Atomic and Molecular astrophysics
Encyclopedia
Atomic physics
Atomic physics is the field of physics that studies atoms as an isolated system of electrons and an atomic nucleus. It is primarily concerned with the arrangement of electrons around the nucleus and...
calculations that will be useful to astronomers and using atomic data to interpret astronomical observations. Atomic physics plays a key role in astrophysics
Astrophysics
Astrophysics is the branch of astronomy that deals with the physics of the universe, including the physical properties of celestial objects, as well as their interactions and behavior...
as astronomers' only information about a particular object comes through the light that it emits, and this light arises through atomic transitions.
Molecular astrophysics, developed into a rigorous field of investigation by theoretical astrochemist
Astrochemistry
Astrochemistry is the study of the abundance and reactions of chemical elements and molecules in the universe, and their interaction with radiation. The discipline is an overlap of astronomy and chemistry. The word "astrochemistry" may be applied to both the Solar System and the interstellar medium...
Alexander Dalgarno
Alexander Dalgarno
Alexander Dalgarno is a British physicist who is Phillips Professor of Astronomy at Harvard University.-Biography:He was educated in mathematics and atomic physics at University College, London. He was an academic at the Queen's University of Belfast and moved to Harvard in 1967...
beginning in 1967, concerns the study of emission
Emission spectrum
The emission spectrum of a chemical element or chemical compound is the spectrum of frequencies of electromagnetic radiation emitted by the element's atoms or the compound's molecules when they are returned to a lower energy state....
from molecule
Molecule
A molecule is an electrically neutral group of at least two atoms held together by covalent chemical bonds. Molecules are distinguished from ions by their electrical charge...
s in space. There are 110 currently known interstellar molecules. These molecules have large numbers of observable transitions. Lines
Spectral line
A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from a deficiency or excess of photons in a narrow frequency range, compared with the nearby frequencies.- Types of line spectra :...
may also be observed in absorption
Absorption (electromagnetic radiation)
In physics, absorption of electromagnetic radiation is the way by which the energy of a photon is taken up by matter, typically the electrons of an atom. Thus, the electromagnetic energy is transformed to other forms of energy for example, to heat. The absorption of light during wave propagation is...
--for example the highly redshift
Redshift
In physics , redshift happens when light seen coming from an object is proportionally increased in wavelength, or shifted to the red end of the spectrum...
ed lines seen against the gravitationally lensed quasar PKS1830-211. High energy radiation, such as ultraviolet light, can break the molecular bonds which hold atoms in molecules. In general then, molecules are found in cool astrophysical environments. The most massive objects in our Galaxy are giant clouds of molecules and dust, creatively named Giant Molecular Cloud
Molecular cloud
A molecular cloud, sometimes called a stellar nursery if star formation is occurring within, is a type of interstellar cloud whose density and size permits the formation of molecules, most commonly molecular hydrogen ....
s. In these clouds, and smaller versions of them, stars and planets are formed. One of the primary fields of study of molecular astrophysics then, is star and planet formation. Molecules may be found in many environments, however, from stellar atmospheres to those of planetary satellites. Most of these locations are cool, and molecular emission is most easily studied via photon
Photon
In physics, a photon is an elementary particle, the quantum of the electromagnetic interaction and the basic unit of light and all other forms of electromagnetic radiation. It is also the force carrier for the electromagnetic force...
s emitted when the molecules make transitions between low rotational energy states. One molecule, composed of the abundant carbon and oxygen atoms, and very stable against dissociation into atoms, is carbon monoxide, CO. The wavelength of the photon emitted when the CO molecule falls from its lowest excited state to its zero energy, or ground, state is 2.6 mm, or 115 gigahertz (billion hertz). This frequency is a thousand times higher than typical FM radio frequencies. At these high frequencies, molecules in the Earth's atmosphere can block transmissions from space, and telescopes must be located in dry (water is an important atmospheric blocker), high sites. Radio telescopes must have very accurate surfaces to produce high fidelity images.
See also
- Alexander DalgarnoAlexander DalgarnoAlexander Dalgarno is a British physicist who is Phillips Professor of Astronomy at Harvard University.-Biography:He was educated in mathematics and atomic physics at University College, London. He was an academic at the Queen's University of Belfast and moved to Harvard in 1967...
(physicist) - AstrophysicsAstrophysicsAstrophysics is the branch of astronomy that deals with the physics of the universe, including the physical properties of celestial objects, as well as their interactions and behavior...
- CosmochemistryCosmochemistryCosmochemistry 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...
- Atomic, molecular, and optical physicsAtomic, molecular, and optical physicsAtomic, molecular, and optical physics is the study of matter-matter and light-matter interactions on the scale of single atoms or structures containing a few atoms. The three areas are grouped together because of their interrelationships, the similarity of methods used, and the commonality of the...
- SpectroscopySpectroscopySpectroscopy is the study of the interaction between matter and radiated energy. Historically, spectroscopy originated through the study of visible light dispersed according to its wavelength, e.g., by a prism. Later the concept was expanded greatly to comprise any interaction with radiative...
- Molecular modellingMolecular modellingMolecular modelling encompasses all theoretical methods and computational techniques used to model or mimic the behaviour of molecules. The techniques are used in the fields of computational chemistry, computational biology and materials science for studying molecular systems ranging from small...