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How fast is the universe expanding? Scientists have proposed that the answer to this question could be found in gravitational waves waving in space-time from a rare astronomical collision. ( SXS | NASA )
A rare collision between a black hole and a neutron star can help experts accurately determine the expansion of the universe
L & # A cataclysmic event would generate gravitational waves, which are ripples in the fabric of space-time created by extremely powerful astronomical events.
These gravitational waves would allow experts to measure the exact distance of these objects from the Earth and the speed at which they are moving away. These are the two essential elements that help scientists calculate the Hubble constant, or the rate of expansion of the universe.
A more accurate Hubble constant would help researchers better understand how the universe began. It will also provide valuable clues as to whether the universe will continue to expand into infinity or whether it will implode on itself.
What is Hubble's constant?
Physicists from the Mbadachusetts Institute of Technology and Harvard University propose a new way to
In an article published in Physical Review Letters the team says that the measurement of Gravitational waves from a rare binary system will give better results than the previous methods.
Since Edwin Hubble discovered that the universe was developing since the Big Bang, scientists have been striving to measure the speed of this expansion.
By observing the distance and speed of stars observed from Earth, Hubble concluded that the universe has increased to 310 million miles / second / megaparsec, but this figure has been the subject of debate since. A megaparsec equals 3.3 million light years
In March 2013, the Hubble constant was set at a much lower rate of 44 million miles / second / megaparsec. However, independent measurements by two of the world's most advanced instruments yielded significantly different results.
NASA's Hubble Space Telescope measurements were based on observation of the distance and velocity of the Cepheid variable stars. These are stars that change brightness regularly every two to 100 days.
On the other hand, the Planck satellite of the European Space Agency examined the fluctuations of the electromagnetic remanence left by the Big Bang.
Gravitational Waves As Salvatore Vitale, an badistant professor of physics at Harvard University, says that gravitational waves coming from a binary system composed of a black hole and a star at neutrons can provide a more precise Hubble constant
spiral one towards the other, they end up crashing into a catastrophic astronomical event that releases gravitational waves.
The measurement of these gravitational waves will enable scientists to determine the exact distance of their source and the speed of movement of the source. "Gravitational waves provide a very direct and easy way to measure distances from their sources," says Vitale.
The team is the first to propose the use of gravitational waves to measure the Hubble constant. In November 2017, scientists detected gravitational waves from the explosive fusion of two neutron stars through the interferometric laser observatory of the National Science Foundation and its Virgo counterpart in Europe [19659018]. The uncertainty was 14%, which makes it much more uncertain than the measurements made by the Hubble and Planck satellites.
The problem here is that collisions between neutron stars produce different types of gravitational waves. Some of them can come directly from the center of the accident, while others can slide across the edges.
Scientists measure gravitational waves according to their degree of clarity. If the signal arrives loud and clear, it can mean two things. First, the gravitational waves come from the center of a distant binary system. Second, they can come from the edges of a much closer system
With a binary neutron star system, scientists find that it is almost impossible to distinguish the two.
Black Hole and Neutron Star System gives accurate measurements
Before the discovery of gravitational waves in 2015, Vitale and his team studied pairs of black holes and neutron stars to see how fast a hole black could turn.
As a side effect of their study, the team found that distance and speed "Due to this better measure of distance, I thought that black hole neutron binaries could be a competitive probe to measure the Hubble constant ", explains Vitale.
The team is confident in their findings that even though they could only find one pair of black hole neutron stars among 50 binary neutron stars, the rare system will always produce a more precise Hubble constant. 9003] MIT and Caltech are ready to bring LIGO back to life in January 2019 with improved equipment. Vitale and his team hope the new, more responsive instruments will help them find up to 25 black hole systems and neutron stars
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