A extra detailed have a look at GRB 221009A is the primary time astronomers noticed the consequences of a gamma-ray burst on the higher ionosphere of Earth.
An inventive impression of a gamma-ray burst from a galaxy virtually two billion light-years away. Credit score: ESA/ATG Europe; CC BY-SA 3.0 IGO
It got here from someplace 2 billion miles away. And when it arrived in October of 2022, the gamma-ray burst lit up the whole ionosphere.
Now astronomers are working in a complete realm of “new physics we are attempting to grasp,” based on astronomer Mirko Piersanti of the College of L’Aquila in Italy.
The occasion isn’t new to science. It’s a sort of hyper-energetic stream of protons created by, basically, destruction. To cost a photon to the wavelengths on the far finish of the electromagnetic spectrum, you want an occasion so energetic that, in some circumstances, it creates a gap in space-time. Like a star snuffing out in a violent supernova and collapsing right into a black hole, which is without doubt one of the situations Piersanti says would possibly have triggered this explicit gamma ray.
So why is that this “new” physics? The occasion, known as GRB 221009A, was the primary time astronomers noticed the consequences of a gamma- ray burst on the higher ionosphere. Measurements going again to no less than 1994 have relied on observations of the decrease ionosphere.
Piersanti and different collaborators, who’re a part of the CSES-Limadou Collaboration, labored to piece collectively information from a number of gamma-ray space observatories concerning the occasion, particularly leaning on information from the European Area Company’s (ESA’s) INTEGRAL satellite. The crew revealed its ends in Nature Communications.
“The arrival of all these energetic photons fully modified the conductivity of the ionosphere when it comes to ionization, and this produced currents within the ionosphere that weren’t anticipated on the latitudes we measured,” Piersanti says. The occasion was measured at round 310 miles (500 kilometers) above Earth’s floor. These results are all new to astronomers — together with that {the electrical} subject fluctuated whereas the magnetic subject didn’t.
Piersanti says the occasion got here in 3 ways — a form of “precursor” occasion that peaks and dips simply earlier than a large spike in power. Then there’s a 3rd spike and peak, much less energetic than the second however extra energetic than the primary. Every peak was highly effective sufficient to have an effect on the whole ionosphere, the form of factor that usually solely the Solar is able to when it spews out a stream of particles that mild up this high-atmospheric layer as a superb aurora.
This space symphony — actually a collection of big clangs — are what lead Piersanti and his colleagues to assume it could possibly be from the demise of a star. The primary peak is the supernova, when a star sheds its outer layers as a result of its core has collapsed. The second sign is the persevering with collapse of the core, now laid naked and able to eat matter round it. The third peak is a part of this stage as effectively.
It additionally wasn’t a fast occasion, however a stream of gamma ray particles bombarding the ionosphere for greater than seven hours after the second peak hit.
There’s the chance, Piersanti says, that whereas nonetheless a supernova occasion, it’s not essentially exhibiting the black hole a lot as completely different levels of a stellar explosion. On this case, the primary peak is the collapse of the star, and the second peak is the explosion. (Not all supernovae create black holes; some create dense remnants referred to as neutron stars.)
As a part of the experiment, Piersanti and crew modeled what would have occurred if a comparably sturdy burst — which was already among the many strongest ever detected — occurred inside our galaxy.
“We developed a quite simple mannequin for the implications of a gamma-ray burst within the higher ambiance — we requested what might occur within the ambiance, if the gamma-ray burst or one thing like that comes from within our galaxy,” Piersanti says. “And the outcomes of the mannequin for the worst case was that the whole ozone layer could be fully depleted.” The implications could be big, as all life on Earth would start receiving harmful ultraviolet radiation from the Solar not mitigated by our ambiance’s protect.
Mercifully, this gamma ray was far-off, so we’re fairly protected from these drastic results — and certainly, no stars are actually anticipated to go supernova in our native neighborhood for some time. The closest star that might go supernova, Betelgeuse, is probably going of no hazard to Earth. And there’s additionally the chance that the supernova speculation is improper for this gamma ray burst and one thing else triggered it.
However the occasion, for now, is about discovering out concerning the highly effective occasions in our universe and attempting to grasp their results. If the same one arrives, astronomers could have one thing to match it in opposition to, and have extra information to work with to unravel among the mysteries on this new realm of physics.
