# Absolute magnitude

**Hbolometric magnitudeabsolute magnitude (H)absolute visual magnitudebrightnessabsolutebolometricmagnitudeabsolute bolometric magnitudeabsolute magnitudes**

Absolute magnitude (M) is a measure of the luminosity of a celestial object, on an inverse logarithmic astronomical magnitude scale.wikipedia

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### Magnitude (astronomy)

**magnitudemagnitudesmag**

Absolute magnitude (M) is a measure of the luminosity of a celestial object, on an inverse logarithmic astronomical magnitude scale.

Astronomers use two different definitions of magnitude: apparent magnitude and absolute magnitude.

### Luminosity

**luminousbolometric luminosityluminosities**

Absolute magnitude (M) is a measure of the luminosity of a celestial object, on an inverse logarithmic astronomical magnitude scale.

Luminosity can also be given in terms of the astronomical magnitude system: the absolute bolometric magnitude (M bol ) of an object is a logarithmic measure of its total energy emission rate, while absolute magnitude is a logarithmic measure of the luminosity within some specific wavelength range or filter band.

### Sun

**solarSolThe Sun**

The Sun has absolute magnitude M V =+4.83. For comparison, Sirius has an absolute magnitude of 1.4, which is brighter than the Sun, whose absolute visual magnitude is 4.83 (it actually serves as a reference point).

The Sun has an absolute magnitude of +4.83, estimated to be brighter than about 85% of the stars in the Milky Way, most of which are red dwarfs.

### Milky Way

**Milky Way Galaxygalaxyour galaxy**

Highly luminous objects can have negative absolute magnitudes: for example, the Milky Way galaxy has an absolute B magnitude of about −20.8.

The integrated absolute visual magnitude of the Milky Way is estimated to be around −20.9.

### Sirius

**Sirius BSirius superclusterDog Star**

For comparison, Sirius has an absolute magnitude of 1.4, which is brighter than the Sun, whose absolute visual magnitude is 4.83 (it actually serves as a reference point).

Sirius A is about twice as massive as the Sun and has an absolute visual magnitude of +1.42.

### Bolometric correction

**bolometric**

To convert from an absolute magnitude in a specific filter band to absolute bolometric magnitude, a bolometric correction (BC) is applied.

In astronomy, the bolometric correction is the correction made to the absolute magnitude of an object in order to convert its visible magnitude to its bolometric magnitude.

### Betelgeuse

**Alpha OrionisBételgeuseα Ori**

Examples include Rigel (−7.0), Deneb (−7.2), Naos (−6.0), and Betelgeuse (−5.6).

It is calculated to be 640 light-years away, yielding an absolute magnitude of about −6.

### Apparent magnitude

**apparent visual magnitudemagnitudevisual magnitude**

For comparison, Sirius has an absolute magnitude of 1.4, which is brighter than the Sun, whose absolute visual magnitude is 4.83 (it actually serves as a reference point). An object's absolute magnitude is defined to be equal to the apparent magnitude that the object would have if it were viewed from a distance of exactly 10 pc, without extinction (or dimming) of its light due to absorption by interstellar matter and cosmic dust.

Absolute magnitude differs from apparent magnitude in that it is a measure of the intrinsic luminosity rather than the apparent brightness of a celestial object, expressed on the same reverse logarithmic scale.

### Deneb

**Alpha CygniAridedα Cyg**

Examples include Rigel (−7.0), Deneb (−7.2), Naos (−6.0), and Betelgeuse (−5.6).

Deneb's absolute magnitude is currently estimated as −8.4, placing it among the visually brightest stars known, with an estimated luminosity nearly.

### Effective temperature

**surface temperatureeffective (surface) temperaturetemperature**

In the case of stars with few observations, it must be computed assuming an effective temperature.

. Notice that the total (bolometric) luminosity of a star is then

### Phase curve (astronomy)

**phase curvephase curvesphase function**

This relationship is referred to as the phase curve.

The brightness usually refers the object's absolute magnitude, which, in turn, is its apparent magnitude at a distance of one astronomical unit from the Earth and Sun.

### Distance modulus

or using apparent magnitude m and distance modulus μ:

The distance modulus \mu=m-M is the difference between the apparent magnitude m (ideally, corrected from the effects of interstellar absorption) and the absolute magnitude M of an astronomical object.

### Parsec

**Mpcpckpc**

For objects within the immediate neighborhood of the Sun, the absolute magnitude M and apparent magnitude m from any distance d (in parsecs) is related by:

In August 2015, the International Astronomical Union (IAU) passed Resolution B2, which, as part of the definition of a standardized absolute and apparent bolometric magnitude scale, mentioned an existing explicit definition of the parsec as exactly 1⁄648000 astronomical units, or approximately 3.08567758149137 metres (based on the IAU 2012 exact SI definition of the astronomical unit).

### Asteroid

**asteroidsminor bodyMinor Planet**

For planets and asteroids a definition of absolute magnitude that is more meaningful for non-stellar objects is used.

The smallest asteroids discovered (based on absolute magnitude H) are with H = 33.2 and with H = 32.1 both with an estimated size of about 1 meter.

### K correction

**adjusted for redshiftsk-correctionkcorrect**

To compare the magnitudes of very distant objects with those of local objects, a K correction might have to be applied to the magnitudes of the distant objects.

I.E. the adjustment to the standard relationship between absolute and apparent magnitude required to correct for the redshift effect.

### Zero Point (photometry)

**zero pointzero points**

In August 2015, the International Astronomical Union passed Resolution B2 defining the zero points of the absolute and apparent bolometric magnitude scales in SI units for power (watts) and irradiance (W/m 2 ), respectively.

However, the IAU has recently defined the absolute bolometric magnitude and apparent bolometric magnitude zero points to be 3.0128×10 28 W and 2.51802×10 −8 W/m 2 respectively.

### Comet of 1729

**C/1729 P1Comet Sarabat**

The Comet of 1729, also known as C/1729 P1 or Comet Sarabat, was an assumed parabolic comet with an absolute magnitude of −3, the brightest ever observed for a comet; it is therefore considered to be potentially the largest comet ever seen.

### Hertzsprung–Russell diagram

**Hertzsprung-Russell diagramHR diagramcolor-magnitude diagram**

The Hertzsprung–Russell diagram, abbreviated as H–R diagram, HR diagram or HRD, is a scatter plot of stars showing the relationship between the stars' absolute magnitudes or luminosities versus their stellar classifications or effective temperatures.

### List of most luminous stars

**most luminousmost luminous starsmost luminous stars known**

Below is a list of stars arranged in order of decreasing luminosity (increasing bolometric magnitude).

### Meteoroid

**meteormeteorsfireball**

For a meteor, the standard distance for measurement of magnitudes is at an altitude of 100 km at the observer's zenith.

Some of the smallest asteroids discovered (based on absolute magnitude H) are with H = 33.2 and with H = 32.1 both with an estimated size of.

### Albedo

**albedosreflectivitygeometrical albedo**

Earth's albedo varies by a factor of 6, from 0.12 in the cloud-free case to 0.76 in the case of altostratus cloud.

The correlation between astronomical (geometric) albedo, absolute magnitude and diameter is:

### Surface brightness

**integrated magnitudeintegrated visual magnitudemag/squ arc sec**

where M_{\odot} and L_{\odot} are the absolute magnitude and the luminosity of the Sun in chosen color-band respectively.

### Astronomical object

**celestial bodiescelestial bodycelestial object**

Absolute magnitude (M) is a measure of the luminosity of a celestial object, on an inverse logarithmic astronomical magnitude scale.

### Logarithmic scale

**logarithmiclogarithmic unitLog**