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Astronomy/Globular Cluster Classification

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Expert: - 11/21/2005


Question
Hi Tom,

My question is this:  How can I interpret the classification scheme of Globular Star Clusters.

Most Globular Clusters appear to come with a class such as M 13 / NGC 6205 has the class 'V' and M 02 / NGC 7089 has the class 'II'.  I have Google'd for Globular Cluster class info a number of times, but always found nought - and they definately have a different class scheme from the Trumpler classification for Open Star Clusters.  
Any ideas please?
Cheers - Shortcake.  PS.  Many thanks for your reply to my last question, very helpfull.

Answer
Hi Shortcake, and cheers to you too....
Well, the Classification system for concentration of the cores
of globular star clusters was initially designed by Harlow
Shapley.
He put the most concentrated cores as Roman Numeral
I and the loosest cores as Roman Numeral XII.
So that makes globulars like M-2 and M-75 (two of the most
dense cores) classified as either I or II,
and very loose globs like M-55 and M-71 as class XI,
although I have seen M-71 as class XII -the most loose,
and easily resolveable right to the core with even a 3 inch
telescope.  On the other hand, M-75 (class I) I can't even
split stars in the core with my 30 inch portable scope as the
core is so densely packed with stars.
As for google, check out this site for more explanations:
http://www.astronomical.org/astbook/intglobular.htm

down near the bottom of the page.
And if you have any astronomy questions to follow, please
feel free to contact me directly at
bwhiting@velocity.net
as I am retired USAF pilot with lots of time on my hands,
and always enjoy answering any astronomy questions.
Clear Skies,
Tom Whiting
Erie, PA  USA

And for great pictures of my new 30 inch portable truss-DOB
scope, please see our club website at
http://www.velocity.net/~bwhiting

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Tom Whiting

Expertise

Astronomy has been my hobby/pasttime for over 50 years.  Currently own 3 telescopes, the largest of which is a 30 inch Newtonian truss Dob that is portable.I taught Astronomy/Meteorology at the University Level for 13 years before retiring in 1995. Being retired and home most of the time, I am able to answer all questions relatively quickly, unless it's a new moon weekend with good observing conditions.  No astrology questions please, or questions about alleged UFO picture identifications.

Experience

Experience: Astronomy has been my hobby and study for over 50 years. We currently now own a 30 inch portable telescope (Updated - Pennsylvania`s largest portable telescope). It can be seen on our website at:http://www.velocity.net/~bwhiting and also attend several regional starparties during the year, and have been on 5 total solar eclipse expeditions.

Organizations: President, Erie County Mobile Observers Group for over 15 years.

Publications: Wrote the "Over Erie Skies" newspaper article in our local newspaper for 11 years (1975-86).

Education: Masters Degree- Taught at the University level for 13 years. Retired 20 years -USAF Pilot - KC-135 with 180 combat missions;  Also Eagle Scout, Philmont staff 2 Yrs, Order of Arrow Lodge Chief, Ham Radio (inactive).

Awards: two discoveries: The mini-coathanger asterism in Ursa Minor (the little dipper) And the mini-ladle- another asterism in the bowl of Ursa Minor. Clients: Currently President of the ECMOG as mentioned above.

Education/Credentials
BS  Metallurgical Engineering Grove City College, PAMaster's Degree, Gannon University, Erie, PA Also retired USAF pilot, 20 years.

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