An explosion in space was picked up by a NASA telescope that appeared to show a jet stream travelling at a greater speed than 99.97% of the speed of light.
But it only seemed to be going at seven times the speed of light due to the illusion of “superliminal” motion.
Two neutron stars collided together causing a blast with a release of energy comparable with a supernova explosion.
The event named GW170817 was seen by NASA’s Hubble Space Telescope in August, 2017, but it has taken until now for astronomers to fully understand what happened with their findings published in the Nature journal.
Neutron stars are the surviving cores of massive stars which have exploded, and while they would weigh more than the Sun, they would fit inside the city of New York due to their incredible density.
Or in other words a teaspoon of the surface material of a neutron star would weigh at least four billion tonnes on Earth.
So when two neutron stars were seen colliding it led to an understandably massive explosion with NASA stating they “ripple the very fabric of time and space in a phenomenon called gravitational waves”.
And the GW170817 event was the first combined detection of gravitational waves and gamma radiation from a neutron star collision.
It saw a jet stream of radiation travelling just short of the speed of light at a greater speed than 99.97% of the speed of light.
A NASA press release stated: "Astronomers used Hubble to measure the motion of a blob of material the jet slammed into. As the jet rocketed away from the site of the explosion, the blob moved outward like a leaf caught on a stream of water from a garden hose.
"The incredible precision, gleaned from Hubble and radio telescopes, needed to measure the blob's trajectory, was equivalent to measuring the diameter of a 12-inch-diameter pizza placed on the Moon as seen from Earth.
"This was a major watershed in the ongoing investigation of neutron star collisions that keep ringing throughout the universe.”
Kunal P. Mooley, lead author of a paper published in Nature magazine said: "I'm amazed that Hubble could give us such a precise measurement, which rivals the precision achieved by powerful radio VLBI telescopes spread across the globe."
The Hubble measurement showed the jet was moving at an apparent speed of seven times the speed of light but this “superliminal” motion is an illusion because in reality nothing can exceed the speed of light.
Basically as the jet is going at practically the speed of light, the light is emitted at a later time when it is then closer to the Earth - so it appears to be going faster than it was in reality.
