Polarissima Borealis (NGC 3172)
History
The galaxy NGC 3127 was discovered by John Herschel on 4 October 1831 while observing from Slough. He listed it as h 250, named it «Polarissima» and noted: «Very faint; round; gradually brighter in the middle; 20" diameter; has a star 11 magnitude 2' south. This nebula is remarkable for its proximity to the pole. Owing to this the AR cannot be determined exactly, and the PD is open to correction.» [466]
Later NGC 3127 was renamed to «Polarissima Borealis» to distinguish it from «Polarissima Australis» (NGC 2573). Due to the precession of the Earth's rotation axis (circle with 23.4° radius in ~25'700 years), NGC 3127 was at time of discovery just 4.5' away from the north celestial pole. Today the celestial pole has wandered about 1° further away.
Physical Properties
| Designation | NGC 3172 |
| Type | Gx (S?) |
| Right Ascension (J2000.0) | 11h 47m 14.5s |
| Declination (J2000.0) | +89° 05' 37" |
| Diameter | 1 × 0.7 arcmin |
| Photographic (blue) magnitude | 15.0 mag |
| Visual magnitude | 14.1 mag |
| Surface brightness | 13.7 mag·arcmin-2 |
| Position Angle | 39° |
| Redshift (z) | 0.020334 |
| Distance derived from z | 85.89 Mpc |
| Dreyer Description | vF, R, gbM, * 11 s 2', Polarissima Borealis |
| Identification, Remarks | h 250; GC 2043; MCG 15-1-11; CGCG 370-8B; CGCG 370-2A; NPM1G +89.0003; Polarissima borealis |
Finder Chart
The galaxy NGC 3172 is located in constellation Ursa Minor, roughly 1.5° away from Polaris. With equatorial mounted telescopes (especially fork mounts) it may be difficult or even impossible to reach it.
Visual Observation
762 mm Aperture: Comfortably slewed to the northernmost NGC galaxy using GoTo. The first look through the eyepiece already revealed NGC 3172 as a galaxy with a bright point-like core embedded in a faint cottony haze. It is clearly recognizable as a galaxy and not as a star. The galaxy PGC 36268 or MCG +15-01-010 is visible only through an EAA exposure. — 30" f/3.3 SlipStream Dobsonian, Hasliberg, 19. 9. 2025, SQM-L 21.11, Eduard von Bergen