In this scenario, most of the star's interior collapsed to form the black hole, but the star's outermost layers didn't feel it at first. The other possibility is that the object appeared when a huge and very hot type of star called a blue supergiant had a misfired explosion and became a black hole. The Cow could be a highly magnetized neutron star rotating about a thousand times a second. Margutti's team thinks there are two leading options. The fastest of this material seems to have slammed into a dense haze of particles surrounding the Cow, heating up the haze and creating the object's radio emissions. When the Cow exploded, some of the debris from the object zoomed outward at more than 18,000 miles a second, or up to a tenth of the speed of light. Meanwhile, the Cow's radio signals show that it behaved like a bull in a foggy china shop. But some of the high-energy x-rays could still leak out from the Cow's clearer poles. These equatorial clouds absorbed the engine's high-energy x-rays, which made the clouds heat up and generate the Cow's visible light. In the model made by Margutti's team, the debris flying from the object's poles moves faster-and gets transparent sooner-than the clouds around the object's equator. “It's really hard to explain this as a spherical event, because if the x-ray source is powering the optical radiation, then how are the x-rays getting out to us?” “One of the jokes is that we always model things as spherical cows, and it was clear that this was an aspherical cow,” says study coauthor Brian Metzger, a physicist at Columbia University. This object, whatever it is, is shrouded in a distinctly asymmetrical blob of material thrown off in some kind of explosion. The current consensus is that a compact “central engine” sits at the Cow's center and spews those high-energy x-rays. “The first reaction when we got the data was, perhaps we did something wrong,” Margutti says. The data showed that a little over a week after it first appeared, the Cow unexpectedly grew a lot brighter in high-energy x-rays. For instance, Margutti's team asked to point NASA's NuSTAR x-ray telescope at the object. The Cow also gave off radiation in unusual ways. What's more, the debris contained hydrogen and helium, which astronomers weren't expecting to find: The stars that explode into supernovae should have long since burned through those elements as nuclear fuel. Hester (Arizona State University)/NASAĮven if the Cow's debris were entirely nickel-56, that wouldn't be enough fuel to power the observed explosion. The blast wave slams into clouds of interstellar gas, causing it to glow and revealing information about the composition of the gas. The formation shown here marks the outer edge of an expanding blast wave from a colossal stellar explosion that occurred about 15,000 years ago. This 1991 image shows a small portion of the Cygnus Loop supernova remnant. A team of astronomers using Hawaii's ATLAS telescopes saw it on June 16, 2018, and flagged the object to other astronomers on June 17-triggering a rush of telescopes turning to point at the explosion. ![]() It's called “the Cow” because of its formal, auto-generated name AT2018cow. ![]() The Cow exploded in the outskirts of CGCG 137-068, a dwarf spiral galaxy about 200 million light-years from Earth. Where is the Cow, and why is it called that? So what do we know about the Cow, and why has it been so hard for astronomers to describe? We've got you covered. And other teams studying the Cow have proposed alternative explanations for its unusual behavior. ![]() The team's data, captured in multiple wavelengths of light, could also mean that a massive star collapsed into a neutron star, a kind of dense stellar corpse. Margutti and her colleagues presented their work this week at the American Astronomical Society's annual meeting in Seattle, Washington, and will soon be publishing their findings in the Astrophysical Journal. “This is the target we've been waiting for for years,” says team leader Raffaella Margutti, an astrophysicist at Northwestern University.
0 Comments
Leave a Reply. |
Details
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |