Astrochemistry
Astrochemistry, representing an overlap of the disciplines of astronomy and chemistry, is the study of chemicals found in outer space, including their identity, formation, interactions, and destruction. More specifically, it involves studies of chemicals in molecular gas clouds present in the interstellar medium[1] beyond the Solar System. The study of chemicals within the Solar System is usually called cosmochemistry.
Detection of chemicals
Methods of detection
For studies in astrochemistry, scientists use telescopes and spectrometers to measure various properties of bodies in space, such as their temperature and composition. Various characteristics of molecules are revealed by their spectra. Thus, by using spectroscopic analysis, researchers can determine the types of molecules in astronomical bodies, such as a star or interstellar cloud.[2]
Limits of detection
However, there are limitations on measurements due to electromagnetic interference and, more problematic, the chemical properties of some molecules. For example, the most common molecule (H2, hydrogen gas), does not have a dipole moment, so it is not detected by radio telescopes. Much easier to detect with radio waves, due to its strong electric dipole moment, is CO (carbon monoxide).
Molecules detected
At one time, the space between stars was thought to empty. Thus when radioastronomy was developed in the 1950s and 60s, astronomers were surprised to discover an abundance of molecular hydrogen in the interstellar medium. Since then, more than 140 types of chemicals (including radicals and ions) have been reported so far. They include water, ammonia, carbon monoxide, and various alcohols, acids, aldehydes, and ketones.
Some scientists have claimed the detection of interstellar glycine,[3] the simplest amino acid, but this claim has stirred considerable controversy.[4] Research is progressing on the way interstellar and circumstellar molecules form and interact, and this research could have a profound impact on our understanding of mechanisms involved in the origin of life on Earth.
The sparseness of matter in interstellar and interplanetary space results in some unusual chemistry, because certain ("symmetry-forbidden") reactions cannot occur except on the longest of timescales. For this reason, molecules and molecular ions that are unstable on Earth can be highly abundant in space, for example, the protonated molecular hydrogen ion (H3+).
Nuclear reactions
Astrochemistry overlaps strongly with astrophysics and nuclear physics in characterizing the nuclear reactions that occur in stars, the consequences for stellar evolution, as well as stellar 'generations'. Indeed, the nuclear reactions in stars produce every naturally occurring chemical element. As the stellar 'generations' advance, the mass of the newly formed elements increases. A first-generation star uses elemental hydrogen (H) as a fuel source and produces helium (He). Hydrogen is the most abundant element, and it is the basic building block for all other elements as its nucleus has only one proton.
Gravitational pull toward the center of a star creates massive amounts of heat and pressure, which cause nuclear fusion. Through the process of merging nuclear masses, heavier elements are formed. Lithium, carbon, nitrogen, and oxygen are examples of elements that are formed in stellar fusion. After many stellar generations, very heavy elements are formed, such as iron and lead.
See also
- Astronomy
- Astrophysics
- Interstellar medium
- Molecular astrophysics
- Molecular cloud
- Spectroscopy
Notes
- ↑ The interstellar medium is the matter that exists between stars within a galaxy.
- ↑ An interstellar cloud is a denser-than-average region of the interstellar medium.
- ↑ Kuan YJ, Charnley SB, Huang HC, et al. (2003). Interstellar glycine. ApJ 593 (2): 848-867.
- ↑ Snyder LE, Lovas FJ, Hollis JM, et al. (2005). A rigorous attempt to verify interstellar glycine. ApJ 619 (2): 914-930.
ReferencesISBN links support NWE through referral fees
- International Astronomical Union, Dariusz C. Lis, Geoffrey A. Blake, and Eric Herbst. 2006. Astrochemistry: Recent Successes and Current Challenges : Proceedings of the 231st Symposium of the International Astronomical Union Held in Pacific Grove, California, USA, August 29 - September 2, 2005. IAU symposium and colloquium proceedings series. Cambridge, UK: Cambridge University Press. ISBN 978-0521852029.
- Pirronello, Valerio, Jacek Krelowski, and Giulio Manicò, eds. 2003. Solid State Astrochemistry. NATO Science Series, v. 120. Dordrecht: Kluwer Academic Publishers. ISBN 978-1402015595.
- Shaw, Andrew M. 2006. Astrochemistry: From Astronomy to Astrobiology. Chichester, England: John Wiley & Sons. ISBN 978-0470091371.
- Singh, P.D., ed. 1997. Astrochemistry of Cosmic Phenomena. International Astronomical Union Symposia. Berlin: Springer. ISBN 0792318250.
External links
- The Astrochemistry Lab at NASA Ames Research Center. Retrieved May 29, 2008.
- What Is Astrochemistry? Retrieved May 29, 2008.
- astrochemistry.net. Retrieved May 29, 2008.
- Astrochemistry Research. Retrieved May 29, 2008.
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