Ancient dust grains from space are found on Earth – and supply information concerning the life cycle of stars

In space there are clouds that contain gas and dirt emitted by stars. Our solar system emerged 4.6 billion years ago from a Molecular cloudMost of those dust grains were destroyed in the course of the formation of the solar system. However, a really small amount of the grains survived and remained in primitive Meteorites. Your name is presolar grains because they’re older than the solar system. I’m a scientist studying the early solar system and beyond, focusing mainly on presolar grains.

The picture shows such a grain, taken with a scanning electron microscope. This grain is Silicon carbide (SiC). The scale is 1 micrometer or one millionth of a meter (39.37 inches). The grain was taken from the Murchison meteorite which fell in Australia in 1969.

Scientists have studied the physical properties of the grain to find out its origin. Carbon has two stable isotopes, ¹²C and ¹³C, whose weights differ barely from one another. The ratio between these isotopes is nearly unchanged by processes within the solar system comparable to evaporation and condensation. In contrast, Nucleosynthetic processes in stars can result in fluctuations within the ¹²C/¹³C ratio between 1 and over 200,000.

If this grain had formed throughout the solar system, its ¹²C/¹³C ratio could be 89. The ¹²C/¹³C ratio of the grain on this image is about 55.1, confirming its stellar origin. Together with other information concerning the grain, the ratio tells us that this grain formed in a style of star called an asymptotic giant branch starThe star was at the top of its life cycle when it produced and ejected large amounts of dust into space over 4.6 billion years ago.

Scientists have found other varieties of presolar grains in meteorites, including diamond, graphite, Oxide And SilicatesPresolar grains just like the one within the image help researchers understand nucleosynthesis in stars, the blending of various zones in stars and stellar ejections, and the temporal variation of the abundances of elements and their isotopes within the galaxy.