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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.

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
preprint ...

~s 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.

~: 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.

~ spectrum
A spectrum that contains bright ~s.
emission nebula
A glowing gaseous nebula whose spectrum has bright ~s.

A bright line in a spectrum caused by the emission of photons from atoms.
Emission Nebula ...

~s. 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.

~ - 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 ...

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.

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 ~ 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.

Narrow Emission Line Galaxy
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.

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.

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

~s 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.

~s: 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.

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

~s with peculiarity
~s with ^P-Cygni//gr 304.446667, 38.032944^ profile
ev ...

The ~ 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 ...

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

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?

~ 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 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.
The faint outer atmosphere of the Sun that is exposed during a total solar eclipse.
On Venus, circular features, not caused by impacts, they are domed plains caused by the rising plumes of molten rock from below.

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.

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.

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 ~s, 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, ...

I think the inverted color picture above is centered on the H-alpha ~, 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 ~s, the Hydrogen Beta ~, 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 ~s at wavelengths that were at odds with all celestial sources then familiar to astronomers.

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

~s 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 ~s, 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 ~s 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 ~s, characteristic of hydrogen, calcium and other elements.

A research team of astronomers, has successfully detected a carbon ~ 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, ~s 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 ~s. The Seyfert galaxies are subdivided into two types depending on their ~s.

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

Astronomers using ISO discovered ~s 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 ~s 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 ~s 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 ~s in the star were the familiar hydrogen-Balmer series, but redshifted by 15%.

Its nucleus (center) has bright ~s, 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.

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

Their spectrum has broad and very intense ~s, 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 ~s of the hydrogen atom as an electron goes from n = 2 to n = 1 ....
-alpha hydrogen radiation at a wavelength
Wavelength ...

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

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

Seyfert galaxy
A spiral galaxy whose nucleus shows bright ~s; 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 ~s 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 ~s 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 "~s" and "absorption lines" that are sort of fingerprints of atoms and molecules that may be ...

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 ~s in the spectra of these nebulas. Examples include the Orion and Lagoon nebulas.

These very hot stars show broad ~s 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 ~s 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.

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 ~s 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 ~s 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: What is the meaning of Emission, Astro, Spectra, Star, Spectrum?

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