Photometric-standard stars are a series of

star A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...

s that have had their

light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 tera ...

output in various

passband A passband is the range of frequencies or wavelengths that can pass through a filter. For example, a radio receiver contains a bandpass filter to select the frequency of the desired radio signal out of all the radio waves picked up by its antenn ...

s of

photometric system In astronomy, a photometric system is a set of well-defined passbands (or optical filters), with a known sensitivity to incident radiation. The sensitivity usually depends on the optical system, detectors and filters used. For each photometric sy ...

measured very carefully. Other objects can be observed using CCD cameras or photoelectric photometers connected to a

telescope A telescope is a device used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation. Originally meaning only an optical instrument using lenses, curved mirrors, or a combination of both to observe ...

, and the ''

flux Flux describes any effect that appears to pass or travel (whether it actually moves or not) through a surface or substance. Flux is a concept in applied mathematics and vector calculus which has many applications to physics. For transport ph ...

'', or amount of light received, can be compared to a photometric-standard star to determine the exact brightness, or

stellar magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's ...

, of the object. A current set of photometric-standard stars for UBVRI photometry was published by

Arlo U. Landolt Arlo Udell Landolt (September 29, 1935 – January 21, 2022) was an American astronomer known for his widely used photometric standards. Life and career Early life Landolt was born in Highland, Illinois to farmers Arlo M. Landolt and Vesta K ...

in 1992 in ''

The Astronomical Journal ''The Astronomical Journal'' (often abbreviated ''AJ'' in scientific papers and references) is a peer-reviewed monthly scientific journal owned by the American Astronomical Society (AAS) and currently published by IOP Publishing. It is one of the ...

''.

References

Star types Standard star {{star-stub