In February 2016, scientists of the Laser Interferometer Gravitational Wave Observatory (LIGO) announced the first detection of gravitational waves (GWs). Since then, several events have been discovered that afforded insight into a cosmic phenomenon that predicted Einstein's Theory of General Theory of Relativity over a century ago.
Just over a year ago, LIGO was decommissioned so upgrades could be made to your instruments that would allow detection "weekly or even more often". After completing the upgrades on April 1, the observatory returned online and ran the expected results, with two probable gravitational wave events detected within two weeks.
LIGO announced the first of two new GW events on April 8, followed by a second announcement on April 1
Thanks to updates from LIGO and Virgo, this scientific collaboration has increased the sensitivity of their instruments by about 40%. In its third observation run (called O3), the astronomical community also benefited from a new public alert system in which the LIGO team sends alerts as soon as surveys are made so that observatories around the world can point their telescopes at the source. [19659002DurchdieBeobachtungderQuellebeiverschiedenenWellenlängen(optischRöntgenultraviolettRadiousw)hoffendieWissenschaftlermehrüberdieUrsachenvonGW-EreignissenundüberdiedahinterstehendeDynamikzuerfahrenFürdieseneuestenEntdeckungenspielteeinTeamvonWissenschaftlernderPennStateUniversity-angeführtvonChadHannaeinemaußerordentlichenProfessorfürPhysikAstronomieundAstrophysik-acrucialrole
How Cody Messick, a physics student at Penn State University and member of the LIGO team, said:
"Penn State is part of a small team of LIGO scientists that analyzes the data almost in real time. We constantly compare the data with hundreds of thousands of different possible gravitational waves and upload all the major candidates into a database as quickly as possible. Although there are several different teams, all of which perform similar analyzes, the Penn State team has uploaded the candidates that were released for these two detections.
For the past nine months, Messick has been responsible for ensuring that newly uploaded GW candidates contain information from all detectors executed at the time of discovery. This helps astronomers locate signals by limiting the predicted area of the sky from which the signal is to be predicted.
LIGO public alerts also include a sky map that indicates the possible location of the source in the sky and the time of the event and what type of event is being accepted. LIGO has also said that following announcements of candidate events, more detailed information will follow in the future as soon as they have the opportunity to thoroughly investigate and study them.
As Ryan Magee, a physics student at Penn State and member of the LIGO team:
"These are real-time measurements of gravitational waves produced by two possible black holes colliding. We discovered the first signal within 20 seconds of its arrival on Earth. We can set up automatic notifications to receive phone calls and texts when a key candidate is identified. I thought I would get a spam call first! "
So far, astronomers have assumed that GW events may be the result of binary black hole merging, a black hole merging with a neutron star, or a binary neutron star fusion. Each of these events generates gravitational waves with very different signals, allowing astronomers to determine the cause.
In this case, it is assumed that the events are the result of binary black hole fusions that will be tested in the coming weeks and months with follow-up observations. Surabhi Sachdev, an Eberly Postdoctoral Research Fellow in physics at Penn State University and a member of the LIGO team, explained the significance of these recent events:
"This is the first LIGO observation to be immediately automated. This is the new LIGO policy that starts with this observation run. Events are automatically published immediately. After the human test, a confirmation or withdrawal is made within hours. "
With the increased sensitivity of their detectors, the LIGO team hopes not only to make more detections, but also to detect a greater variety of signals. So far, events have been discovered that are due to merging between two black holes or neutron stars. It is hoped that in the near future the team could detect a signal that results from the fusion of a black hole with a neutron star.
Whatever the next events will be, you can assume that we will hear about it! The public can follow public alerts at https://gracedb.ligo.org/latest/ or download the notification app from Gravitational Wave Events iPhone App.
Further reading: PSU LIGO Caltech