A powerful collision and a super-fast throw
According to the known laws of physics, nothing can travel faster than light. And it is rare to see space objects traveling at speeds anywhere, even near the speed of light, although some relativistic jets of exotic phenomena like black holes, pulsars, and quasars sometimes travel almost as fast. But now astronomers have discovered a superfast jet, streaking through space at speeds over 99.97% of the speed of light. Wow!
NASA said on October 12, 2022 that astronomers used the Hubble Space Telescope to measure the speed of this jet, which they say originated when two neutron stars collided. They named this event GW170817 and said the energy of the collision was comparable to that of a supernova, or exploding star, which can emit more energy in seconds than our sun will emit during its lifetime. lifetime of billions of years. NASA said the discovery and analysis of the jet was:
… A major turning point in the ongoing investigation into these extraordinary collisions. The consequences of this merger have been observed collectively by 70 observatories around the world and in space, over a wide band of the electromagnetic spectrum in addition to the detection of gravitational waves.
The study was published on October 13, 2022 in the peer-reviewed journal Nature.
Here is what happened
Astronomers first noticed the explosion of a neutron star in August 2017. And they said:
Scientists quickly directed Hubble to the site of the explosion two days later. Neutron stars collapsed into a black hole whose powerful gravity began to pull matter towards it. This material formed a rapidly spinning disk that generated outward-moving jets from its poles. The roaring jet slammed into and swept away the material in the expanding envelope of debris from the explosion. This included a blob of material through which a jet emerged.
While the event took place in 2017, it took scientists several years to find a way to analyze data from Hubble and data from other telescopes to paint this full picture.
Hubble’s observation was combined with observations from several National Science Foundation radio telescopes working together for very long baseline interferometry (VLBI). Radio data was taken 75 days and 230 days after the explosion.
Kunal P. Mooley of Caltech in Pasadena, California, senior author of the Nature paper, commented:
I’m amazed that Hubble can give us such a precise measurement, which rivals the accuracy achieved by the powerful VLBI radio telescopes spread around the world.
The authors used Hubble data with data from ESA’s (European Space Agency) Gaia satellite, in addition to VLBI, to achieve pinpoint accuracy. Jay Anderson of the Space Telescope Science Institute in Baltimore, Maryland, explained:
It took months of careful data analysis to make this measurement.
Ultra-fast jet faster than light?
By combining the various observations, they were able to locate the site of the explosion. The Hubble measurement showed the jet was moving at an apparent speed of seven times the speed of light. Radio observations show that the jet then slowed to an apparent speed four times the speed of light.
But, as noted at the top of this page, nothing can travel faster than light, according to the known laws of physics. Today’s astronomers therefore agree that this superluminal movement is an illusion. Astronomers explain:
Because the jet is approaching Earth at nearly the speed of light, the light it emits later has a shorter distance to travel. Essentially, the jet is chasing its own light. In reality, more time has elapsed between the emission of light by the jet than the observer thinks. This results in an overestimate of the object’s speed – in this case, apparently exceeding the speed of light.
Wenbin Lu from the University of California at Berkeley confirmed:
Our result indicates that the jet was traveling at least 99.97% of the speed of light when launched.
Why astronomers are excited
These astronomers called the work a “significant breakthrough” for two emerging and interrelated fields of study. One is time-domain astronomy (studying how space objects change over time). And the other is multi-messenger astronomy (using various types of signals, like light and gravitational waves, to study a single astrophysical object or event).
They said the Hubble measurements, combined with the VLBI measurements (announced in 2018:
…dramatically strengthen the long-presumed link between neutron star mergers and short-lived gamma-ray bursts. This connection requires the emergence of a fast jet, which has now been measured in GW170817.
They also said that this work paves the way for more precise studies of neutron star mergers, adding:
With a large enough sample over the next few years, relativistic jet observations could provide another avenue of research for measuring the rate of expansion of the universe, associated with a number known as the Hubble constant.
Conclusion: Astronomers have discovered and have now measured an ultrafast jet, believed to be the result of the collision of 2 neutron stars. The matter in the jet is moving at 99.97% of the speed of light!
Source: Optical measurement of superluminal motion in neutron star mergers GW170817
Via Hubblesite
#EarthSky #Ultrafast #reactor #explosions #neutron #star #collision