Published January 11, 2019
"We know from the theory that black holes and neutron stars are formed when a star dies but we have never seen them right after they are born. Never! "Raffaella Margutti, assistant professor of physics and astronomy at Northwestern University, said about the mysterious bright object that has confused astronomers called" The Cow ". "A" lightbulb "deep inside the explosion ejecta. It would have been difficult to see this in a normal star explosion. But the cow had very small ejecta mass, which allowed us to see the central engine's radiation directly."
With the help of WM Keck Observatory at Maunakea, Hawaii and the University of Hawaii Institute for Astronomy's ATLAS Twin Telescope, the multinational team now has evidence that they probably captured the exact moment a star collapsed to form a compact object, such as a black hole or a neutron star .
The cow shown in the picture above is only visible as one of two light spots in the lower right quadrant of the spiral galaxy classified as CGCG 137-068.
The stellar crime, approaching and swirling around the object's horizon, caused the remarkable bright glow. The research, which will be featured in The Astrophysical Journal, was announced today at a press conference at the 233 United States Astronomical Society meeting in Seattle.
This rare event will help astronomers better understand the physics of gambling within the first moments of the creation of a black hole or a neutron star.
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"Because of its X-ray and UV emission," the cow "may have been caused by a black hole which consumes a white dwarf, but further observations of other wavelengths across the spectrum led to our interpretation that "The Cow" is actually the formation of a responsible black hole or a neutron star, "says lead author Margutti, a faculty member of Northwestern's CIERA (Center for Interdisciplinary Research and Astrophysics Research).
The cow was first discovered on June 16 after the ATLAS telescope on Haleakala and Maunaloa captured a spectacularly light anomaly 200 million light-years away in the Hercules constellation. The object quickly grew up and disappeared almost as quickly.
The event immediately caught international interest and left astronomers scratching their heads. "We thought it had to be a supernova," Margutti said. "But what we observed challenged our current concepts of star death."
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For the anomaly was unnatural light – 10 to 100 times brighter than a typical supernova. It also grew up and disappeared much faster than other known star explosions, with particles flying at 30,000 kilometers per second (or 10 percent of light speed).
Within just 16 days, the object had already abandoned most of its power. In a universe where some phenomena last for millions and billions of years, it is two weeks that blink in the eye.
"We knew right away that the source went from idle to brightness within a few days," said Co author Ryan Chornock, assistant physics and astronomy professor at Ohio University. "It was enough to get everyone excited because it was so unusual and with astronomical standards it was very close."
With the help of the Northwestern access to the Keck Observatory's twin telescope, Margutt's team looked closer at the object's makeup with the Low-Resolution Imaging Spectrometer (LRIS) on the Keck I telescope as well as the DEep Imaging and Multi Object Spectrograph (DEIMOS) on Keck II.
"Keck was crucial in determining the chemical composition and geometry of AT2018cow," said Co author Nathan Roth, a JSI postdoctoral fellow at the University of Maryland. "Keck's unique niche is its ability to monitor The Cows late behavior. This can be difficult; when more time passes after the event, the fewer it gets. But with Keck's late-time spectroscopy, we could pierce through the" interiors of the explosion. "This revealed AT2018cow's red-shifted spectral Features Very Good. "
" The cow is an excellent example of a type of observation that becomes critical in astronomy: rapid response to transient events, "said Keck Observatory Chief Scientist John O & # 39; Meara. "We look forward to implementing new observational and telescopic instruments that allow us to be so quick in the sky and in the science that we can."
The team also received optical images from the MMT Observatory in Arizona as the southern astrophysical research SOAR telescope in Chile.
When Margutti and her team examined the chemical composition of the cow, they found clear evidence of hydrogen and helium, which excludes models of compact objects that merge – like those that produce gravitational waves.  "It took us a while to realize what we were looking at, I would say months," says co-author Brian Metzger, associate physics professor at Columbia University. "We tried several possibilities and were forced to go back to the drawing board several times. We were finally able to interpret the result due to the hard-committed team work.
Astronomers have traditionally studied star death in the optical wavelength, using telescopes to capture visible light.  Margut's team on the other hand, used a more comprehensive strategy.After ATLAS discovered the object, Margutti's team quickly performed follow-up observations with several observatories to analyze The Cow in different wavelengths.
The researchers considered the object in hard X-rays. by NASA's Nuclear Spectroscopic Telescope Array (NuSTAR) and the European Space Agency (ESA) INTErnational Gamma Ray Astrophysics Laboratory (INTEGRAL), in soft X-rays (ten times more powerful than regular X-rays) using ESA's X-Ray Multi-Mirror Mission (XMM-Newton) and in radio waves using National Radio Astronomer y Observatory (NRAO) Very Large Array (VLA). This allowed them to continue studying anomaly for a long time after its initial visible brightness faded.
Margutti attributes the cow's relative nakedness to potentially unraveling this intergalactic mystery. Although the stars can coincide in black holes all the time, the vast amount of material around the newborn blocks black astronomers' vision.
Fortunately, about 10 times less ejected around Cow compared to a typical star explosion. The lack of material allowed astronomers to permeate right through to the object's "central engine", which revealed itself as a likely black hole or neutron star.
The Margutti team also benefited from the star's relative proximity to the earth. Although it was embedded in the remote dwarf galaxy, called CGCG 137-068, astronomers consider it "right around the corner."
"Two hundred million light years are close to us," Margutti said. "This is the closest transient object of this kind that we have ever found."
Daily galaxy via Keck Observatory