An amateur astronomer tested a new camera and accidentally photographed a supernova flash

Supernova SN 2016gkg of type IIb (circled in red) around the galaxy NGC 613. For comparison, the brightness of the marked stars

On a clear night of September 20, 2016, an amateur Argentinean astronomer named Víctor Buso decided that it was a good time to test the new camera on his 40-centimeter telescope. He decided to check on the spiral galaxy NGC 613 in the constellation Sculptor - and rare luck smiled at the man. An enthusiast saw that in one of the branches of the galaxy in some later pictures an object appeared. It turned out that he was lucky to catch a flash of a supernova in the camera lens. As a result, now the name of Victor Buso is printed next to the names of serious scientists - the authors of a scientific article, which was published in the journal Nature on February 21, 2018.

In a scientific article, scientists estimated the probability of such a discovery at 10 ⁻⁶ , given the duration of the phenomenon of 1 hour and suggesting the appearance of one supernova in one galaxy once a century. If we take into account the probability of clear sky and the possibility of observing a specific area from a certain region on Earth, then the probability decreases by one more order - to the level of 10 ⁻⁷ , that is, one chance out of ten million. Or, to put it bluntly, if you make ten million such observations on a single piece of sky, then statistically you can also count on taking photographs of a supernova. Or if ten million people simultaneously make such observations each in their own region of the starry sky, only one of them will take a supernova. In general, this is an extremely rare luck.

In fact, many lovers had previously managed to photograph previously unknown supernovae. But they usually found out about this fact when they took archival images of a certain region of the sky, dating back several months or years earlier, and checked that at that time there were no objects at a particular point, but now they are. But Victor did not have to raise any archives. The supernova exploded literally before his eyes (if you do not take into account the distance of millions of light years): it was not on the first photographs taken, and after a few minutes it appeared. This is the uniqueness of the discovery. It makes it possible to study the earliest stage of a supernova explosion.

The difference between the first and last pictures is noticeable in the following illustrations. The left side shows the combined image of the first 40 shots, and the right side shows the combined image made up of the 21 most recent photos.



The new object, which appeared closer to the lower right corner of the frame in recent photos, is clearly visible. This is the type II supernova, which was assigned the number SN 2016gkg. In stars of this type, the core collapses to a density comparable to the density of the atomic nucleus, rapid compression and explosion, followed by release of energy and a sharp increase in the luminosity of the star (10 ⁸ - 10 ¹⁰ times). When compressed, a sphere weighing 2.8e ³⁰ kg is compressed from a radius of 2100 km to 10 km in 30 ms. After the explosion, the remaining nucleus can turn into a neutron star or a black hole, depending on the mass of the nucleus.

Supernova explosions are one of the most interesting phenomena in astrophysics. Observations on such phenomena are hampered by the fact that the process is unpredictable and rather transient. No one knows at which point the next supernova explodes, except for exceptional cases, such as the planned merger of the KIC 9832227 dual system in the constellation Cygnus only 1600 light years away - although this is not a supernova, the Earth inhabitants will be able to watch the explosion with the naked eye in about 2022 (plus or minus one year). But it is usually very difficult to photograph the first hours after the explosion, not to mention the first minutes. Therefore, the photos of Victor Buso can be called such incredible luck. He was with a suitable instrument, which was at the right moment directed to the desired part of the sky.

The dynamics of changes in brightness immediately after the explosion allows astrophysicists to make assumptions about the processes that occur in a star. Specialists have already begun to work: they are developing hydrodynamic explosion models that will help identify the individual phases of the evolution of a star and the processes that are responsible for them. Information from the photos of Victor Buso became for them an invaluable find.

The scientific article was published on February 21, 2018 in the journal Nature (doi: 10.1038 / nature25151, pdf ).