When the universe was only 700 million years old, some of its galaxies were already filled with lots of dust. But where did all of this dust come from? Astronomers using NASA's Spitzer Space Telescope think they may have found the source in type II supernovae, the violent explosions of the universe's most massive stars.
Cosmic dust is an important component of galaxies, stars, planets, and even life. Until recently, astronomers knew of only two places where dust formed: in the outflows of old sun-like stars that are billions of years old, and in space through the slow condensation of molecules. The problem with these two scenarios is that neither explains how the universe got so dusty only a few hundred million years after its birth. Astronomers have theorized that the missing dust might be produced in supernova explosions, but evidence for this has been hard to find.
Using the space-based Spitzer and Hubble Space Telescopes and the ground-based Gemini North Telescope atop Mauna Kea in Hawaii, Dr. Ben Sugerman of the Space Telescope Science Institute in Baltimore, Md. and his colleagues found a significant amount of heated dust in the remains of a massive star called supernova SN 2003gd. The supernova remnant is located approximately 30 million light-years away in the spiral galaxy M74.
Stars like the progenitor of supernova SN 2003gd have relatively short lives of just tens of millions of years. Since Sugerman's work shows supernovae produce copious amounts of dust, he believes the explosions could account for much of the dust in the early universe. His findings will be published in the June 8 issue of Science Express.
"This discovery is interesting because it is finally showing that supernovae are significant contributors to dust formation, when evidence up to now has been inconclusive," said Sugerman.
Because supernovae fade fairly quickly, scientists need very sensitive telescopes to study them even a few months after the initial explosions. Scientists have suspected that most supernovae do produce dust, but their ability to study this dust production in the past has been limited by technology.
"People have suspected for 40 years that supernovae could be producers of dust, but the technology to confirm this has only recently become available," said Sugerman. "The advantage of using Spitzer is that we can actually see the warm dust as it forms."
"Dust particles in space are the building blocks of comets, planets, and life, yet our knowledge of where this dust was made is still incomplete. These new observations show that supernovae can make a major contribution to enriching the dust content of the universe," said Dr. Michael Barlow of University College London in the United Kingdom.
This research is part of a collaboration called the Survey for Evolution of Emission from Dust in Supernovae (SEEDS), which is led by Barlow.