Gravitational wave astronomy is growing. These ripples in the space-time structure are created by accelerating the mass, which moves outward from their origin at the speed of light. Anything with mass can generate gravitational waves (GW), but currently only the largest event can be detected. Two black holes collide, two neutron stars collide with each other, or a combination of the two.
The first GW was detected by the Laser Interferometer Gravity Wave Observatory (LIGO) in 2015, and two black holes about 1.3 billion light-years apart collided with each other. LIGO consists of two interferometers located in Louisiana and Washington. These interferometers are L-shaped vacuum tunnels about 2.5 miles long on each side. If a laser is fired from the core of L to the mirrors at the ends on each side and one of those laser beams arrives with a slight delay, the delay beam is recorded by the detector. The detector is sensitive enough to pick up noise near the earth, such as passing trucks or falling trees.These events can be masked
Or to mimic a gravitational wave signal, placing the two detectors far apart helps scientists distinguish between actual GW vibrations and false alarms.
The actual detector that discovered the first gravitational wave is now in the Nobel Prize Museum in Stockholm, Sweden, as the 2017 Nobel Prize in Physics was awarded for this discovery. But LIGO didn’t stop there. A few months later, in collaboration with the newly completed Virgo interferometer in Italy, LIGO detected another gravitational wave event. This time it was generated by the collision of a neutron star. This discovery also corresponded to the discovery of a short gamma-ray burst followed by a merged site with an optical telescope. However, within a few days of its critical discovery, LIGO went offline due to a scheduled upgrade.
On April 1, 2019, the detector was turned on again due to a new observation run called O3, which was highly anticipated by the astronomy community. The new upgrade means that LIGO will be able to find more GW in space during the year, and working with Virgo will give even greater accuracy as to where the detected merger took place in space. Meaned. What does LIGO discover this time?
LIGO team member Alena Ananyeva is working on a hardware upgrade prior to the third run of LIGO. (Credit: LIGO / CalTech / MIT / Matt Heintze)
Detection of astronomical phenomena
The data for the first half of O3 has been released, and it is clear that LIGO has entered a new stage with O3. “We are moving from the discovery stage of the GW event to our day-to-day operations,” explains Samaya Nissanke, an astrophysicist at the University of Amsterdam and a member of the LIGO collaboration. Observations are made before O3 detects an event of only 11GW. Dozens were detected by running O3. Almost overnight, the discovery of giant black holes colliding with each other millions of light-years away from us was almost routine.
In addition, LIGO has sent real-time alerts for each new detection, just as observatories routinely perform astronomical events that require rapid follow-up. These alerts were automatically delivered when both the Virgo detector and the LIGO detectors in Louisiana and Washington simultaneously detected what appeared to be a GW signal. The alert also included a skymap, called localization, showing where the signal came from. Once published, these messages were delivered to astronomers, apps, and even the LIGO Twitter feed through automatic alerts. The alerts were initially flooded with events due to local interference with the Earth, but “it was a slightly rocky start,” admits Nissan Ke. From the merger of GW. Plans are underway to apply automated algorithms and machine learning techniques to make alerts more accurate in the future.
However, it was clear that LIGO was growing black hole samples faster as verified O3 detection progressed. “The number of black holes detected has doubled, and as it grows, we have better ideas for population,” said Lionel London, MIT astrophysicist, specializing in modeling the next GW signature: is. LIGO’s black hole. One notable example, called GW190814 (because it was detected on August 14, 2019), is exciting because it was either the heaviest neutron star or the lightest black hole ever discovered. did.
Earlier, astronomers have noticed that the heaviest known neutron star weighs about twice as much as the Sun, and the smallest known black hole weighs three times as much as the Sun. A confused scientist called this “mass gap” -was there a physical reason for it, or was something still not found to fill that gap? GW190814 was one of the first residents to fill it. One of the two components was about 2.6 times the mass of the sun. The jury hasn’t yet considered exactly what the object is, but it’s something weird and ends with a black hole that’s 23 times the mass of our own sun. It is clear that we have arrived. Together, the two formed a black hole about 26 times larger than the Sun. For example, it is larger than a black hole created by a dying star, about 800 million light-years away from Earth.
This figure shows the masses of all gravitational wave detections published by LIGO, as well as black holes and neutron stars previously obtained by electromagnetic observations. (Credit: LIGO-Virgo-Kagra / Aaron Geller / Northwestern)
Scientific discoveries also came from real-time detection alerts. Most notable is the possibility of light detection from two colliding black holes, reported by the California Institute of Technology’s Zwicky Transient Facility (ZTF), for the first time such detection was claimed. .. Black holes are notorious for being so dense that light cannot escape, and the merger of two black holes is not expected to emit light under normal circumstances. However, in this case, the team claims that the flash observed by the ZTF corresponds to the May 21, 2019 Golden Week event, where the two black holes merged. Researchers claim that the angular momentum from the merger itself led to an interaction with the surrounding gas. It is this interaction that was able to give off the sudden flash of light they observed.
However, beyond individual events, a catalog of black hole detection is invaluable for testing your understanding of physics itself. Each part of GW detection consists of several components, such as the inspiration for the two objects, the collision itself, and the echoing aftershocks of the merger. The extreme physics of these moments provide a new hotbed for testing theories related to gravity, from general relativity to the mysterious dark energy that drives the expansion of the universe. “When it comes to theoretical interpretations, these are really early stages,” explains London. “Some tests are really rudimentary.” However, as the sample of events grows and the signatures are better understood, scientists can use statistics to look at physics in a whole new way. I can do it.
Unfortunately, in March 2020, a coronavirus pandemic shortened O3 execution. However, GW scientists are confident that the next run, O4, will be even more exciting when it begins in December 2022. Not only will they look into space more than before, but in 2020 they will observe the new GW detector, the Kamioka gravitational wave. The detector (KAGRA) is now online in Japan. Working in conjunction with LIGO and Virgo devices, KAGRA will be able to more accurately estimate the source of GW. Looking further ahead, LIGO-India is currently working and will begin observations in 2026. This will greatly improve the ability to pinpoint exactly where the gravitational waves came from in the sky. This will allow astronomers to locate space collisions more than ever before.
“We are opening an astrophysically formed black hole zoo, and it’s exciting to see what’s there,” the Nissan family observes.