Definitions

1. Luminosity is a measurement of brightness.
2. Luminosity is a measure of how bright something is intrinsically. (Web site)
3. The luminosity was measured by counting the number of Bhabha events at the interaction point of the electron and the positron beams. (Web site)
4. Luminosity: An expression of the true brightness of a star as compared to the Sun. (Web site)
5. The luminosity is an important value to characterize the performance of an accelerator. (Web site)

Luminosity

1. It is a measure of the intensity of the incident light, wavelength-weighted by the luminosity function to correlate with human brightness perception. (Web site)
2. The integrated luminosity is the integral of the luminosity with respect to time.
3. Luminosity has different meanings in several different fields of science.
4. The luminous flux (or visible energy) in a light source is defined by the photopic luminosity function.
5. The standard luminosity function is normalized to a peak value of unity at 555 nm (see luminous coefficient).

Human Eye

1. The curve which measures the response of the human eye to light is a defined standard, known as the luminosity function.
2. For everyday light levels, the photopic luminosity function best approximates the response of the human eye.
3. Photopic (black) and scotopic [1] (green) luminosity functions. (Web site)
4. The luminosity function or luminous efficiency function describes the average sensitivity of the human eye to light of different wavelengths. (Web site)

Color

1. The "L" in HSL color space is sometimes said to stand for luminosity. (Web site)
2. The small excess fractional value comes from the slight mismatch between the definition of the lumen and the peak of the luminosity function.
3. Also included is the option to apply custom color filters and set the density of such filters with or without the preservation of luminosity.

Solar

1. The luminosity and mass of stars and galaxies is generally given in terms of the solar mass and solar luminosity. (Web site)
2. It lies 79 light-years away and has a luminosity almost 60 times solar, and a mass about triple that of the Sun.
3. Solar luminosity : is defined as the amount of energy emitted per second by the sun in all direction. (Web site)
4. A relationship between luminosity and mass for stars that are on the main sequence, specifying how bright a star of a given mass will be.

Luminous Intensity

1. In photometry, luminosity is sometimes incorrectly used to refer to luminance, which is the density of luminous intensity in a given direction. (Web site)
2. Luminance (also called luminosity) is a photometric measure of the density of luminous intensity in a given direction. (Web site)
3. Luminance (also called luminosity) is a photometric measure of the density of luminous intensity in a given direction. (Web site)
4. In photometry, luminosity is sometimes incorrectly used to refer to luminance, which is the density of luminous intensity in a given direction. (Web site)

Apparent Magnitude

1. Since only apparent magnitude can be measured observationally, an estimate of distance is required to determine the luminosity of an object.
2. In measuring star brightnesses, luminosity, apparent magnitude (brightness), and distance are interrelated parameters.
3. Note that absolute magnitude is directly related to luminosity, but apparent magnitude is also a function of distance.
4. The equivalent measure of luminosity, absolute magnitude, is the apparent magnitude an object would have if seen from a distance of 10 parsecs. (Web site)
5. Astronomers measure the brightness of a star by measuring its magnitude and luminosity.

Radiates

1. It is easy to see that a star's luminosity, temperature, radius, and mass are all related. (Web site)
2. In astronomy, luminosity is the amount of energy a body radiates per unit time. (Web site)
3. Imagine a point source of light of luminosity L that radiates equally in all directions. (Web site)
4. It depends both on the luminosity and the distance, since distant objects appear fainter. (Web site)

Photosphere

1. Solar scientists have found suggestions that extremely small magnetic features in the solar photosphere are responsible for the changes in the luminosity. (Web site)

Standard Candles

1. Supernovae are suddenly appearing dying stars in the sky, whose luminosity in the optical light outshine an entire galaxy for days to weeks. (Web site)
2. Bright objects of a known luminosity are called standard candles (though, in our modern day we should perhaps call them ``standard bulbs''). (Web site)
3. The luminosity distances of these objects are determined by methods that employ relations between SN Ia luminosity and light curve shape.

Period-Luminosity Relation

1. Leavitt did not know the distances to the Magellanic Clouds, so she could not tell what the actual value of the luminosity part of the relation was. (Web site)
2. In the calibration process Shapley put actual values to the luminosity part of the period-luminosity relation. (Web site)

Parsecs

1. Finding distances to other galaxies enables you to find their mass, luminosity, and star formation history among other things. (Web site)

Agn

1. For the starburst galaxies we find a steepening of the luminosity function at the faint end and their comoving space density increases with redshift.
2. Our sample therefore occupies the extreme faint end of the AGN luminosity function. (Web site)

Earth

1. A bright star (that is, one having large apparent brightness) is a powerful emitter of radiation (high luminosity), is near Earth, or both. (Web site)
2. Rung 5b: Luminosity or Size of Bright Feature Cepheids are found in other nearby galaxies to get their distance. (Web site)
3. Professor Ellis added that as the luminosity increases, one of the things physicists at Cern will be looking for is a mini- black hole. (Web site)

Blazars

1. Using this data-set, we derived number counts, luminosity functions, and cosmological evolution of blazars and radio galaxies at microwave frequencies.
2. However, due to their low luminosity, individual red dwarfs cannot easily be observed. (Web site)

Illuminance

1. Also, the luminosity functions excluding the binary millisecond pulsars and other pulsars with low magnetic fields are constructed.
2. Luminosity functions for various field sizes and levels of retinal illuminance. (Web site)

Luminosities

1. The dwarf galaxies extend by three orders of magnitude in luminosity the correlation between IR and CO luminosities found for spiral galaxies. (Web site)
2. There is no universal globular cluster luminosity function that applies to all galaxies. (Web site)
3. Kormendy and Freeman have discovered that the properties of the dark matter "halos" that surround galaxies correlate with galaxy luminosity. (Web site)

Red Giant

1. In particular, M31 appears to have significantly more common stars than the Milky Way, and the estimated luminosity of M31 is double that of our own galaxy. (Web site)
2. The mean metallicity of the stellar halo, estimated using the mean colors of red-giant branch stars, correlates with the parent galaxy luminosity. (Web site)

Globular Clusters

1. The luminosity of the nucleus is in excess of the most luminous globular clusters. (Web site)
2. As the gas is expelled and the core is visible, the color of the star becomes much bluer and moves to the left in the HR diagram at constant luminosity. (Web site)
3. The gravity and X-ray luminosity of the neutron star act to disrupt the wind, producing an extended wake of dense gas trailing behind the neutron star. (Web site)

Lux

1. So we've established that lux are the number of photons striking a unit area per unit time, weighted by a luminosity function.
2. In the past, it was expressed in Hefner Candlepower, but nowadays Lux is used to express the amount of luminosity. (Web site)

Luminosity Function

1. The luminous flux (or visible energy) in a light source is defined by the photopic luminosity function. (Web site)
2. RR-Lyrae have the same time-averaged luminosity (about 49 solar luminosities or an absolute magnitude M V = +0.6). They pulsate with periods < 1 day. (Web site)
3. The thermal and mechanical luminosity of these early black holes dominates the energy output of young stars forming in the proto-galaxy. (Web site)

Quasars

1. Active galaxies that emit high-energy radiation in the form of x-rays are classified as Seyfert galaxies or quasars, depending on the luminosity.
2. The luminosity profiles of both elliptical galaxies and bulges are well fit by Sersic's law. (Web site)
3. VII. The hard X-ray luminosity function of AGNs up to z = 4: More absorbed AGNs at low luminosities and high redshifts. (Web site)

Supernova

1. In this type of cluster, the luminosity continues to steadily increase all the way to the core region. (Web site)
2. The distance was crucial to determining the supernova's luminosity and establishing it as the brightest ever recorded. (Web site)

H-R Diagram

1. For stars in this evolutionary stage, the surface temperature and radius, hence spectral type and luminosity class, are determined by stellar mass.
2. A modified H-R diagram of the stars in a cluster of unknown distance can be used to determine the absolute magnitude, or luminosity, of the stars. (Web site)
3. The Hertzsprung-Russell diagram relates stellar classification with absolute magnitude, luminosity, and surface temperature.

Cepheid Variables

1. He examined the cepheid variables in the clusters and would use their period–luminosity relationship for distance estimates. (Web site)
2. Once this period-luminosity relationship is calibrated, the luminosity of a given Cepheid whose period is known can be established. (Web site)

Apparent Brightness

1. By comparing a Cepheid's apparent brightness with its luminosity, you can determine the star's distance from the inverse square law of light brightness. (Web site)
2. A star's absolute luminosity or intrinsic brightness is the total amount of energy radiated by the star per second.

Supergiants

1. Our Sun is classified as spectral class G2 and luminosity class V, placing it on the main sequence nearly in the middle. (Web site)
2. Supergiants can have masses from 10 to 70 solar masses and brightness from 30,000 up to hundreds of thousands times the solar luminosity. (Web site)
3. Polaris is a G2 star with supergiant luminosity, G2Ib. (Web site)

Cepheids

1. The luminosity of Type II Cepheids is, on average, less than classical Cepheids by about 1.5 magnitudes (but still brighter than RR Lyrae stars). (Web site)
2. The primary standard candle in astronomy is the Cepheid variable, a star with a luminosity that is set by its pulsation period. (Web site)
3. The Sun is a weakly variable star and its luminosity therefore fluctuates.

Main Sequence

1. The Sun has steadily increased in luminosity over the course of its life, increasing by 40% since it first became a main-sequence star.
2. The luminosity of the Sun will grow by 10% over the next 1.1 Gyr (1.1 billion years) and by 40% over the next 3.5 Gyr. (Web site)
3. Red giants have relatively low surface temperatures of about 3,600 K, but they also have a high luminosity due to their large exterior surface area. (Web site)

Categories

1. Encyclopedia of Keywords > Information > Science > Astronomy
2. Science > Physics > Optics > Light
3. Encyclopedia of Keywords > Places > Earth > Atmosphere
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