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Encyclopedia > Astronomical spectroscopy
High resolution spectrum of the Sun showing thousands of elemental absorption lines (fraunhofer lines).
High resolution spectrum of the Sun showing thousands of elemental absorption lines (fraunhofer lines).

Astronomical spectroscopy is the technique of spectroscopy used in astronomy. As spectroscopy is described in its own article, this article focuses on its use in astronomy. The object of study is the spectrum of electromagnetic radiation, including visible light, which radiates from stars and other celestial objects. Spectroscopy can be used to derive many properties of distant stars and galaxies, such as their chemical composition and also their motion, via the Doppler shift. Image File history File links Download high resolution version (8192x5464, 2848 KB)A high resolution version of the spectrum of the Sun, this image was created from a digital atlas observed with the Fourier Transform Spectrometer at the McMath-Pierce Solar Facility at Kitt Peak National Observatory, near Tucson, Arizona... Image File history File links Download high resolution version (8192x5464, 2848 KB)A high resolution version of the spectrum of the Sun, this image was created from a digital atlas observed with the Fourier Transform Spectrometer at the McMath-Pierce Solar Facility at Kitt Peak National Observatory, near Tucson, Arizona... Solar Fraunhofer lines In physics and optics, the Fraunhofer lines are a set of spectral lines named for the German physicist Joseph von Fraunhofer (1787--1826). ... Extremely high resolution spectrum of the Sun showing thousands of elemental absorption lines (fraunhofer lines) Spectroscopy is the study of spectra, that is, the dependence of physical quantities on frequency. ... Radio telescopes are among many different tools used by astronomers Astronomy (Greek: αστρονομία = άστρον + νόμος, astronomia = astron + nomos, literally, law of the stars) is the science of celestial objects and phenomena that originate outside the Earths atmosphere, such as stars, planets, comets, auroras, galaxies, and the cosmic background radiation. ... Legend: γ = Gamma rays HX = Hard X-rays SX = Soft X-Rays EUV = Extreme ultraviolet NUV = Near ultraviolet Visible light NIR = Near infrared MIR = Moderate infrared FIR = Far infrared Radio waves: EHF = Extremely high frequency (Microwaves) SHF = Super high frequency (Microwaves) UHF = Ultrahigh frequency VHF = Very high frequency HF = High frequency... Electromagnetic radiation can be conceptualized as a self propagating transverse oscillating wave of electric and magnetic fields. ... Radiant energy is the energy of electromagnetic waves. ... The Pleiades star cluster A star is a massive body of plasma in outer space that is currently producing or has produced energy through nuclear fusion. ... The Doppler effect is the apparent change in frequency or wavelength of a wave that is perceived by an observer moving relative to the source of the waves. ...

Contents


Stars

Astronomical spectroscopy began with Isaac Newton's initial observations of the light of the Sun, dispersed by a prism. He saw a rainbow of colour, and may even have seen absorption lines. These dark bands which appear throughout the solar spectrum were first described in detail by Joseph von Fraunhofer. Most stellar spectra share these two dominant features of the Sun's spectrum: emission at all wavelengths across the optical spectrum (the continuum) with many discrete absorption lines superimposed on top. Sir Isaac Newton, PRS, (4 January 1643 – 31 March 1727) [OS: 25 December 1642 – 20 March 1727] was an English mathematician, physicist, astronomer, alchemist, chemist, inventor, and natural philosopher who is generally regarded as one of the most influential scientists and mathematicians in history. ... The Sun is the star at the center of Earths solar system. ... If a shaft of light entering a prism is sufficiently small such that the coloured edges meet, a spectrum results In optics, a prism is a device used to refract light, reflect it or break it up (to disperse it) into its constituent spectral colours (colours of the rainbow). ... A complete half-circle rainbow at Lake Zurich. ... A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from an excess or deficiency of photons in a narrow frequency range, compared with the nearby frequencies. ... Joseph von Fraunhofer Joseph von Fraunhofer (March 6, 1787 – June 7, 1826) was a German physicist. ... Look up continuum in Wiktionary, the free dictionary. ... A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from an excess or deficiency of photons in a narrow frequency range, compared with the nearby frequencies. ...


Fraunhofer's original (1817) designations of absorption lines in the solar spectrum

Letter Wavelength (nm) Chemical origin
A
759,37
atmospheric O2
B
686,72
atmospheric O2
C
656,28
hydrogen alpha
D1
589,59
neutral sodium
D2
589,00
neutral sodium
E
526,96
neutral iron
F
486,13
hydrogen beta
G
431,42
CH molecule
H
396,85
ionized calcium
K
393,37
ionized calcium


Fraunhofer and Angelo Secchi were among the pioneers of spectroscopy of the Sun and other stars. Secchi is particularly noted for classifying stars into spectral types, based on the number and strength of the absorption lines in their spectra. Later the origin of the spectral types was found to be related to the temperature of the surface of the star: particular absorption lines can be observed only for a certain range of temperatures; because only in that range are the involved atomic energy levels populated. Look up letter in Wiktionary, the free dictionary. ... The wavelength is the distance between repeating units of a wave pattern. ... The metre, or meter (symbol: m) is the SI base unit of length. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless Atomic mass 15. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless Atomic mass 15. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... General Name, Symbol, Number sodium, Na, 11 Chemical series alkali metals Group, Period, Block 1, 3, s Appearance silvery white Atomic mass 22. ... General Name, Symbol, Number sodium, Na, 11 Chemical series alkali metals Group, Period, Block 1, 3, s Appearance silvery white Atomic mass 22. ... General Name, Symbol, Number iron, Fe, 26 Chemical series transition metals Group, Period, Block 8, 4, d Appearance lustrous metallic with a grayish tinge Atomic mass 55. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... In chemistry, a molecule is an aggregate of at least two atoms in a definite arrangement held together by special forces. ... General Name, Symbol, Number calcium, Ca, 20 Chemical series alkaline earth metals Group, Period, Block 2, 4, s Appearance silvery white Atomic mass 40. ... General Name, Symbol, Number calcium, Ca, 20 Chemical series alkaline earth metals Group, Period, Block 2, 4, s Appearance silvery white Atomic mass 40. ... Pietro Angelo Secchi (1818–1878) was an Italian astronomer. ... In astronomy, stellar classification is a classification of stars based initially on photospheric temperature and its associated spectral characteristics, and subsequenly refined in terms of other characteristics. ... A quantum mechanical system can only be in certain states, so that only certain energy levels are possible. ...


The absorption lines in stellar spectra can be used to determine the chemical composition of the star. Each element is responsible for a different set of absorption lines in the spectrum, at wavelengths which can be measured extremely accurately by laboratory experiments. Then, an absorption line at the given wavelength in a stellar spectrum shows that the element must be present. Of particular importance are the absorption lines of hydrogen (which is found in the atmosphere of nearly every star); the hydrogen lines within the visual spectrum are known as Balmer lines. General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... Different stars have different atmospheres. ... A Balmer line is a hydrogen spectral line. ...


In 1868, Sir Norman Lockyer observed strong yellow lines in the solar spectrum which had never been seen in laboratory experiments. He deduced that they must be due to an unknown element, which he called helium, from the Greek helios (sun). Helium wasn't conclusively detected on earth until 25 years later. Sir Joseph Norman Lockyer or Norman Lockyer (May 17, 1836 – August 16, 1920) was an English scientist and astronomer. ... General Name, Symbol, Number helium, He, 2 Chemical series noble gases Group, Period, Block 18, 1, s Appearance colorless Atomic mass 4. ...


Also in the 1860s, emission lines (particularly a green line) were observed in the coronal spectrum during solar eclipses that did not correspond to any known spectral lines. Again it was proposed that these were due to an unknown element, provisionally named coronium. It was not until the 1930s that it was discovered that these lines were due to highly-ionised iron and nickel, the high ionisation being due to the extreme temperature of the solar corona. The corona is the luminous plasma atmosphere of the Sun extending millions of kilometres into space, most easily seen during a total solar eclipse, but also observable in a coronagraph. ... General Name, Symbol, Number iron, Fe, 26 Chemical series transition metals Group, Period, Block 8, 4, d Appearance lustrous metallic with a grayish tinge Atomic mass 55. ... General Name, Symbol, Number nickel, Ni, 28 Chemical series transition metals Group, Period, Block 10, 4, d Appearance lustrous, metallic Atomic mass 58. ...


In conjunction with atomic physics and models of stellar evolution, stellar spectroscopy is today used to determine a multitude of properties of stars: their distance, age, luminosity and rate of mass loss can all be estimated from spectral studies, and Doppler shift studies can uncover the presence of hidden companions such as black holes and exoplanets. In astronomy, stellar evolution is the sequence of changes that a star undergoes during its lifetime, the hundreds of thousands, millions or billions of years during which it emits light and heat. ... The Doppler effect is the apparent change in frequency or wavelength of a wave that is perceived by an observer moving relative to the source of the waves. ... A black hole is a concentration of mass great enough that the force of gravity prevents anything past its event horizon from escaping it except through quantum tunnelling behaviour (known as Hawking Radiation). ... Infrared Image of a possible extrasolar planet (lower left) in the Constellation Taurus, taken by the Hubble Space Telescope. ...


Nebulae

In the early days of telescopic astronomy, the word nebula was used to describe any fuzzy patch of light that didn't look like a star. Many of these, such as the Andromeda Nebula, had spectra that looked in many ways a lot like stellar spectra, and these turned out to be galaxies. Others, such as the Cat's Eye Nebula, had very different spectra. When William Huggins looked at the Cat's Eye, he found no continuous spectrum like that seen in the Sun, but just a few strong emission lines. These lines did not correspond to any known elements on earth, and so just as helium had been identified in the Sun, astronomers suggested that the lines were due to a new element, nebulium (occasionally nebulum or nephelium). In fact, it was discovered in the 1920s that the lines were due to oxygen, a very familiar element. But nebulae are typically extremely rarefied, much less dense than the hardest vacuum ever produced on earth. In these conditions, atoms behave quite differently and lines can form which are suppressed at normal densities. These lines are known as forbidden lines, and are the strongest lines in most nebular spectra. The Triangulum Emission Nebula NGC 604 lies in a spiral arm of Galaxy M33, 2. ... If you are looking for an article about the galaxy, please see Andromeda Galaxy. ... This article is about a celestial body. ... The Cats Eye Nebula (NGC 6543) is a planetary nebula in the constellation of Draco. ... William Huggins Sir William Huggins, OM , FRS (February 7, 1824 – May 12, 1910) was a British astronomer. ... A spectral line is a dark or bright line in an otherwise uniform and continuous spectrum, resulting from an excess or deficiency of photons in a narrow frequency range, compared with the nearby frequencies. ... General Name, Symbol, Number helium, He, 2 Chemical series noble gases Group, Period, Block 18, 1, s Appearance colorless Atomic mass 4. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless Atomic mass 15. ... Look up Vacuum in Wiktionary, the free dictionary For other uses, see vacuum (disambiguation) A vacuum is a volume of space that is empty of matter, including air, so that gaseous pressure is much less than standard atmospheric pressure. ...


Galaxies

The spectra of galaxies look somewhat similar to stellar spectra, as they consist of the light from millions of stars combined. Galactic spectroscopy has led to many fundamental discoveries. Edwin Hubble discovered in the 1920's that, apart from the nearest ones (those in what is known as the Local Group), all galaxies are receding from the Earth. The further away a galaxy, the faster it is receding (see Hubble's Law). This was the first indication that the universe originated from a single point, in a Big Bang. NGC 4414, a typical spiral galaxy in the constellation Coma Berenices, is about 56,000 light years in diameter and approximately 60 million light years distant. ... Edwin Hubble Edwin Powell Hubble (November 20, 1889–September 28, 1953) was an American astronomer, noted for his discovery of galaxies beyond the Milky Way and the cosmological redshift. ... Map of the local group The Local Group is the group of galaxies that includes our galaxy, the Milky Way. ... Hubbles law is the statement in physical cosmology that the redshift in light coming from distant galaxies is proportional to their distance. ... According to the Big Bang theory, the universe emerged from an extremely dense and hot state (bottom). ...


Doppler shift studies of clusters of galaxies by Fritz Zwicky found that most galaxies were moving much faster than seemed to be possible, from what was known about the mass of the cluster. Zwicky hypothesised that there must be a great deal of non-luminous matter in the galaxy clusters, which became known as dark matter. The Doppler effect is the apparent change in frequency or wavelength of a wave that is perceived by an observer moving relative to the source of the waves. ... Galaxy groups and clusters are super-structures in the spread of galaxies of the cosmos. ... Fritz Zwicky (February 14, 1898 – February 8, 1974) was an American-based Swiss astronomer. ... In cosmology, dark matter refers to hypothetical matter particles, of unknown composition, that do not emit or reflect enough electromagnetic radiation to be detected directly, but whose presence can be inferred from gravitational effects on visible matter such as stars and galaxies. ...


Quasars

In the 1950s, some strong radio sources were found to be associated with very dim objects that seemed to be very blue. These were named Quasi-stellar radio sources, or quasars. When the first spectrum of one of these objects was taken, it was something of a mystery, with absorption lines at wavelengths where none were expected. It was soon realised that what was being seen was a normal galactic spectrum, but highly redshifted. According to Hubble's Law, this implied that the quasar must be extremely distant, and therefore highly luminous. Quasars are now thought to be galaxies forming, with their extreme energy output being powered by super-massive black holes. This view, taken with infrared light, is a false-color image of a quasar-starburst tandem with the most luminous starburst ever seen in such a combination. ... Redshift of spectral lines in the optical spectrum of a supercluster of distant galaxies (right), as compared to that of the Sun (left). ... Hubbles law is the statement in physical cosmology that the redshift in light coming from distant galaxies is proportional to their distance. ... A black hole is a concentration of mass great enough that the force of gravity prevents anything past its event horizon from escaping it except through quantum tunnelling behaviour (known as Hawking Radiation). ...


Planets and asteroids

Planets and asteroids shine only by reflecting the Sun's light. The reflected light contains absorption bands due to minerals in the rocks present for rocky bodies, or due to the elements and molecules present in the atmospheres of the Gas giants. Asteroids can be classified into three main types, according to their spectra: the C-types are made of carbonaceous material, S-types consist mainly of silicates, and M-types are 'metallic'. C- and S-type asteroids are the most common. A planet is generally considered to be a relatively large mass of accreted matter in orbit around a star that is not a star itself. ... An asteroid is a small, solid object in our Solar System, orbiting the Sun. ... Minerals are natural compounds formed through geological processes. ... A gas giant is a large planet that is not composed mostly of rock or other solid matter. ... In chemistry, a silicate is a compound consisting of silicon and oxygen (SixOy), one or more metals, and possibly hydrogen. ...


Comets

The spectra of comets consist of a reflected solar spectrum from the dusty clouds surrounding the comet, as well as emission lines formed when the solar wind collides with gases surrounding the comet. Analysis of the composition of comets has shown that they are made of pristine material from the earliest days of the solar system. Many organic chemicals are known to exist in comets, and it has been suggested that cometary impacts provided the Earth with much of the water for its oceans and the chemicals necessary for the formation of life. It has even been suggested that life may have been brought to earth from interstellar space by comets (the Panspermia theory). Comet Hale-Bopp, showing a white dust tail and blue gas tail (February 1997) A comet is a small astronomical object similar to an asteroid but composed largely of ice. ... The plasma in the solar wind meeting the heliopause For the British comic, see Solar Wind (comic). ... An organic compound is any member of a large class of chemical compounds whose molecules contain carbon, with the exception of carbides, carbonates, carbon oxides and gases containing carbon. ... [[Image:http://www. ... Look up life, living in Wiktionary, the free dictionary. ... The interstellar medium (or ISM) is a term used in astronomy to describe the rarefied gas and dust that exists between the stars (or their immediate circumstellar environment) within a galaxy. ... Panspermia is the hypothesis that the seeds of life are ubiquitous in the Universe, that they may have delivered life to Earth, and that they may deliver or have delivered life to other habitable bodies; also the process of such delivery. ...


See also

  • Gunn-Peterson troughu suck

An effect seen in the spectra of quasars with redshift greater than 6 that is explained as due to absorption of quasar emission due to neutral hydrogen (hydrogen atoms). ... In astronomical spectroscopy, the Lyman alpha forest is the sum of absorption lines seen in spectra of distant galaxies and quasars, beginning from the Lyman alpha line at 121. ... Photometry is a technique of astronomy concerned with measuring the flux, or intensity of an astronomical objects electromagnetic radiation. ... // Headline text Bold text:For Acoustic uses in spectrographs of sound waves, see below. ...

External links

  • The Science of Spectroscopy - supported by NASA. Spectroscopy education wiki and films - introduction to light, its uses in NASA, space science, astronomy, medicine & health, environmental research, and consumer products.
  • Libraries of stellar spectra - D. Montes, UCM

  Results from FactBites:
 
Spectroscopy - Wikipedia, the free encyclopedia (1753 words)
Spectroscopy is the study of spectra, that is, the dependence of physical quantities on frequency.
Spectroscopy is often used in physical and analytical chemistry for the identification of substances, through the spectrum emitted or absorbed.
Raman spectroscopy uses the inelastic scattering of light to analyse vibrational and rotational modes of molecules.
Astronomical spectroscopy - Wikipedia, the free encyclopedia (1195 words)
Astronomical spectroscopy is the technique of spectroscopy used in astronomy.
Spectroscopy can be used to derive many properties of distant stars and galaxies, such as their chemical composition and also their motion, via the Doppler shift.
Astronomical spectroscopy began with Isaac Newton's initial observations of the light of the Sun, dispersed by a prism.
  More results at FactBites »

 
 

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