The jet appeared to be
moving at seven times the speed of light, according to Hubble's measurements.
Radio observations later revealed that the jet had decelerated to speeds four
times faster than light. This, however, is a "cosmic illusion,"
because nothing travels faster than light.
A collision between two
neutron stars propelled a jet through space at 99.97% the speed of light. This
is according to Hubble Space Telescope measurements from NASA. The explosive
event, designated GW170817, occurred in August 2017. The blast was estimated to
have the same energy as a supernova explosion.
The first gravitational
wave and gamma-ray signals were detected simultaneously as a result of the
binary neutron star merger. These extraordinary collisions were a watershed
moment in the investigation. Seventy observatories on Earth and in space
observed the aftermath of this merger. They discovered gravitational waves as
well as a wide range of electromagnetic radiation. This event occurred in 2017.
A historical remark
This was a monumental
achievement in time domain and multi-messenger astrophysics. The study of the
universe as it evolves over time through the use of various
"messengers" such as light and gravitational waves. Within two days
of the explosion, scientists directed Hubble's attention to the site. When
neutron stars collided, they created a black hole whose gravity drew matter
toward it. Jets emerged from a rapidly spinning disc from those poles. The
roaring jet smashed into the expanding debris cloud and swept it up during the
explosion. Finally, an emergent jet appeared through a material blob.
Scientists have spent
years analyzing Hubble data and data from other telescopes to create this
complete image. For very long baseline interferometry, Hubble observations were
combined with observations from multiple National Science Foundation radio
telescopes (VLBI). Data was gathered 75 and 230 days after the explosion.
"I'm astounded
that Hubble could provide us with such a precise measurement, which rivals the
precision achieved by powerful radio VLBI telescopes scattered around the
world," said Kunal P. Mooley of Caltech in Pasadena, California. He is the
lead author of a paper that will be published in Nature magazine on October
13th.
Extensive precision
Furthermore, to achieve
extreme precision, the authors combined Hubble data with data from the Gaia
satellite and VLBI. According to Jay Anderson of the Space Telescope Science
Institute in Baltimore, Maryland, this measurement was made after months of
careful data analysis. Their collective observations assisted them in locating
the explosion site. The jet appeared to be moving at seven times the speed of
light, according to Hubble's measurements. Radio observations later revealed
that the jet had decelerated to speeds four times faster than light.
This
"superluminal" movement is an illusion because nothing can move
faster than light. Because the jet is approaching Earth at nearly the speed of
light, the light it emits later will travel a shorter distance. The jet
essentially chases its own light. As a result, the light from the jet was
emitted much later than the observer expected. As a result, the object's speed
is overestimated and exceeds the speed of light.
At the time of launch,
the jet was travelling at 99.97% of the speed of light, according to Wenbin Lu
of the University of California, Berkeley. A 2018 announcement of a combination
of Hubble and VLBI measurements supports the theory that neutron star mergers
are related to short-duration gamma-ray bursts. This connection requires an
emerging fast-moving jet, as measured in GW170817.
Hubble's constant
Furthermore, this
research enables more in-depth studies of neutron star mergers detected by the
gravitational wave observatories LIGO, Virgo, and KAGRA. Over the next few
years, a large enough sample of relativistic jets may provide another method
for measuring the Hubble constant. This constant represents an estimate of the
rate of expansion of the universe.
The Hubble constant
values for the early universe and the nearby universe differ. This is one of
astrophysics' greatest mysteries. Differences in values are based on extremely
precise measurements of Type Ia supernovae by Hubble and other observatories,
as well as measurements of the Cosmic Microwave Background by the Planck
satellite. A better understanding of relativistic jets could help astronomers
solve the puzzle.
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