How do astronomers measure the distance to stars?
Quick Answer
For nearby stars, they use parallax, the tiny apparent shift seen from opposite sides of Earth’s orbit. More distant stars require other methods, such as standard candles.
The Full Story
Parallax is the most direct way to measure stellar distances. Astronomers observe a nearby star from two points in Earth’s orbit, typically six months apart, and measure how much the star appears to shift against more distant background stars. The smaller the shift, the farther away the star is. The European Space Agency’s Gaia mission has measured parallax for more than a billion stars, creating a vastly improved map of the Milky Way. For stars too distant for precise parallax, astronomers use other techniques like Cepheid variables or supernovae as standard candles.
Key Facts
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