Apparently it’s the summer for gamma-ray bursts (GRBs). First we reported on a gamma-ray mystery, then space gold, and now compact mergers. Turns out, they all may be one in the same.

Long-duration gamma-ray bursts are associated with supernova, but elusive short-duration GRBs last less than two seconds, making it hard for astronomers to determine their origin. But we are in luck! Increased detection leads to improved knowledge, and now we may have true answers.

The same short-duration GRB (named GRB 130603B) seen on June 3rd that produced a few moons’ worth of gold was still visible nine days later when the Hubble Space Telescope observed its remains.

Hubble saw a faint red object, which a team of researchers led by Nial Tanvir of the University of Leicester identified as the common signature of a kilonova.

Kilonovas usually result from compact merger events in which decaying elements produce a recognizable optical signal. Because the kilonova and the gamma-ray burst happened together, astronomers can assume causation rather than just correlation.

“This observation finally solves the mystery of the origin of short gamma-ray bursts,” Tanvir said. “Many astronomers, including our group, have already provided a great deal of evidence that long-duration gamma-ray bursts (those lasting more than two seconds) are produced by the collapse of extremely massive stars. But we only had weak circumstantial evidence that short bursts were produced by the merger of compact objects. This result now appears to provide definitive proof supporting that scenario.”

The new knowledge can be used to revise the sequence of events preceding a GRB. First, two extremely dense stars move close together, and approach one another as their gravitational waves disrupt space-time nearby. The stars then “merge into a death spiral that kicks out highly radioactive material,” according to NASA. This explosion culminates with a kilonova. These collisions are about 1,000 times brighter than a nova, but between one tenth and one one-hundredth the brightness of a supernova.

“Previously, astronomers had been looking at the aftermath of short-period bursts largely in optical light, and were not really finding anything besides the light of the gamma-ray burst itself,” explained Andrew Fruchter of the Space Telescope Science Institute and a member of Tanvir’s research team. “But this new theory predicts that when you compare near-infrared and optical images of a short gamma-ray burst about a week after the blast, the kilonova should pop out in the infrared, and that’s exactly what we’re seeing.”

As always, this is only the first step in a major discovery. Stay tuned as the research develops!

The findings were published earlier this month in Nature.

Alyssa Keimach is an astronomy and astrophysics student at the University of Michigan and interns for the Morrison Planetarium.

Image: NASA, ESA, N. Tanvir (University of Leicester), A. Fruchter (STScI), and A. Levan (University of Warwick)

The newest cosmic mystery: four distinct high-energy flashes! (Is the Universe trying to get our attention?) Astronomers are calling them Fast Radio Bursts, but we have yet to determine their origins.

Radio astronomers detected the first burst about six years ago, but it seemed so strange that many people thought it was a fluke. Dan Thornton, a PhD student at England’s University of Manchester and Australia’s Commonwealth Scientific and Industrial Research Organization, decided to investigate. He spent the next six years looking for these strange flashes.

So far Thornton and his team have found four radio bursts. Astonishingly, the flashes—taken from only a small section of the sky—indicate that there should be one of these signals going off every ten seconds.

“The bursts last only a tenth of the blink of an eye,” explained Max-Planck Institute Director and Manchester professor, Michael Kramer. “With current telescopes we need to be lucky to look at the right spot at the right time. But if we could view the sky with ‘radio eyes’ there would be flashes going off all over the sky every day.”

Astronomers have ruled out terrestrial sources for the Fast Radio Bursts and the origins in the high galactic latitudes suggest that they originate from beyond the Milky Way.

The brightness and distance of the mysterious flashes also hint that they originated when the Universe was about half its current age. “They have come such a long way that by the time they reach the Earth, the Parkes telescope would have to operate for one million years to collect enough to have the equivalent energy of a flying mosquito,” said Thornton.

Co-author Professor Matthew Bailes, from the Swinburne University of Technology in Melbourne, Australia, thinks that burst energies indicate that they come from events involving relativistic objects—maybe even from a type of neutron star called a magnetar. “Magnetars can give off more energy in a millisecond than our Sun does in 300,000 years and are a leading candidate for the burst.”

Astronomers have a lot more research to do before we can solve the radio burst puzzle, but the findings may also help crack some other astronomical mysteries. “We are still not sure about what makes up the space between galaxies, so we will be able to use these radio bursts like probes in order to understand more about some of the missing matter in the Universe,” said Ben Stappers, from Manchester’s School of Physics and Astronomy.

So these Fast Radio Bursts could even speed up cosmic discovery!

Alyssa Keimach is an astronomy and astrophysics student at the University of Michigan and interns for the Morrison Planetarium.

Image: Diceman Stephen West