Editing Gold (section)

=== Gold production in the universe ===
[[File:Vredefort crater cross section 2.png|thumb|upright=1.8|Schematic of a NE (left) to SW (right) cross-section through the 2.020-billion-year-old [[Vredefort impact structure]] in [[South Africa]] and how it distorted the contemporary geological structures. The present erosion level is shown. [[Johannesburg]] is located where the [[Witwatersrand Basin]] (the yellow layer) is exposed at the "present surface" line, just inside the crater rim, on the left. Not to scale.]]

Gold in the universe is produced through several cosmic processes and was present in the [[solar nebula|dust]] from which the [[Solar System]] formed.<ref>{{Cite journal |doi=10.1086/190111 |title=Nucleosynthesis of Heavy Elements by Neutron Capture |date=1965 |last1=Seeger |first1=Philip A. |last2=Fowler |first2=William A. |last3=Clayton |first3=Donald D. |journal=The Astrophysical Journal Supplement Series |volume=11 |page=121 |bibcode=1965ApJS...11..121S |url=http://tigerprints.clemson.edu/cgi/viewcontent.cgi?article=1307&context=physastro_pubs}}</ref> Scientists have identified three main cosmic sources for gold formation: [[supernova nucleosynthesis]], [[Neutron star merger|neutron star collisions]],<ref>{{cite news |url=https://pweb.cfa.harvard.edu/news/earths-gold-came-colliding-dead-stars |title=Earth's Gold Came from Colliding Dead Stars |work=David A. Aguilar & Christine Pulliam |publisher=cfa.harvard.edu |date=17 July 2013 |access-date=16 May 2025}}</ref> and magnetar flares.

All three sources involve a process called the [[r-process]] (rapid neutron capture), which forms elements heavier than [[iron]].<ref>{{cite web |url=http://chandra.harvard.edu/xray_sources/supernovas.html |title=Supernovas & Supernova Remnants |publisher=[[Chandra X-ray Observatory]] |access-date=28 February 2014}}</ref> For decades, scientists believed [[supernova nucleosynthesis]] was the primary mechanism for gold formation. More recently, research has shown that [[neutron star merger|neutron star collisions]] produce significant quantities of gold through the r-process.<ref>{{cite journal |last1=Berger |first1=E. |first2=W. |last2=Fong |first3=R. |last3=Chornock |date=2013 |title=An r-process Kilonova Associated with the Short-hard GRB 130603B |journal=The Astrophysical Journal Letters |volume=774 |issue=2 |page=4 |doi=10.1088/2041-8205/774/2/L23 |arxiv=1306.3960 |bibcode=2013ApJ...774L..23B|s2cid=669927 }}</ref>

In August 2017, the spectroscopic signatures of heavy elements, including gold, were directly observed by electromagnetic observatories during the [[GW170817]] neutron star merger event.<ref>{{cite news |title=LIGO and Virgo make first detection of gravitational waves produced by colliding neutron stars |url=https://www.ligo.org/detections/GW170817/press-release/pr-english.pdf |archive-url=https://web.archive.org/web/20171031030151/http://www.ligo.org/detections/GW170817/press-release/pr-english.pdf |archive-date=31 October 2017 |url-status=live |publisher=[[LIGO]] & [[Virgo interferometer|Virgo]] collaborations |date=16 October 2017 |access-date=15 February 2018}}</ref> This confirmed neutron star mergers as a source of gold, after years of only indirect detection.<ref>"we have no spectroscopic evidence that [such] elements have truly been produced," wrote author Stephan Rosswog.{{cite journal |last=Rosswog |first=Stephan |date=29 August 2013 |title=Astrophysics: Radioactive glow as a smoking gun |journal=[[Nature (journal)|Nature]] |volume=500 |issue=7464 |pages=535–536 |doi=10.1038/500535a |bibcode=2013Natur.500..535R |pmid=23985867|s2cid=4401544 }}</ref> This single event generated between 3 and 13 [[Earth mass]]es of gold, suggesting that neutron star mergers might produce enough gold to account for most of this element in the universe.<ref>{{cite news |title=Neutron star mergers may create much of the universe's gold |work=Sid Perkins |publisher=Science AAAS |url=https://www.science.org/content/article/neutron-star-mergers-may-create-much-universe-s-gold |date=20 March 2018 |access-date=24 March 2018}}</ref>

However, neutron star mergers alone cannot explain all cosmic gold, particularly in older stars, because these mergers occur relatively late in galactic history and are infrequent (approximately once every 100,000 years).<ref>{{cite journal |last1=Patel |first1=Anirudh |last2=Metzger |first2=Brian D. |last3=Cehula |first3=Jakub |last4=Burns |first4=Eric |last5=Goldberg |first5=Jared A. |last6=Thompson |first6=Todd A. |title=Direct Evidence for r-process Nucleosynthesis in Delayed MeV Emission from the SGR 1806–20 Magnetar Giant Flare |journal=The Astrophysical Journal Letters |volume=984 |issue=1 |pages=L29 |date=April 29, 2025 |doi=10.3847/2041-8213/adc9b0 |doi-access=free |bibcode=2025ApJ...984L..29P }}</ref> This created a timing paradox in explaining the presence of gold in stars formed early in the universe.

In 2025, researchers resolved this paradox by confirming that giant flares from [[magnetar]]s (highly magnetic neutron stars) are also a significant source of gold formation.<ref>{{cite journal |last1=Patel |first1=Anirudh |last2=Metzger |first2=Brian D. |last3=Cehula |first3=Jakub |last4=Burns |first4=Eric |last5=Goldberg |first5=Jared A. |last6=Thompson |first6=Todd A. |title=Direct Evidence for r-process Nucleosynthesis in Delayed MeV Emission from the SGR 1806–20 Magnetar Giant Flare |journal=The Astrophysical Journal Letters |volume=984 |issue=1 |pages=L29 |date=April 29, 2025 |doi=10.3847/2041-8213/adc9b0 |doi-access=free |bibcode=2025ApJ...984L..29P }}</ref> Analysis of a 2004 magnetar flare showed these events produce heavy elements through the same r-process as neutron star mergers. The amount of heavy elements created in a single magnetar flare can exceed the mass of Mars.<ref>{{cite news |last=Patel |first=Kasha |title=We figured out where gold comes from. The answer is explosive. |newspaper=The Washington Post |date=May 4, 2025 |url=https://www.washingtonpost.com/science/2025/05/04/first-gold-universe-heavy-metals-magnetar/ |access-date=May 5, 2025}}</ref> Since magnetars existed earlier in cosmic history and flare more frequently than neutron star mergers occur, they help explain gold's presence in older stars. Scientists estimate magnetar flares may contribute approximately 1-10% of all elements heavier than iron in our galaxy, including gold.<ref>{{cite news |title=Astronomers spot a gold mine in massive cosmic flares |work=Science.org |date=May 2025 |url=https://www.science.org/content/article/astronomers-spot-gold-mine-massive-cosmic-flares |access-date=May 5, 2025}}</ref>