Object of the Week 31st December 2017: NGC 2362, the Tau Canis Majoris Cluster

Object of the Week December 31st, 2017: NGC 2362, the Tau Canis Majoris Star Cluster


Type: Open Star Cluster
Constellation: Canis Major
RA: 07h 18.7m
DEC: -24° 57’
Magnitude: 4.1v
Size: 6' diameter

Winter evenings can be cold, or really frigid cold, but during clear nights the skies can be spectacular. The winter Milky Way arches above, and goes through the Great Dog, Canis Major, which hosts the sky’s brightest star, Sirius. Canis major does have a profusion of open star clusters, but there is one that is glorious indeed: NGC 2362, a superb star cluster surrounding the 4.4 magnitude star Tau Canis Majoris.

Attachment 2850
DSS image of NGC 2362

This cluster, which was discovered sometime around 1654 by Giovanni batista Hodierna, consists of more than 60 stars tightly packed in a 6 arc-minute clump around Tau. At the cluster’s estimated distance of 5,000 light years, NGC 2362’s true diameter corresponds to about 9 light years. The Tau Can Maj cluster is amongst the youngest star clusters known, with an age of only a few million light years, and almost all its stars are of spectral types O, B, and A. Desite it’s young age, NGC 2362 does not have any distinct nebulosity associated with it, but deep photographs do show that is surrounded by a 5 degree wide faint nebula centered on the cluster, named Sharpless 310.

Attachment 2851
Photo source: http://www.conferringwiththesky.org/...ge.php?pid=256

Astrophysics aside, for me NGC 2362 is one of the most beautiful and spectacular open star clusters in the sky. There is simply no chance I will not check out NGC 2362 if during my observing session is above the horizon. Its telescopic appearance is simply captivating. A brilliant bluish white star surrounded tightly by several fainter suns, an image that is equally stunning whether I use my 18” dob, my 5 and 6” achros, or my 3, 4, or 5” apos. What’s more, although the image through every scope is pretty much similar (differing only in the brightness and number of fainter stars seen, depending on the scope’s aperture), every scope gives this cluster a different character. My 18 Obsession adds diffraction spikes on brilliant Tau, and brings out many of the fainter members of the cluster which would normally hide in Tau’s blinding glare. My apos show Tau as a splendid bluish white pinpoint star, cleanly separated by several fainter stars arranged in a roughly triangular pattern around it, and my achros give this image a somewhat softer touch, adding a bit of warmth to the icy cold bluish shades of the cluster.

So, next time you are out in the cold winter nights, turn your scope to Canis major, spot NGC 2362, and…

Give it a go and let us know!