Supernova shocker: Scientists observe flattest explosion 180 million light years away

Scientists have observed a rare Fast Blue Optical Transient (FBOT), known as "the cow", which is an explosion class that is much less common than other explosions, such as supernovas.
Kavita Verma
Slim Boom
The image shows an artist's impression of the flattest explosion ever seen in space, resembling a disc.

Credit: Philip Drury, University of Sheffield 

An explosion 180 million light years away that appeared much flatter than astronomers had previously anticipated challenges our understanding of explosions in space.

The discovery was made after scientists spotted a flash of polarized light entirely by chance. Using the astronomical equivalent of polaroid sunglasses, they were able to measure the polarization of the blast with the Liverpool Telescope located on La Palma and measure the shape of the explosion. By reconstructing the 3D shape of the explosion, scientists were able to map the edges of the blast and see just how flat it was.

"We never thought that explosions could be this aspherical. There are a few potential explanations for it: the stars involved may have created a disk just before they died or these could be failed supernovas, where the core of the star collapses to a black hole or neutron star which then eats the rest of the star," said Dr. Justyn Maund, the lead author of the study from the University of Sheffield's Department of Physics and Astronomy, in a statement.

Age-old theories challenged

These mysterious explosions are too bright and evolve too quickly, behaving differently than exploding stars should. With only a few FBOTs ever discovered, the new observation makes them even weirder. The discovery challenges our preconceptions of how stars might explode in the Universe, and it is hoped that it will bring us closer to understanding Fast Blue Optical Transients.

The Liverpool Telescope used to observe the explosion has a mirror only 2.0m in diameter. However, by studying the polarization, the astronomers were able to reconstruct the shape of the explosion as if the telescope had a diameter of about 750km. Researchers will now undertake a new survey with the international Vera Rubin Observatory in Chile to discover more FBOTs and further understand them.

Accidental observations unveil new phenomena

This latest discovery highlights the importance of chance discoveries in scientific research. Scientists often have to rely on accidental observations to uncover new phenomena or challenge existing theories.

The Liverpool Telescope used to observe the explosion is just one example of the cutting-edge technology used in modern astronomy. Advances in telescope technology and data analysis have enabled scientists to study the Universe in unprecedented detail, leading to new discoveries and insights into the mysteries of the cosmos.

The results have been published in the journal Monthly Notices of the Royal Astronomical Society.

Study abstract:

The astronomical transient AT2018cow is the closest example of the new class of luminous, fast blue optical transients (FBOTs). Liverpool telescope RINGO3observations of AT 2018cow are reported here, which constitute the earliest polarimetric observations of an FBOT. At 5.7days post-explosion, the optical emission of AT2018cow exhibited a chromatic polarization spike that reached ∼7 per cent at red wavelengths. This is the highest intrinsic polarization recorded for a non-relativistic explosive transient and is observed in multiple bands and at multiple epochs over the first night of observations, before rapidly declining. The apparent wavelength dependence of the polarization may arise through depolarization or dilution of the polarized flux, due to conditions in AT 2018cow at early times. A second ‘bump’ in the polarization is observed at blue wavelengths at ∼12days⁠. Such a high polarization requires an extremely aspherical geometry that is only apparent for a brief period (<1 d), such as shock breakout through an optically thick disk. For a disk-like configuration, the ratio of the thickness to radial extent must be ∼10 per cent⁠.

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