|Kayla Young 3/10/09
Mr. Guastella Science Research
An open cluster is a group of stars that are held together by gravity and whose stars lay at essentially the same distance from the earth. They are all thought to have formed at the same time, from the same materials, and under identical conditions (Chaisson 2005). Numerous amounts of astronomers for many of years have viewed open clusters. Due to new technologies and the development of the CCD imager, advanced analysis of many celestial objects can be made. The study of these celestial objects is important because they can provide information on the structure of the galaxy, provide clues to stellar evolution, and aid in calibrating knowledge of star brightnesses. (Moffat 1972).
In this study, the three clusters that were analyzed were NGC 6633; NGC 104 and NGC 6694. The data for the star clusters NGC 6633 and NGC 6694 was retrieved from the RBSE website in the form of fits files. The fits images were taken in the both the blue and visible color filters. The apparent magnitudes were then found for each star using the program ImageJ. The measurements from ImageJ’s astronomy plug-in were put into an excel file where then the numbers were analyzed. The apparent magnitudes were calculated first with the formulas [21.6-2.5 log10 (sourcev/vexposure)] was used to find the apparent magnitudes In the v filter; and [21.5-2.5 log10 (source/b exposure) ] was for the b filter. The blue filter apparent magnitude - visible filter apparent magnitude was then calculated. B-V is very crucial to find out several things about a star cluster such as age and distance. Once B-V and apparent magnitude was found the distance of the clusters were found using the formula [Mapparent – Mabsolute = 5 log (distance in parsecs) -5 + 3.1* Excess(B-V)]. The distance of cluster NGC 6633 was found to be about 550 parsecs (actual distance 376 parsecs). The distance of cluster NGC 6694 was found to be about 1300 parsecs (actual distance about 1500 parsecs). The distance, apparent magnitudes and the b-v was then used to find the absolute magnitude in the formula (mapparent- 5*log(distance/10)= absolute). The absolute magnitude for star cluster NGC 6633 was found to be about 2.6. The absolute magnitude for star cluster NGC 6694 was found to be 1.3. The ages for both of the clusters were determined using the b-v data.
The cluster NGC 104’s data was taken from a science lab in an astronomy course. The lab provided apparent magnitudes as well as b-v data. The distance of the cluster was taken from starry night, and other internet sources. The absolute magnitude was found using the same formula for NGC 6633 and NGC 6694. The age of the cluster was found using b-v data as well.
After comparing the data of ages and absolute magnitudes a correlation between ages and brightnesses were found; the oldest cluster NGC 104 had the highest brightness, and the youngest cluster NGC 6694 had the lowest brightness. Future research for this project could include a search of exoplants around certain stars in a cluster, as well as aging more clusters and determine their absolute magnitudes to have more support of my hypothesis.