A report on Apparent magnitude

Asteroid 65 Cybele and two stars, with their magnitudes labeled
Image of 30 Doradus taken by ESO's VISTA. This nebula has a visual magnitude of 8.
Graph of relative brightness versus magnitude

Measure of the brightness of a star or other astronomical object observed from Earth.

- Apparent magnitude
Asteroid 65 Cybele and two stars, with their magnitudes labeled

30 related topics with Alpha

Overall
People have interpreted patterns and images in the stars since ancient times. This 1690 depiction of the constellation of Leo, the lion, is by Johannes Hevelius.

Star

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Astronomical object comprising a luminous spheroid of plasma held together by its gravity.

Astronomical object comprising a luminous spheroid of plasma held together by its gravity.

People have interpreted patterns and images in the stars since ancient times. This 1690 depiction of the constellation of Leo, the lion, is by Johannes Hevelius.
Infrared image from NASA's Spitzer Space Telescope showing hundreds of thousands of stars in the Milky Way galaxy
Stellar evolution of low-mass (left cycle) and high-mass (right cycle) stars, with examples in italics
An example of a Hertzsprung–Russell diagram for a set of stars that includes the Sun (center) (see Classification)
Betelgeuse as seen by ALMA. This is the first time that ALMA has observed the surface of a star and resulted in the highest-resolution image of Betelgeuse available.
Onion-like layers at the core of a massive, evolved star just before core collapses
The Crab Nebula, remnants of a supernova that was first observed around 1050 AD
Artist's impression of the Sirius system, a white dwarf star in orbit around an A-type main-sequence star
This view of NGC 6397 includes stars known as blue stragglers for their location on the Hertzsprung–Russell diagram.
Some of the well-known stars with their apparent colors and relative sizes
The Pleiades, an open cluster of stars in the constellation of Taurus. These stars share a common motion through space.
Surface magnetic field of SU Aur (a young star of T Tauri type), reconstructed by means of Zeeman–Doppler imaging
The reflection nebula NGC 1999 is brilliantly illuminated by V380 Orionis. The black patch of sky is a vast hole of empty space and not a dark nebula as previously thought.
The asymmetrical appearance of Mira, an oscillating variable star
Internal structures of main sequence stars with masses indicated in solar masses, convection zones with arrowed cycles, and radiative zones with red flashes. Left to right, a red dwarf, a yellow dwarf, and a blue-white main sequence star
A cross-section of the Sun
Overview of consecutive fusion processes in massive stars

Astronomers can determine stellar properties—including mass, age, metallicity (chemical composition), variability, distance, and motion through space—by carrying out observations of a star's apparent brightness, spectrum, and changes in its position in the sky over time.

Hubble Space Telescope image of Sirius A and Sirius B. The white dwarf can be seen to the lower left. The diffraction spikes and concentric rings are instrumental effects.

Sirius

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Brightest star in the night sky.

Brightest star in the night sky.

Hubble Space Telescope image of Sirius A and Sirius B. The white dwarf can be seen to the lower left. The diffraction spikes and concentric rings are instrumental effects.
Sirius (bottom) and the constellation Orion (right). The three brightest stars in this image—Sirius, Betelgeuse (top right) and Procyon (top left)—form the Winter Triangle. The bright star at top center is Alhena, which forms a cross-shaped asterism with the Winter Triangle.
The orbit of Sirius B around A as seen from Earth (slanted ellipse). The wide horizontal ellipse shows the true shape of the orbit (with an arbitrary orientation) as it would appear if viewed straight on.
A Chandra X-ray Observatory image of the Sirius star system, where the spike-like pattern is due to the support structure for the transmission grating. The bright source is Sirius B. Credit: NASA/SAO/CXC
Comparison of Sirius A and the Sun, to scale and relative surface brightness
Size comparison of Sirius B and Earth
A bust of Sopdet, Egyptian goddess of Sirius and the fertility of the Nile, syncretized with Isis and Demeter
Sirius midnight culmination at New Year 2022 local solar time
Yoonir, symbol of the universe in Serer religion

With a visual apparent magnitude of −1.46, Sirius is almost twice as bright as Canopus, the next brightest star.

Diffuse reflection on sphere and flat disk

Absolute magnitude

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Measure of the luminosity of a celestial object, on an inverse logarithmic astronomical magnitude scale.

Measure of the luminosity of a celestial object, on an inverse logarithmic astronomical magnitude scale.

Diffuse reflection on sphere and flat disk
Brightness with phase for diffuse reflection models. The sphere is 2/3 as bright at zero phase, while the disk can't be seen beyond 90 degrees.
Asteroid 1 Ceres, imaged by the Dawn spacecraft at phase angles of 0°, 7° and 33°. The left image at 0° phase angle shows the brightness surge due to the opposition effect.
Phase integrals for various values of G

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.

The Sun has an intrinsic luminosity of 3.83 watts. In astronomy, this amount is equal to one solar luminosity, represented by the symbol L⊙. A star with four times the radiative power of the sun has a luminosity of 4 L⊙.

Luminosity

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Absolute measure of radiated electromagnetic power , the radiant power emitted by a light-emitting object over time.

Absolute measure of radiated electromagnetic power , the radiant power emitted by a light-emitting object over time.

The Sun has an intrinsic luminosity of 3.83 watts. In astronomy, this amount is equal to one solar luminosity, represented by the symbol L⊙. A star with four times the radiative power of the sun has a luminosity of 4 L⊙.
Point source S is radiating light equally in all directions. The amount passing through an area A varies with the distance of the surface from the light.

Apparent magnitude is a logarithmic measure of apparent brightness.

Magnitude (astronomy)

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Unitless measure of the brightness of an object in a defined passband, often in the visible or infrared spectrum, but sometimes across all wavelengths.

Unitless measure of the brightness of an object in a defined passband, often in the visible or infrared spectrum, but sometimes across all wavelengths.

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

☉

Sun

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Star at the center of the Solar System.

Star at the center of the Solar System.

☉
Illustration of the Sun's structure, in false color for contrast
Illustration of a proton-proton reaction chain, from hydrogen forming deuterium, helium-3, and regular helium-4.
Illustration of different stars's internal structure, the Sun in the middle has an inner radiating zone and an outer convective zone.
High-resolution image of the Sun's surface taken by the Daniel K. Inouye Solar Telescope (DKIST)
During a total solar eclipse, the solar corona can be seen with the naked eye, during the brief period of totality.
The Sun's transition region taken by Hinode's Solar Optical Telescope
Sunlight and glare seen overlooking from the International Space Station
Once outside the Sun's surface, neutrinos and photons travel at the speed of light
Visible light photograph of sunspot
Measurements from 2005 of solar cycle variation during the previous 30 years
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The size of the current Sun (now in the main sequence) compared to its estimated size during its red-giant phase in the future
The Solar System, with sizes of the Sun and planets to scale. The terrestrial planets are on the right, the gas and ice giants are on the left.
The Trundholm sun chariot pulled by a horse is a sculpture believed to be illustrating an important part of Nordic Bronze Age mythology.
Sol, the Sun, from a 1550 edition of Guido Bonatti's Liber astronomiae.
False-color image taken in 2010 as seen in 30.4-nanometer ultraviolet light wavelength
A false-color of a coronal hole on the Sun forming a question mark (22 December 2017)
A false-color solar prominence erupts in August 2012, as captured by the Solar Dynamics Observatory
The Sun seen from Earth, with glare from the lenses. The eye also see glare when looked towards the Sun directly.
Sun and Immortal Birds Gold Ornament by ancient Shu people. The center is a sun pattern with twelve points around which four birds fly in the same counterclockwise direction, Shang dynasty

The Sun is by far the brightest object in the Earth's sky, with an apparent magnitude of −26.74.

Some major asterisms, which feature many of the brightest stars in the night sky.

List of brightest stars

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Some major asterisms, which feature many of the brightest stars in the night sky.

This is a list of stars arranged by their apparent magnitude – their brightness as observed from Earth.

The naked eye

Naked eye

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Practice of engaging in visual perception unaided by a magnifying, light-collecting optical instrument, such as a telescope or microscope, or eye protection.

Practice of engaging in visual perception unaided by a magnifying, light-collecting optical instrument, such as a telescope or microscope, or eye protection.

The naked eye
A photographic approximation of a naked eye view of the night sky from a small rural town (top) and a metropolitan area (bottom). Light pollution dramatically reduces the visibility of stars.
The Milky Way is visible over the Very Large Telescope, demonstrating clear atmosphere above Paranal Observatory.

Ability to see faint stars up to +8 magnitude under a perfectly dark sky.

Sir John Herschel in 1846

Betelgeuse

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Usually the tenth-brightest star in the night sky and, after Rigel, the second-brightest in the constellation of Orion.

Usually the tenth-brightest star in the night sky and, after Rigel, the second-brightest in the constellation of Orion.

Sir John Herschel in 1846
1998/9 UV HST images of Betelgeuse showing asymmetrical pulsations with corresponding spectral line profiles
AAVSO V-band magnitude of Betelgeuse, between September 2018 and February 2021
Comparison of SPHERE images of Betelgeuse taken in January 2019 and December 2019, showing the changes in brightness and shape
Image showing Betelgeuse (top left) and the dense nebulae of the Orion molecular cloud complex ( Rogelio Bernal Andreo )
NRAO's Very Large Array used to derive Betelgeuse's 2008 distance estimate
AAVSO V-band light curve of Betelgeuse (Alpha Orionis) from Dec 1988 to Aug 2002.
Orion, with Betelgeuse at its usual magnitude (left) and during the unusually deep minimum in early 2020 (right)
Radio image from 1998 showing the size of Betelgeuse's photosphere (circle) and the effect of convective forces on the star's atmosphere
Infrared image of Betelgeuse, Meissa and Bellatrix with surrounding nebulae
Size comparison of Betelgeuse, Mu Cephei, KY Cygni, and V354 Cephei, according to Emily Levesque
Orion OB1 association
Image from ESO's Very Large Telescope showing the stellar disk and an extended atmosphere with a previously unknown plume of surrounding gas
Artist's rendering from ESO showing Betelgeuse with a gigantic bubble boiling on its surface and a radiant plume of gas being ejected to six photospheric radii or roughly the orbit of Neptune
Exterior view of ESO's Very Large Telescope (VLT) in Paranal, Chile
Interior view of one of the four 8.2-meter Unit Telescopes at ESO's VLT
This infrared image from the ESO's VLT shows complex shells of gas and dust around Betelgeuse – the [[:File:Nebula and betelgeuse VLT.jpg|tiny red circle]] in the middle is the size of the photosphere.
Hertzsprung–Russell diagram identifying supergiants like Betelgeuse that have moved off the main sequence
Celestia depiction of Orion as it might appear from Earth when Betelgeuse explodes as a supernova, which could be brighter than the supernova that exploded in 1006
An illustration of Orion (horizontally reversed) in al-Sufi's Book of Fixed Stars. Betelgeuze is annotated as Yad al-Jauzā ("Hand of Orion"), one of the proposed etymological origins of its modern name, and also as Mankib al Jauzā' ("Shoulder of Orion").
Dunhuang Star Chart, circa AD 700, showing 参宿四 Shēnxiùsì (Betelgeuse), the Fourth Star of the constellation of Three Stars

It is a distinctly reddish semiregular variable star whose apparent magnitude, varying between +0.0 and +1.6, has the widest range displayed by any first-magnitude star.

Just-saturated RGB-camera discs

Stellar classification

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Classification of stars based on their spectral characteristics.

Classification of stars based on their spectral characteristics.

Just-saturated RGB-camera discs
Main-sequence stars arranged from O to M Harvard classes
The Hertzsprung–Russell diagram relates stellar classification with absolute magnitude, luminosity, and surface temperature.
Montage of false color spectra for main-sequence stars
Guide for Secchi spectral types ("152 Schjellerup" is Y Canum Venaticorum)
Proper motion of stars of early type in ± 200,000 years
The movement of stars of late type around the apex (left) and antapex (right) in ± 200,000 years
The spectrum of an O5V star
B-class stars in the Jewel Box cluster (Credit: ESO VLT)
Class A Vega (left) compared to the Sun (right)
Canopus, an F-type supergiant and the second-brightest star in the night sky
The Sun, a G2 main-sequence star, with dark sunspots
Arcturus, a K1.5 giant compared to the Sun and Antares
UGC 5797, an emission-line galaxy where massive bright blue stars are formed
Hubble Space Telescope image of the nebula M1-67 and the Wolf–Rayet star WR 124 in the center
Artist's impression of an L-dwarf
Artist's impression of a T-dwarf
Artist's impression of a Y-dwarf
Image of the carbon star R Sculptoris and its striking spiral structure
Sirius A and B (a white dwarf of type DA2) resolved by Hubble

The brightest-known M class main-sequence star is Lacaille 8760, class M0V, with magnitude 6.7 (the limiting magnitude for typical naked-eye visibility under good conditions is typically quoted as 6.5), and it is extremely unlikely that any brighter examples will be found.