“The only thing that can be that small is a compact object - either a neutron star or black hole,” Pasham says. By this reasoning, he calculated that the size of the object must be no larger than 1.3x10 8 centimeters, or roughly 1,000 kilometers wide. In this case, the size of the pulsing object cannot be larger than the distance that the speed of light can cover in 4.4 milliseconds. Pasham seized on this pulse, recognizing that its frequency could be used to directly calculate the size of whatever was pulsing. They focused on the X-rays and found that the Cow appeared to be giving off bursts at a frequency of 225 hertz, or once every 4.4 milliseconds. The team looked through the data to identify X-ray signals emanating near AT2018cow, and confirmed that the emissions were not from other sources such as instrument noise or cosmic background phenomena. This data was recorded in a publicly available archive, which Pasham and his colleagues downloaded and analyzed. NICER started observing the Cow about five days after its initial detection by optical telescopes, monitoring the signal over the next 60 days. The team looked to X-ray data collected by NASA’s Neutron Star Interior Composition Explorer (NICER), an X-ray-monitoring telescope aboard the International Space Station. So, I wanted to test out the idea that there is a black hole or compact object at the core of the Cow.” “To me, the first thing that comes to mind is, some really energetic phenomenon is going on to generate X-rays. “This signal was close and also bright in X-rays, which is what got my attention,” Pasham says. Pasham wondered whether an answer could be found in X-ray data. However, the data collected by optical telescopes haven’t resolved the source of the signal in any definitive way. Or it could have resulted from a middle-weight black hole stripping away material from a passing star. For instance, it could have been a product of a black hole born in a supernova. And the question was, what could produce this additional source of energy?”Īstronomers have proposed various scenarios to explain the super-bright signal. “The amount of energy was orders of magnitude more than the typical core collapse supernova. “It was exciting because loads of data started piling up,” Pasham says. Its powerful flash - up to 100 times brighter than a typical supernova - was detected by a survey in Hawaii, which immediately sent out alerts to observatories around the world. The signal is among a few dozen known FBOTs, and it is one of only a few such signals that have been observed in real-time. The “cow” in its name is a random coincidence of the astronomical naming process (for instance, “aaa” refers to the very first astronomical transient discovered in 2018). We think this new evidence opens possibilities for finding baby black holes or baby neutron stars.”ĪT2018cow is one of many “astronomical transients” discovered in 2018. “This happens in normal supernovae, but we haven’t seen it before because it’s such a messy process. “We have likely discovered the birth of a compact object in a supernova,” says lead author Dheeraj “DJ” Pasham, a research scientist in MIT’s Kavli Institute for Astrophysics and Space Research. The newborn object continued to devour surrounding material, eating the star from the inside - a process that released an enormous burst of energy. Their findings, published today in the journal Nature Astronomy, strongly suggest that AT2018cow was likely a product of a dying star that, in collapsing, gave birth to a compact object in the form of a black hole or neutron star. By astrophysical standards, such an object would be considered compact, much like a small black hole or a neutron star. They traced hundreds of millions of such X-ray pulses back to the Cow, and found the pulses occurred like clockwork, every 4.4 milliseconds, over a span of 60 days.īased on the frequency of the pulses, the team calculated that the X-rays must have come from an object measuring no more than 1,000 kilometers wide, with a mass smaller than 800 suns. In addition to a bright optical flash, the scientists detected a strobe-like pulse of high-energy X-rays.

Now an MIT-led team has found strong evidence for the signal’s source. The signal, procedurally labeled AT2018cow, has since been dubbed simply “the Cow,” and astronomers have catalogued it as a fast blue optical transient, or FBOT - a bright, short-lived event of unknown origin. The powerful burst appeared at first to be a supernova, though it was much faster and far brighter than any stellar explosion scientists had yet seen. In June of 2018, telescopes around the world picked up a brilliant blue flash from the spiral arm of a galaxy 200 million light years away.

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