Why does the North Star appear to be stationary if I’m not seeing it from the North Pole? I ask because from the Northern Hemisphere I see it at about 60 degrees rather than directly overhead. How does that work? Is it actually moving in a very small circle?
It is moving in a very slight apparent circle as it is about 0.75º from the North Celestial Pole. Given the tiny parallax of the Earth’s rotation even at the equator, the difference is not clearly visible to the naked eye and would require a very large fixed sextant or equatorial mount telescope to actually measure the arc that it makes.
Stranger
Polaris is 434 light-years away from Earth.
Imagine you’re looking down a road at a car that’s many, many, miles away. If you cross the street does the position of the car change?
The difference between viewing Polaris at the Pole and at the Equator is nothing compared to crossing that street.
And remember, despite Earth’s average distance from the Sun, 92,956,050 miles -185,912,100 miles from ‘side to side’ (January 1st to July 1st), even at the Pole Polaris is still directly overhead.
This smells like the source of confusion right here.
The parallax others have mentioned has nothing to do with it. For all eyeball-precision practical purposes, Polaris is directly aligned with the Earth’s polar axis.
The big thing that matters is your latitude. if you were standing on the North Pole, Polaris would be 90 degrees overhead = straight up. If you’re standing on the Equator, Polaris would be sitting on the northern horizon.
The reason for the difference is not the linear displacement between the centerline of the earth and the equator. The difference is entirely which way is “straight up” when you’re standing someplace on a sphere.
If you claim Polaris appears to be about 60 degrees north of straight up (= 30 degrees above the northern horizon) where you are, I predict your latitude is very close to 90 - 60 = 30 degrees.
Thanks, Dopers! It’s still over my head (heh) but makes more sense now.
It is, almost exactly, the dot your sky bowl rotates around.
Consider the following hypothetical: As you drive around a traffic circle, the tower in the center appears to be stationary. It’s always directly out your left window (unless you’re in the UK)
A propos, 1 parsec (parallax of 1 second) = approximately 200000 au, or 3.26 light-years. But, according to astrometric data, the parallax of Polaris is 7.56 milli-arcseconds, not really much for your eyeballs.
Hmmm, not sure how to reply to multiple posts.
So, naita and Honolulu_Lulu, yeah I get the basic idea. What was really confounding me is that Polaris doesn’t appear directly overhead. LSLGuy’s reference to “standing someplace on a sphere” gave me some perspective.
Thanks to all. Very interesting subject. I had a quick look online for an explanation before posting. In the Wikipedia entry alone (Polaris), there’s an astounding amount of information, from etymology to astronomy.