A mysterious object has been spotted zooming through space at about 1.6 million km/h (1 million miles per hour), so fast that it could exit the Milky Way entirely – and scientists are trying to work out what it is.
Currently 400 light years from Earth, the object – known as CWISE J1249 – is very unlikely to be a probe due to its large size. Around 30,000 times more massive than Earth, CWISE J1249 is 8 per cent of the Sun’s mass.
This unusual size puts J1249 “somewhere between a star and a planet,” Dr Darren Baskill, astronomy lecturer at the University of Sussex, told BBC Science Focus.
“Such rapidly moving stars are unusual. Locally, only one or two stars out of every thousand are moving at such a speed, and a star moving as rapidly as J1249 would be leaving our Milky Way galaxy in just a few ten million years: a blink-of-an-eyes for such stars that can live for tens of billions of years.”
While the gigantic object is only moving at 0.001 per cent of the speed of light, it could break free from our galaxy and soar off into intergalactic space.
Baskill explained: “To put the speed of J1249 into perspective, it is moving 2.6 times faster than the fastest space probe ever launched, which is the speed that the Parker space probe reached when it looped around the Sun in June 2024.”
The fast-moving object was discovered by citizen scientists volunteering their time for a NASA project known as Backyard Worlds: Planet 9. For this, they scoured through online images from NASA’s Wide-field Infrared Explorer (WISE) and NEOWISE missions, hoping to spot something exciting.
Three volunteers – Martin Kabatnik, Thomas P Bickle, and Dan Caselden – noticed the faint, fast-moving object moving across the WISE images.
“I can't describe the level of excitement,” said Kabatnik. “When I first saw how fast it was moving, I was convinced it must have been reported already.”
Due to be published in The Astrophysical Journal Letters, a new study has confirmed these findings using ground-based telescopes and characterised the object. (Currently, the study is awaiting peer review at Cornell's arXiv site.)
The research team led by scientists at the University of California, San Diego (USA), believe the object could be a low-mass star or a brown dwarf: a star larger than a planet but without the mass for nuclear fusion to be sustained in its core.
Further observations for the study also revealed the strange composition of the object, which contains far less iron and other metals than in stars and brown dwarfs. According to NASA, this unusual composition could be a sign the object might be one of the first ever stars in our galaxy.
So why do the researchers think it’s moving so fast? The strange object could be the remnants of a binary system gone wrong: its companion, a white dwarf, might have exploded in a supernova after pulling off too much material from J1249.
Or, they think, it may have come from a cluster of stars which were rapidly dispersed after encountering a pair of black holes.
“One way to get to such extreme speeds is to fall towards an object… and miss,” explained Baskill. “Such gravitational slingshots are how we accelerate space probes to such extreme speeds to allow us to explore the solar system up-close over reasonable timescales.
“That technique could also explain the speed of J1249 – the star may have originated from the densely populated centre of our galaxy, where it fell towards a star, missed, but was accelerated to extreme speeds in the process.”
About our expert
Dr Darren Baskill is an outreach officer and lecturer in the department of physics and astronomy at the University of Sussex. He previously lectured at the Royal Observatory Greenwich, where he also initiated the annual Astronomy Photographer of the Year competition.
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