More than 70 observatories around the world have observed the collision and merger of a pair of neutron stars, and a year later, scientists around the world are still recalling the surprise and joy of the time, the arrival of multi-messenger astronomy and astrophysics, and they imagined the future of science. In the early morning of August 17, 2017, the researchers of the gamma-ray telescope were "woken up" by the alarm sound of the gamma-ray burst monitor, and a very strong detection signal showed that an astronomical event of a gamma-ray burst occurred in outer space, and only 2 seconds later, three laser interferometer gravitational wave observatories in the United States and Europe accepted the gravitational wave signal, and more than 70 astronomical observatories around the world were "awakened" by the information sharing system and successively put into the observation of neutron star collision events.
The researchers determined the location and distance of the event, and the dual source of electromagnetic and gravitational waves is located in the galaxy NGC 4993. Dead stars through gravitational collapse to form neutron stars, the collision event of two neutron stars verified the existing theoretical model, marking the arrival of a new era of astronomy and astrophysics, traditional astronomy with the help of optical observation methods, gravitational wave astronomy opened another window of astronomical observation, gravitational wave observation means as if "like a tiger to add wings", researchers in the "Galileo telescope" on the basis of a greater leap, gravitational wave astronomy helps people understand the basic problems of cosmology.
The binary neutron star emitted electromagnetic radiation and gravitational wave signals during the collision, and after about a week, the gravitational wave observatory stopped functioning for planned maintenance and upgrades to better put it into operation. The "8.17 gravitational waves" event corresponded to radio and X-ray signals, and a year later, the intensity of these signals entered the final stage of the fading period. Astronomers figuratively liken gravitational waves to ripples in the ocean of space-time, which produce gravitational waves when any massive object changes in the speed of motion, and an object dragged by gravity stimulates gravitational waves around space-time. Two massive neutron stars collided and merged, producing drastic velocity changes from them, releasing strong gravitational waves.
The source of the "8.17 gravitational wave" event is 130 million light-years away from the Earth, and the gravitational force is strong enough to allow the gravitational waves to travel through multiple interstellar matter and reach the ground gravitational wave observatory. At 12:41 UTC on August 17, 2017, two laser interferometer gravitational wave observatories in Hanford, Washington, and Livingston, Louisiana, recorded gravitational wave signals that had never been discovered before, and recorded several previous gravitational wave signals for a few seconds, this time recording gravitational wave signals for more than 100 seconds, and the LIGO Gravitational Wave Observatory and the Virgo Gravitational Wave Detector in Pisa, Italy, simultaneously recorded gravitational wave signals. Incoming gravitational waves from three directions help researchers lock in the source of gravitational wave signals.
The 8.17 gravitational wave was observed using gamma-ray telescopes and optical telescopes, and astronomers later used radio telescopes and X-ray telescopes to make follow-up observations of the binary neutron star event, including the very large radio array in New Mexico and the Chandra X-ray Space Telescope. More than 200 days after the event, the intensity of radio and X-rays increased significantly and then began to fade. The merger process of two neutron stars is complex, astronomers strive to put the multi-messenger astronomical signals into the entire "event map", so as to achieve a precise understanding of the neutron star merger events, and the data collected and analyzed so far verify the theoretical model of "supernovae".
In 2010, Brian Metzger, an astronomy professor at Columbia University, introduced astronomical terms: meganova or kilonova, as an astronomical term , " thousand supernova " is a particularly bright supernova , a thousand times brighter than a supernova , a nuclear synthesis reaction occurs in the core region of a thousand supernovae or supernova , producing what astrophysicists call a rapid neutron capture process or r process , where some of the universe's heavy elements, such as gold, platinum, and silver, are produced. Their distribution in the universe is not rare, and their rarity on earth has caused people to "wear gold and silver" luxury demand. Neutron stars either become a more massive neutron star during collisions and mergers, or collapse into a black hole of "cosmic monsters" together.
In addition to testing the validity of theoretical models in observations of neutron star collision events, astrophysicists also use observational data to calculate the hubble parameters or hubble constant, the most important measure of the expansion of the universe. Researchers have published more than 800 papers in the context of the "8.17 gravitational waves" event, and they have either won a series of scientific awards or received research funding, and the 2017 Nobel Prize in Physics was awarded to three physicists who made important contributions to the discovery of gravitational waves. The discovery of gravitational waves brought immediate results, and new starting points emerged in astronomy and astrophysics.
For centuries, scientists received information from the sky only by means of electromagnetic waves, and they now have a new way of observing and understanding the universe, depicting entirely new images of the universe with gravitational wave signals. In early 2019, two gravitational wave detection teams from LIGO and Virgo launched a new round of detection programs that expect to detect collisions of about 10 neutron stars each year, something scientists could not do under previous observational conditions. In the next process of dealing with the "data tide", they reset the automated data processing system, carried out extensive international exchanges and cooperation, and thousands of scientists around the world jointly detected gravitational waves, as if they were going to a scientific feast.
In future gravitational wave detections, astronomers are full of hope, not only to find typical neutron stars colliding with each other, but also to find the collision of neutron stars and black holes, they are particularly interested in a question, when the neutron star and the black hole "encounter", is the neutron star falling into the black hole, or the neutron star disappears into the "shattered bones"? It seems that many netizens are worried about the question: when someone falls into a black hole, is it the body that falls into the black hole and is torn to pieces by the gravitational tide, or is someone "swimming" in the center of the black hole? While studying the black hole event horizon— the "non-turnable point" at which neutron stars and human bodies enter the black hole region, observations of neutron stars and black hole collision events suggest a new approach. Through the collision events of neutron stars, astronomers observed the jet phenomenon in it, and the release of energy produced a powerful beam, and when a distant strong jet pointed at our Earth, astronomers had the opportunity to capture the signal of the beam.
In the case of the "8.17 gravitational wave", the neutron stars collide with each other to produce jets, but the jets form an angle with the earth, and when the angle is zero, the jets are pointed vertically to the earth, and the jets will appear brighter. Astronomers will continue to observe changes in beam intensity for months and years to come. The collision of neutron stars and black holes could create jets, and researchers plan to launch more sensitive X-ray and gamma-ray space probes. The government "pays" for the space exploration program of researchers, which not only satisfies the curiosity of scientists, but also derives many unknown technologies in the process of exploration. New areas of exploration and means of detection have inspired enthusiasm among young people and young scientists, whose efforts have influenced the future of humanity's understanding of the mysteries of the universe.
(Compiled: 2018-8-25)
Deng Rushan - Zhihu