured at longer wavelengths, but they dissipate quickly. Space-based observatories must work in tandem with Earth-based telescopes to spot them.
GRBs have been firing since the formation of the first stars, which were probably massive, bright, and short-lived. GRBs can be analyzed from other galaxies in different epochs, and these might provide clues of the composition of the early Universe.
Reference: “Messages from the early Universe” by Eric Hand, 16 May 2012, Nature.