The sudden occurrence of a strong explosion from a nearby galaxy last year sent astronomers around the world into rotation.
Soon it became clear that an explosion, called AT2018cow – or simply a "cow" – was nothing like astronomers.
After more than six months of persecution, cows are still confused.
But many of the latest data presented today at the 233rd meeting of the American Astronomical Society in Seattle show an entirely new type of supernova created by a massive star that has collapsed and formed a black hole or a fast-known neutron star. like a magnet.
If so, this would be the first time that we have ever seen such an event in real time, said Raffaella Margutti of the Northwestern University in Chicago, who represents the work of her team at the conference.
Other astronomers say that there is still an outside possibility that an explosion would cause a star bursting out of a black hole – a phenomenon known as the event of a tidal disturbance.
Whatever it is, it does not fit any of the models, said Daniel Perley, an astronomer from Liverpool University John Moores in the United Kingdom, who led another international team.
"It has very different characteristics from what we have already seen," said Dr. Perley.
Not your regular supernova
The cow lies in the dwarf galaxy, 200 million light-years away from us in the Herkul constellation.
When the word came to the realization that ATLAS telescopes were observed in our cosmic environment on 16 June, astronomers observed its ascent and fall through the global telescope network.
"This can be the most prominent astronomical source," said Dr. Perley.
"The only thing that will compete would be the detection of a gravitational wave ahead of a year and a half," he said, referring to the observation of fireworks that were caused by collisions of two old stars.
Dr Perley and his team used optical telescopes, which followed the cow every night for more than a month.
While the supernova needs two to three weeks to reach its peak, the cow became very bright within two to three days before it quickly disappeared. The most brilliant was the equivalent of 100 billion times the brightness of our Sun – much lighter than the typical supernova.
An even more intense picture of the cow began to emerge when other astronomical teams, who watched the event in other parts of the energy spectrum, from radio waves to X-rays, joined the drama during the next six months.
Tara Murphy and her doctoral student Dougal Dobie of the University of Sydney used the Australian Telescopic Compact System CSIRO in Narrabria, New South Wales, to observe the radio emissions caused by the impact wave.
"We can see that shock waves travel about a tenth of the speed of light and we have seen that the light of this source in the radio increases over time," said Dr. Murphy.
Rising brightness was also observed in shorter wavelengths by team leader and astronomer Caltech Anna Ho and her colleagues using telescopes in Hawaii and Chile.
"The fact that time has become brighter and especially at higher frequencies suggests that there must be something that still drives the energy of an explosion in this material," said Dr. Murphy.
"Not only this explosion happened and then disappeared, there must be something that is still there, which makes it different from the typical supernova we see."
She said that the radio data showed the presence of magnetists in the center of the supernova.
The central engine in the center of the cow
The Marguttti team also monitored the cow, using 16 telescopes around the world to study radio waves, gamma rays, and spectrum, which is usually not used for the study of supernovae: X-ray rays, which are 10 times stronger than conventional X-rays rays.
Unlike the normal supernova, the cow has very little material that revolves around it, allowing the team to look straight into his heart.
"The most striking feature in cows is what we find in hard X-rays," said Dr. Margutti.
These strong x-ray rays have shown that laying deep in the center of the cow is a central engine that continues to pump energy for at least 100 days after the explosion.
This type of long-lasting source of energy is not known in normal supernovae or gamma rays, but it can appear as a material that revolves around a compact object, such as a newly born black hole or a swiveling magnet.
"The big question we are trying to figure out is why in the first place we have a low mass."
Dr. Margutti said that an explosion could have been caused by the death of a big blue superstar star.
"There is a possibility that these types of stars simply go straight to ruin, without causing even a little explosion."
Dr. Margutti said that radio data showed that the cow was not created with an already existing black hole that removed the star.
For black holes, which are assumed to be large enough to remove a star on the edge of the galaxy where the cow was found, it is assumed that they occur when stars join in low density environments, such as globular clusters.
Instead, she said that the cow was formed in an environment with a high density which is more in line with those around big stars that enrich their environment with their winds before they collapse.
Perley said that the exotic supernova hypothesis so far is most convincing, but did not explain all the characteristics of optical data, for example, why the central engine was so opaque.
"They did a very good job to explain it as well as we can with the tools we have now," said Dr. Perley.
He also agreed that there were a number of problems with an alternative black hole hypothesis that would tear the asterisk, but she said that it was too early to exclude her.
"The earlier partial disturbances of the star could have caused some of the already existing dense gas, or a black hole could have an acre disc," he explained.
A new type of cosmic boom
Brad Tucker, an Australian national university, has not explored cows, but has investigated the supernova events discovered by Kepler and now, the TESS telescope.
Among all the hypotheses presented by the teams, he tried to create a black hole by the unsuccessful supernova.
"I do not know whether the data is favorable to one or the other. But the reason I like is simple – it does not require any special physical mechanism.
"We know that blue supergers exist and explode. We know they explode in different regimes. Does that not mean that it could create a black hole?"
"Every time we see a blue supergiant, it's a little weird."
Less likely, as he thought, was the idea of a tide disorder event.
"If there is no supernova, we always say:" Is this an event with tidal disturbances? "and look at him and in general the answer is" no "," said Dr. Tucker.
"But again, these are things we always seek and try to understand.
"We squeeze and resolve things, but what we can finally conclude is that there is another type of explosion or kind of star that falls on the night when we just started to discover."
Now the emphasis is on finding more items like cow to definitely figure out how they were designed, Perley said.
"It should not be unique," he said.
"There were some events that had similar characteristics that they had seen in previous research, but no one really recognized them … and they were never monitored in real time or even in real time.
"So, now we know what to look for, we go on to find more and get more data."