Cosmic dust formation mystery solved

Pictured: Cosmic dust forms planets and stars in the universe. Source: ESO/R. Colombari.

By Matthew Jordan

Scientists believe they have solved a longstanding mystery as to how cosmic dust forms using new observations of a nearby supernova.

Made up of heavy elements, cosmic dust is mainly formed within large stars such as red giants and blown off either slowly through solar wind or in-mass in a large stellar explosion. It then spreads with huge amounts of dust being observed in the interstellar medium.

But there was previously little idea as to how so much cosmic dust could exist in interstellar space when so much of it should have been destroyed in supernovae; wiped out in the powerful shockwaves produced as massive stars die. However, new observations of the closest supernova to Earth reveals not so much that dust is surviving the star-shattering explosion but that it is actually reforming after it is wiped out.

NASA’s research aircraft, the Stratospheric Observatory for Infrared Astronomy (SOFIA), has detected dust in a significant set of rings within supernova 1987A. These results show that the amount of cosmic dust in the rings is actually growing rapidly, with around ten times more dust present than predicted by theoretical simulations.

A paper published in a recent issue of Monthly Notices of the Royal Astronomical Society looks at these results and suggests that dust is actually reforming after it is obliterated in the supernova’s blast. The idea that the post-shock environment would be immediately ready to form dust is new and marks a significant change in the popular understanding of dust formation and destruction.

“We already knew about the slow-moving dust in the heart of 1987A,” commented Dr. Mikako Matsuura, lecturer at Cardiff University’s School of Physics and Astronomy and the lead author of the paper.

“It formed from the heavy elements created in the core of the dead star. But the SOFIA observations tell us something completely new.”

When cosmic dust particles are heated they glow and irradiate between infrared and millimetre wavelengths. While millimetre wavelength emissions can be observed using ground telescopes, infrared observations are very difficult due to interference from carbon dioxide and water molecules in the atmosphere.

SOFIA flies high in the atmosphere, above most of such molecules which may obscure its vision, providing it with access to parts of the infrared spectrum not observable from the ground.