Object of the Week, March 27: Polaris - and the first degrees around
Object of the Week, March 27: Polaris - and the first degrees around
Objects:
- Polaris (star)
- "Engagement Ring" (asterism)
- PGC 138464 (galaxy)
- NGC 3172 "Polarissima Borealis" (galaxy)
- NGC 188 (open cluster)
- "Polaris Flare" (galactic cirrus cloud)
Many of us starts our session with looking at Polaris - by checking the Seeing conditions, testing the collimation, adjust the finder telescope or setting the EQ-mount. But what is around?
Starting with Polaris itself, the star is in real a triple star system. The brightest component Aa is around 2vmag bright and part of the variable Cepheid family. The yellow supergiant with 5.4 solar masses is around 450 ly (Gaia) away. The brighter and further off component B with its 8.7vmag can easily resolved at 18.4" distance to Aa. The bright enough companion Ab with its 9.2vmag is only 0.17" away from Aa and so not reachable for amateur astronomy.
Looking at the finder telescope or searching eyepiece with low power or binoculars, we can find a nice asterism directly south of Polaris. The "Engagement Ring", "Polaris Ring" or simply "Diamond Ring" consists of around a dozen stars in a nearly one degree circle.
Going deeper, we can ask which is the nearest Deep Sky object around Polaris. To be more precise, Polaris is around 0.7° away from the North Celestial Pole, but let us assume Polaris as zero. With common telescopes, PGC 138464 could be the culprit. The nice spindle is around 5' north of Polaris. Infrared measuring listed the galaxy with 14mag. My own observation with 27-inch was positive. I could catch a somewhat elongated glow just with direct vision, when Polaris was out the field. I have no clue what minimum aperture is needed, but that is your turn to find out.
The more prominent neighbour galaxy is NGC 3172 which is also called "Polarissima Borealis". With its distance of around 1.5° east of Polaris it still don't need any tracking of the telescope, a funny side issue of this object. The nearly round and very diffuse galaxy looks boring at the first impression. But the direct neighbourhood with its more or less faint companion galaxies makes it more attractive. Brightest galaxy is MCG+15-01-010 only 1.6' SW. With 16bmag it needs a mid size telescope to see it. Stretched images shows a large 3.5'x3' ring around the galaxy. I could not see this ring but it could maybe a target for very large telescopes?
4° south we can find the very interesting open cluster NGC 188 Interesting and beautiful even for larger instruments. With an age at five to six billion years, the object counts to the most ancient of the known open clusters. It is worth a note that the cluster lies far above the plane of our galaxy because of the mentioned age and his drift apart. While the cluster is famous for its low surface brightness, I could catch it during very good transparency with my 8x30 binoculars. Larger instruments shows the many of the around 120 member stars of the cluster.
If all the described stuff is not fascinating enough, the region offers another very faint but spectacular object - the galactic cirrus called "Polaris Flare". Péter Csordás showed a 7° field around Polaris with its very faint nebula. Expert Mel Bartels sketched and described the nebula as faint among the huge number of observed ISM. I observed this region several times and always had less difficulties to see the nebula as for example the more famous ISM near M 81/82.
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