Molecules in stars

Stellar molecules are molecules that exist or form in or around stars. Such formations can take place when the temperature is low enough for molecules to form, otherwise the stellar matter is restricted to atoms (chemical elements) in the forms of gas or – at very high temperatures – plasma.

Background

Matter is made up by atoms (formed by protons and other subatomic particles). When the environment is right, atoms can join together and form molecules, which give rise to most materials studied in materials science. But certain environments, such as high temperatures, don't allow atoms to form molecules. Stars have very high temperatures, primarily in their interior, and therefore there are few molecules formed in stars. For this reason, a chemist (who studies atoms and molecules) would not have much to study in a star, so stars are better explained by physicists. However, low abundance of molecules in stars isn't equated with no molecules at all. Published scientific papers from 1990s show evidence of existence of stellar molecules.^[1]

Evidence and research

Although the Sun is a star, its photosphere has a low temperature of 6,000 kelvin and therefore molecules can form. According to Roald Hoffmann, molecules are abundant in stellar ejecta.^[1] In 1995, L. Wallace and others published an article in Science showing evidence of water on the Sun, and a 2013 paper in Astrophysical Journal Letters by S. Xu, M. Jura, D. Koster, B. Klein, and B. Zuckerman gives evidence of H₂ in white dwarf stellar atmospheres.^[1][2]

Cooler stars include absorption band spectra that are characteristic of molecules. Similar absorption bands are found in sun spots which are cooler areas on the Sun. Molecules found in the Sun include MgH, CaH, FeH, CrH, NaH, OH, VO, and TiO.

In March 2015, NASA scientists reported that, for the first time, the building blocks of DNA and RNA, the complex organic compounds of life, including uracil, cytosine and thymine, have been formed in the laboratory under outer space conditions, using starting chemicals, such as pyrimidine, found in meteorites. Pyrimidine, like polycyclic aromatic hydrocarbons (PAHs), the most carbon-rich chemical found in the Universe, may have been formed in red giants or in interstellar dust and gas clouds, according to the scientists.^[3]

References

1. "Stellar Molecules » American Scientist". American Scientist. doi:10.1511/2013.105.403. Retrieved 24 October 2013.
2. Xu, S.; Jura, M.; Koester, D.; Klein, B.; Zuckerman, B. (2013). "DISCOVERY OF MOLECULAR HYDROGEN IN WHITE DWARF ATMOSPHERES". The Astrophysical Journal. 766 (2): L18. arXiv:1302.6619. Bibcode:2013ApJ...766L..18X. doi:10.1088/2041-8205/766/2/L18. ISSN 2041-8205.
3. Marlaire, Ruth (3 March 2015). "NASA Ames Reproduces the Building Blocks of Life in Laboratory". NASA. Retrieved 5 March 2015.