Gravitational wave detector LIGO is back online after a 3-year upgrade

After a three-year gap, scientists in the United States have turned on the capable detectors Measuring Gravitational Waves – Small waves in space travel through the universe.

Unlike light waves, gravitational waves are almost Unobstructed by galaxies, stars, gas and dust It fills the universe. This means that by measuring gravitational waves, Astrophysicists like me We can see directly into the heart of some of these amazing phenomena in the universe.

As of 2020, the Laser Interferometric Gravitational-Wave Observatory – commonly known as LIGO – Idle while undergoing some awesome upgrades. These improvements will be Increases sensitivity significantly LIGO should allow observation of more distant objects that produce small ripples. space time.

By finding more events that produce gravitational waves, astronomers will have a greater chance of observing light produced by those same events. Looking at an event Through multiple information channelsapproach called Multiple Messenger AstronomyProvides astronomers Rare and desirable opportunities To learn about physics beyond the scope of any laboratory experiment.

Waves in spacetime

According to Einstein’s theory of general relativity, mass and energy distort the shape of space and time. The curvature of spacetime determines how objects move relative to each other – something people experience as gravity.

Gravitational waves are created when massive objects such as black holes or neutron stars collide with each other, creating sudden, large changes in space. The process of space warping and flexing sends waves throughout the universe Wave across the calm pond. These waves travel in all directions from an obstacle, bending small gaps as they do so, and ever so slightly changing the distance between objects in their path.

Although the astronomical phenomena that produce gravitational waves involve some of the most massive objects in the universe, the expansion and contraction of space is infinitesimally small. A strong gravitational wave passing through the Milky Way would change the diameter of the entire galaxy by only three feet (one meter).

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The first gravitational wave observations

Although first predicted by Einstein in 1916, scientists of that era lacked confidence in measuring the small changes in distance postulated by the theory of gravitational waves.

In 2000, scientists from Caltech, the Massachusetts Institute of Technology, and other universities around the world completed the construction of the most accurate ruler ever built. LIGO Laboratory.

LIGO consists of two separate observatories, one in Hanford, Washington, and the other in Livingston, Louisiana. Each observatory has a giant L shape with 2.5-mile-long (four-kilometer-long) arms that extend from the facility’s center at 90 degrees to each other.

To measure the gravitational waves, the researchers shine a laser from the center of the facility to the bottom of the L. There, the laser is split so that a beam travels down each arm, reflects off a mirror and returns to the base. If a gravitational wave passes through the arms while the laser is shining, the two beams return to the center at slightly different times. By measuring this difference, physicists can tell when a gravitational wave has passed through the facility.

LIGO is up and running in the early 2000s, but it was not sensitive enough to detect gravitational waves. So, in 2010, the LIGO team temporarily shut down the facility where the program was held Upgrades to increase sensitivity. An upgraded version of LIGO is launched Data collection in 2015 and almost immediately Gravitational waves were detected Formed from the merger of two black holes.

As of 2015, LIGO is complete Three observational runs. The first, Run O1, lasted about four months; the second, O2, about nine months; The third, O3, ran for 11 months before the Covid-19 pandemic closed the facility. Starting with Run O2, LIGO is observing in conjunction with a An Italian observatory called Virgo.

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Between each run, scientists improved the detectors’ physical components and data analysis methods. At the end of the O3 run in March 2020, researchers in the LIGO and Virgo collaboration made the discovery About 90 gravitational waves From the merger of black holes and neutron stars.

The observatories are still there They have not yet reached their maximum design sensitivity. Therefore, in 2020, both observatories were closed for upgrades Again.

Makes some improvements

Scientists are working Many technological improvements.

A particularly promising upgrade included the addition of a 1,000-foot (300-meter) Optical cavity to improve a A technique called pressing. Using the quantum properties of light allows scientists to reduce detector noise. With this upgrade, the LIGO team will be able to detect much weaker gravitational waves than before.

Me and my teammates Data scientists in the LIGO collaboration, and we are working on various improvements. Software used to process LIGO data and authentication mechanisms Among those data are signs of gravitational waves. These algorithms work by searching for matching patterns Millions of theoretical models Possible black hole and neutron star merger events. The improved algorithm can more easily pick out the faintest signs of gravitational waves from the background noise in the data than previous versions of the algorithms.

Astronomers have captured both gravitational waves and light from a single event, the merger of two neutron stars. The change in light can be seen in the upper right inset over a few days. (Hubble Space Telescope, NASA and ESA)

Astronomy is a hi-def era

In early May 2023, LIGO began a short test run — called an engineering run — to make sure everything was working. On May 18, LIGO detected gravitational waves A neutron merges from a star into a black hole.

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LIGO’s 20-month observing run 04 will officially take place From May 24, It will then be joined by Virgo and a new Japanese observatory – the Kamioka Gravitational Wave Detector, or Gagra.

Although this flow has many scientific goals, a particular focus is on detecting and localizing gravitational waves in real time. If the team can identify a gravitational wave event, figure out where the waves came from, and quickly alert other astronomers to these findings, it could help astronomers point other telescopes collecting visible light, radio waves or other types of data to the source. Gravitational wave. Gathering information across multiple channels at a single event – Multi-Messenger Astrophysics – Like adding color and sound to a black and white still image and can provide a deeper understanding of astrophysical phenomena.

Astronomers have observed only one phenomenon In both gravitational waves and visible light To date – link Two Neutron Stars Discovered in 2017. But from this single event, physicists were able to study expansion of the universe and confirms the origin of certain energetic phenomena in the universe Gamma ray bursts.

With Run O4, astronomers will hopefully gain access to the most sensitive gravitational wave observatories in history and collect more data than ever before. My colleagues and I hope to launch one – or several – multi-mission observations in the coming months that will push the boundaries of modern astrophysics.

This article has been republished Conversation Under Creative Commons License. Read on Original article.

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