A new study proposes an answer to the mystery of what powers gamma-ray bursts – the brightest and most powerful explosions in the universe that take place when a star goes supernova. Research from an international team of astrophysicists indicates that the specific reason for this phenomenon, when two gigantic jets of light-emitting plasma shoot out materials at ultra-high speeds, might lie in the collapse of a star's magnetic field.
The gamma-ray bursts (GRBs), occurring when a star implodes to form a neutron star or a black hole, are so violent that they release as much energy in just a few seconds as the Sun does in its whole lifetime of 10 billion years. The bursts can last from ten milliseconds to several hours while their longer "afterglow" can be observed from Earth.
As the press release from the University of Bath highlights, the baryonic jet model explains GRBs as flashes produced by repeated violent collisions between the materials involved in the explosions around a dying star.
The second hypothesis on the origin of the bursts is the magnetic model, which got a boost from the new research. The idea behind this is that when a star explodes, its large magnetic field collapses, unleashing the tremendous energy that powers a GRB.
The team of researchers involved in the study found evidence to support the magnetic model by examining data from the collapse of a large star in a galaxy that's 4.5 billion light-years away. They knew about the star's collapse from a gamma-ray burst (named GRB 190114C), which was detected by NASA's Neil Gehrels Swift Observatory, operating from space in Earth's low orbit.
Cosmic death beams: Understanding gamma ray bursts
The researchers spotted a clue to the role of the magnetic field in the very low level of polarization observed in the gamma ray burst right after the star's collapse. This pointed to the explosion destroying the magnetic field.
The paper's lead author, Nuria Jordana-Mitjans of Bath University in the U.K., explained that, "From previous studies, we expected to detect polarisation as high as 30% during the first hundred seconds after the explosion. So we were surprised to measure just 7.7% less than a minute after the burst, followed by a sudden drop to 2% soon after."
This indicated to the scientists that the magnetic fields "collapsed catastrophically straight after the explosion, releasing their energy and powering the bright light detected across the electromagnetic spectrum."
The new study was conducted by the University of Bath in cooperation with scientists from the Liverpool John Moore University UK, the University of Ferrara Italy, the University of Nova Gorica Slovenia, the South African Astronomical Observatory, the Instituto de Astrofisica de Canarias, Spain, Lomonosov Moscow State University and Irkutsk State University Russia.
Check out their study published in The Astrophysical Journal.
Interestingly, a study released earlier in 2020 from the University of Warwick pointed to binary star systems offering special conditions that are favorable to creating gamma-ray bursts. This field continues to offer fascinating developments.
We’ve tired the electromagnetic spectrum when it comes to examining the universe. Now, astronomers are fiddling with a whole new aperture, gravitational waves. A little over 100 years ago, Einstein first predicted gravitational waves as something that would happen throughout space-time as a result of dramatic events. September’s announcement proved him right, although he himself thought we’d never be able to detect them, the results being so slight.
Officials at the National Science Foundation, LIGO, MIT, Caltech, and other institutions have now made a second groundbreaking announcement, the detection of gravitational waves from another astronomical event, the merging of two neutron stars. This latest signal was detected on Aug. 17. A neutron star is the remnant of a larger star whose core has collapsed. Usually, this is followed by a supernova, where the outer layer of the star blows off in a colossal explosion.
The neutron stars that merged were each 1.1 to 1.4 times the mass of our sun. An event of this magnitude only occurs once in 80,000 years, LIGO scientists say. The light emitted by this neutron star collision resulted in a “fireball,” which is an intense burst of gamma radiation. Such a fireball or kilonova creates the heaviest known elements, such as gold, platinum, and lead, and sends them careening throughout the cosmos.
See an animated clip of a neutron star collision here:
These are small, dense stars. One teaspoon worth would weigh more than 10 million tons, more than the entire population of Earth. As the core continues to collapse, the gravity inside gets so strong it fuses protons and electrons together, forming neutrons, hence the name. When two neutron stars merge, one of two things happen. Either an even bigger neutron star is born or a black hole is made. This event, now known as GW170817, created an ultra-dense neutron star.
Though it occurred approximately 130 million years ago, the resulting gravitational waves reached Earth last August, with the ripples arriving one second before the light did. This is the very first time scientists recorded an astronomical event through both light and gravitational waves.
Over 1,200 scientists from 100 institutions around the world work at the LIGO Scientific Collaboration. LIGO is comprised of two observatories, one in Hanford, Washington, and the other in Livingston, Louisiana. Each contains an instrument so sensitive it can detect a single ripple in space-time lasting just a fraction of a second. In addition to the LIGO detectors, the newly launched Virgo observatory in Italy helped to zero-in on the location of the explosion. Other such observatories are in the works for Japan and India, which will further help pinpoint an event’s location.
Each observatory consists of an L-shaped tunnel. Laser light is sent by mirror down each of them. When there are no gravitational fluctuations, the laser bounces back normally. But when there are ripples in space-time, it squeezes and pulls the beam which gives scientists a reading.
Artist concept of neutron star falling into its neighbor. Credit: NASA
Caltech’s David H. Reitze is the executive director of the LIGO Laboratory. In a press release, he explained the importance of the groundbreaking even. “This detection opens the window of a long-awaited ‘multi-messenger’ astronomy. It’s the first time that we’ve observed a cataclysmic astrophysical event in both gravitational waves and electromagnetic waves — our cosmic messengers,” Dr. Reitze said, “Gravitational-wave astronomy offers new opportunities to understand the properties of neutron stars in ways that just can’t be achieved with electromagnetic astronomy alone.”
The event also solidified another of Einstein’s predictions. Not only does it further confirm the existence of gravitational waves but that they travel at the speed of light. Its little wonder that the scientists who put together LIGO won this year’s Nobel Prize in Physics.
See the announcement of this historic event in astronomy here:
