Try to imagine the difference between the lamp in your living room and the floodlights in a football stadium. That’s the contrast between an ordinary gamma-ray burst and the GRB 221009A event, observed in 2022. Now, this colossal event has been covered in a series of papers published in the The Astrophysical Letterswho begin to understand him better.
When GRB 221009A was discovered on October 9 last year, scientists thought it was an explosion in our own galaxy, more or less close to the core. However, it was soon discovered that the glow was in a galaxy far, far away — 2.4 billion light-years from Earth.
This means that the source was much more powerful than usual. In fact, this was the most energetic gamma-ray event ever observed by astronomers and probably the largest ever to occur during human history.
Its radiation swept through intergalactic space, our Milky Way and reached the Solar System, reaching from Voyager 1 — currently traveling through interstellar space — to reaching astronomical instruments in Earth orbit. The main one was Swift, launched into space precisely to detect gamma rays.
Other telescopes that detected the event or its effects include the Fermi Gamma-Ray Space Telescope, XMM-Newton, the Solar Orbiter probe and BepiColombo, as well as the Gaia and SOHO observatories. Even today the residual radiation is still visible and will remain so for a few more years, continuously providing data to be collected and studied.
In the series of papers published now, the researchers explore the opportunity to learn about this cosmic explosion. Considering that the radiation traveled through intergalactic space for over two billion years before reaching us, there is a lot that can be discovered about the source of the glow.
By analyzing the interactions between the particles and the matter they encountered along the way, the scientists found that they encountered the first dust cloud when they reached the Milky Way, 60,000 years ago. The last cloud interacted with these particles 1,300 years ago. With each interaction, circular rings were formed in the clouds.
With that, astronomers analyzed data from all these rings — 20 in total — to determine the most accurate possible distance to each of these dust clouds. Furthermore, they were able to deduce the properties of the dust grains in these clouds and concluded that they were mainly composed of graphite.
In the image above, composed of photos captured between two and five days after the explosion, you see 19 of the 20 rings detected by the XMM-Newton X-ray telescope. The largest of these is comparable to the apparent size of a full moon and came from dust clouds relatively close to the Solar System. The innermost ring is 61,000 light-years away, on the other side of the galaxy.
Ultimately, they used the data to reconstruct the X-ray emission from GRB 221009A, as this wavelength has not been observed directly by any instrument. Thus, they found similarities with some examples of type Ic supernovae, but no remnants, such as nebulae or neutron stars, were detected.
The absence of a remnant suggests that the star was massive enough to immediately become a supernova black hole, gobbling up all the matter ejected in the explosion. The researchers will now dedicate themselves to looking for other clues, such as heavy metals normally formed from powerful supernovae like this one.
Source: The Astrophysical Letters, ESA
