Science & Technology

Fossils of pristine meteorite stars refer to ancient stars that died before the formation of the Sun.


Electron micrograph of micron-sized silicon carbide, SiC, and stardust particles (bottom right) extracted from a primitive meteorite. Stardust grains have a surface coated with meteorite organic matter (dark gunk on the left side of the grain). Such particles were formed over 4.6 billion years ago in the cooling air lost from the surface of low-mass carbon-rich stars near the end of their lifespan. This (upper left) is represented by the Hubble Space Telescope image of the asymptotic giant branch. U Camello Pardalis. Laboratory analysis of such small dust particles provides unique information about the nuclear reactions of low-mass stars and their evolution. (1 mm is one millionth of a meter.) Credits: NASA, Nan Liu, Andrew Davis

Some pristine meteorites contain records of the original components of the solar system, including particles formed by ancient stars that died before the formation of the Sun. One of the biggest challenges in studying these presolar particles is determining the type of star from which each particle is derived.

Nan Liu, assistant professor of physics in arts and sciences at Washington University in St. Louis, is the first author of a new study in the Astrophysical Journal Letters that analyzes different sets of pre-solar particles with the aim of achieving true stellar origin. is.

Liu and her team used a state-of-the-art mass spectrometer called NanoSIMS to measure isotopes of a range of elements in presolar silicon carbide (SiC) particles, including N and Mg-Al isotopes. ..By improving the analysis protocol and leveraging a new generation plasma As an ion source, scientists have been able to visualize samples with better spatial resolution than previously achieved in previous studies.

SiC grain Nano SIMS image

Nano SIMS image of SiC particles. The upper panel shows an image taken at a spatial resolution of about 1 μm, which is typical of previous analyzes. The lower panel shows an ion image of the same particle taken at 100 nm spatial resolution. This is the resolution achieved in this study.Credit: Image courtesy of Nan Liu

“Presolar particles have been embedded in meteorites for 4.6 billion years, and their surfaces may be covered with solar material,” Liu said. “Thanks to the improved spatial resolution, our team confirmed the Al contamination on the surface of the particle and included only the signal from the core of the particle during data reduction to characterize the true star. I was able to get it. “

Scientists used an ion beam to sputter particles for extended periods of time, exposing clean internal particle surfaces for isotope analysis. Researchers have found that the N isotope ratio of the same particle increases significantly after being exposed to prolonged ion sputtering.

It is rarely possible to measure the isotope ratio of a star, with the two exceptions of the C and N isotopes. The new C and N isotope data for presolar particles reported in this study link particles directly to different types of carbon stars, based on the observed isotope ratios of these stars.

“The new isotope data from this study is exciting for stellar physicists and nuclear astrophysicists like me,” said Maurizio Busso, co-author of a study based at the University of Perugia in Italy. I am. “Certainly, the” strange “N isotope ratio of presolar SiC particles has been a noteworthy source of concern over the last two decades. The new data explains the difference between what was originally present in presolar stardust particles and what was later attached, allowing the community to solve long-standing puzzles. “

This study also includes an important study of the radioisotope aluminum-26 (26Al), an important heat source during the evolution of young planets in the early solar system and other exoplanets.Scientists have speculated on the mass initial existence 26Al of all measured particles, as predicted by the current model.How much the study has decided 26Al was produced by the “parent star” of the particles they measured. Liu and her collaborators 26Al is at least twice as high as the particle data.

Data model offsets are likely to indicate the uncertainty of the associated nuclear reaction rates and will motivate nuclear physicists to pursue better measurements of these reaction rates in the future.

The team’s results associate some of the presolar particles in this collection with lesser-known carbon stars with unique chemical compositions.

Particle isotope data show the H-combustion process that occurs on such carbon stars at higher than expected temperatures. This information helps astrophysicists build stellar models to better understand the evolution of these stellar objects.

“As we learn more about the sources of dust, we can gain additional knowledge about the history of the universe and how the various stellar objects in it evolve,” says Liu. I did.

See: “New Multi-Elemental Isotope Compositions of Presolar SiC Particles: Their Impact on Stellar Origins”, Nan Liu, Jens Barosch, Larry R. Nittler, Conel M. O’D.Alexander, Jean Fawan, Sergio Cristallo, Mauriziobusso, Sara Palmerini, October 12, 2021 Astrophysical Journal Letter..
DOI: 10.3847 / 2041-8213 / ac260b

Nan Liu, Baroche Jens, Larry R. Nittler, Connell M. Odd Alexander, Janfawan, Sergio Cristallo, Mauriziobusso, Sara Palmerini (2021). New multi-element isotopic compositions of presolar SiC particles: their impact on stellar origin. The Astrophysical Journal Letter is being printed.

Fossils of pristine meteorite stars refer to ancient stars that died before the formation of the Sun. Fossils of pristine meteorite stars refer to ancient stars that died before the formation of the Sun.

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