Presolar grains

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Boeing Delta II rocket carrying the Stardust spacecraft waiting for launch. Stardust had a close encounter with the comet Wild 2 in January 2004 and also collected interstellar dust containing pre-solar interstellar grains. Delta II 7426 with Stardust before launch.jpg
Boeing Delta II rocket carrying the Stardust spacecraft waiting for launch. Stardust had a close encounter with the comet Wild 2 in January 2004 and also collected interstellar dust containing pre-solar interstellar grains.

Presolar grains are interstellar solid matter in the form of tiny solid grains that originated at a time before the Sun was formed. Presolar grains formed within outflowing and cooling gases from earlier presolar stars. The study of presolar grains is typically considered part of the field of cosmochemistry and meteoritics.

Contents

The stellar nucleosynthesis that took place within each presolar star gives to each granule an isotopic composition unique to that parent star, which differs from the isotopic composition of the Solar System's matter as well as from the galactic average. These isotopic signatures often fingerprint very specific astrophysical nuclear processes [1] that took place within the parent star or formation event and prove their presolar origin. [2] [3]

Terminology

Presolar grains are individual solid grains which condensed around distant stars or as part of novae, and potentially supernovae outflows, which were accreted in the early solar nebula and remain in relatively unaltered chondritic meteorites. As they were accreted before the formation of the Solar System, they must be presolar. Presolar grains also exist in the interstellar medium. [4] Researchers occasionally use the term stardust to refer to presolar grains, particularly in science communication, though the term is sometimes used interchangeably in the scientific literature.

History

Presolar grains of the Murchison meteorite Murchison-meteorite-stardust.jpg
Presolar grains of the Murchison meteorite

In the 1960s, the noble gases neon [5] and xenon [6] were discovered to have unusual isotopic ratios in primitive meteorites; their origin and the type of matter that contained them was a mystery. These discoveries were made by vaporizing a bulk sample of a meteorite within a mass spectrometer, in order to count the relative abundance of the isotopes of the very small amount of noble gases trapped as inclusions. During the 1970s similar experiments discovered more components of trapped xenon isotopes. [7] Competing speculations about the origins of the xenon isotopic components were advanced, all within the existing paradigm that the variations were created by processes within an initially homogeneous solar gas cloud.

A new theoretical framework for interpretation was advanced during the 1970s when Donald D. Clayton rejected the popular belief among meteoriticists that the Solar System began as a uniform hot gas. [8] Instead he predicted that unusual but predictable isotopic compositions would be found within thermally condensed interstellar grains that had condensed during mass loss from stars of differing types. He argued that such grains exist throughout the interstellar medium. [8] [9] Clayton's first papers using that idea in 1975 pictured an interstellar medium populated with supernova grains that are rich in the radiogenic isotopes of Ne and Xe that had defined the extinct radioactivities. [10] Clayton defined several types of presolar grains likely to be discovered: stardust from red giant stars, sunocons (acronym from SUperNOva CONdensates) from supernovae, nebcons from nebular condensation by accretion of cold cloud gaseous atoms and molecules, and novacons from nova condensation. [8] Despite vigorous and continuous active development of this picture, Clayton's suggestions lay unsupported by others for a decade until such grains were discovered within meteorites.

The first unambiguous consequence of the existence of presolar grains within meteorites came from the laboratory of Edward Anders in Chicago, [11] who found using traditional mass spectrometry that the xenon isotopic abundances contained within an acid-insoluble carbonaceous residue that remained after the meteorite bulk had been dissolved in acids matched almost exactly the predictions for isotopic xenon in red giant dust condensate. [9] It then seemed certain that presolar grains were contained within Anders' acid-insoluble residue. Finding the actual presolar grains and documenting them was a much harder challenge that required locating the grains and showing that their isotopes matched those within the red-giant star. There followed a decade of intense experimental searching in the attempt to isolate individual grains of those xenon carriers. But what was really needed to discover presolar grains was a new type of mass spectrometer that could measure the smaller number of atoms in a single grain. Sputtering ion probes were pursued by several laboratories in the attempt to demonstrate such an instrument. But the contemporary ion probes needed to be technologically much better.

In 1987 diamond grains [12] and silicon carbide grains [13] were found to exist abundantly in those same acid-insoluble residues and also to contain large concentrations of noble gases. Significant isotopic anomalies were in turn measured by improvements in secondary ion mass spectrometry (SIMS) within the structural chemical elements of these grains. [14] Improved SIMS experiments showed that the silicon isotopes within each SiC grain did not have solar isotopic ratios but rather those expected in certain red-giant stars. The finding of presolar is therefore dated 1987. [13] To measure the isotopic abundance ratios of the structural elements (e.g. silicon in an SiC grain) in microscopic presolar grains had required two difficult technological and scientific steps: 1) locating micron-sized presolar grains within the meteorite's overwhelming mass; 2) development of SIMS technology to a sufficiently high level to measure isotopic abundance ratios within micron-sized grains. Ernst Zinner became an important leader in SIMS applications to microscopic grains. [15] [16]

In January 2020, analysis of the Murchison meteorite found in Australia in 1969 revealed that 40 grains of presolar silicon carbide formed 5 to 7 billion years ago, older than Earth's 4.6 billion year-old sun, making the grains the oldest solid material ever discovered on Earth. [17] [18]

In meteorites

Vial of suspended presolar grains from the Orgueil meteorite. Vial of presolar grains in suspension.jpg
Vial of suspended presolar grains from the Orgueil meteorite.

Presolar grains are the solid matter that was contained in the interstellar gas before the Sun formed. The presolar component can be identified in the laboratory by their abnormal isotopic abundances and consists of refractory minerals which survived the collapse of the solar nebula and the subsequent formation of planetesimals. [19]

To meteorite researchers, the term presolar grains has come to mean presolar grains found in meteorites, of which 99% are stardust. Many other types of cosmic dust have not been detected in meteorites. Presolar grains comprise only about 0.1 percent of the total mass of particulate matter found in meteorites. Such grains are isotopically-distinct material found in the fine-grained matrix of meteorites, such as primitive chondrites. [20] Their isotopic differences from the encasing meteorite require that they predate the Solar System. The crystallinity of those clusters ranges from micrometer-sized silicon carbide crystals (up to 1013 atoms), down to that of nanometer-sized diamond (about 1000 atoms), and unlayered graphene crystals of fewer than 100 atoms. The refractory grains achieved their mineral structures by condensing thermally within the slowly cooling expanding gases of supernovae and of red giant stars. [20]

Characterization

Presolar grains are investigated using scanning or transmission electron microscopes (SEM/TEM), and mass spectrometric methods (noble gas mass spectrometry, resonance ionization mass spectrometry (RIMS), secondary ion mass spectrometry (SIMS, NanoSIMS)). Presolar grains that consist of diamonds are only a few nanometers in size and are, therefore, called nanodiamonds. Because of their small size, nanodiamonds are hard to investigate and, although they are among the first presolar grains discovered, relatively little is known about them. The typical sizes of other presolar grains are in the range of micrometers.

Presolar grains consisting of the following minerals have so far been identified:

Information on stellar evolution

The study of presolar grains provides information about nucleosynthesis and stellar evolution. [3] Grains bearing the isotopic signature of "r-process" (rapid neutron capture) and alpha process (alpha capture) types of nucleosynthesis are useful in testing models of supernova explosions. [30]

1% of presolar grains (supernova grains) have very large excesses of calcium-44, a stable isotope of calcium which normally composes only 2% of the calcium abundance. The calcium in some presolar grains is composed primarily of 44Ca, which is presumably the remains of the extinct radionuclide titanium-44, a titanium isotope which is formed in abundance in Type II supernovae such as SN 1987A after rapid capture of four alpha particles by 28Si, after the process of silicon burning normally begins, and prior to the supernova explosion. [31] However, 44Ti has a half-life of only 59 years, and thus it is soon converted entirely to 44Ca. Excesses of the decay products of the longer-lived, but extinct, nuclides calcium-41 (half-life 99,400 years) and aluminium-26 (730,000 years) have also been detected in such grains. The rapid-process isotopic anomalies of these grains include relative excesses of nitrogen-15 and oxygen-18 relative to Solar System abundances, as well as excesses of the neutron-rich stable nuclides 42Ca and 49Ti. [32]

Other presolar grains provide isotopic and physical information on asymptotic giant branch stars (AGB stars), which have manufactured the largest portion of the refractory elements lighter than iron in the galaxy. Because the elements in these particles were made at different times (and places) in the early Milky Way, the set of collected particles further provides insight into galactic evolution prior to the formation of the Solar System. [33]

In addition to providing information on nucleosynthesis of the grain's elements, solid grains provide information on the physico-chemical conditions under which they condensed, and on events subsequent to their formation. [33] For example, consider red giants — which produce much of the carbon in our galaxy. Their atmospheres are cool enough for condensation processes to take place, resulting in the precipitation of solid particles (i.e., multiple atom agglomerations of elements such as carbon) in their atmosphere. This is unlike the atmosphere of the Sun, which is too hot to allow atoms to build up into more complex molecules. These solid fragments of matter are then injected into the interstellar medium by radiation pressure. Hence, particles bearing the signature of stellar nucleosynthesis provide information on (i) condensation processes in red giant atmospheres, (ii) radiation and heating processes in the interstellar medium, and (iii) the types of particles that carried the elements of which we are made, across the galaxy to the Solar System. [34]

See also

Related Research Articles

<span class="mw-page-title-main">Nucleosynthesis</span> Process that creates new atomic nuclei from pre-existing nucleons, primarily protons and neutrons

Nucleosynthesis is the process that creates new atomic nuclei from pre-existing nucleons and nuclei. According to current theories, the first nuclei were formed a few minutes after the Big Bang, through nuclear reactions in a process called Big Bang nucleosynthesis. After about 20 minutes, the universe had expanded and cooled to a point at which these high-energy collisions among nucleons ended, so only the fastest and simplest reactions occurred, leaving our universe containing hydrogen and helium. The rest is traces of other elements such as lithium and the hydrogen isotope deuterium. Nucleosynthesis in stars and their explosions later produced the variety of elements and isotopes that we have today, in a process called cosmic chemical evolution. The amounts of total mass in elements heavier than hydrogen and helium remains small, so that the universe still has approximately the same composition.

<span class="mw-page-title-main">Natural abundance</span> Relative proportion of an isotope as found in nature

In physics, natural abundance (NA) refers to the abundance of isotopes of a chemical element as naturally found on a planet. The relative atomic mass of these isotopes is the atomic weight listed for the element in the periodic table. The abundance of an isotope varies from planet to planet, and even from place to place on the Earth, but remains relatively constant in time.

<span class="mw-page-title-main">Cosmochemistry</span> Study of the chemical composition of matter in the universe

Cosmochemistry or chemical cosmology is the study of the chemical composition of matter in the universe and the processes that led to those compositions. This is done primarily through the study of the chemical composition of meteorites and other physical samples. Given that the asteroid parent bodies of meteorites were some of the first solid material to condense from the early solar nebula, cosmochemists are generally, but not exclusively, concerned with the objects contained within the Solar System.

The slow neutron-capture process, or s-process, is a series of reactions in nuclear astrophysics that occur in stars, particularly asymptotic giant branch stars. The s-process is responsible for the creation (nucleosynthesis) of approximately half the atomic nuclei heavier than iron.

<span class="mw-page-title-main">Carbon star</span> Star whose atmosphere contains more carbon than oxygen

A carbon star is typically an asymptotic giant branch star, a luminous red giant, whose atmosphere contains more carbon than oxygen. The two elements combine in the upper layers of the star, forming carbon monoxide, which consumes most of the oxygen in the atmosphere, leaving carbon atoms free to form other carbon compounds, giving the star a "sooty" atmosphere and a strikingly ruby red appearance. There are also some dwarf and supergiant carbon stars, with the more common giant stars sometimes being called classical carbon stars to distinguish them.

<span class="mw-page-title-main">Asymptotic giant branch</span> Stars powered by fusion of hydrogen and helium in shell with an inactive core of carbon and oxygen

The asymptotic giant branch (AGB) is a region of the Hertzsprung–Russell diagram populated by evolved cool luminous stars. This is a period of stellar evolution undertaken by all low- to intermediate-mass stars (about 0.5 to 8 solar masses) late in their lives.

<span class="mw-page-title-main">Murchison meteorite</span> Meteorite found in Victoria, Australia

The Murchison meteorite is a meteorite that fell in Australia in 1969 near Murchison, Victoria. It belongs to the carbonaceous chondrite class, a group of meteorites rich in organic compounds. Due to its mass and the fact that it was an observed fall, the Murchison meteorite is one of the most studied of all meteorites.

<span class="mw-page-title-main">Cosmic dust</span> Dust floating in space

Cosmic dust – also called extraterrestrial dust, space dust, or star dust – is dust that occurs in outer space or has fallen onto Earth. Most cosmic dust particles measure between a few molecules and 0.1 mm (100 μm), such as micrometeoroids and meteoroids. Cosmic dust can be further distinguished by its astronomical location: intergalactic dust, interstellar dust, interplanetary dust, and circumplanetary dust. There are several methods to obtain space dust measurement.

Supernova nucleosynthesis is the nucleosynthesis of chemical elements in supernova explosions.

<span class="mw-page-title-main">Nuclear astrophysics</span> Field of nuclear physics and astrophysics

Nuclear astrophysics is an interdisciplinary part of both nuclear physics and astrophysics, involving close collaboration among researchers in various subfields of each of these fields. This includes, notably, nuclear reactions and their rates as they occur in cosmic environments, and modeling of astrophysical objects where these nuclear reactions may occur, but also considerations of cosmic evolution of isotopic and elemental composition (often called chemical evolution). Constraints from observations involve multiple messengers, all across the electromagnetic spectrum (nuclear gamma-rays, X-rays, optical, and radio/sub-mm astronomy), as well as isotopic measurements of solar-system materials such as meteorites and their stardust inclusions, cosmic rays, material deposits on Earth and Moon). Nuclear physics experiments address stability (i.e., lifetimes and masses) for atomic nuclei well beyond the regime of stable nuclides into the realm of radioactive/unstable nuclei, almost to the limits of bound nuclei (the drip lines), and under high density (up to neutron star matter) and high temperature (plasma temperatures up to 109 K). Theories and simulations are essential parts herein, as cosmic nuclear reaction environments cannot be realized, but at best partially approximated by experiments. In general terms, nuclear astrophysics aims to understand the origin of the chemical elements and isotopes, and the role of nuclear energy generation, in cosmic sources such as stars, supernovae, novae, and violent binary-star interactions.

<span class="mw-page-title-main">Extraterrestrial materials</span> Natural objects that originated in outer space

Extraterrestrial material refers to natural objects now on Earth that originated in outer space. Such materials include cosmic dust and meteorites, as well as samples brought to Earth by sample return missions from the Moon, asteroids and comets, as well as solar wind particles.

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Andrew M. Davis is an American meteoriticist and professor of astronomy and geoscience at the University of Chicago. He is the son of American chemist and physicist Raymond Davis Jr., a Nobel Prize in Physics laureate. His main field of study is the origin of the elements by stellar nucleosynthesis. He currently is the head of a project to build a new instrument called the ion nanoprobe, which will allow isotopic and chemical analysis at finer scales than any contemporary instrument. He is also studying the cometary dust and contemporary interstellar dust returned to Earth by the Stardust spacecraft in 2006. In 2018, he was made Fellow of the American Association for the Advancement of Science.

<span class="mw-page-title-main">Donald D. Clayton</span> American astrophysicist (1935–2024)

Donald Delbert Clayton was an American astrophysicist whose most visible achievement was the prediction from nucleosynthesis theory that supernovae are intensely radioactive. That earned Clayton the NASA Exceptional Scientific Achievement Medal (1992) for “theoretical astrophysics related to the formation of (chemical) elements in the explosions of stars and to the observable products of these explosions”. Supernovae thereafter became the most important stellar events in astronomy owing to their profoundly radioactive nature. Not only did Clayton discover radioactive nucleosynthesis during explosive silicon burning in stars but he also predicted a new type of astronomy based on it, namely the associated gamma-ray line radiation emitted by matter ejected from supernovae. That paper was selected as one of the fifty most influential papers in astronomy during the twentieth century for the Centennial Volume of the American Astronomical Society. He gathered support from influential astronomers and physicists for a new NASA budget item for a gamma-ray-observatory satellite, achieving successful funding for Compton Gamma Ray Observatory. With his focus on radioactive supernova gas Clayton discovered a new chemical pathway causing carbon dust to condense there by a process that is activated by the radioactivity.

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Edward Anders is a Latvian-born American chemist and emeritus professor of chemistry at the University of Chicago. His major areas of research have included the origin and ages of meteorites, the existence of presolar grains in meteorites, the solar-system abundance of chemical elements, and mass extinctions in earth history. In the 1970s, he was one of the 142 principal investigators who studied lunar samples brought back to Earth by the Apollo program. After retiring from scientific research in 1991, he became a prominent researcher, speaker and writer on issues related to the Holocaust in Latvia.

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<span class="mw-page-title-main">Dust astronomy</span> Branch of astronomy

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References

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  5. ↑ Black, D.C.; Pepin, R.O. (1969). "Trapped neon in meteorites — II". Earth and Planetary Science Letters. 6 (5): 395–405. Bibcode:1969E&PSL...6..395B. doi:10.1016/0012-821X(69)90190-3.
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  7. ↑ Xenon has nine stable isotopes that differ in mass because they have different numbers of neutrons in their atomic nuclei. The mass spectrometer records the number of detected xenon atoms at atomic weights A=124, 126, 128, 129, 130, 131, 132, 134, and 136. By measuring these at several temperature steps in the heating of the sample it was demonstrated that trapped xenon had differing components within its total. It was speculated that one such component was xenon created when an unknown superheavy nucleus that was assumed to exist in the early Solar System underwent fission.
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  13. 1 2 Bernatowicz, Thomas; Fraundorf, Gail; Ming, Tang; Anders, Edward; Wopenka, Brigitte; Zinner, Ernst; Fraundorf, Phil (1987). "Evidence for interstellar SiC in the Murray carbonaceous meteorite". Nature. 330 (6150): 728–730. Bibcode:1987Natur.330..728B. doi:10.1038/330728a0. S2CID   4361807.
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  16. ↑ Clayton, Donald (2016). "Ernst K. Zinner". Physics Today. 69 (2): 61–62. Bibcode:2016PhT....69b..61C. doi: 10.1063/PT.3.3088 . Zinner died in 2015 at age 78. His obituary in February 2016 Physics Today by Donald Clayton tells more of Zinner's relationship to SIMS discoveries.
  17. ↑ Weisberger, Mindy (13 January 2020). "7 Billion-Year-Old Stardust Is Oldest Material Found on Earth - Some of these ancient grains are billions of years older than our sun". Live Science . Retrieved 13 January 2020.
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  23. ↑ Bernatowicz, Thomas J.; Cowsik, Ramanath; Gibbons, Patrick C.; Lodders, Katharina; Fegley, Bruce; Amari, Sachiko; Lewis, Roy S. (1996). "Constraints on Stellar Grain Formation from Presolar Graphite in the Murchison Meteorite". The Astrophysical Journal. 472 (2): 760–782. Bibcode:1996ApJ...472..760B. doi:10.1086/178105. S2CID   55542326.
  24. ↑ Fraundorf, P.; Wackenhut, M. (2002). "The Core Structure of Presolar Graphite Onions". The Astrophysical Journal. 578 (2): L153–L156. arXiv: astro-ph/0110585 . Bibcode:2002ApJ...578L.153F. doi:10.1086/344633. S2CID   15066112.
  25. ↑ Daulton, T.; Bernatowicz, T. J.; Lewis, R. S.; Messenger, S.; Stadermann, F. J.; Amari, S. (June 2002). "Polytype distribution in circumstellar silicon carbide". Science. 296 (5574): 1852–1855. Bibcode:2002Sci...296.1852D. doi:10.1126/science.1071136. PMID   12052956. S2CID   208322.
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  27. ↑ Hutcheon, I. D.; Huss, G. R.; Fahey, A. J.; Wasserberg, G. J. (1994). "Extreme Mg-26 and O-17 enrichments in an Orgueil corundum: Identification of a presolar oxide grain" (PDF). Astrophysical Journal Letters. 425 (2): L97–L100. Bibcode:1994ApJ...425L..97H. doi:10.1086/187319.
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  29. ↑ Ireland, Trevor R. (1990). "Presolar isotopic and chemical signatures in hibonite-bearing refractory inclusions from the Murchison carbonaceous chondrite". Geochimica et Cosmochimica Acta. 54 (11): 3219–3237. Bibcode:1990GeCoA..54.3219I. doi:10.1016/0016-7037(90)90136-9.
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  32. ↑ McSween, Harry; Gary R. Huss (2010). Cosmochemistry (1st ed.). Cambridge University Press. p. 139. ISBN   978-0-521-87862-3.
  33. 1 2 Bennett, Jay (January 13, 2020). "Meteorite Grains Are the Oldest Known Solid Material on Earth". Smithsonian Magazine. Retrieved 14 January 2020.
  34. ↑ Starr, Michelle (January 13, 2020). "The Oldest Known Material on Earth Is Officially Older Than The Solar System". sciencealert.com. Retrieved 14 January 2020.
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