M3 and M13: globular star clusters

Event Date: February 5th

Time: 1:00 AM

Brief

   Yesterday, I showed the "magnificent" Hercules star cluster; a globular which is bright enough to see with binoculars, and much more impressive with a telescope.  Along with another globular I will show, M3 in the constellation of Canis Venatici a little further west and south of M13, I will give some stats about the two, regarding magnitude, angular diameter, and more.

The first image shows both four hours before the time used yesterday, with M3 magnified the same as M13 yesterday: a little under 100x.  The second image shows the two clusters, followed by some hopefully-helpful ways to find M3.

click on images to enlarge: courtesy of Starry Night Pro Plus, version 6.4.3, by Simulation Curriculum Corp.

Detailed

   The two globular clusters are a little over 38º apart, and almost exactly the same apparent magnitude (7.0).  The angular size differs, as M3 is is about 33% larger at 48 arc-minutes compared to M13's 36.  Also, whien it comes down to distance, M3 is 10,000 light years further, at 35k compared to M13's 25k.  As a result, we don't see too much more to M3 when compared "sparkly" or "snowflake-y" M13 (I have heard both, yet not sure why!)

However, I personally like M3 almost as much, and one reason for that is as follows: in the early-spring evening sky, most easy-to-see deep-sky objects are below the horizon during much of the evening, seen only well after nightfall or early in the morning before Sunrise; M3 up before several of them, seemingly getting that part of the sky to itself.  Okay...that may sound strange, yet for us mid-northern latitude viewers, it gives us something to think about!

   As a little background and reminder, the stars that make up each globular--as well as open--clusters are from the same molecular cloud.  Globulars are tightly bound by gravity while open ones are bound much less, and seem "loose" when we view them in a telescope. 

   Although image one shows M3 labeled, look below it to notice bright Arcturus, featured a couple of weeks ago.  If a line is drawn straight from Arcturus to M3, it will extend to a 2,8 magnitude star named Cor Caroli; Latin for Charles' Heart, and much more info can be found with the provided link.  I purposely did not label Cor Caroli, because I want your eyes to get familiar with the east-northeastern sky when it and the cluster.  M3 is close to between it and Arcturus, yet a little closer to Arcturus. 

Now that we have reviewed these two gems of deep sky, what other globular clusters or any other sights can you find in the pre-dawn sky?  Use some binoculars or a wide-field telescope to search around.