Astronomers have found that two neutror stars collided about 130 million light-years from Earth,media CNET reported. On August 17, 2017, a collision between some of the densest objects in the universe produced gravitational waves and X-rays. Dozens of telescopes on Earth captured the rare merger at different wavelengths of the electromagnetic spectrum. First, a burst of high-energy gamma rays, followed by a burst of light and ultraviolet, radio, and infrared signals.
About nine days after the collision, NASA’s Chandra Observatory received X-ray signals. According to astronomers’ understanding of neutre stars, it should have disappeared by now.
But in a new study published Monday in the Journal of the Royal Astronomical Society, researchers studied the neutrtar collision, called GW170817, and found that X-ray signals could still be detected 1,000 days later.
“We really don’t know what to expect from this point of view, because all of our models predict that there are no X-rays,” Elonora Troja, an astrophysicist at NASA’s Goddard Space Flight Center and lead author of the study, said in a press release.
GW170817 is the first neutronic consetar merger event detected by three gravitational wave observatories on Earth. The three observatories were able to triangularly measure the merged position in the immediate aftermath of the merger, allowing researchers to turn the telescope into space and take a closer look at the event.
Since no neutre star collisions have been observed (only two have been recorded and confirmed so far), scientists have had to rely on models to predict the consequences. In most cases, these models are consistent with the test results of GW170817. When two neutre stars collide, they release gamma-ray jets and huge bursts of bright gas, known as “thousands of new stars.” These events are short-lived — by observing them for a few days or weeks, they disappear.
But Chandra, NASA’s X-ray observatory, was still detecting X-rays at the site when it focused on the merger in February, two-and-a-half years after it burst into life. The latest measurements show that the signal has subsided, but the X-ray signal can still be detected. Why are these X-rays still detectable? This is a difficult problem that researchers are trying to solve.
It’s possible that there’s an extra component in the neutrtar merge that the model didn’t take into account before. It’s also possible that the dynamics of the energy released after a collision are somewhat different from what scientists expected. An exciting possibility is that the combined debris represents an X-ray neutrtar — although more analysis is needed to determine the source of the signal. Astronomers will turn the telescope to GW170817 in December, providing another opportunity to demysties the merger.
“Whatever happens, this event is changing our understanding of neutron star merging and rewriting our model,” Troja said.