How do astronomers measure the distance to nearby stars?
Quick Answer
They use parallax: a star’s apparent shift against distant background stars is measured from opposite sides of Earth’s orbit. For very nearby stars, this gives distances in light-years with high precision.
The Full Story
Astronomers measure nearby stellar distances with trigonometric parallax, a method refined by modern space telescopes. As Earth orbits the Sun, a close star appears to shift slightly relative to very distant background stars; the angle of that shift is used to calculate distance. The European Space Agency’s Gaia mission, launched in 2013, has measured parallax for more than a billion stars and transformed stellar mapping. One parsec equals about 3.26 light-years and is defined by a parallax of one arcsecond.
Key Facts
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"The tiny star wobble that lets us measure the Galaxy."
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