So far, we’ve only had close calls from gamma-ray bursts, which scientists say are so large that if they occur in our solar vicinity (less than 1,000 light-years away), they could potentially trigger a mass extinction on Earth.
Reportedly about 440 million years ago Nature, a nearby gamma-ray burst may have wiped out much of life on Earth. University of Kansas astrophysicist Adrian Melott and colleagues hypothesize that the fossil record from the end of the Ordovician fits how such a cosmic explosion a few thousand light-years away might have altered the environment. At that time, more than 100 families of marine invertebrates became extinct; it was the second most devastating mass extinction in our planet’s history.
cosmos at the bottom of the sea
GRB rocks Andromeda
In 2014, telescopes around the world pointed to our neighboring Andromeda galaxy (above), which peered into all wavelengths of light to learn more about a gamma-ray burst reported by NASA’s Swift satellite and believed to be an explosion from the Collision of two neutron stars was – the dead cores of massive stars, with the mass of our sun squashed to the size of a small city.
neutron star collision
When these neutron stars merge, the explosion is so powerful it can be seen from across the universe. Astronomers suspect that up to a third of all brief gamma-ray bursts come from merging neutron stars in globular clusters of old stars, blinding entire galaxies with high-energy radiation and destroying nearby worlds.
“Blind entire galaxies, destroy millions of worlds” – Rare brief gamma-ray burst discovered
The colliding neutron stars exploded in less than a second (while optical light can take a few hours before fading) and glowed in gamma rays that traveled undisturbed for 2.5 million years until they struck NASA’s Swift satellite, which captured the 35-year-old puzzle about the origin of gamma-ray bursts, which scientists believe are the birth cries of black holes. Within minutes, telescopes around the world were following him, and an hour later, people around the world were following him on Twitter.
“Usually the universe moves slowly, with huge galaxies spinning around in slow motion by human standards, and just the occasional pop, and it’s a race against time to record and learn everything you can,” said Alan Duffy from the Swinburne University Center for Astrophysics.
The titanic GRB blasts create shock waves that propagate at nearly the speed of light into the surrounding gas, which then glows at X-ray, optical, and radio wavelengths. Because the shocks move almost at the speed of light, the reported Harvard Center for Astrophysics (CfA)Einstein’s special theory of relativity must be used in calculating what an observer would see.
“The GRB appeared as a small ring expanding faster than the speed of light”
“Contrary to common sense,” says the CfA, the relativistic shock predicted by Einstein’s general theory of relativity due to gravitational microlensing will appear to an observer as a small ring expanding faster than the speed of light. The ring will appear small due to the enormous distance to the GRB – equivalent to spotting a wedding ring two million miles away; like an “o” seen on this side of the moon.”
“Ground-based telescopes,” reports the CfA, “are limited to about one arc second resolution by turbulence in our atmosphere. Better resolution is achieved in space, but the apparent magnitude of the GRB shock is still more than 100,000 times smaller than the Hubble Space Telescope resolution of 0.1 arcsecond.”
“The night sky, seen in high-energy light, flashes non-stop as titanic explosions bright enough to be seen the length of the universe erupt and travel toward us. It’s a violent world out there,” noted Duffy.
Much closer to home – An object with a magnetic field a thousand trillion times stronger than that of our Sun
Fast forward to 4:42 a.m. US Eastern Time on April 15, 2020, when a giant GRB flare swept past Mars, announcing satellites, a spacecraft, and the International Space Station orbiting our planet. And it only took 140 milliseconds, about the blink of an eye.
A research team at the University of Johannesburg, led by Soebur Razzaque, a coordinator of the GRB and GW science group of the Fermi-Large Area Telescope (LAT) Collaboration, revealed that this giant GRB flare, 200415A, is just short of another possible one Source is GRBs, which was also very close to home cosmically. It erupted from a rare, powerful neutron star called Magnetar, a type of young neutron star and the most magnetic objects in the universe, with a gravity a billion times that of Earth and a magnetic field a thousand trillion times stronger than that of our sun.
“Cosmic Broadcasts” – bursts of energy from the strongest magnetic fields in the universe
The Inter Planetary Network (IPN), a consortium of scientists, found that GRB 200415A exploded from a magnetar in the galaxy NGC 253, about 11.4 million light-years from Earth, towards the Sculptor constellation. All GRBs known so far have been traced back to supernovae or two neutron stars spiraling into each other. NGC 253 is outside of our home, the Milky Way, but it is only 11.4 million light-years from us. That’s relatively close when it comes to the nuclear destructive power of a giant GRB flare.
The Milky Way is home to tens of thousands of neutron stars
Previously detected GRBs came from relatively far away from our home galaxy, the Milky Way. But this one was much closer to home from a cosmic point of view. “There are tens of thousands of neutron stars in the Milky Way,” says Razzaque. “Of those, only 30 are currently known to be magnetars.
Dark Hearts of the Cosmos – Dazzling new mergers of black holes and neutron stars
“Although gamma-ray bursts emanate from a single star, we can detect them very early in the history of the universe. Even back in time when the universe was a few hundred million years old,” says Razzaque. “This is at an extremely early stage in the evolution of the universe. The stars that died back then…we only see their gamma-ray bursts because light takes time to travel. This means gamma-ray bursts can tell us more about how the universe is expanding and evolving over time.”
Source: High-energy emission from a giant magnetar flare in the Sculptor galaxy. Natural Astronomy (2021). DOI: 10.1038/s41550-020-01287-8
the daily galaxy, Maxwell Moeastrophysicist, NASA Einstein FellowUniversity of Arizona, via Technical University of Swinburne, AAAS/University of Johannesburg, Harvard CFA
Photo Credits: Magnetar, Shutterstock License
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Maxwell Moe, Astrophysicist, NASA Einstein Fellow, University of Arizona. Max can be found at Kitt Peak National Observatory two nights a week exploring the mysteries of the universe. Max received his PhD in astronomy from Harvard University in 2015.
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