From the USA, is the North Star always visible at the same location all times of the year? And the Big Dipper which rotates around it in close proximity, i don't always see it all the time, and I'm wondering why, 'cause i always see the North Star.
Posts: 625 | Location: Boston | Registered: 06-13-02
The most famous star in Ursa Minor is Polaris, the North Star. This is the star that is nearest to the North Celestial Pole. If you stood at the north pole, Polaris would be almost directly overhead. If you can spot Polaris in the sky, you can always tell which way is north. In addition, the angle of Polaris above the horizon tells you your latitude on the Earth. Because of this, Polaris was the most important star for navigating at sea.
Northern Hemisphere: The larger the Declination of a constellation (the closer it is to 90 degrees), the larger the fraction of the year it will be visible. For example, Polaris (Dec=89 degrees) is visible all year. What time are you looking? For every hour after 9:00 PM, the best date to see a constellation moves ahead half a month. For every hour before 9:00 PM, the best date moves back half a month. http://www.astro.wisc.edu/~dolan/constellations/extra/Positions.html *********************************************************** 09-11-02, 08:50 PM trueview Gerry, Saturday night, my son and I went out to a good viewing area. I had no trouble finding Polaris and most of its other stars but I couldn't see the big dipper. The seeing was to good. But we did see the Northern Lights. Tonight, Wednesday I went to the bluff on Lake Huron early in the evening and the seeing was not so good. I could see both of them with no problem. Too many stars masks the Big Dipper.
Lee
09-11-02, 10:34 PM Julieta Martinez what are the northern lights?
09-11-02, 10:45 PM anguilla Gerry, I think your question is still unanswered.
The stars rise 4 minutes earlier every night (just as the Moon rises 50 minutes later every night).
This applies to the Big Dipper, too, of course. As it rises earlier and earlier, it will eventually be rising during the daytime -- so you won't see it during that part of the year.
So, over the course of a year, the Big Dipper appears to orbit around the North Star.
Only if you are very far north will you be able to see the Big Dipper throughout the year.
I hope this helps.
==== Julieta, the northern lights are electrical effects caused by the Solar Wind interacting with Earth's magnetic field. The Solar Wind is the name for the particles that the Sun emits in every direction. When they hit Earth's magnetic field near the North and South Poles -- which are effectively the North and South poles of a giant magnet (Earth)...and a magnet is strongest at its poles -- the particles of the Solar Wind cause the atmosphere to glow. The northern (& southern) lights seem to ripple because the Solar Wind is affecting different parts of the magnetic fields at different times. It doesn't happen all at once.
I hope this makes sense!
09-12-02, 09:57 PM trueview Gerry and I both live close to 42 Deg. N. Lat. or higher. I can never remember the Big Dipper being below the horizon. Someone please correct me if I am wrong.
09-12-02, 11:45 PM anguilla You don't need correcting; you're right.
As seen from Minneapolis (about 45 degrees north latitude), the Big Dipper never sets. It approaches the northern horizon, but passes above the horizon without setting, and then gets higher in the sky again.
And you are at 42 degrees -- even further north
Source: Oop! Lost the record of my source!
09-13-02, 10:30 AM gerry Ang...
I haven't done much serious looking lately, the darn city lights usually spoil the view of the heavens, but I'm wondering, if I see the dipper to the left of the North star at say 9PM, then at 3AM, will it now have moved above or to the right of the North Star, or does it take another season to do that? I would think that It must rotate once each day around the star, due to earth's motion on its axis?
09-13-02, 12:19 PM methos the stars do in fact rotate once per ~24 hours. A rotation of once per 24 hours still means that many of them won't be visible because they will be overhead at the same time as the sun. The movement of the earth relative to the sun, however, changes which stars are visible at which time of year.
09-14-02, 12:26 PM mahal (Don't the stars rotate because we rotate? Once per 24 hours seems just about right!) wink
09-14-02, 02:35 PM Minnesota The Big Dipper itself can be seen as far south as -30 degrees. (South Africa, Brisbane). Polaris, which belongs to the the Little Dipper group of stars is visible as far south as -10 degrees (no notable cities).
09-14-02, 07:34 PM methos yes mahal, the stars appear to rotate because the earth is rotating.
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