The Cosmic Cow
Updated: Feb 19, 2022
A bright blast from a remote galaxy 200 million light years away acquainted the astronomers with a subcategory of supernova explosions, making up only 0.1% of such cosmic blasts. The cow was which was 10 times as bright as a regular supernova and stayed bright and hot for nearly three weeks. The primary such cosmic blast occurred in June 16, 2018 was named as AT2018cow, and is mostly noted as cow. These cows are defined by the way they brighten up, glow brilliantly in UV and blue light and still shine for months in higher energy X-rays and lower energy radio waves.
Why the name “Cow”?
There is a format for naming the astronomical transients. The primary astronomical transient was named as “aaa” and the letter system somehow fell on “cow” at the very moment this bright blast happened within the cosmos.
How was cosmic cow produced?
NASA’s Neutron Star Interior Composition Explorer (NICER) is an X-ray monitoring telescope embarked on International Space Station, which observed the cow for about five days after its initial detection. The information revealed a vibrant pulse of high energy X-rays. They were able to trace hundreds of millions of X-rays back to source of the signal, tracing every single photon to when it hit the detector by 100 nanoseconds. They found that these X-rays pulses flickered once every 4.4 milliseconds for 60 days. Using that information, the team determined the dimensions of the object from which the X-ray pulses originated. The object could be no over 1000 kms wide with a mass less than 800 suns, which implies that it is incredibly dense. The two objects that could hold that much mass in an exceedingly small body are a newly born neutron star or a black hole. The findings suggest that the cow signal was produced after a star died and gave birth to a neutron star then continued to swallow the star from inside, eating up the surrounding material and then producing a sudden burst of energy.
Recently scientists have found another member of the cow class which is additionally the brightest one when seen in X-rays. It’s been named as AT2020mrf. This is the fifth cosmic cow found up to now. AT2020mrf glowed 20 times as bright as the original cow a month after the blast. Even one year after its discovery, its X-rays were 200 times as bright as those from the first cow. The burst of this new cow took place on June 12, 2020. The Zwicky Transient Facility at Caltech’s Palomar Observatory near San Diego, California noted a bright burst of light on the specified date. But didn’t realize what it was. In April 2021, researchers spotted the event using Spektrum-Roentgen-Gamma space telescope which was captured during July 2020. The brightest spot of the blast was invisible within the X-rays captured in January, but in July it had been hard to miss.
Dr. Raffaella Margutti of Northwestern University in Chicago and his team were following the cow using 16 telescopes around the world to study radio waves, hard X-rays and gamma rays. Unlike the regular supernova, the Cow has a tiny material swirling around it. Using hard X-rays, they found that lying deep within the core of the Cow was a central engine which pumped out energy for at least 100 days after the blast.
Researches are sill going on to find whether the cow has left behind a black gap or a neutron star. Further observations and capturing of these objects with multiple types of light will help scientists learn more about this new category of supernova and what type of star eventually explodes as cow.
- By Sakthi
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