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| Space on Jul 11, 2012

Does Mars have a North Star?

Earth’s north star – Polaris – is located nearly directly above Earth’s north pole. There’s a star above Mars’ north pole, too, but it’s very faint.

Mars, 4th planet from our sun, as seen by the Hubble Space Telescope.

The North Star for Earth is Polaris. Does our next-door neighbor planet, Mars, have the same North Star as Earth? If not, does Mars have star located more or less above its north pole?

Every planet in our solar system spins on its axis. Earth spins once in about 24 hours. And if you continue the imaginary line of a planet’s axis out into space – in a northern direction as measured from earthly north – it might point to a star that’s visible to the eye. We call such a star a pole star, or North Star. On Earth, that star is Polaris.

More about Polaris: The North Star

Meanwhile, Earth’s Southern Hemisphere doesn’t have a comparable South Star. The nearest visible star to the south celestial pole of Earth is about 9 degrees away.

So, does Mars have a North or South Star?

Sunset on Mars, as seen by the Mars rover Spirit in 2005. More about this image. The night sky must be beautiful from the surface of desolate Mars. Image Credit: NASA

Time-lapse composite of the two tiny martian moons, as seen from Mars’s surface. Phobos is the brighter moon. Deimos is fainter. Acquired by Mars rover Spirit on August 26, 2005. Tiny streaks mark the trails of background stars moving across the sky or the impact of cosmic rays lighting up random groups of pixels in the image. More about this image. Image Credit: NASA

The answer is no reliable north pole star and only a modestly-bright south pole star. In the northern sky as seen from Mars, the best candidate is a star half a degree off from the north celestial pole – closer than Polaris is to Earth’s north celestial pole. But, while Polaris is pretty bright (50th brightest of all stars in the night sky), Mars’ north pole star is faint. It’s barely within the limit of visibility to the eye alone.

Mars’ north pole points to a spot in the sky that’s about midway between Deneb, the brightest star in the constellation Cygnus the Swan, and Alderamin, the brightest star in the constellation Cepheus the King. Click here to see the position of Mars’ north celestial pole between the constellations Cygnus and Cepheus.

Meanwhile, in the southern sky as seen from Mars, Kappa Velorum – a fairly bright star in the constellation Vela – is near the martian south celestial pole at about three degrees away.

On the other hand, if you were standing outside at night on the surface of Mars, you’d see some other cool stuff! For example, as seen from Mars, you could see Earth’s moon orbiting around Earth once each month. From Earth, we can’t see any other planets’ satellites with the unaided eye, but this amazing sight on Mars would be visible to the eye alone. Both the Earth and the moon would appear starlike.

In general, the Earth as seen from Mars would somewhat mimic our view of Venus as seen from Earth. By that we mean that – like Venus in relationship to Earth – Earth in relationship to Mars is an inner planet. It orbits closer to the sun. Thus Earth as seen from Mars would be a morning or evening “star” – just as Venus is as seen from our world. And although both the Earth and moon would appear as stars to the unaided eye, observers on Mars with telescopes would sometimes see them as crescent worlds – just as we do Venus.

So … no North Star for Mars. But stargazers wouldn’t lack for things to see!