Messier 2: not more that 200 stars?

Of the many striking stellar clusters in the great galactic clouds extending through Ophiuchus, and Scorpio, none has received as much attention as Messier II, the very rich open aggregation of stars in the small constellation of Scutum Sobieski. Discovered by Kirch two hundred and thirty-five years ago, it has since been observed and described by nearly all students of clusters, nebulae, and comets….

This is the beginning of a paper by Harlow Shapley published in 1917 on The Astrophysical Journal. He made a catalogue of 458 stars within four minutes of arc of the center of the “open” galactic cluster Messier II, claiming a  resulting color-index that does not exceed a tenth of magnitude.

One very interesting thing, he states in the conclusions that “it seems probable that the cluster proper is composed of not more than 200 stars” (!!). Today we know that the stars are much more numerous, since modern estimate talk of about 100,000 stars (but we cannot blame Shapley because of the instrumentation available at his epoch).


Messier 22 imaged by Hubble Space Telescope (Credit: NASA/STScI/WikiSky)

Messier 2 was discovered by Maraldi on September 11, 1746. Rediscovered by Messier on September 11, 1760, it has an interesting observation history.

Our cluster’s entry for M2 is

Introducing gclusters 11.12, “Hergest Ridge”

Hello, just a few lines to let you know that the gclusters website (also known as Galactic Globular Clusters Database, GGC-DB) has been updated this morning. The present release is 11.12 “Herdest Ridge” (our codename being based upon Mike Oldfield discography, this supersedes the previous Ommadawn release), in which the most recent values of parameters has been loaded from the 2010 compilation of W.E. Harris (see this astro-ph for details on Harris 2010).

I thinks some words are needed to illustrate the details of the this release. You may already know that the 2o1o version of the Harris’  catalogue do present some modification, for what concerns the details of the listed parameters (more info at ). Given that I had built the website of gclusters following closely the Harris’ 2003 release, I had to take a few decision during the update to the latest Harris catalogue.

After a lot of thinking (and some attempt..) I choose to follow this rationale:

– For the time being, no major modification have been done in gclusters, for that concerns the list of parameters to display (they mimiks closely Harris 2003, plus all the “bonus” of gclusters, i.e., bibliography, color magnitude diagrams, etc…)

– Where available, “old” values of parameters (Harris 2003) have been superseded by “new” values (Harris 2010)

– Columns not listed anymore by Harris 2010, are still present in gclusters, but their values has not been globally updated (there are some handpicked updates available, anyway: you may notice the red dot, here and there…)

– In the near future, some of the new columns choosen by Harris 2010, could be imported in gclusters as well.

If you are a user of gclusters, I strongly encourage you to let me know of any problem you may find with this new release (and/or any other feedback); this will help me a lot in giving a useful product to the community !

Meanwhile, do not forget to have a look at the early release of the VOGCLUSTERS web application, that you can find at

Marco Castellani :: INAF – Rome Astronomical Observatory

VOGCLUSTERS, Data Mining WebApp on GCs

Dear friend, just  a line to let you know that our upcoming  web application on Globular  Clusters (codename VOGCLUSTERS) is moving towards its first release.

Our Logo


“The goal of the project VOGCLUSTERS is the design and development of a web application specialized in the data and text mining activities for astronomical archives related to globular clusters. Main services are employed for the simple and quick navigation in the archives (uniformed under VO standards and constraints) and their manipulation to correlate and integrate internal scientific information. The project has not to be intended as a straightforward website for the globular clusters, but as a web application…”

We are on private testing, and hope to open the first web app to the general public as soon as possible. Check the quoted webpage for more info and to know when will be avaliable (if you want to be notified, leave a comment to this post)

Stay tuned😉

Kind regards,

Marco C.

New address for gclusters

Dear friend,

just a couple of fast updates on the gcluster project, since it’s a lot of time from our last post. We have good news: the building of a web application (VOGCLUSTERS) is still under developement, but we’re getting quite near to a first public release😉

Meanwhile, the “classical” website of gcluster, for technical problems, has changed address: you can find it now at

We also have an associated group on Mendeley, where we collect relevant papers for globular clusters aficionados:

Feel free to subscribe, if you’re in that network too😉

Marco Castellani


Dear friends, while it may seems that the gclusters project (The Galactic Globular Clusters Database) has not been interested by much activities lately, as a matter of fact we have worked setting the stage for a big improvement: gclusters is on its way to became a real web application. This means that a lot of new feature will be implemented, such as the possibility (for registered users) to submit information in the database, an extensive and complete system to perform searches, a lot of more data available online, etc..

The web application (codename VOGCLUSTERS) is being developed under the DAME Project (in particular, see the DAME Science page): “DAME (DAta Mining & Exploration) is a project aimed at designing and developing instruments and tools for scientific data mining, based on information and comunication technology. DAME is an evolution of the Astroneural and VO-Neural projects and is funded by the Italian Ministry of Foreign Affairs as well as by the European project VOTECH (Virtual Observatory Technological Infrastructures) and by the Italian PON-S.Co.P.E.” (from DAME webpage).

In the past months, I had several contacts with the kind people of the DAME Working group , and I’m extremely  satisfied about their work on the project, which is now in an advanced phase of realisation (we have defined a complete and detailed document about Software Requirement Specification, and the work on the webpages is already started).

I’ll use this blog to keep you updated about the status of VOGCLUSTERS; meanwhile, as you may understand, I do not plan to make major improvements in the current implementation of gclusters (which anyway well remain online and fully operative). If you desire more detailed information, you’re invited to contact me (let a comment in this blog, in case)

Needless to say, I’m quite excited about the upcoming steps for gclusters/VOGCLUSTERS…😉

Marco Castellani

[Jan. 09] A remote repository for gclusters

Dear friends, first of all, accept my best wishes for a good and peaceful new year!

Speaking about the Globular Clusters Database, I should say that work is still in progress, even if at a slow rate, also for my involvement as a developer in the ESA-GAIA project, that takes much of my time at the moment.

I have just put all the files of gcluster on a remote website, in order to allow other person to see the code, send bug report, and even make modifications to the files themselves. If you are interested (even in sending bug report or just to have a quick look at the PHP code) please email me at m.castellani (at), and I’ll give you access to the remote repository.

Specifically, the files of the project has now put under git ( a software of revision control); the remote repository is hosted by This should turn very useful to keep track of all modifications in the files and to work towards a distribuite collaboration (well, that’s still my dream!)

The location of the reporitory is

As specified above, (at the moment) an allowed account is needed to access the project (source code). Conversely, bug submission is free to all registered inDefero users, and listing of submitted bugs is free for all.

Do not hesitate to ask if you have questions😉

Kind regards,

Marco Castellani