Gold Dust of Kilonovae: Unraveling the Late Glow ✦
Mergers of neutron stars give birth to kilonovae—flashes in which heavy elements like gold and platinum are forged. Scientists have unraveled the cause of the mysterious infrared glow from these flashes: in the ejected material, dust grains form from refractory metals (such as tungsten). Now, this 'cosmic dust' helps us figure out how many precious elements were born in the universe.
When two ultra-dense neutron stars collide, an explosion called a kilonova erupts. This cosmic cataclysm is the main forge of heavy elements, from gold to uranium. The ejected material is heated to millions of degrees and resembles a metallic vapor. But as it expands and cools, the vapor begins to condense: just as moist air gives birth to dew, here the tiniest solid dust grains form (cosmic dust). Their composition — tungsten, osmium, perhaps gold — is striking: because of their high melting points, these metals are the first to “rain out” of the cloud. Unlike dust from supernovae, which is rich in light elements, here rare and precious metals dominate — a true cosmic treasure chest. The process is rapid — taking only a few hours — and the particles remain hot, radiating in the infrared. It is this glow that telescopes caught days after the outburst. With the help of James Webb and spectroscopy, scientists were able to split the light into colors and from them determine the dust’s composition. Now the late glow of kilonovae is not a mystery but a tool. It tells us how heavy elements disperse across galaxies and, ultimately, may become part of new planets — and even jewelry.
🎯 These cosmic dust grains are so tiny — hundreds would fit on the tip of a hair — yet each one glows like a hot ember and could be made of pure gold.