What is a standard candle?

An object with a known absolute magnitude (like a Type Ia supernova or Cepheid variable), allowing distance measurement via the distance modulus.

What distance modulus corresponds to 10 Mpc?

m - M = 5 log10(10^7/10) = 5 × 6 = 30. Such large moduli apply to distant galaxies.

Yes. Dust dims light (extinction), making objects appear farther than they are. Corrections for reddening are essential.

Calculate the distance to a star from the difference between apparent and absolute magnitudes: d = 10^((m - M + 5) / 5).

Apparent Magnitude (m)

Absolute Magnitude (M)

Distance

206.06 pc

Distance Modulus (m - M)6.57 mag

Distance (ly)672.09 ly

Distance vs Apparent Magnitude (m)

The distance modulus (m - M) connects apparent and absolute magnitudes to distance.

d = 10^((m - M + 5) / 5) parsecs

This is the inverse of the magnitude-distance relation and is fundamental to the cosmic distance ladder.

A Cepheid variable has m = 1.43 and M = -5.14.

Compute apparent magnitude from distance.

Find intrinsic brightness.

Explore distance methods.