Requires very precise measurements of stellar positions, and long baselines

Trigonometric Parallax

• Requires very precise measurements of stellar positions, and long baselines

• Need telescopes with high resolution, and must observe over several years.

• Hipparchos satellite measured distances to tens of thousands of stars within 1,500 light-years of the Sun.

2) The Standard Candle

• Use knowledge of physical and/or empirical properties of an object to determine its Luminosity, which yields distance via the Inverse Square Law of Light.

• Ex: Cepheid Variables, Supernovae, TRGB, Tully-Fisher

• Considered to be relative until tied to an absolute calibration.

Cepheid Variable Stars

• There is a kind of giant star whose surface pulsates in and out with a regular period. That period of pulsation is related to the Luminosity of the star.

• LMC contains hundreds of known Cepheids all at the same distance. Which allows for robust determination of the Period Luminosity Relationship.