Astronomers Just Found a Star Orbiting a Black Hole at 1 Percent the Speed of Light

NASA/CXC/M.Weiss

Astronomers have just spotted a star whizzing around a vast black hole at about 2.5 times the distance between Earth and the Moon, and it takes only half an hour to complete one orbit.

To put that into perspective, it takes roughly 28 days for our Moon to do a single lap around our relatively tiny planet at speeds of 3,683 kilometres (2,288 miles) per hour, meaning this star is moving at some mind-boggling, break-neck speeds.

Using data from an array of deep space telescopes, a team of astronomers have measured the X-rays pouring from a binary star system called 47 Tuc X9, which sits in a cluster of stars about 14,800 light-years away.

The pair of stars aren't new to astronomers - they were identified as a binary system way back in 1989 - but it's now finally becoming clear what's actually going on here.

"For a long time, it was thought that X9 is made up of a white dwarf pulling matter from a low mass Sun-like star," said researcher Arash Bahramian.

When a white dwarf pulls material from another star, the system is described as a cataclysmic variable star. But back in 2015, one of the objects was found to be a black hole, throwing that hypothesis into serious doubt.

Data from Chandra has confirmed large amounts of oxygen in the pair's neighbourhood, which is commonly associated with white dwarf stars. But instead of a white dwarf ripping apart another star, it now seems to be a black hole stripping the gases from a white dwarf.

White dwarfs are super dense objects that are usually the remnants of a star - think of something with the mass of our Sun but only as big as our planet - so pulling material from its surface would require some impressive gravity.

The real exciting news, however, is regular changes in the X-rays' intensity suggest this white dwarf takes just 28 minutes to complete an orbit, making it the current champion of cataclysmic dirty dancers.

That's good news for future scientists keen to study gravitational waves; while the current technology used by the Laser Interferometer Gravitational-Wave Observatory isn't able to spot the slow pulses emitted by X9, it's not out of the question that progress in that field will one day allow us to detect lower frequency waves.

This research was published in arXiv.org