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Since the inception of the universe with the big bang, the primordial composition primarily consisted of hydrogen, helium, and trace amounts of lithium. In the aftermath, heavier elements such as iron were formed through stellar processes. However, a significant enigma in astrophysics arises: how did the initial elements beyond iron, such as gold, come into being and spread throughout the cosmos?
“This question is fundamental to understanding the origin of complex matter in the universe,” remarked Anirudh Patel, a doctoral candidate at Columbia University in New York. “It’s an intriguing puzzle that remains unsolved.”
Patel led a groundbreaking study utilizing two decades’ worth of archived data from NASA and ESA telescopes, uncovering compelling evidence that a significant source of these heavier elements may be flares from highly magnetized neutron stars, known as magnetars. The research findings are published in The Astrophysical Journal Letters.
The authors of the study propose that giant flares from magnetars could account for as much as 10% of all elements heavier than iron in the galaxy. Given that magnetars emerged relatively early in cosmic history, it is conceivable that these flares were responsible for the first formation of gold.
“This research addresses one of the major questions of the century and sheds light on a mystery using archival data that had nearly been overlooked,” stated Eric Burns, a co-author and astrophysicist from Louisiana State University in Baton Rouge.
Neutron stars are the remnants of stars that have gone supernova, collapsing under their own gravity. Their density is astounding; just a teaspoon of material from a neutron star would weigh approximately a billion tons on Earth. A magnetar is characterized by its exceptionally strong magnetic field.
Occasionally, magnetars emit bursts of high-energy radiation during events known as “starquakes,” which fracture their crusts similar to earthquakes. These starquakes can trigger powerful magnetar giant flares, which have the potential to influence Earth’s atmosphere. To date, only three such flares have been recorded within our Milky Way galaxy and the adjacent Large Magellanic Cloud, with seven more observed beyond.
Patel and his team, including his advisor Brian Metzger, a professor at Columbia University and a senior research scientist at the Flatiron Institute, speculate that the radiation from these giant flares may correlate with the formation of heavy elements. This process occurs rapidly, as neutrons combine with lighter atomic nuclei to forge heavier ones.
The number of protons in an atom determines its identity on the periodic table: for example, hydrogen has one proton, helium has two, and lithium has three. In addition to protons, atoms possess neutrons, which do not alter their identity but increase their mass. Occasionally, an atom may capture an additional neutron, leading to instability and a nuclear decay process that converts a neutron into a proton, effectively moving the atom up the periodic table. This mechanism explains how a gold atom can absorb an extra neutron and transform into mercury.
In the extreme environment of a disrupted neutron star, where neutron density is exceptionally high, a fascinating phenomenon occurs: single atoms can rapidly capture numerous neutrons, undergoing multiple decays that result in the formation of much heavier elements, such as uranium.
In 2017, astronomers observed the collision of two neutron stars using NASA telescopes and the Laser Interferometer Gravitational-Wave Observatory (LIGO), alongside various ground-based and space-borne telescopes that followed up on this ground-breaking discovery. This event was believed to have produced gold, platinum, and other heavy elements. However, neutron star mergers occur relatively late in the universe’s evolution and cannot fully account for the earliest appearances of gold and similar elements. Recent studies involving co-authors Jakub Cehula from Charles University in Prague, Todd Thompson from The Ohio State University, and Metzger have suggested that magnetar flares can heat and eject neutron star crustal material at significant speeds, positioning them as a plausible source of these elements.
Initially, Metzger and his team anticipated that the signatures of heavy element creation associated with a magnetar would manifest in visible and ultraviolet light, leading to published predictions. However, Burns proposed the possibility of detecting a gamma-ray signal that could also be significant. After further investigation, they concluded that such a signature might indeed be present.
“Eventually, we decided to inquire with astronomers about any corresponding observations,” Metzger recounted.
Burns scrutinized the gamma-ray data from the last observed giant flare in December 2004, realizing that while the initial outburst had been explained, a subtle secondary signal had been recorded from the magnetar, thanks to ESA’s INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL), an esteemed, recently retired mission with contributions from NASA. “This detail was noted but lacked any clear interpretation back then,” Burns noted.
Metzger remarked that Burns expressed disbelief, considering the close alignment between their model’s prediction and the enigmatic signal within the 2004 data. Essentially, the gamma-ray signal detected over 20 years ago matched the expected characteristics of element generation and dispersion during a magnetar giant flare.
Patel expressed immense excitement, stating, “For the next week or two, it consumed my thoughts entirely.”
The researchers bolstered their findings with data from two NASA heliophysics missions: the retired RHESSI (Reuven Ramaty High Energy Solar Spectroscopic Imager) and the active NASA’s Wind satellite, both of which had also monitored the magnetar giant flare. Additional collaborators on this new study include Jared Goldberg at the Flatiron Institute.
Looking ahead, NASA’s upcoming COSI (Compton Spectrometer and Imager) mission intends to explore these findings further. Slated for launch in 2027, this wide-field gamma-ray telescope aims to investigate energetic cosmic phenomena, including magnetar giant flares. COSI will have the capability to identify specific elements formed during these events, advancing our comprehension of elemental origins in the universe. It represents just one element in a suite of telescopes designed to detect “transient” changes across the cosmos.
The research team is also committed to examining other archival data in search of hidden insights from additional magnetar giant flares.
“It’s fascinating to consider how materials in devices like my phone or laptop have their origins in the extreme explosions that have shaped our galaxy’s history,” Patel reflected.
Source
science.nasa.gov