Hubble detects a jet blasting from star crash at 99.97% the speed of light

NASA’s Hubble Space Telescope measured the colliding stars, which appeared to be traveling at a higher velocity, due to an illusion.
Brittney Grimes
Artist's rendition of two neutron stars colliding.
Artist's rendition of two neutron stars colliding.


A jet of radiation from the collision of two neutron stars is traveling at speeds greater than 99.97% the speed of light.

The collision and formation

The event, named GW170817, was observed in 2017 by astronomers from around the world and in space. The huge blast gave off energy that was almost like a supernova explosion.

Two days later, astronomers aimed the Hubble Telescope at the site of the explosion, where the neutron stars collapsed into a black hole and the gravity began pulling material towards it. That material formed a spinning disk that generated jets moving outward. The fast-moving jet slammed into each other and swept up material and debris. Part of this debris included substance that formed the jet.

Locating the explosion

The Hubble Telescope measurements were combined with observations from different astronomical radio equipment, including the various National Science Foundation radio telescopes working together for very long baseline interferometry (VLBI). The statistics from the radio telescopes were taken 75 days and 230 days after the crash.

By combining the various observations, scientists could identify the location of the explosion with accuracy.

Speed of the jet

The rapid speed of the jet happened to be an illusion, appearing to go faster than the speed of light, although such an outcome is not possible. “The Hubble measurement showed the jet was moving at an apparent velocity of seven times the speed of light. The radio observations show the jet later had decelerated to an apparent speed of four times faster than the speed of light,” NASA said on its website.

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The agency stated that the motion and speed of the jet appears to be going so quickly “because the jet is approaching Earth at nearly the speed of light, the light it emits at a later time has a shorter distance to go. In essence the jet is chasing its own light.”

This observation allows future astronomers to observe precise studies of neutron mergers.

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