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Astronomers could come one step closer to uncovering still-hidden cosmic secrets, such as the nature of dark matter and the presence of widespread distortions in space-time, researchers reported at the 237th. Meeting of the American Astronomical Society, which took place practically this week.
The existence of dark matter, an invisible substance believed to make up over four-fifths of all matter in the universe, can help explain a variety of cosmic puzzles, such as how galaxies can spin as fast as they can. they do it without tearing themselves apart. . However, much about the nature of black matter – and even if it exists – remains unknown.
To help identify the properties of dark matter, the researchers sought to directly measure the gravitational effects dark matter is expected to have on the speed at which stars move through the Milky Way. They focused on galactic lighthouses known as pulsars, or rotating neutron stars that emit two beams of radio waves from their magnetic poles as they rotate. (Neutron stars are the remnants of large stars that perished in catastrophic explosions called supernovae.)
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“It’s a very, very small number that we’re trying to measure,” lead study author Sukanya Chakrabarti, an astrophysicist at the Rochester Institute of Technology in New York, said at a press conference on Monday 11. January. “In terms of shifting, it’s just a few inches per second, or about the speed of a crawling baby, and not a very fast baby at that.”
Pulsars rotate at very regular rates, so they can serve as precise clocks. By monitoring tiny variations in the spin of 14 pulsars, the researchers were able to estimate the speeds of movement of these pulsars and thus deduce the gravitational force that dark matter exerts on them.
Scientists have found that across the galaxy, the average amount of dark matter may be slightly lower than previous estimates. The researchers also calculated that the amount of dark matter contained in the volume of the Earth is only 1.63 lbs. (740 grams), said Chakrabarti. These findings may in turn help current experiments seeking to directly detect dark matter “to try to understand the nature of dark matter particles,” she added. For example, this could affect how often these particles would be expected to interact with detectors.
In addition, scientists are currently analyzing an unusually large number of gamma rays from the center of the Milky Way to see if they could come from the annihilation of dark matter particles. Previous research suggested that dark matter could be made up of new types of particles, those that annihilate when they come into contact with each other, generating high-energy gamma rays.
Based on 11 years of NASA data Fermi Gamma-Ray Space Telescope“We can tell which are the right candidates for dark matter,” said lead study author Mattia di Mauro, an astrophysicist at the National Institute of Nuclear Physics in Turin, Italy, at the same conference in hurry. These include weakly interacting massive particles, or WIMPS, hypothetical elementary particles that barely interact with ordinary matter except through their gravitational pull.
“In the future, the Large Hadron Collider or other particle physics detectors could test these specific candidates,” he added.
The gravitational background
Researchers at the First Astronomy Conference also reported finding the first possible clues to a mysterious new type of gravitational wave, cosmic ripples that warp the fabric of space and time itself.
Scientists reported the very first direct detection of gravitational waves in 2016 using the Laser interferometer gravitational wave observatory (LIGO), a discovery that won the 2017 Nobel Prize in Physics. The space-time distortions observed by the researchers were created when two black holes collided about 130 million light-years from Earth. Since then, LIGO has observed dozens of other such signals.
But the gravitational waves that LIGO detects best are the most powerful, loud explosions released when extraordinarily massive objects collide. Researchers now also want to detect gravitational waves that sound more like the background noise of casual conversation at a crowded party.
In theory, the fusion of galaxies and other cosmic events should generate such a “gravitational wave background”. Detecting this regular buzzing could shed light on mysteries like the growth of galaxies over time.
However, these waves are huge, posing a major challenge for the detection of this gravitational wave background. While existing gravitational wave observatories on Earth are designed to search for gravitational waves on the order of seconds, the ripples in the gravitational wave background last for years, if not decades.
Now, researchers say they may have detected a strong signal from the background of gravitational waves using a US and Canadian project called the North American Nanohertz Observatory for Gravitational Waves (NANOGrav).
“We are seeing incredibly significant evidence for this signal,” study lead author Joseph Simon, an astrophysicist at the University of Colorado at Boulder, said at the AAS press conference. “Unfortunately, we can’t say what it is yet.”
NANOGrav uses ground-based telescopes to monitor dozens of pulsars. Gravitational waves can alter the constantly flickering pattern of pulsar light, tightening and widening the distances these rays travel in space.
“When these waves pass us, the Earth is pushed very slightly,” Simon said. “As the Earth is brought closer to the pulsars in one part of the sky, the pulses from these pulsars will appear a little earlier than expected, and the pulses from the pulsars in the other part of the sky seem to come a little later.
Analysis of this pulsar light could therefore help scientists detect signs of a gravitational wave background.
“By monitoring the signals of a large number of these pulsars, we have created a detector of gravitational waves the size of a galaxy in our own Milky Way,” said Simon.
To find these subtle clues, scientists at NANOGrav attempted to observe as many pulsars as possible for as long as possible. So far, they have observed 45 pulsars for at least three years, and in some cases for more than a dozen years.
“These pulsars spin about as fast as your kitchen blender,” Simon said in a statement. “And we’re looking at deviations in their timing of a few hundred nanoseconds.”
Now, the researchers said they have detected potential evidence of a common process distorting the light of many pulsars. At this time, they can’t verify if this signal is evidence of gravitational wave background, “but we don’t have any evidence against that either,” Simon said.
Scientists warn they still need to examine more pulsars and monitor them for longer periods to confirm if the gravitational background is the cause.
If researchers can verify that they’ve detected the background of gravitational waves, then they want to identify the causes of those waves and what those signals can tell scientists about the universe.
Scientists detailed their findings Jan. 11 at an American Astronomical Society online meeting. Chakrabarti and his colleagues detailed their discoveries in a study accepted in the journal Astrophysical Journal Letters. Simon and his colleagues detailed their discoveries NANOGrav online December 24 in The Astrophysical Journal Letters.
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