Scientists have discovered something quite extraordinary inside a meteorite that landed in Antarctica. A speck of actual stardust was embedded deep within the space rock. We don’t know how long it has been there, but we know that the star that produced it must have been long gone by the time the Solar System formed.
As reported in Nature Astronomy, the team suspects the dust grains, now dubbed LAP-149, to have originated in a nova. This type of stellar events happens when a white dwarf has stolen enough material from a companion to ignite it. This produces an outburst, which forges new elements and launches them into space.
Every planet, moon, asteroid, and comet in the Solar System is made of materials that were once in other stars, but that material has changed over the last 4.5 billion years. That’s why even finding a trace of pristine pre-solar ashes is important. The material survived unchanged interstellar travel and the ages of the Solar System before it was found.
"As actual dust from stars, such presolar grains give us insight into the building blocks from which our solar system formed," lead author Pierre Haenecour, from the University of Arizona, said in a statement. "They also provide us with a direct snapshot of the conditions in a star at the time when this grain was formed."
So how can we tell that this sample is an unchanged mote of dust from another star? Researchers were able to conduct a detailed analysis of the composition of the grain. It consists of graphite containing oxygen-rich silicate inclusion, something not seen in other stellar grains. It also has a phenomenal amount of carbon-13 (13C), a special carbon isotype that makes about 1 percent of all carbon on Earth.
"The carbon isotopic compositions in anything we have ever sampled that came from any planet or body in our solar system varies typically by a factor on the order of 50," explained Haenecour. "The 13C we found in LAP-149 is enriched more than 50,000-fold. These results provide further laboratory evidence that both carbon- and oxygen-rich grains from novae contributed to the building blocks of our solar system."
The dust grain opens a window into the pre-Earth Milky Way but it is unfortunately limited. Given that the sample was so small, the researchers weren’t able to date it. They hope that future samples might be larger.
"If we could date these objects someday, we could get a better idea of what our galaxy looked like in our region and what triggered the formation of the solar system," added co-author Professor Tom Zega,
The meteor that encased the grain is a carbonaceous chondrite and it is believed to be similar in composition to asteroid Bennu, currently being studied by NASA’s OSIRIS-REx mission with the plan of bringing back a sample to Earth in the hope of finding material that has barely changed since the formation of our Solar System. Until then, to find something here on Earth that survived a star going nova, the chaotic birth of the Solar System, being packed into an asteroid, and falling to Earth is incredible.