1 parsec how many au

Close just your left eye and observe where your finger appears against the background; next, open your left eye and close your right. Your finger will appear to shift because each eye views it from a slightly different angle. Translated to the stars in the sky, two photographs of the same nearby star taken six months apart will show it appearing to move against the background of more distant stars because Earth has moved to the other side of the Sun in its orbit.

And a parsec is the distance — 3. Although astronomers often measure distant objects in parsecs or megaparsecs 1 megaparsec is 1 million parsecs , only nearby objects have parallaxes, or shifts on the sky, that we can actually measure.

It can measure, to within 20 percent accuracy, the distances of stars that lie tens of thousands of light-years away. Receive news, sky-event information, observing tips, and more from Astronomy's weekly email newsletter. View our Privacy Policy. By signing up you may also receive reader surveys and occasional special offers. We do not sell, rent or trade our email lists.

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