Gamma-ray bursts are explosions so powerful they outshine our entire galaxy. Find out how scientists detected the brightest gamma-ray burst ever observed, and what it means for our understanding of the universe.
One of the rewards of being a stargazer is that, whatever our circumstances, the night sky is always freely available. When we combine our knowledge of the starry skies with an understanding of the science behind what we’re seeing, the rewards are even greater.
For example, whenever I notice a particular star, I’m reminded of its complex and fascinating life cycle. It begins as a cloud of gas and dust that collapses from its own gravity.
Then, it passes through its main sequence, winding up as a red giant, like Betelgeuse in the constellation Orion. Finally, the star will collapse as a hypernova or supernova.
Super-Energized Jet of Particles Releasing Gamma Rays
When one of those collapsing stars has a strong magnetic field and rotates rapidly, it can produce what scientists call a gamma-ray burst (GRB). The collapsing material forms a super-energized jet of particles that release enormously energetic gamma rays.
Military satellites first detected gamma-ray bursts in the late 1960s. The Pentagon’s Vela program used satellites to track nuclear explosions by monitoring gamma rays.
A team of scientists at Los Alamos reviewed the data from the Vela satellites and noticed that gamma-ray bursts reach the Earth from deep space. These bursts were over in the blink of an eye, and they weren’t coming from any known celestial bodies.
Reveal Early Universe and Nature of Black Holes
Astrophysicists continue to actively study gamma-ray bursts. They can tell us more about the early universe, the nature of black holes and their underlying processes.
Professor Edo Berger is an astronomer at the Harvard-Smithsonian Center for Astrophysics. He’s been studying supernovae, the interstellar medium and gamma-ray bursts since 2002.
This week, the journal Astrophysical Journal Letters published a groundbreaking discovery by Professor Berger and his team: the brightest gamma-ray burst ever recorded. As he explained, “I have been studying these events for more than twenty years, and this one was as exciting as the first GRB I ever observed.”
Brightest Gamma-Ray Burst Also Lasted a Very Long Time
The study combined observations using radio to gamma waves, including the Center for Astrophysics’ Submillimeter Array in Hawaii. In addition to being the brightest gamma-ray burst, it lasted a very long time — more than five minutes, in fact.
Scientists believe that such long gamma-ray bursts signal the birth of a black hole. The brand new black hole appears as the star collapses under its own weight.
The collapse unleashes unimaginably potent jets of plasma at almost the speed of light. The jets of plasma stab their way through the newly formed black hole, emitting intense gamma-rays
Afterglow of Light Across Entire Spectrum
Because this was the brightest gamma-ray burst ever seen, the researchers weren’t sure what to expect after the burst ended. They knew there would likely be an afterglow of light across the entire spectrum, but since they didn’t know how long it would last, they had to move fast.
That’s why Professor Berger and his colleague Professor Yvette Cendes used the Submillimeter Array in Hawaii to quickly gather the data. “This burst, being so bright, provided a unique opportunity to explore the detailed behaviour and evolution of an afterglow with unprecedented detail,” Professor Berger explained. “We did not want to miss it!”
As the Submillimeter Array’s project scientist, Professor Garret Keating explained, “The team was excited to see just how bright the afterglow of this GRB was, which we were able to continue to monitor for more than 10 days as it faded.” The team combined this data with observations from other data from telescopes around the world.
“Just Don’t Behave as Expected”
They were astounded to realize that the millimetre and radio wave measurements were far brighter than the visible and X-ray light readings suggested. Professor Cendes explained, “This is one of the most detailed datasets we have ever collected, and it is clear that the millimetre and radio data just don’t behave as expected.”
This seems to be a previously unknown process for producing the millimetre and radio waves. “It is possible that the visible and X-ray light are produced by one portion of the jet, while the early millimetre and radio waves are produced by a different component,” Professor Cendes suggested.
Gamma-ray bursts are some of the most energetic and violent events in our universe. In addition to black holes, they can also result from the mergers of neutron stars or the collapse of supermassive stars.
Reference Points From Which to Probe Early Universe
Studying gamma-ray bursts and their afterglows enables astronomers to measure their distance and use them as cosmic beacons — reference points from which to probe the early universe. This can shed light on how the first stars and galaxies formed and events that took place when our universe was only 3% of its current age.
Research into the origins of gamma-ray bursts also provides astrophysicists with insights into the the mass, spin and other key properties of black holes. Understanding these properties will provide deeper insights into the conditions in the early universe leading to their formation.
And Another Thing…
Discoveries like these are a kind of call to action. They remind of us of the need to embrace a new story for humanity that recognizes our place in the web of life and the universe that created it.
Professor Berger wound things up, saying, “Luckily, this afterglow is so bright that we will continue to study its radio emission for months and maybe years to come. With this much longer time span we hope to decipher the mysterious origin of the early excess emission.”
We always have more to learn if we dare to know.
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