The flattest detonation ever recorded and the first instance of an uncommon
occurrence known as a rapid blue optical transient were both produced by a
peculiar object known as "the Cow." (FBOT).
Scientists were shocked by a bizarre cosmic explosion in 2018, and it has
now become even weirder. According to a recent analysis of the polarized
light from the first known fast blue optical transient (FBOT) explosion,
AT2018cow, also known as "the Cow," the explosion is the most asymmetrical
one that astronomers have ever observed, bursting into space in the shape of
a flattened pancake rather than a typical sphere.
The explosion, which had a form resembling the solar system and happened
180 million light-years from Earth, may cast doubt on how scientists
currently think explosive events like FBOTs take place.
Justyn Maund, a senior professor in astronomy at the University of Sheffield in the
U.K., said, "This discovery tells us that these explosions aren't
spherically symmetric—in fact, the disk we think we've observed is really
flat." and the new study's main author, informed Live Science via email.
This implies that any model attempting to account for these FBOTs must
acknowledge that they are not round occurrences.
Scientists were already baffled by FBOTs like the Cow. Only four other
comparable transients have been seen since the finding of the Cow in 2018,
so very little is known about FBOTs or what triggers them. Nevertheless, one
thing is certain: They don't act the same way as normal supernovas, the most
prevalent kind of space explosion, which happen when massive stars run out
of nuclear fuel and fall under their own gravity.
The brightness of FBOTs drops off sharply after they suddenly appear,
according to Maund. "Unlike regular supernovae, there are no radioactive
elements to power the brightness, so the power has to come from somewhere
else," he said. "FBOTs are bright, they're really bright — brighter than
some superluminous supernovae."
While this analysis of the Cow does not yet reveal the origins of FBOTs,
the Cow's flatness demonstrates that FBOTs are even more distinct from
supernovas than scientists previously believed. In their latest work, Maund
and his team again examined the light from the Cow that was first observed
in June 2018, this time studying how the light was polarized — how the
vibrations in the light waves traveled in a single plane.
The spike hit 7% on the first night, according to Maund, "and then we saw a
huge surge in the polarization and then it fell down. This is not at all
what we are accustomed to because we have never observed supernovae with
such high levels of polarization or polarization that has developed so
rapidly.
Light from the Cow was measured using the Liverpool Telescope, whose
primary mirror is only 6.5 feet (2 meters) in diameter. The team used these
data to create a 3D model of the explosion, with polarization allowing them
to reconstruct it as if it had been spotted by a telescope with a diameter
of about 388 miles (625 kilometers). This allowed them to map the explosion
to its edges, rudimentarily determine the shape of the Cow, and to determine
its strangeness.
When this number came out of the analysis, Maund and his co-authors
repeated all of the data reduction and analysis several times to make sure.
"Based on previous work on supernovae we see things that look a bit oblate,
a bit like a hamburger, or a bit prolate, more like a rugby ball, but not
hugely aspherical," Maund said."
The team will now use the Legacy Survey of Space and Time survey, which
will be carried out by the Vera Rubin Observatory in Chile, to search for
more FBOTs to see how many show polarization similar to the Cow's, and thus
determine if they are also pancake-like disks.
Maund presently has a few theories about what could possibly cause FBOTs,
and the team is hopeful that this closer examination of the Cow may cast
light on these uncommon, powerful events.
"The disruption of a star passing a black hole or a failed supernova in
which the core collapses but does not result in a supernova but instead
collapses into a black hole or neutron star and starts chewing up the
insides is powering what we see as the FBOT," Maund said, are two
possibilities for the origin of FBOTs.
The team's research was published March 30 in the journal
Monthly Notices of the Royal Astronomical Society
