After sorting through samples of stardust collected by NASA's Stardust probe, astronomers, along with a group of online volunteers, report that they have found seven dust motes that most probably came from outside of our solar system.
These stardust particles, which astronomers believe came from an ancient supernova, would be the first dust samples confirmed as originating in interstellar space.
In 1999, NASA sent its Stardust spacecraft on a mission to fly through dust left by Comet Wild-2. It collected this dust on one side of its body, while its other side collected what astronomers hoped was interstellar dust. Although these samples returned to Earth in 2006, it took scientists, led by the University of Berkeley's Space Sciences Laboratory, along with 30,000 online citizen scientists, to sort through the samples and analyze them.
The search was like finding a needle in a haystack. Most of the particles, each measuring less than a thousandth of a millimeter across, were not what astronomers were looking for. After careful study under a microscope, scientists analyzed the dust grains and identified which pieces of dust actually came from interstellar space. They found seven.
Scientists believe that the dust originates from a supernova that occurred millions of years ago.
"For several years, we have been studying so-called 'pre-solar' grains - particles from other stars that happen to have survived the violent processes in the solar nebula as it was becoming the solar system," says Berkeley physicist Andrew Westphal. "We think that we have just taken the first baby step in understanding the complexity and diversity of individual contemporary interstellar dust particles."
The discovery of the interstellar stardust is important because it gives us a peek into how the solar system formed billions of years ago.
The dust particles themselves are different than previously thought. Each speck of dust not only has its own chemical composition, but are also sized differently. Astronomers believe that each has its own story. Some of the dust particles even have a crystalline snowflake-like structure, suggesting that they came from the disks around stars outside our solar system, but underwent changes as they traveled.
"We seem to be getting our first glimpse of the surprising diversity of interstellar dust particles, which is impossible to explore through astronomical observations alone," says Westphal.
Westphal and his team state that they'll run more tests before definitively confirming these particles as coming from outside our solar system, but they feel confident in their initial analysis.
