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Emission Line

Astronomy  Emission  Emission Nebula

Emission Line
An emission line will appear in a spectrum if the source emits specific wavelengths of radiation. This emission occurs when an atom, element or molecule in an excited state returns to a configuration of lower energy.


Emission lines are used in physics, chemistry, and astronomy to determine what kind of gas is doing the emission. Every element has a different electronic structure, and will thus have a different emission line fingerprint.

EMISSION LINES
Figure 4.2 Continuous and Emission Spectra When passed through a slit and split up by a prism, light from a source of continuous radiation (a) gives rise to the familiar rainbow of colors.

EMISSION LINES
The spectra we encountered in Chapter 3 are examples of continuous spectra.

emission line: a more or less narrow range of wavelengths in a spectrum that is brighter than neighboring wavelengths. Emission lines are seen in quasars.

Emission Line Variability of the Accreting Young Brown Dwarf 2MASSW J1207334-393254: From Hours to Years
July 13, 2007 STELZER B., SCHOLZ A. & JAYAWARDHANA R.
ApJ.
preprint ...

Emission lines and the far-UV spectrum. Since recombination lines (and a few others) are powered ultimately by parts of the spectrum we can't see directly, they may give our only information on what happens between the UV and soft X-ray ranges.

Emission Line: A bright line in a spectrum caused by the emission of photons from atoms.
Emission Nebula: A cloud of gas that is excited by the ultraviolet radiation from hot stars.

emission line spectrum
A spectrum that contains bright emission lines.
emission nebula
A glowing gaseous nebula whose spectrum has bright emission lines.

Emission lines. Specific wavelengths of light that are brighter than adjoining wavelengths seen in spectra.
Ephemeris. A table or list of the predicted position of an object such as a planet.
Epoch. An instant in time for which the positions of celestial objects are given.

Emission Line - A narrow, bright region of the spectrum. Emission lines are produced when electrons in atoms jump from one energy level to lower energy level
Energy Flux - The rate at which a wave carries energy through a given area ...

emission line
Within a spectrum, an excess amount of energy that is emitted at a specific wavelength. Emission lines in a spectrum usually appear as slender slivers of light on a dark background.

Emission Lines
Bright lines produced in a spectrum by a luminous source, such as a star or a bright nebula. Compare absorption lines.
Emission Measure (EM) ...

The Emission Line Corona
Click on image for larger version.
Early observations of the visible spectrum of the corona revealed bright emission lines at wavelengths that did not correspond to any known materials.

Broad emission lines
If you can't see honest-to-goodness Keplerian motion, at least you can see evidence for very high velocities.
Q: How fast is the gas in this galaxy moving? Use the H-alpha line for your measurement.

Narrow Emission Line Galaxy
Neodymium
A toxic silvery element belonging to the lanthanoid series of metals. It occurs in association with other lanthanoids. Neodymium is used in various alloys, as a catalyst, in compound form in carbon-arc searchlights, etc., and in the glass industry.

Emission lines
Absorption lines
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.

Emission Line
A bright line in a spectrum caused by emission of light. Each chemical element emits and absorbs radiated energy at specific wavelengths. The collection of emission lines in a spectrum corresponds to the chemical elements contained in a celestial object.
Far-Infrared Spectrum ...

emission line Bright line in a specific location of the spectrum of radiating material, corresponding to emission of light at a certain frequency.

Emission lines are produced by hot gas. If the hot gas is moving at a pretty good rate of speed, then the Doppler effect comes into play - the emission lines could be shifted to different wavelengths.

Emission Lines: The bright lines seen against a darker background, created when a hot gas emits photons characteristic of the elements of which the gas is composed.

emission line - (n.)
A wavelength at which radiation is emitted, creating a bright line in the spectrum.
emission nebula - (n.) ...

Emission lines with peculiarity
eq
Emission lines with ^P-Cygni//gr 304.446667, 38.032944^ profile
ev ...

Emission lines result from transitions of an atom from a high energy level to a lower level (as a result of collisions or radiative decay from a yet-higher level), resulting in the emission of photons with characteristic energies or wavelengths.

The emission line for Fe XI, occurs at 789.2 nanometres (nm), and the first images of the corona at this wavelength reveal some surprises, notably that the emission extends out at least three solar radii and has localised regions of enhanced density of iron ions.

21-cm emission line
The important radio radiation at 21-cm wavelength from interstellar neutral atomic hydrogen.
aberration of starlight ...

We get emission lines like this if I have a hot star off to the right shining its light on a nebula straight in front of me. The nebula is going to absorb all the light that is coming from that star off to the right.

Spectral emission lines suggest an expanding shell of gas surrounding the star.
Other Designations For This Star
Hipparcos Identifier (HIP Number) ...

Note that the emission lines in the above diagram are not representative of the exact colour or line thickness of the real hydrogen emission lines. The line thickness varies, with red normally being the broadest line and violet the thinnest.

emission line. In spectroscopy, a particular wavelength of emitted radiation, more intense than the background continuum. emission measure. The integral of the square of the electron density over volume; the units are inverse volume (per cubic m). ephemeris.

What produces an emission line spectrum? Do you need a thermal source in the background?
Can you see emission lines if a thermal source is in the background? What does their visibility depend on?

emission line A minute range of wavelength (or frequency) in the electromagnetic spectrum within which radiant energy is being emitted by a radiating substance. See spectral line, emission spectrum.

emission line emission nebula emission spectrum Spectrum containing bright lines or a set of discrete wavelengths produced in a rarefied incandescent gas. energy The ability of a physical system to do work when it changes from one describable state to another.

A spectrum in which there are no absorption or emission lines.
Corona
The faint outer atmosphere of the Sun that is exposed during a total solar eclipse.
Coronae
On Venus, circular features, not caused by impacts, they are domed plains caused by the rising plumes of molten rock from below.

Continuous spectrum A spectrum showing emission at all wavelengths, unbroken by either absorption lines or emission lines. Convection The physical up-welling of hot matter, thus transporting energy from a lower, hotter region to a higher, cooler region.

continuum The continuous spectrum that any object would produce if no absorption or emission lines were present. Any body above absolute zero emits a spectrum, the shape of which is dependant on its temperature.

SHELL STAR: A type of star which is believed to be surrounded by a thin envelope of gas, which is often indicated by bright emission lines in its spectrum.
SHEPHERD MOON: A satellite which constrains the extent of a planetary ring through gravitational forces.

Wolf-Rayet stars (NASA Thesaurus) Very luminous, very hot (as high as 50,000K) stars whose spectra have broad emission lines (mainly He I and He II, which are presumed to originate from material ejected from the stars at very high velocities.

Both types have emission line spectra from their nucleus arising from a nonstellar source.

If the gas is rarefied, then the photon emitted from an individual atom will be able to escape from the gas without being altered and you will see the appropriate emission lines (Law 2). The gas needs to be kept warm so there will be a source of energy to permit the emission of light.

1943 - Carl Keenan Seyfert identifies six spiral galaxies with unusually broad emission lines, named Seyfert galaxies,
1949 - J.G. Bolton, G.J. Stanley, and O.B. Slee identify NGC 4486 (M87) and NGC 5128 as extragalactic radio sources, ...

Thermal emission from the inner parts of the accretion disk may be visible as a big blue bump in the optical/UV spectrum, and Doppler-broadened emission lines from the small ($ region will not be obscured.

I think the inverted color picture above is centered on the H-alpha emission line, so we are seeing the abundant hydrogen, mostly in the sun's photosphere. But then, on the left hand side of the disk you can notice some fuzzy floating thing.

These filters only pass the two Oxygen III emission lines, the Hydrogen Beta emission line, and the wavelengths between these two, making them most useful for observing emission or planetary nebulae.

Optical photographs subsequently taken of their spectra showed locations for emission lines at wavelengths that were at odds with all celestial sources then familiar to astronomers.

SPIN-FLIP TRANSITION - Origin of the 21-cm emission line that originates with a neutral 1H atom. The proton and the electron each have a quantum “spin,' which points either “up' or “down.

Emission lines result from warm gas overlying a cold background so that the intensity (or flux or radiation temperature) at the line frequency is sharply higher compared to nearby wavelengths.

The spectral type gives an indication of the surface temperature of the star, along with size and any special properties such as emission lines, variability or an unspecificed peculiarity. For historical reasons, the spectral sequence, from hotter to cooler, runs O B A F G K M.

Central star temperatures are commonly calculated by using the intensity of nebular emission lines to estimate the amount of ultraviolet radiation from the star and then comparing that to the amount of visual radiation derived from the visual magnitude.

In addition, however, sunlight also contains many bright emission lines, characteristic of hydrogen, calcium and other elements.

A research team of astronomers, has successfully detected a carbon emission line in the most distant radio galaxy known so far in the early universe. Their investigation of the detected carbon line showed that a significant amount of carbon existed as early as 12.

The spectral type of stars is a system of classification of stars based on the stars' spectra, emission lines that correlate with each star's surface temperature (and color). There are seven major spectral types. Stars range from blue and hot to red and cool.

A class of spiral and barred spiral galaxies with small but very bight nuclei whose spectra show emission lines. The Seyfert galaxies are subdivided into two types depending on their emission lines.

CMY has an advatage of covering forbidden oxygen and hydrogen beta emission lines around 500nm (major components of the light from emission and planetary nebulas) which are frequently excluded by RGB filters.

Astronomers using ISO discovered emission lines from interstellar water vapor in a variety of sources including star forming regions, planetary nebulae and near formed stars. ISO also discovered for the first time hydrogen cyanide ice molecules in a dusty cloud surrounding a newly forming star.

BZ Crucis is a Be star classified as a B1IVe class star, a B class subgiant showing emission lines in its spectrum. It is a Gamma Cassiopeiae type variable star, which is to say a shell star that has a circumstellar gas disk around the equator. BZ Crucis is an X-ray source.

It was the first planetary nebula to be observed with a spectroscope; the observers were surprised to find emission lines in the spectrum of this object. This started the controversy whether planetaries are numerous stars or, as it turned out to be, clouds of diffuse gas.

Schmidt puzzled over the photographic spectrum for months before he recognized that the strong, broad emission lines in the star were the familiar hydrogen-Balmer series, but redshifted by 15%.

Spectral plots showing the emission line of water at a wavelength of 39.37 microns in the atmospheres of Jupiter, Saturn, Uranus, Neptune and Saturn's moon Titan. These mid-infrared spectra were obtained by the ISO satellite.

Its nucleus (center) has bright emission lines, including visible wavelengths. The brightness varies over relatively short time periods (less than a year). They may have massive black holes at their centers. Seyfert galaxies were first described by Carl Seyfert in 1943.

Their surface composition is extremely exotic, being dominated by helium rather than hydrogen, and typically showing broad wind emission lines of elements like carbon (WC type), nitrogen (WN type), or oxygen: the products of core nucleosynthesis.

where νobs is the observed frequency of an emission line, and νemit is the emitted frequency of the emission line.

A type of star which is believed to be surrounded by a thin envelope of gas, which is often indicated by bright emission lines in its spectrum.
Shepherd Satellite
A satellite that constrains the extent of a planetary ring through gravitational forces. Also known as a shepherd moon.

Their spectrum has broad and very intense emission lines, probably indicative of violent surface activity. They may be protostars in the later stages of formation, young stars that are not yet stable main sequence stars in the Hertzsprung-Russell Diagram.

In physics, the Lyman series is the series of transitions and resulting emission lines of the hydrogen atom as an electron goes from n = 2 to n = 1 ....
-alpha hydrogen radiation at a wavelength
Wavelength ...

The "Bastille Day" solar flare as seen by SOHO's EIT instrument in the 195 Å emission line.
10 of 31
Why Sun's Atmosphere Is 'So Darned Hot' ...

6.08 Gas surrounding a star may absorb energy, causing...
absorption lines.
an explosion.
emission lines.
indigestion.

Seyfert galaxy
A spiral galaxy whose nucleus shows bright emission lines; one of a class of galaxies first described by C. Seyfert.

Other stars have spots, as well. Called starspots, these patches can't be seen directly, but are inferred by measurements of the effects of magnetic fields and rotation upon the narrow emission lines of atoms on the star's surface.
Filed Under: Celestial Objects, Solar System Observing
First Name: ...

It is an emission nebula created by a fast stellar wind of a Wolf-Rayet star, an evolved, massive star showing strong emission lines of helium and nitrogen or helium, carbon and oxygen. It is approximately 5,000 light-years distant.

Spectrometers are instruments that spread light out into wavelengths called "spectra," which look something like rainbow-colored bars. Using the spectra, scientists can look for and study the "emission lines" and "absorption lines" that are sort of fingerprints of atoms and molecules that may be ...

Seyfert galaxy - Galaxy with a bright nucleus coupled with spectral emission lines, first discovered by Carl Seyfert in 1943.

In addition, there are a special class of stars called Wolf-Rayet stars (W-R stars), which have temperatures greater than 20,000 K (and may be as high as 90,000 K) and have anamalously strong and borad emission lines. These are thought to be very massive stars ( ...

Emission Nebula
An interstellar cloud of gas and dust in which hot embedded stars ionize much of the cloud's gas atoms causing the nebula to emit its own light. The name is derived from the pattern of emission lines in the spectra of these nebulas. Examples include the Orion and Lagoon nebulas.

These very hot stars show broad emission lines and strong stellar winds (about 500 to 800 km/sec, sometimes even significantly higher). How the gas of the atmosphere is accelerated to reach such an high velocity is not yet known.
This double can be viewed with small telescopes.

Often, the redshift of an object can be measured by examining atomic absorption or emission lines in its spectrum. Redshifts can be caused by the motion of a source away from an observer. For distant objects, redshifts can be caused by the expansion of the Universe.

In an optical spectroscope, the detector is your eye, which senses the different colors and the presence of dark absorption lines or bright emission lines in the spectrum of the source being viewed. In a spectrograph, some other device is used to sense the light.

The serendipitous spectrum reveals the tell-tale meteor emissions of oxygen and nitrogen atoms and nitrogen molecules. The VLT spectrum was the first to reveal the far red range where carbon emission lines are predicted; ...

However, the deeper, hot corona of Star Aa is much more variable than that of Star Ab. The extreme ultraviolet spectra of Stars Aa and Ab display the presence of iron emission lines from Fe XV to Fe XXIV (more). The two stars have a combined luminosity of over 150 times that of Sol.

See also: See also: Emission, Astro, Spectra, Star, Spectrum

Astronomy  Emission  Emission Nebula

 
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