Growth Rate Of The Universe Will Be Measured By Studying Black Hole-Neutron Star Binaries

Posted: Jul 13 2018, 6:09pm CDT | by , in News | Latest Science News

Growth Rate of The Universe Will Be Measured By Studying Black Hole-Neutron Star Binaries
Image Credit: Dana Berry/NASA

Expansion Rate of The Universe Might Soon Be Solved By Scientists

Scientists from Massachusetts Institute of Technology and Harvard University are trying a new method to measure the expansion rate of our universe, they will be studying gravitational waves emitted by rare binary systems that are comprised of a black hole and neutron star.

Big bang event occurred around 13.8 billion years ago, with that came into being all the galaxies, star systems, planets, satellites and other celestial objects. Since its inception with the big bang explosion, the universe has been expanding outwards at a very fast speed.

The scientific unit for measurement of this universal expansion is known as Hubble Constant, and scientists have been trying to figure out the rate at which this expansion is taking place.

To do so many observatories have pointed their telescopes to different stars and other celestial objects, and regularly measures their distance from Earth to figure out the exact rate of the Hubble Constant.

But there has been a problem with the results, as all different observations came out with different values in their results, the exact rate of the expansion cannot be yet confirmed and agreed upon.

Finding the exact rate of Hubble Contact holds a lot of significance for the scientists, it will provide insights about the origin of the universe and about what will happen in the future, whether the universe will keep on expanding or it will collapse down and cease to exist.

A team of scientists from Harvard University and MIT have come up with a new method to accurately measure the Hubble Constant , to do so they will be observing a neutron star spiralling around a black hole, on their collision huge burst of light and gravitational waves will be produced and the event will be very similar to the big bang.

If the gravitational waves reach the Earth and the scientists can measure the speed of light emitted during the collision, it will be the most accurate estimate of the expansion rate of the Universe. Pairs of a black hole and a neutron star are very rare and hard to find, still, the scientists are confident that finding only a few of such binary systems will provide enough data to precisely measure the Hubble Constant.

"Black hole-neutron star binaries are very complicated systems, which we know very little about," says Salvatore Vitale, assistant professor of physics at MIT and lead author of the paper. "If we detect one, the prize is that they can potentially give a dramatic contribution to our understanding of the universe."

Two individual attempts to measure the Hubble Constant were recently made by NASA and European Space Agency, NASA used Hubble Space Telescope to observe the brightness data from a star called Cepheid variable and a supernova event, ESA used Planck satellite to study the cosmic microwave fluctuations that were left after the big bang.

Even though both observations provided precise results, there was a lot of difference in the Hubble Constant calculated by each of them.

So, the scientists used a new system that detects and calculates the speed of gravitational waves emitted by such systems.

"Gravitational waves provide a very direct and easy way of measuring the distances of their sources," Vitale says. "What we detect with LIGO is a direct imprint of the distance to the source, without any extra analysis."

In 2017, LIGO, or the Laser Interferometry Gravitational-Wave Observatory and Italian Virgo used this method to calculate the gravitational waves released during the collision of two neutron stars. Although they were both able to measure the gravitational waves and speed of light emitted during the event, they also had a variation of around 14 percent in their calculations.

These variations are even larger than the earlier attempts that were made by Hubble Space Telescope and the Planck satellite.

"We measure distance by looking at how 'loud' the gravitational wave is, meaning how clear it is in our data," Vitale says. "If it's very clear, you can see how loud it is, and that gives the distance. But that's only partially true for neutron star binaries."

The scientists explained that the variation in the results is due to the difference in the source of the gravitational waves, it is not easy to estimate whether the gravitational waves were released from the centre of the neutron binary system or from its edges. This distance in the source of such waves creates difficulty in measuring a correct value of the Hubble Constant.

"With neutron star binaries, it's very hard to distinguish between these two situations," Vitale says.

After facing these challenges, the team shifted their focus on the black hole and neutron star binaries, and during the computer simulations, they found that these systems provided more similar results in the calculation of the Hubble Constant.

Because of the spin of a black hole and neutron star the scientists can more precisely measure the source of the gravitational waves.

"Because of this better distance measurement, I thought that black hole-neutron star binaries could be a competitive probe for measuring the Hubble constant," Vitale says. "Since then, a lot has happened with LIGO and the discovery of gravitational waves, and all this was put on the back burner."

In 2019, LIGO will again start with such observations, and the scientists stated that if they can find more of the black hole and neutron star binary systems, they will be able to provide more precise estimates about the speed of the Hubble Constant.

"Is the fact that every black hole-neutron star binary will give me a better distance going to compensate for the fact that potentially, there are far fewer of them in the universe than neutron star binaries?" Vitale says.

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<a href="/latest_stories/all/all/2" rel="author">Luigi Lugmayr</a>
Luigi Lugmayr () is the founding chief Editor of I4U News and brings over 15 years experience in the technology field to the ever evolving and exciting world of gadgets. He started I4U News back in 2000 and evolved it into vibrant technology magazine.
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