Rare Star’s giant gamma ray burst GRB 204015A captured near our home galaxy
The Earth is blasted by slight short gamma-ray bursts (GRBs) almost every day. But sometimes a giant torch like GRB 200415A hits our galaxy, sweeping away the energy that eclipses our sun. In fact, the most powerful explosions in the universe are gamma-ray bursts.
Now scientists have shown that GRB 200415A came from another possible source for short GRBs. He broke out of a very rare, powerful neutron star called a magnetar.
The previously detected GRBs came from relatively far away from our home galaxy, the Milky Way. But this one was much closer to home, in cosmic terms.
GRB explosions can disrupt cell phone reception on earth, but they can also be messengers of the very earliest history of the universe.
A different end game
“Our sun is a very ordinary star. When it dies, it will grow bigger and become a giant red star. After that, it will collapse into a small, compact star called white dwarf.
“But stars which are much more massive than the sun play a different end game,” says Professor Soebur Razzaque of the University of Johannesburg.
Razzaque led a GRB behavior prediction team for research published in Nature astronomy January 13, 2021.
“When these massive stars die, they explode into a supernova. What remains after that is a very small, compact star, small enough to fit in a valley about 20 km in diameter. This star is called a neutron star. It’s so dense that a spoonful weighs tons on earth, ”he says.
It is these massive stars and what is left of them that cause the biggest explosions in the universe.
On April 15, 2020, a giant wave of X and gamma rays lasting only a fraction of a second swept through the solar system, triggering detectors NASA and European spacecraft. Event GRB 200415A was a giant eruption of a magnetar, a type of city-sized neutron star that has the strongest magnetic fields known. Professor Soebur Razzaque from the University of Johannesburg explains what happens during a giant rocket and how these powerful explosions can tell us more about the history of the universe. Animation credit: NASA Goddard Space Flight Center / Chris Smith (USRA / GESTAR). Video credit: Therese van Wyk, University of Johannesburg.
A revealing fraction of a second
Scientists have known for some time that supernovas spout long GRBs, which are bursts of longer than two seconds. In 2017, they discovered that two neutron stars that coiled into each other could also emit a short GRB. The 2017 burst came from a security 130 million light-years away.
But that couldn’t explain any of the other GRBs that researchers could detect in our skies almost daily.
That changed in a fraction of a second at 4:42 a.m. EDT on April 15, 2020.
That day a giant GRB rocket swept through March. It announced itself to satellites, a spacecraft and the International Space Station orbiting our planet.
It was the first known giant rocket since the 2008 launch of NASA’s Fermi Gamma Space Telescope. And it only lasted 140 milliseconds, in the blink of an eye.
But this time around, telescopes and instruments in orbit captured much more data on the giant GRB rocket than the previous one detected 16 years earlier.
Gust from another source
The elusive cosmic visitor was called GRB 200415A. The Inter Planetary Network (IPN), a consortium of scientists, discovered where the giant rocket came from. GRB 200415A exploded from a magnetar in galaxy NGC 253, in Sculptor’s constellation, they say.
All previously known GRBs have been attributed to supernovae or two neutron stars that coiled into each other.
“In the Milky Way, there are tens of thousands of neutron stars,” explains Razzaque. “Of these, only 30 are currently known to be magnetars.
“Magnetars are up to a thousand times more magnetic than ordinary neutron stars. Most emit x-rays from time to time. But so far we only know of a handful of magnetars that have produced giant eruptions. The brightest we could detect was in 2004. Then GRB 200415A arrived in 2020. ”
The Galaxy NGC 253 is outside our home, the Milky Way, but it is only 11.4 million light years away from us. It’s relatively close when we talk about the nuclear frying power of a giant GRB torch.
A giant eruption is so much more powerful than the solar flares of our sun, it’s hard to imagine. Large solar flares caused by our sun sometimes disrupt cell phone reception and electricity networks.
The giant GRB torch in 2004 also disrupted communication networks.
Second wave caught for the first time
“No two gamma-ray bursts (GRBs) are the same, even if they happen the same way. And there are no two identical magnetars either. We’re still trying to figure out how stars end their lives and how these very energetic gamma rays are produced, says Razzaque.
“It is only in the last 20 years or so that we have all the instruments in place to detect these GRB events in different ways – including gravitational waves, radio waves, visible light, x-rays and gamma rays. “
“GRB 200415A was the first time in history that the first and second explosion of a giant rocket were detected,” he says.
Understanding the second wave
In the 2005 research, Razzaque predicted a first and second explosion in a giant eruption.
For current research in Nature astronomy, he led a team including Jonathan Granot of the Open University in Israel, Ramandeep Gill of the George Washington University and Matthew Baring of the Rice University.
They developed an updated theoretical model, or prediction, of what a second explosion in a giant GRB rocket would look like. After April 15, 2020, they could compare their model with data measured from GRB 200415A.
“Data from the Fermi Gamma Ray Burst Monitor (Fermi GBM) tells us about the first explosion. Data from the Fermi Large Area Telescope (Fermi LAT) tells us about the second, ”explains Razzaque.
“The second explosion happened about 20 seconds after the first one and has much higher gamma ray energy than the first. It also lasted longer. We still have to figure out what happens after a few hundred seconds. “
Deep time messengers
If the next giant GRB rocket hits closer to our home galaxy, the Milky Way, a powerful ground-based radio telescope like MeerKAT in South Africa may be able to detect it, he says.
“It would be an excellent opportunity to study the relationship between very high energy gamma ray emissions and radio wave emissions during the second explosion. And that would tell us more about what works and what doesn’t in our model.
The better we understand these fleeting explosions, the better we can understand the universe in which we live.
A star dying soon after the start of the universe could disrupt cellphone reception today.
“Even though gamma-ray bursts explode from a single star, we can detect them very early in the history of the universe. Even going back to the time when the universe was a few hundred million years old, ”explains Razzaque.
“It is at an extremely early stage in the evolution of the universe. The stars that died then… we only detect their gamma-ray bursts now, because light takes time to travel.
“This means that gamma-ray bursts can tell us more about how the universe develops and changes over time.”
Reference: January 13, 2021, Nature astronomy.
DOI: 10.1038 / s41550-020-01287-8