NGC 2112 (also known as Collinder 76, C 0551-0031, OCL 509) is a northern open cluster of intermediate age, located in the constellation of Orion with Celestial coordinates of Right Ascension: 05h 53m 44s and Declination: +00° 24â 38â.
It was discovered by William Herschel in 1785 and is estimated to be around 2.0 +/- 0.3 Gyr (log(age)= 9.30). LyngÄ (1987) reported that NGC 2112 has a diameter of approximately 18 arcmin.
The cluster is located at a distance of approximately 940 parsecs from Earth with a magnitude of around 9.10.
Radial velocity (refers to the movement of an object along the line of sight of an observer) of NGC 2112 is 30.861 km/s.
Although this cluster has not been studied in detail, its location in the Milky Way galaxy and its combination of suspected old age and low metal abundance makes it a fascinating object to study in the context of the chemical evolution of the galactic disc, according to Carraro, Ng & Portinari (1998).
The cluster contains around 100 stars. The individual stars within the cluster have different visual magnitudes. The brightest stars in the cluster are around visual magnitude 11-12, while the faintest are around visual magnitude 18-19. The overall brightness of the cluster is affected by the number and brightness of the stars within it.
The initial study of NGC 2112 was conducted by Richtler (1985). He called attention to this potentially old and overlooked cluster by obtaining photographic BV photometry for 80 stars down to V = 15. He proposed that NGC 2112 had a reddening of approximately 0.5 mag and was located around 800 pc away from the Sun. Later Richtler & Kaluzny (1989) studied 500 stars in a field of 200 arcmin. The results they arrived at were that NGC 2112 was heavily polluted with stars and was between 3 to 5 billion years old, located 700 to 800 parsecs from the Sun, and had a reddening of E(BâV) = 0.60 mag (The color excess E(B-V) is a measure of the amount of reddening caused by dust in the line of sight towards a star or star cluster). They found the value -1 for the metallicity (refers to the abundance of elements heavier than helium in the stars in the cluster) of NGC 2112.
Using high-resolution spectroscopy, Brown et al. (1996) determined the metal abundance of NGC 2112 by selecting a few members of the cluster based on their radial velocity. As a result, they were able to obtain a more accurate estimate of the metal content, which was found to be [Fe/H] = -0.15, slightly lower than the solar value.
There are varied estimates of the distance and age of NGC 2112, which leads to a significant level of uncertainty.
The Washington photometry reported by Geisler (1987) and Geisler, ClariĂ & Minniti (1991) apparently corroborated the previous suggestions that NGC 2112 was very metal poor ([Fe/H] â â1.3)
There have been conflicting studies on the metallicity of the cluster, with some suggesting a low metallicity and others suggesting a higher metallicity. Bilir et al. (2008) found a slightly lower metallicity of -0.19, while a more recent study by Samal & Pandey (2017) found a higher metallicity of +0.12. More research is needed to fully understand the metallicity and formation history of NGC 2112.
there is no evidence to suggest that blue stragglers are present in open star clusters like NGC 2112. Blue stragglers are typically found in globular clusters, which are much denser and have a higher concentration of stars. Open star clusters like NGC 2112 have a much lower density and typically consist of younger, less massive stars that have not yet had time to evolve into blue stragglers. However, there may be other interesting objects and phenomena in NGC 2112 that are worth studying, such as variable stars, young stellar objects, and star-forming regions.
There is a nebula associated with NGC 2112 called the NGC 2112 reflection nebula. It is a blue reflection nebula, which means it reflects the light of nearby stars rather than emitting its own light like an emission nebula. The nebula is illuminated by the light of a young star or stars in NGC 2112, and it appears blue because the star’s light is scattered by tiny dust particles in the nebula. The NGC 2112 reflection nebula is relatively faint and can be difficult to observe without a telescope, The surrounding reflection nebula is primarily composed of gas and dust, including hydrogen, carbon, and silicon compounds. The nebula is illuminated by the light of the stars in the cluster, which is scattered by the dust particles in the nebula, giving it a blue color. The properties of the nebula, such as its size, mass, and composition, are still uncertain and the subject of ongoing study by astronomers.
Studying NGC 2112 presents several challenges for astronomers, including the low surface brightness of the reflection nebula, the presence of nearby bright stars, and uncertainties in the membership of the star cluster. Despite these difficulties, astronomers are using various techniques such as high-resolution imaging and spectroscopy to investigate the properties and evolution of the young stars in NGC 2112 and its surrounding environment.
See all these information above? I found all of them on different astronomical websites and was so excited that in the cluster assignment I managed to find these value and facts related to NGC 2112 (without searching the articles and papers) by myself. Here I tell you how:
There is this cool website called Skynet, you can choose your telescopes to see any objects in the sky. I requested images of NGC 2112 to be taken by Prompt telescopes (in this case prompt 5, prompt-usask, for better pixels prompt are better choices) 5 times with 1.0 hour between for each these three filters (15 images in general). B filter (115 seconds exposure), V filter (45 seconds exposure and R (25 seconds exposure). why three different filters? Because I wanted to make a colored image of this cluster and needed the data related; here is the colored image I made:
This colored image of NGC 2112 was made from 15 stacked images with three filters. I made this using afterglow.Using all the pictures and make a colored image now I had the necessary data to make my own HR diagram using Cluster Pro Plus. I uploaded the data, and this is how it looks like:
The values I have found to get the above graph and the black line to be fit with them are as follows:
The distance from earth = 990 parsecs
Log(Age) = 9.29
Metallicity = 0.18
E(V_B) = 0.6
Motion in RA = -2.7 +/- 0.2
Motion in Dec = 4.3 +/- 0.2
As mentioned above we expect the open cluster not to have blue stragglers; in the graph there is no evidence to show that either, as there is no blue dots among the data.
Comparing these values to what I have found on different websites mentioning above, and some other websites we see:
| Distance(parsec) | Log(age(yr)) | E(V-B) | metallicity | Motion in RA | Motion in Dec | |
| My values | 990 | 9.29 | 0.6 | 0.18 | -2.7+/- 0.2 | 4.3 +/- 0.2 |
| Richtler/ Richtler & Kaluzny | 700-1000 | 9.477 â 9.70
(3-5 Gyr) |
0.5/0.6 | -1.0 | ||
| Jstor.org | 940 | 9.25 | 0.6 | -1.48 +/- 0.92 | 1.55+/- 0.99 | |
| Academic.oup.com | 920 | 9.30 | 0.63 | -0.15 |
It seems like we have an accurate, reliable value for E(V_B), 0.6; but there are differences in other values, distance, age metallicity, motion in RA and Dec.
There are two main reasons for these differences:
- Heavy field star contamination and
- High interstellar reddening (E(V_B) = 0.6
As mentioned, this cluster has not been studied very much in detail. As a result there are obvious uncertainties in all of the values (beside E(V_B)), specifically metallicity. I believe more research is needed on this cluster to have more accurate values.
For me it was really fascinating to study the NGC 2112, to find my own numbers and values, make my own Star Cluster Pro graph and to make a very beautiful colored picture out of a black and white image. I can say I was quite satisfied with the results; although I am not an astronomer, I did a pretty good job studying this beautiful Cluster.
References:
https://academic.oup.com/mnras/article/336/1/259/992673
http://simbad.cds.unistra.fr/simbad/sim-ref?bibcode=1985A%26AS…59..491R
https://theskylive.com/sky/deepsky/ngc2112-object
https://cs.astronomy.com/asy/m/starclusters/490963.aspx
https://in-the-sky.org/data/object.php?id=NGC2112
https://observing.skyhound.com/archives/jan/NGC_2112.html
https://adsabs.harvard.edu/full/1985A%26AS…59..491R