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Standard Candles in Astronomy


Contents

Parallax
Cepheid Variables
Planetary Nebulae Luminosity Function
Tully-Fisher Relation
VLBI
TypeIa Supernovae
Sunyaev-Zeldovich Effect
Gravitationally Lensed Quasars

A standard candle is a class of astrophysical objects, such as supernovae or variable stars, which have known luminosity due to some characteristic quality possessed by the entire class of objects. Thus, if an extremely distant object can be identified as a standard candle then the absolute magnitude M (luminosity) of that object is known. Knowing the absolute magnitude, the distance D (in cm) can be calculated from the apparent magnitude m as shown in the formula below.

m = M - 97.5 + 5xlog(D) ---------- (1)

Figure 01 below shows the different kind of "standard Candles", including the Cepheid Variables (star), the planetary nebulae, and the Type Ia supernovae (together with other distance measuring tools).

Standard Candles

Figure 01 Standard Candles