An aspherical “cow” – a strange explosion the size of our solar system baffles astronomers -Se

Astronomers have observed an explosion 180 million light-years away that challenges our current understanding of cosmic explosions, displaying a significantly flatter appearance than previously thought.

• Astronomers have observed an explosion 180 million light-years away that challenges our current understanding of explosions in space, which appear much flatter than ever thought.
• Bursts are almost always expected to be round, because the stars themselves are round, but this is the flattest one seen so far.
• The observed burst was an extremely rare fast blue optical transient (FBOT) – known to astronomers as a “cow” – and only four have ever been seen, and scientists don’t know how they occur, but the discovery helps solve part of the puzzle.
• One possible explanation for how this explosion occurred is that the star itself may have been surrounded by a dense disk or that it may have been a failed supernova.

An explosion the size of our solar system has surprised scientists, as part of its shape — like an extremely flat disk — challenges everything we know about explosions in space.

The observed explosion was a bright fast blue optical transient (FBOT) – an extremely rare class of explosions that is far less common than other explosions such as supernovae. The first bright FBOT was discovered in 2018 and was nicknamed “Cow.”

Starbursts in the universe are almost always spherical, because the stars themselves are spherical. However, this burst, which occurred 180 million light-years away, is the most aspherical seen in space, emerging in a disk-like shape days after its discovery. This part of the explosion comes from material created by the star just before the explosion.

It is not yet clear how bright FBOT bursts occur, but it is expected that this observation was recently published in the journal Monthly Bulletin of the Royal Astronomical Societywill bring us closer to understanding them.

Dr Justin Mound, lead author of the study at the University of Sheffield’s Department of Physics and Astronomy, said: “Very little is known about FBOT explosions — they don’t behave like exploding stars, they are very bright and they evolve very quickly. Simply put, they’re weird, and this new observation makes them even weirder.

“Hopefully this new discovery will help us shed a little more light on them – we never thought the explosions could be so aspherical. There are a couple of possible explanations for this: the stars involved may have formed a disk just before they died, or they may have been failed supernovae. , where the core of the star collapses into a black hole or neutron star which then eats up the rest of the star.

“What we now know for sure is that the recorded anomaly levels are a key part of understanding these mysterious explosions, and it challenges our preconceived notions of how they might have exploded in the universe.”

Scientists made the discovery after spotting a flash of fully polarized light by chance. They were able to measure the polarization of the burst — using the astronomical equivalent of Polaroid sunglasses — with the Liverpool Telescope (owned by Liverpool John Moores University) in La Palma.

By measuring the polarization, this allowed them to measure the shape of the explosion, effectively looking at something the size of our solar system but in a galaxy 180 million light-years away. They were then able to use the data to reconstruct the 3D shape of the blast and map the edges of the blast – they could see how flat it was.

The Liverpool Telescope’s mirror is only 2.0 meters in diameter, but by studying the polarization astronomers were able to reconstruct the size of the burst as if the diameter of the telescope were about 750 km.

The researchers will now conduct a new survey with the International Vera Rubin Observatory in Chile, which is expected to help discover and understand more FBOTs.

Reference: “A Polarized Optical Light Pointing to an Aspherical ‘Cow'” by Justin R. Mound, Peter A. Hoeflich, Ian A. Steele, Yi Yang, Klaus Wiersema, Shiho Kobayashi, Nuria Jordana-Mitjans, Carol Mundel, Andreja Gombok. By Cristiano Guidorzi and Robert J. Smith, 21 February 2023, Monthly Bulletin of the Royal Astronomical Society.
DOI: 10.1093/mnras/stad539