Astronomers around the world are absolutely mesmerized by an unusually long and bright high-energy pulse that occurred on October 9. swept the earth without prior notice. The powerful emission came from a ‘gamma ray burst’ (GRB), the most powerful type of explosion in the Universe, and was one of the brightest and most luminous events known so far. Normally, this type of phenomenon only lasts a few seconds.
That day was Sunday, and early in the morning a wave of X-rays and Gamma rays passed through our Solar System, activating the detectors of NASA’s Fermi Gamma-ray Telescope, the Swift Observatory and the Wind spacecraft, among others. Immediately, telescopes around the world pointed to the source of the emission to study its aftermath. Today, a week later, the observations continue.
Listed as GRB 221009A, the explosion quickly became the star of the 10th Fermi Symposium, a gathering of gamma-ray astronomers taking place in Johannesburg, South Africa. “It’s safe to say this meeting started off with a bang — everyone’s talking about this,” said Judy Racusin, assistant Fermi project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, one of the attendees.
The signal, which originated in the direction of the constellation Sagitta (Arrow), had to travel approximately 1.9 billion years to reach Earth. Astronomers believe it represents the ‘birth cry’ of a new black hole, originating in the heart of a massive star that collapsed under its own weight. Under these circumstances, a nascent black hole is capable of launching powerful jets of particles that travel at nearly the speed of light. The jets pass through the star, emitting X-rays and gamma rays as they travel out into space.
The Swift X-ray Telescope captured the afterglow of GRB 221009A about an hour after it was first detected.
The outburst also provided the long-awaited opportunity to inaugurate the combined observation of two experiments on the International Space Station: NASA’s NICER X-ray telescope and Japan’s All-Sky X-ray Imaging Monitor detector ( MAXI). Activated in April, the connection between the two instruments is called the Orbiting High Energy Monitor Alert Network (OHMAN), and allows NICER to quickly and automatically observe bursts detected by MAXI, something that previously required manual intervention by scientists on the ground. .
In this way, explains Zaven Arzoumanian, NICER scientific leader at Goddard, “OHMAN provided an automatic alert that allowed NICER to track the phenomenon in less than three hours, as soon as the source became visible to the telescope. Future opportunities could result in response times of a few minutes.”
The bright light from this ancient and distant explosion brings with it new insights into, among other things, stellar collapse, the birth of a black hole, the behavior and interaction of matter at near light speed, and the conditions in a distant galaxy. Another GRB this bright might not be produced again for decades.
A ten hour burst
According to a preliminary analysis, Fermi’s Large Area Telescope (LAT) detected the outburst for more than 10 hours. One of the reasons for the event’s unusual brightness and longevity is that, for a GRB, it occurred relatively close to us.
“This burst has occurred much closer than typical GRBs,” explains Roberta Pillera, a member of the Fermi LAT Collaboration who led the initial communications about the burst, “which is exciting because it allows us to detect many details that would otherwise have been too much. weak to see But it’s also among the most energetic and luminous outbursts ever observed, regardless of distance, which makes it doubly exciting.”