Astrophysics (Index)About

standard candle

(astronomical object whose brightness can be determined)

A standard candle is any type of astronomical object whose brightness is known or can be determined irrespective of distance. When an instance is discovered, its distance can be determined by its brightness, as well as the distance to objects determined to be near it. For example, a galaxy's distance can be determined if a Type Ia supernova is observed in it because the supernova's brightness relates to how long it lasts, so by timing it, its brightness can be determined, and by how bright it is seen from Earth, its distance from Earth. Standard candles are keys to the cosmic distance ladder. A number of standard candles have been identified, whose consistency varies (given their usefulness, even a rough or probabilistic relationship is of interest):

The latter are sometimes referred to as scaling relations, the scale of the object has a mathematical relation with some observable quantity.

Further reading:

Referenced by pages:
blue horizontal branch (BHB)
Cepheid variable (CEP)
cosmic distance ladder
distance modulus (μ)
Hubble diagram
planetary nebula luminosity function (PNLF)
red clump (RC)
RR Lyrae variable (RRL)
supernova (SN)
supernova light curve (SN light curve)
supernova survey
standard siren
Tully-Fisher relation (TFR)
tip of the red-giant branch (TRGB)
Type Ia supernova
X-ray burster (XRB)