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| Slim Boom. Credit: Phil Drury, University of Sheffield |
An explosion the size of our solar system has baffled scientists, as part of
its shape—similar to that of an extremely flat disk—challenges everything we
know about explosions in space.
The explosion observed was a bright Fast Blue Optical Transient (FBOT)—an
extremely rare class of explosion which is much less common than other
explosions, such as supernovas. The first bright FBOT was discovered in 2018
and given the nickname "the cow."
Explosions of stars in the universe are almost always spherical in shape, as
the stars themselves are spherical. However, this explosion, which occurred
180 million light years away, is the most aspherical ever seen in space,
with a shape like a disk emerging a few days after it was discovered. This
section of the explosion may have come from material shed by the star just
before it exploded.
It's still unclear how bright FBOT explosions occur, but it's hoped that
this observation, published in Monthly Notices of the Royal Astronomical
Society, will bring us closer to understanding them.
Dr. Justyn Maund, Lead Author of the study from the University of
Sheffield's Department of Physics and Astronomy, said, "Very little is known
about FBOT explosions—they just don't behave like exploding stars should,
they are too bright and they evolve too quickly. Put simply, they are weird,
and this new observation makes them even weirder."
"Hopefully this new finding will help us shed a bit more light on them—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 blackhole or neutron star which then eats the rest
of the star."
"What we now know for sure is that the levels of asymmetry recorded are a
key part of understanding these mysterious explosions, and it challenges our
preconceptions of how stars might explode in the universe."
Scientists made the discovery after spotting a flash of polarized light
completely by chance. They were able to measure the polarization of the
blast—using the astronomical equivalent of polaroid sunglasses—with the
Liverpool Telescope (owned by Liverpool John Moores University) located on
La Palma.
By measuring the polarization, it allowed them to measure the shape of the
explosion, effectively seeing 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 explosion, and were able to map the edges
of the blast—allowing them to see just how flat it was.
The mirror of the Liverpool Telescope is only 2.0m in diameter, but 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, which is expected to help discover more FBOTs
and further understand them.
Reference:
Justyn R Maund et al, A flash of polarized optical light points to an
aspherical 'cow', Monthly Notices of the Royal Astronomical Society (2023).
DOI: 10.1093/mnras/stad539
Tags:
Space & Astrophysics