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Astronomers discovered gravitational waves.Now they want to see the universe



The Green Shore Telescope in West Virginia is helping to find the background of gravitational waves.

The Green Shore Telescope in West Virginia is helping to find the background of gravitational waves.
photo: ANDREW CABALLERO-REYNOLDS/AFP via Getty Images (Getty Images)

Using signals from dozens of fast-rotating dead stars, astrophysicists have come closer to achieving their goal of detecting the background rumble of gravitational waves in the universe.

When the existence of gravitational waves is Confirmed in 2016, Opened up a new field of astronomy research. The two black holes collided, causing ripples in the space-time structure. This was detected on Earth because it caused spots in the sensitive instruments of the Laser Interferometer Gravity Wave Observatory. Since then, scientists have picked up more gravitational waves produced by large-scale impacts, but they have also been looking for ways to observe the so-called background of gravitational waves. To use an analogy: we have detected the big waves shaking our planetary ships, and now we want to see the mess of waves in the entire ocean.

Last month, the North American NHz Gravitational Wave Observatory Published The latest data set is in the Astrophysical Journal Letters.The data (accounting for 12 and a half years of data) is based on the Green Bank Telescope in West Virginia and the United States The recently collapsed Arecibo Observatory In Puerto Rico. This paper describes that the light from 45 pulsars may be a pattern that tells a story. This is a step in determining the background of the gravity wave.

Joseph Simon, an astrophysicist at the University of Colorado at Boulder and the lead author of the latest paper, said at the press conference: “What we have discovered in particular is the low-frequency signal, which is the common among all pulsars in the array. Signal.” Today’s meeting. Simon said the signal “is the initial indication of the gravitational wave background we expect.”

Pulsars are dense, rotating remnants of dead stars. Millisecond pulsars rotate very fast (hundreds of times per second), while the rotation speed of a few pulses is reliable enough that researchers can classify small changes in the relative position of planets relative to these pulsars. The research team used the electric wave pulses emitted by pulsars in the Milky Way to effectively construct a galactic-sized low-frequency gravitational wave detector network, which is generated by the orbit of a supermassive black hole rather than by collision. The gravitational background the team is looking for seems to be continuous in time and space, chaotic noise, rather than isolated spots like the kind of isolated spots found by LIGO in 2016.

The array consists of pulsars scattered throughout the Milky Way.

The array consists of pulsars scattered throughout the Milky Way.
photo: MARIANA SUAREZ/AFP via Getty Images (Getty Images)

Gravitational waves are predicted by general relativity. Decades of analysis of celestial bodies have concluded that such waves cause changes in the time at which pulsar light reaches the earth.Gravitational wave background will affect us from Pulsars based on each person’s position and relative position, and some related pattern related to that light, will indicate the gravity wave background. The team has not officially found this pattern, but they think they have found the beginning of this pattern.

Although astrophysicists have checked data from pulsar arrays for more than 12 years, they still need more time and more pulsars to determine the pattern. The wavelength of the wave recorded by the team is much larger than the gravitational wavelength detected by LIGO in 2016, so the research progress is gradual.

One of the challenges is to use atomic clocks to time the pulses of pulsars, which may lose their accuracy. Scott Ransom, an astronomer at the National Radio Astronomical Observatory in the United States, said, but recent data ruled out atomic clock errors.

Ransom is analogous to gravitational waves The waves in the ocean in time and space come from different sources near and far. Gravitational waves interfere with each other, clinging to the earth swaying in the ocean, causing the planet to stretch and compress so slightly.

Ransom said on the phone: “We can infer from it, like you can see whether the ocean is calm or rough.” “Just by looking at this background signal, we can get the complete history of the universe and how galaxies merged. And interact with a lot of information.”

Both Simon and Ransom are saddened by the loss of the Arecibo Observatory’s radio disc collapsed In December after two cable failures. The research team has been acquiring data from the observatory until the first cable is disconnected, and the most recent paper only contains data from 2017. Their current data set will provide Arecibo’s afterlife, which will help find the background of gravitational waves in the coming years.


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