Astronomers Astounded by Unexplained Brightness Colossal Explosion

Short Gamma-Ray Burst Credit: NASA, ESA, W. Fong (Northwestern University), and T. Laskar (University of Bath, UK)

Astronomers have discovered the brightest infrared light from a short gamma-ray burst ever seen, with a bizarre glow that is more luminous than previously thought was possible.

Its half-second flash of light, detected in May, came from a violent explosion of gamma rays billions of light-years away that unleashed more energy in a blink of an eye than the Sun will produce over its entire 10-billion-year lifetime.

NASA’s Hubble Space Telescope quickly captured the glow within just three days after the burst and determined its near-infrared emission was 10 times brighter than predicted, defying conventional models.

“These observations do not fit traditional explanations for short gamma-ray bursts,” said Fong. “Given what we know about the radio and X-rays from this blast, it just doesn’t match up. The near-infrared emission that we’re finding with Hubble is way too bright.”

To zero in on this new phenomenon’s exact brightness, the team used W.M. Keck Observatory on Maunakea to pinpoint the precise distance of its host galaxy.

Using Keck Observatory’s Low-Resolution Imaging Spectrometer (LRIS) and DEep Imaging and Multi-Object Spectrograph (DEIMOS), the team determined the burst came from a galaxy located at a redshift of z = 0.55 – quite a bit farther than the initial calculated distance.

Lasting less than two seconds, short gamma-ray bursts are among the most energetic, explosive events known; they live fast and die-hard. Scientists think they’re caused by the merger of two neutron stars, extremely dense objects about the mass of the Sun compressed into the volume of a small city. A neutron star is so dense that on Earth, one teaspoonful would weigh a billion tons!

The study has been accepted in The Astrophysical Journal and will be published online later this year. A pre-print is available on arXiv.org.

“It’s amazing to me that after 10 years of studying the same type of phenomenon, we can discover unprecedented behavior like this,” said Wen-fai Fong, assistant professor of physics and astronomy at Northwestern University and lead author of the study. “It just reveals the diversity of explosions that the universe is capable of producing, which is very exciting.”

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