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Canopus III

February 24, 2015

If you’re south of about Dallas, the star Canopus can serve as a navigational beacon tonight. It passes due south around 9 or 9:30. And it’s the second-brightest star in the night sky, so it really stands out. But it’s quite low, so you need a clear horizon to find it.

There’s evidence that Canopus helped folks get their bearings for centuries. And it’s still a popular beacon today — not for people, but for spacecraft.

One early use for Canopus may have been as a calendar marker in ancient Arabia. Its first appearance in the early morning sky may have heralded the start of a new year.

Later, Canopus helped Polynesian sailors navigate from island to island. It also helped European sailors when they began to journey through the southern hemisphere.

When NASA began planning missions to the Moon and planets in the 1960s, it needed a star to serve as a handy navigational beacon. Locking on to the star and the Sun would keep a craft on target.

Canopus was the obvious choice. Not only is it bright, it’s also well away from the ecliptic — the Sun’s path across the sky. That means there’s always a good separation between Sun and star, so they’re both always in view. And there are no other bright stars or planets around it to confuse the tracking system.

Canopus made its debut with the Surveyor missions to the Moon and Mariner missions to the planets. And it still helps guide spacecraft today — on journeys across the solar system and beyond.


Script by Damond Benningfield, Copyright 2014

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