Unlike the terrestrial North Pole, the heavenly version is easily accessible any clear night of the year. We explore curiosities within one degree of the celestial north pole and take a journey back in time.
What could be more appropriate in January than a jaunt to the north celestial pole? When the polar vortex comes howling and temperatures plummet, consider a visit to the origin of all things north.
To keep things truly boreal, we're going to restrict ourselves to within one degree of the pole, or north of declination +89°. First and most obvious is the Pole Star itself — Polaris. The star's singular position at the sky's celestial pivot point has served to inflate its reputation into a common misconception. People think it's the brightest star in the sky! Yet the North Star's hardly in the running, ranking only 48th in brightness.
Because Earth's axis points squarely at Polaris, as the planet rotates the star remains almost motionless in the heavens while all the others appear to turn about it. You can easily determine the height of Polaris above the local horizon by knowing your latitude. Live in Boston, Massachusetts, at 42° north? That's how high the North Star is above the northern horizon. Any stars within 42 degrees of Polaris never set and are said to be "circumpolar." Stars beyond that limit get cut off by the horizon for a period of time before rising into view again.
Through a 2.4-inch or larger telescope, Polaris is a pleasing double star with a considerably dimmer 9th-magnitude companion. When the brighter, showier Albireo (Beta Cygnii) is visible, I enjoy showing groups this star first and then surprising them with Polaris. Many will miss the fainter companion on a quick look but then have the pleasure of discovering it themselves with just a bit of effort.
Things can be lonely at the pole, a relatively empty region of the sky, but Polaris glitters like a diamond atop a lovely asterism dubbed the "Engagment Ring," a loopy band of 9th-magnitude stellar gems plainly visible in telescopes and even in 50-mm binoculars under dark skies.
Moving deeper, we encounter a pair of deep sky objects located just 55′ from the polar pivot, the spiral galaxy NGC 3172 and MCG +15-1-10. Also called Polarissima Borealis because of its proximity to the north celestial pole, NGC 3712 glows feebly at magnitude 13.6 and will prove a challenge for a 10-inch telescope under dark skies. In my 15-inch Obsession it's a dim, round patch with a brighter center. For those who like their fuzzies faint, try spotting its 15th-magnitude neighbor about 2′ to the west.
One of the bonuses of observing objects near the celestial pole is not having to worry about tracking your target. An object centered in the field of view will stay there for many minutes without the need to nudge the telescope — a real pleasure for those with non-motorized Dobsonian reflecting telescopes.
The closest "bright" star to the north celestial pole is 9.7 magnitude SAO 3788, presently about 15′ (1/4°) away. Due to the precession of Earth's axis, Polaris has only been close enough to assume the role of pole star since the early medieval days. Around the time of Caesar, both it and Kochab, an equally bright star in the Little Dipper's bucket, were nearly equidistant from the pole.
Polaris has been inching poleward for centuries and will reach a minimum distance of 27′ — just under 1/2° or one Full Moon diameter — in March 2100. The news will undoubtedly be a hot topic on what remains of the Internet in that distant year. Will someone scheme up a doomsday scenario where the pole star focuses magnetic beams on a hapless humanity? Don't doubt it.
Long before the reign of Polaris, when the Great Pyramid was built in Giza around 2550 BC, 3.6-magnitude Thuban (Alpha Draconis) marked the polar point. At magnitude 2.0, Polaris has been the brightest pole star since 12,000 BC when Vega last had a run at it. Once Polaris begins its slow departure in 2100, it won't return again to polar glory until AD 28,000!
Can't find the pole star? Let a Sky & Telescope Star Wheel guide you!