Two mysterious X-ray sources flash near the Milky Way

American astronomers discovered from archived data two mysterious light sources flashed a total of six times and lasted for one minute before disappearing.

X-ray source (circled) near galaxy NGC 5128. Photo: NASA.

A team of astronomers led by Jimmy Irwin at the University of Alabama, USA, found two bright X-ray sources on the edges of two neighboring galaxies, Virgo (NGC 4636) and Centaurus A (NGC 5128). The research results were published yesterday in the journal Nature, according to International Business Times.

Scientists previously detected two very short, intense X-ray flares near the galaxy NGC 4697. Irwin and colleagues decided to look for similar flares by re-examining observations of 70 galaxies near the Milky Way using the Chandra X-ray Observatory.

The team identified two additional sources. One flashed once, while the other flashed five times. Each flash lasted less than a minute and faded over the course of about an hour. The flares were brighter than any neutron star. What was remarkable was that the source appeared to be nestled among other long-lived objects.

Typically, a flare source can be identified by looking at the duration of its brightness and the number of times it repeats. A non-repeating flare lasting about a minute usually signals the death of a massive star. But the source must be in a population of young stars. Repeating flares also only appear under certain conditions, which the team did not find in the strange X-ray source.

The researchers believe that the source of the X-rays could be a black hole undergoing some kind of movement. "The first possibility, as the authors suggest, is that there is an intermediate-mass black hole (100-1,000 times the mass of the Sun) at the center of each source. For some reason, they emit X-rays for about an hour. Another possibility is that a low-mass black hole is shining X-rays directly at Earth. A binary star system with an unpredictable orbit could lead to repeated flashes from the source near NGC 5128," said Sergio Campana, a researcher at the Institute of Astrophysics in Italy.

Campana also stressed that more observations are needed to explain the X-rays, especially their repetition rate.

According to VNE