By using the global detector network, the research team identified 35 gravitational wave events, which brought the total number of events observed since 20 15 to 90.
The new gravitational wave event was observed by three international detectors in 20 19 165438+2020 10. Two advanced laser interferometer gravitational wave observatory (LIGO) detectors and Italy's advanced Virgo detector are located in Louisiana and Washington respectively. A team of scientists from LIGO Scientific Cooperation Organization, Virgo Cooperation Organization and Kagerah Cooperation Organization carefully analyzed the data of the three detectors. A new paper describes the new event catalogue in the second half of LIGO's third observation operation.
Debnandini Mukherjee, a postdoctoral researcher at Pennsylvania State University and a member of LIGO Cooperation Organization, said: "In the third observation run of LIGO and Virgo, we have begun to detect more elusive gravitational wave events. These include heavy black holes, binary stars with more extreme mass ratios and neutron star-black hole condensation detection with higher confidence. We are in an exciting era, and this observation has begun to question the traditionally known astrophysics and help to understand the formation of such celestial bodies more clearly. "
New test results
Of the 35 events detected, 32 are most likely to be black holes merging-two black holes rotate with each other and finally combine to emit gravitational waves.
The black holes involved in these mergers have a series of sizes, the largest of which is about 90 times the mass of our sun. The mass of these merged black holes is more than 100 times that of the sun, and they are classified as medium-mass black holes. This marks the first observation of this type of black hole, and astrophysicists have long put forward this theory.
Of these 35 events, two may be the merger of neutron stars and black holes-a rarer event, which was first discovered in the latest observations of LIGO and Virgo. One of the newly detected mergers seems to indicate that a massive black hole with a mass of about 33 times that of the sun collided with a low-mass neutron star with a mass of about 1. 17 times that of the sun. This is one of the lowest quality neutron stars detected by gravitational waves or electromagnetic observations so far.
The mass of black holes and neutron stars is the key clue to how massive stars survive and eventually die in supernova explosions.
Becca Ewing, a graduate of Penn State University and a member of the LIGO team of Penn State University, said: "In the latest update of this catalogue, we can finally observe the merger of black holes and neutron stars, which was not found in any previous observation. With each new observation run, we will find new and different signals and expand our understanding of the appearance and behavior of these systems. In this way, we can begin to improve our understanding of the universe more and more with each new observation. "
The final gravitational wave event comes from the merger of a black hole with a mass about 24 times that of the sun and an extremely light black hole or an extremely heavy neutron star with a mass about 2.8 times that of the sun. The research team concluded that it is most likely a black hole, but it is not completely certain. 2065438+August 2009, LIGO and Virgo discovered similar fuzzy events. The mass of this lighter object is puzzling, because scientists predict that the maximum mass of neutron stars before they collapse to form black holes is about 2.5 times that of our sun. However, no black hole with a mass less than about 5 suns was found in electromagnetic observation. This leads scientists to infer that in this range, stars will not collapse into black holes. The new gravitational wave observation results show that these theories may need to be revised.
Important progress
Since gravitational waves were first detected in 20 15, the number of gravitational waves detected has increased at lightning speed. In just a few years, gravitational wave scientists have observed many events every month, even on the same day, since they first observed these vibrations in the cosmic structure. During this third observation, the gravitational wave detector achieved the best performance ever, thanks to the continuous upgrading and maintenance plan to improve the performance of these groundbreaking instruments.
With the improvement of gravitational wave detection rate, scientists have also improved their analysis techniques to ensure the high accuracy of the results. The growing catalogue of observations will enable astrophysicists to study the characteristics of black holes and neutron stars with unprecedented accuracy.
In another major development of this recent operation, within a few minutes of the initial gravitational wave detection, astronomers appealed to other observatories and detectors around the world. This network of neutrino detectors and electromagnetic observation stations focuses on the sky area where Apollo comes from in an attempt to identify the focal events. Cosmic events that produce gravitational waves can also produce neutrinos and electromagnetic radiation, which, if detected, can provide additional information about cosmic events. However, the newly announced gravitational wave has no corresponding wave reported.
Bryce Cousins, an assistant researcher at Pennsylvania State University and a member of the LIGO cooperation project, said: "It is very important to communicate with other observatories quickly to detect peers and contribute to multi-messenger astronomy. By studying a cosmic event with multiple signals, we can not only understand the specific properties of black holes and neutron stars, but also study a wider field of astrophysics, such as the evolution of stars and the expansion of the universe. The alarm system and observatory network established in this observation operation are very important for detecting the peers we need to better understand these topics in future observation operations. "
In the next comprehensive observation, which is expected to start next summer, KAGRA Observatory in Japan will also join the search. KAGRA is located deep in a mountain, and successfully completed its first observation in 2020, but it did not join the joint observation of LIGO and Virgo. With more detectors, potential events can be located more accurately.
"KAGRA's participation in the detector network can help to improve the sky positioning area of gravitational wave candidate sources, which is about 2 times, and then it can be beneficial to the detection of corresponding objects, because knowing the exact position of the source in the sky is very important for telescope observation," said Shio Sakon, a graduate student at Pennsylvania State University and a partner of LIGO. "With the development of the detection pipeline, the upgrade of LIGO and Virgo, and KAGRA joining the detector network, we expect that gravitational wave candidate events will be detected and analyzed more frequently than before, and issuing high-quality low-delay public alarms will be crucial to the development of multi-messenger astronomy."