In October 2022, a global group of researchers, together with Northwestern College astrophysicists, noticed the brightest gamma-ray burst (GRB) ever recorded, GRB 221009A.

Now, a Northwestern-led group has confirmed that the phenomenon chargeable for the historic burst — dubbed the B.O.A.T. (“brightest of all time”) — is the collapse and subsequent explosion of an enormous star. The group found the explosion, or supernova, utilizing NASA’s James Webb House Telescope (JWST).

Whereas this discovery solves one thriller, one other thriller deepens.

The researchers speculated that proof of heavy components, reminiscent of platinum and gold, may reside inside the newly uncovered supernova. The in depth search, nevertheless, didn’t discover the signature that accompanies such components. The origin of heavy components within the universe continues to stay as one among astronomy’s largest open questions.

The analysis might be printed on Friday (April 12) within the journal Nature Astronomy.

“Once we confirmed that the GRB was generated by the collapse of an enormous star, that gave us the chance to check a speculation for a way a few of the heaviest components within the universe are fashioned,” stated Northwestern’s Peter Blanchard, who led the examine. “We didn’t see signatures of those heavy components, suggesting that extraordinarily energetic GRBs just like the B.O.A.T. don’t produce these components. That does not imply that each one GRBs don’t produce them, however it’s a key piece of data as we proceed to grasp the place these heavy components come from. Future observations with JWST will decide if the B.O.A.T.’s ‘regular’ cousins produce these components.”

Blanchard is a postdoctoral fellow at Northwestern’s Heart for Interdisciplinary Exploration and Analysis in Astrophysics (CIERA), the place he research superluminous supernovae and GRBs. The examine contains co-authors from the Heart for Astrophysics | Harvard & Smithsonian; College of Utah; Penn State; College of California, Berkeley; Radbound College within the Netherlands; House Telescope Science Institute; College of Arizona/Steward Observatory; College of California, Santa Barbara; Columbia College; Flatiron Institute; College of Greifswald and the College of Guelph.

Start of the B.O.A.T.

When its gentle washed over Earth on Oct. 9, 2022, the B.O.A.T. was so vivid that it saturated a lot of the world’s gamma-ray detectors. The highly effective explosion occurred roughly 2.4 billion light-years away from Earth, within the path of the constellation Sagitta and lasted just a few hundred seconds in length. As astronomers scrambled to watch the origin of this extremely vivid phenomenon, they had been instantly hit with a way of awe.

“So long as we’ve been capable of detect GRBs, there is no such thing as a query that this GRB is the brightest we’ve ever witnessed by an element of 10 or extra,” Wen-fai Fong, an affiliate professor of physics and astronomy at Northwestern’s Weinberg Faculty of Arts and Sciences and member of CIERA, stated on the time.

“The occasion produced a few of the highest-energy photons ever recorded by satellites designed to detect gamma rays,” Blanchard stated. “This was an occasion that Earth sees solely as soon as each 10,000 years. We’re lucky to dwell in a time when we’ve the know-how to detect these bursts taking place throughout the universe. It is so thrilling to watch such a uncommon astronomical phenomenon because the B.O.A.T. and work to grasp the physics behind this distinctive occasion.”

A ‘regular’ supernova

Somewhat than observe the occasion instantly, Blanchard, his shut collaborator Ashley Villar of Harvard College and their group needed to view the GRB throughout its later phases. About six months after the GRB was initially detected, Blanchard used the JWST to look at its aftermath.

“The GRB was so vivid that it obscured any potential supernova signature within the first weeks and months after the burst,” Blanchard stated. “At these occasions, the so-called afterglow of the GRB was just like the headlights of a automotive coming straight at you, stopping you from seeing the automotive itself. So, we needed to await it to fade considerably to present us an opportunity of seeing the supernova.”

Blanchard used the JWST’s Close to Infrared Spectrograph to watch the thing’s gentle at infrared wavelengths. That is when he noticed the attribute signature of components like calcium and oxygen sometimes discovered inside a supernova. Surprisingly, it wasn’t exceptionally vivid — just like the extremely vivid GRB that it accompanied.

“It is not any brighter than earlier supernovae,” Blanchard stated. “It seems pretty regular within the context of different supernovae related to much less energetic GRBs. You may count on that the identical collapsing star producing a really energetic and vivid GRB would additionally produce a really energetic and vivid supernova. However it seems that is not the case. We now have this extraordinarily luminous GRB, however a traditional supernova.”

Lacking: Heavy components

After confirming — for the primary time — the presence of the supernova, Blanchard and his collaborators then looked for proof of heavy components inside it. Presently, astrophysicists have an incomplete image of all of the mechanisms within the universe that may produce components heavier than iron.

The first mechanism for producing heavy components, the fast neutron seize course of, requires a excessive focus of neutrons. Up to now, astrophysicists have solely confirmed the manufacturing of heavy components through this course of within the merger of two neutron stars, a collision detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO) in 2017. However scientists say there have to be different methods to supply these elusive supplies. There are just too many heavy components within the universe and too few neutron-star mergers.

“There’s probably one other supply,” Blanchard stated. “It takes a really very long time for binary neutron stars to merge. Two stars in a binary system first should explode to depart behind neutron stars. Then, it may well take billions and billions of years for the 2 neutron stars to slowly get nearer and nearer and at last merge. However observations of very previous stars point out that components of the universe had been enriched with heavy metals earlier than most binary neutron stars would have had time to merge. That is pointing us to another channel.”

Astrophysicists have hypothesized that heavy components additionally could be produced by the collapse of a quickly spinning, huge star — the precise sort of star that generated the B.O.A.T. Utilizing the infrared spectrum obtained by the JWST, Blanchard studied the interior layers of the supernova, the place the heavy components must be fashioned.

“The exploded materials of the star is opaque at early occasions, so you possibly can solely see the outer layers,” Blanchard stated. “However as soon as it expands and cools, it turns into clear. Then you possibly can see the photons coming from the interior layer of the supernova.”

“Furthermore, totally different components take in and emit photons at totally different wavelengths, relying on their atomic construction, giving every component a singular spectral signature,” Blanchard defined. “Due to this fact, taking a look at an object’s spectrum can inform us what components are current. Upon analyzing the B.O.A.T.’s spectrum, we didn’t see any signature of heavy components, suggesting excessive occasions like GRB 221009A aren’t main sources. That is essential data as we proceed to attempt to pin down the place the heaviest components are fashioned.”

Why so vivid?

To tease aside the sunshine of the supernova from that of the brilliant afterglow that got here earlier than it, the researchers paired the JWST information with observations from the Atacama Massive Millimeter/Submillimeter Array (ALMA) in Chile.

“Even a number of months after the burst was found, the afterglow was vivid sufficient to contribute plenty of gentle within the JWST spectra,” stated Tanmoy Laskar, an assistant professor of physics and astronomy on the College of Utah and a co-author on the examine. “Combining information from the 2 telescopes helped us measure precisely how vivid the afterglow was on the time of our JWST observations and permit us to fastidiously extract the spectrum of the supernova.”

Though astrophysicists have but to uncover how a “regular” supernova and a record-breaking GRB had been produced by the identical collapsed star, Laskar stated it could be associated to the form and construction of the relativistic jets. When quickly spinning, huge stars collapse into black holes, they produce jets of fabric that launch at charges near the velocity of sunshine. If these jets are slender, they produce a extra targeted — and brighter — beam of sunshine.

“It is like focusing a flashlight’s beam right into a slender column, versus a broad beam that washes throughout an entire wall,” Laskar stated. “In truth, this was one of many narrowest jets seen for a gamma-ray burst thus far, which provides us a touch as to why the afterglow appeared as vivid because it did. There could also be different components accountable as properly, a query that researchers might be learning for years to return.”

Further clues additionally might come from future research of the galaxy during which the B.O.A.T. occurred. “Along with a spectrum of the B.O.A.T. itself, we additionally obtained a spectrum of its ‘host’ galaxy,” Blanchard stated. “The spectrum reveals indicators of intense star formation, hinting that the delivery surroundings of the unique star could also be totally different than earlier occasions.”

Staff member Yijia Li, a graduate scholar at Penn State, modeled the spectrum of the galaxy, discovering that the B.O.A.T.’s host galaxy has the bottom metallicity, a measure of the abundance of components heavier than hydrogen and helium, of all earlier GRB host galaxies. “That is one other distinctive facet of the B.O.A.T. that will assist clarify its properties,” Li stated.

The examine, “JWST detection of a supernova related to GRB 221009A with out an r-process signature,” was supported by NASA (award quantity JWST-GO-2784) and the Nationwide Science Basis (award numbers AST-2108676 and AST-2002577). This work relies on observations made with the NASA/ESA/CSA James Webb House Telescope.

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