Hubble detects a stellar collision of the Titanic that shakes space and time

Collision of two neutron stars

This is an artist’s impression of the collision of two neutron stars. The collision between two dense stellar remnants releases the energy of 1000 standard stellar nova explosions. As a consequence of the collision, a radiation torch is ejected at almost the speed of light. The jet is directed along a narrow beam confined by strong magnetic fields. The roaring jet crashed and dragged material into the surrounding interstellar medium. Credit: Elizabeth Wheatley (STScI)

More than 299,000,000 meters per second: an ultra-fast jet leaving a crashed star.

Neutron stars are the surviving “trash-compacted” cores of massive stars that exploded. Despite weighing more than our Sun, they would fit inside New York City. With this unimaginable density, a single teaspoon of material from the surface would weigh at least 4 billion tons on Earth.

If that doesn’t make you wonder, imagine what happens when two of these condensed cannonballs collide head-on. They ripple the very fabric of time and space in a phenomenon called[{” attribute=””>gravitational waves, which can be measured by detectors on the ground on Earth.

The explosive event, named GW170817, was observed in August 2017. The blast released energy comparable to that of a supernova explosion. It was the first combined detection of gravitational waves and gamma radiation from a

Two neutron stars, the surviving cores of massive stars that exploded, collided, sending a ripple through the fabric of time and space in a phenomenon called gravitational waves. As a consequence, a radiation torch was ejected at nearly the speed of light, striking the material surrounding the erased pair. The astronomers used Hubble to measure the motion of a blob of material the jet slammed into. Credit:[{” attribute=””>NASA’s Goddard Space Flight Center; Lead Producer: Paul Morris

Astronomers using NASA’s Hubble Space Telescope have made a unique measurement indicating that a jet was blasted across space at speeds faster than 99.97% the speed of light by a titanic collision between two neutron stars.

The explosive event, dubbed GW170817, occurred in August 2017. The blast generated energy comparable to a supernova explosion. It was the first time gravitational waves and gamma rays were detected together from a binary neutron star merger.

This was a significant turning point in the research of these extraordinary collisions. In addition to the discovery of gravitational waves, 70 observatories across the world and in space saw the aftermath of this merger across a large swath of the electromagnetic spectrum. This signaled an important development in the area of Time Domain and Multi-Messenger Astrophysics, which makes use of a number of “messengers” including gravitational waves and light to analyze the progression of the universe through time.

Just two days later, scientists quickly aimed Hubble toward the explosion’s location. The neutron stars collapsed into a

The authors used Hubble data together with data from ESA’s (the European Space Agency) Gaia satellite, in addition to VLBI, to achieve extreme precision. “It took months of careful analysis of the data to make this measurement,” said Jay Anderson of the Space Telescope Science Institute in Baltimore, Maryland.

By combining the different observations, they were able to pinpoint the explosion site. 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 decelerated to an apparent speed of four times faster than the speed of light.

In reality, nothing can exceed the speed of light, so this “superluminal” motion is an illusion. 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. In actuality, more time has passed between the jet’s emission of the light than the observer thinks. This causes the object’s velocity to be overestimated – in this case seemingly exceeding the speed of light.

“Our result indicates that the jet was moving at least at 99.97% the speed of light when it was launched,” said Wenbin Lu of the University of California, Berkeley.

The Hubble measurements, combined with the VLBI measurements, announced in 2018, greatly strengthen the long-presumed connection between neutron star mergers and short-duration gamma-ray bursts. That connection requires a fast-moving jet to emerge, which has now been measured in GW170817.

This work paves the way for more precision studies of neutron star mergers, detected by the DOI: 10.1038/s41586-022-05145-7


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