Stellar Parallax: Definition, Formula, and Importance in Astronomy

Context: Astronomers have shown that spacecraft can navigate deep space using just two stars as reference points through a method called stellar parallax.

About Stellar Parallax

• As Earth orbits the Sun, we look at a star from two opposite sides of Earth’s orbit (say, in January and July).
• The star seems to move slightly against the background of more distant stars.
• This apparent shift is called stellar parallax.
• By measuring the parallax angle (the apparent displacement of the star), astronomers can calculate the distance to the star using trigonometry.
  • Small parallax → star is far away.
  • Larger parallax → star is closer.
• Uses:
  • Space navigation allows spacecraft to autonomously determine their location without constant signals from Earth.

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