Telekop James Webb

Illustration of two neutron stars colliding and merging, an event called a kilonova. Image: Robin Dienel/The Carnegie Institution for Science

SPACE — Using the James Webb Space Telescope (JWST), astronomers have tracked a very bright gamma-ray burst (GRB) to its source, which is a violent collision between two neutron stars.

The gold known on Earth most likely contains atoms formed in collisions of neutron stars like this one, which are also known as kilonovas.

As well as detonating long-duration GRBs, kilonovas are believed to be places where the universe’s heaviest elements were forged, elements that cannot be synthesized in the nuclear furnaces at the hearts of stars. These elements are theorized to be created by a mechanism called “neutron capture” or the r-process, which allows atomic nuclei to capture neutrons, creating new, heavier elements, including gold, platinum, and uranium. R-processes can only take place under extreme and harsh conditions, such as those found around colliding neutron stars.

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This is the first time James Webb has used it to detect emissions from such an event. The powerful space telescope is also capable of detecting the signatures of heavy elements faked in the event of the explosion. In particular, the research team saw evidence of the heavy element tellurium and the creation of the lanthanides, a group of 15 metals heavier than lead.

“These observations demonstrate that nucleosynthesis in GRBs can make r-process elements across a broad range of atomic masses and play a central role in the nucleosynthesis of heavy elements throughout the universe,” the research team wrote in a paper detailing their findings. The research team was led by Andrew Levan, a professor at Radboud University in the Netherlands.

Designated GRB 230307A, it was originally detected by NASA’s Fermi Gamma-ray Space Telescope on March 7, 2023, and is the second-brightest GRB ever seen. The GRB lasts about 34 seconds and is visible to several other telescopes, which allows astronomers to triangulate it back to its source. Team member Brian Metzger, of Columbia University, discussed the milestone in a series of tweets on Thursday, July 6, 2023.

“In work led by Andrew Levan, we detected kilonova emissions (for the first time!) with JWST, after the GRB. In perhaps the biggest storyline: the GRB, the second-brightest of all time, lasted half a minute, i.e. the second ‘long’ burst accompanied by r-process production,” Metzger wrote.

James Webb observed the kilonova twice, once 29 days after the GRB and again 61 days after the radiation burst. Kilonova quickly fades in brightness and transitions from blue to red between these observations. That hints at its kilonova nature.

The team identified several bright galaxies around the kilonova as possible locations for the collision of the neutron star, and thus, the source of GRB 230307A. What the team highlighted is the brightest galaxy, which is about 8.3 million light years from Earth and offset from the source of the GRB by about 130,000 light years.

Kilonova can also be seen in other types of emission besides light. Collisions of neutron stars cause the fabric of space-time to ‘ring’ in the form of gravitational waves. These ripples can be detected on Earth by detectors such as the Laser Interferometer Gravitational-Wave Observatory (LIGO), but LIGO is inactive when GRB 230307A is on. The facility was on a three-year outage at the time, receiving upgrades to make it more sensitive. It will be back online in May 2023.

The research team’s findings are undergoing peer review before being published in a journal. An earlier version of the paper, which may be revised, has been published on the arXiv research repository. Source: Space.com

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2023-07-10 13:50:26
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