Astronomers may be approaching the discovery of still hidden cosmic secrets, such as the nature of dark matter and the presence of widespread distortions in space-time, researchers reported in the 237th. American Astronomical Society meeting, held virtually this week.
The existence of dark matter, the invisible substance thought to make up more than four-fifths of all matter in the universe, can help explain a variety of cosmic mysteries, such as how galaxies can rotate as fast as they can do without being ripped apart. Much about the nature of dark matter – and even if it exists at all – remains unknown.
To determine the properties of dark matter, researchers have tried to determine the gravitational effects that dark matter must have on the velocity at which stars in the dark matter. Milky Way. They focused on galactic lighthouses, known as pulses, or rotating neutron stars that emit dual radio waves from their magnetic poles as they rotate. (Neutron stars are the remnants of big stars that perished in catastrophic explosions, known as supernovae.)
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“This is a very, very small number that we are trying to measure,” lead author Sukanya Chakrabarti, an astrophysicist at the Rochester Institute of Technology in New York, told a news conference on Monday (January 11). “In terms of speed change, it’s just a few inches per second, or about the speed of a crawling baby, and not a very fast baby.”
Pulsars rotate at a very steady rate so that they can serve as exact clocks. By monitoring small variations in the rotation of 14 pulses, the researchers were able to estimate the velocity at which these pulses move, thus deriving the gravitational force that the dark matter exerts on them.
The scientists found that the average amount of dark matter across the galaxy may be slightly lower than the previous estimate. The researchers also calculated that the amount of dark matter contained within the volume of the earth is only £ 1.63. (740 grams), Chakrabarti said. These findings, in turn, could help current experiments directly detect dark matter “to try to understand the nature of dark matter particles,” she added. For example, it can affect how often one can expect such particles to interact with detectors.
In addition, scientists are now analyzing an extremely high number of gamma rays from the center of the Milky Way to see if it could possibly be due to the destruction of dark matter particles. Previous research has suggested that dark matter can be made from new types of particles, which are destroyed when they come in contact with each other and generate high-energy gamma rays.
Based on 11 years of NASA data Fermi gamma ray space telescope“We can say what good candidates for dark matter are,” said lead author Mattia di Mauro, an astrophysicist at the National Institute for Nuclear Physics in Turin, Italy, during the same news conference. These include massive particles with poor interaction, or WIMPS, hypothetical elementary particles that only rarely interact with ordinary matter, except by their gravity.
“In the future, the Large Hadron Collider or other particle physics trackers could test these specific candidates,” he added.
The gravity background
Researchers at the first astronomy conference also reported that they found the first possible hints of a mysterious new kind of gravitational wave, cosmic wrinkles that distort the fabric of space and time itself.
Scientists conducted the first direct detection of gravitational waves in 2016 using the Laser Interferometer Gravitational-Wave Observatory (LIGO), a discovery that won the Nobel Prize in Physics in 2017. The space-time distortions that the researchers saw were created when two black holes collided with each other about 130 million light-years from Earth. Since then, LIGO has observed dozens more such signals.
But the gravitational waves that LIGO can best detect are the strongest, hard eruptions released when extraordinarily massive objects collide. Researchers now also want to detect gravitational waves that are more like the background noise of talks at a busy party.
In theory, fusing galaxies and other cosmic events should generate such a “gravitational wave background”. The detection of this persistent hum can shed light on mysteries such as how galaxies have grown over time.
However, these waves are very large, which is a big challenge in detecting this gravitational wave background. While existing gravitational wave observations on Earth are designed to search for gravitational waves in the order of seconds, ripples of the gravitational wave background are years or even decades long.
Now researchers say they may have detected a strong signal from the gravitational wave background using a U.S. and Canadian project called the North American Nanohertz Observatory for gravitational waves (NANOGrav).
“We see incredibly important evidence for this signal,” lead author Joseph Simon, an astrophysicist at the University of Colorado Boulder, told the AAS press conference. “Unfortunately, we still can’t quite say what it is.”
NANOGrav uses telescopes on the ground to monitor dozens of pulses. Gravity waves can change the constant flashing light pattern of the pulses and express and expand the distances these rays travel through space.
“When these waves pass us, the earth is pushed around a bit,” Simon said. “As the Earth is pushed closer to the pulses in one part of the sky, the pulses of the pulses will appear a little faster than expected, and pulses of the pulses in the other part of the sky will appear a little later. . “
The analysis of this pulse light can therefore help to detect scientists’ signs of the background of gravity.
“By monitoring signals from a large number of these pulses, we have created a gravity wave detector in our own Milky Way,” Simon said.
To find these subtle tips, NANOGrav scientists have been trying for as long as possible to observe as many pulsars as possible. So far, they have observed 45 pulses for at least three years, and in some cases, more than a dozen years.
“These pulsars rotate about as fast as your kitchen mixer,” Simon said in a statement. “And we look at deviations in their timing of just a few hundred nanoseconds.”
Now, the researchers said they’d found potential evidence of a common process that distorts the light of many of the pulses. From now on, they can not verify whether this signal is evidence for the gravitational wave background, “but we also have no evidence against it,” Simon said.
The scientists warn that they still need to look at more pulses and monitor them for longer periods of time to confirm if the gravity background is the cause.
If the researchers can verify that they have detected the gravitational wave background, they will then want to determine what is causing the waves and what such signals scientists can tell about the universe.
The scientists presented their findings on January 11 at an online meeting of the American Astronomical Society. Chakrabarti and her colleagues set out their findings in a study accepted in the journal Astrophysical Journal Letters. Simon and his colleagues set out their NANOGrav findings online December 24 in The Astrophysical Journal Letters.
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