This ancient stardust is the oldest ever to be examined in a lab

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Ancient
stardust extracted from a meteorite contains specks that are up to about 3 billion years older
than the solar system
,
making them the oldest solids ever dated in a lab, researchers report.

Unlike
most of the other stardust that went into building our solar system, these
microscopic grains have remained intact since they were shed by aging stars
billions of years ago. The exotic makeup of the silicon carbide grains, from a meteorite that landed in Australia more than 50 years ago, tipped
scientists off that the minerals were older than the solar system (SN:
11/22/19
).

Measuring
levels of neon-21 in dozens of grains revealed how much older. Neon-21 is a
form of the chemical element that builds up when silicon carbide is bombarded
with high-energy particles called galactic cosmic rays in interstellar space.
The higher a grain’s neon-21 concentration, the longer it must have drifted in
space before being embedded in a hunk of space rock during the solar system’s
formation 4.6 billion years ago.

The
oldest grains are estimated to be around 7 billion years old, some 2 billion to
3 billion years older than the solar system, researchers report online January
13 in the Proceedings of the National Academy of Sciences. Before this
analysis, the oldest stardust dated in a lab was estimated to predate the solar
system by about 1 billion years.

Such
old stardust grains can serve as time capsules that provide clues about
goings-on in the Milky Way from before the sun’s birth. For instance, in
addition to the few extremely old grains, the new study uncovered a surprising
number of grains that formed less than 300 million years before the solar
system. That glut of relatively younger dust probably came from an especially
high number of stars reaching the late, dust-releasing stage of their lives
around that time. The finding suggests that there was a “baby boom of star
formation” in the galaxy a couple of billion years before that, says coauthor Philipp
Heck, a cosmochemist at the Field Museum of Natural History in Chicago and the
University of Chicago.  

“Using
these microscopic dust grains to tell us something about large-scale events in
the presolar history of our galaxy is pretty cool,” says Larry Nittler, a
cosmochemist at the Carnegie Institution for Science in Washington, D.C., not
involved in the work.

Finding
and dating more extremely old dust grains lodged in meteorites may give scientists
a more complete picture of the Milky Way’s history even further back in time.

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