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Finding the Center of the Milky Way Galaxy Using Globular Star Clusters

Difficulty
Time Required Average (6-10 days)
Prerequisites None
Material Availability Access to the Internet is required.
Cost Very Low (under $20)
Safety No issues

Abstract

The Milky Way is the edgewise view of our home galaxy, a disk made up of billions of stars. The Sun resides on one of the spiral arms of the disk, 30,000 light-years from the thick hub of the galaxy. The actual center, with a black hole 3-4 million times the Sun's mass, is hidden by dust clouds in space. In this astronomy science fair project, you will use astronomical data to locate the center of this galaxy.

Objective

The objective of this astronomy science fair project is to use Internet-based software tools and databases to locate the center of the galaxy, based on the distribution of globular clusters.

Credits

Jacob Arnold and Jean Brodie, University of California. Santa Cruz, Department of Astronomy

Edited by David Whyte, PhD, Science Buddies
Edited by Sandra Slutz, PhD, Science Buddies

Cite This Page

MLA Style

Science Buddies Staff. "Finding the Center of the Milky Way Galaxy Using Globular Star Clusters" Science Buddies. Science Buddies, 11 Oct. 2014. Web. 21 Oct. 2014 <http://www.sciencebuddies.org/science-fair-projects/project_ideas/Astro_p032.shtml?From=Blog>

APA Style

Science Buddies Staff. (2014, October 11). Finding the Center of the Milky Way Galaxy Using Globular Star Clusters. Retrieved October 21, 2014 from http://www.sciencebuddies.org/science-fair-projects/project_ideas/Astro_p032.shtml?From=Blog

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Last edit date: 2014-10-11

Introduction

Our solar system is located nearly 25,000 light-years from the center of our Milky Way galaxy. We now know that we live in a spiral galaxy, consisting of billions of stars, and that our galaxy is just one of hundreds of billions of galaxies in the universe. However, the location of our Sun in the Milky Way, the size of our galaxy, the number of stars in it, and its structure were all unknown just 100 years ago. During the early 20th century, astronomers were trying to answer these questions using a variety of techniques. You will use one such method to determine the location of the center of our galaxy.

The most direct approach, adopted by Jacobus Kapteyn in order to determine the structure of the Milky Way, inferred distances for a number of stars in various directions to create a 3-dimensional view of our galaxy. Kapteyn found that our Sun lies at the very center of a nearly spherical distribution of stars, and he incorrectly concluded that we lie at the center of the galaxy. What Kapteyn was unaware of was that our galaxy is filled with starlight-absorbing dust, or interstellar dust. This means that stars far away from our Sun appear dimmer or are not even visible from Earth. This effect means we preferentially see the stars nearest to our Sun and cannot easily observe the other side of the galaxy. Therefore, this is not a good technique to use in determining the structure of the Milky Way.

Instead, you will adopt a method, used by Harlow Shapley, that correctly infers the direction of the center of our galaxy. Throughout most of the galaxy, stars are separated by a few light-years. However, globular star clusters contain anywhere from 10,000 to 1 million stars, densely packed into a region only a few tens to a few hundred light-years wide. Figure 1 shows a nearby galaxy surrounded by globular clusters. Because globular clusters contain so many stars, they are much brighter than individual stars and can be seen in the Milky Way, even at very far distances. Unlike stars, which tend to rotate around the Milky Way Galaxy in a flattened disk, globular clusters are distributed in a roughly spherical distribution around the center of the Galaxy. Thus, if we look toward the center of the Galaxy, we should see more globular clusters than if we look in the opposite direction.

Image of Sombrero Galaxy

Figure 1. The famous Sombrero galaxy (M104) is a nearby bright spiral galaxy. The prominent dust lane and halo of stars and globular clusters (globular clusters are the bright white spots) give this galaxy its name. (Wikipedia, 2009.)

In this science fair project, using a compiled list of the Milky Way's globular clusters (approximately 150), you will count the number of clusters found in each constellation. Constellations, like the Big Dipper or Orion, serve as a way to orient ourselves and define directions in our galaxy. You will determine which top three constellations contain the most globular clusters, and therefore, in which direction most Milky Way globular clusters exist. Using Google Earth in sky mode, you will determine a best-guess location for the center of the galaxy and compare this to the correct location.

Terms and Concepts

  • Solar system
  • Light-year
  • Milky Way galaxy
  • Spiral galaxy
  • Jacobus Kapteyn
  • Interstellar dust
  • Harlow Shapley
  • Globular star cluster
  • Spherical distribution
  • Constellation
  • Google Earth

Questions

  • What is a globular star cluster?
  • Why are clusters better than individual stars for creating a 3-dimensional view of our galaxy?
  • How are globular clusters distributed around galaxies?
  • How big is the Milky Way?
  • What is a constellation?

Bibliography

The original data for this project can be found at:

You'll need to download Google Earth to do this science project:

These resources contain good information about astronomy in general and the Milky Way in particular:

Materials and Equipment

  • Personal computer with Internet access and Google Earth installed; see the Experimental Procedure below for more details
  • Lab notebook

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Experimental Procedure

  1. Do your background research so that you are knowledgeable about the terms, concepts, and questions above.
  2. Below is a table listing all of the known globular clusters in the Milky Way
    1. Columns 1-3 are names, or other identifiers, commonly used when to referring to each globular cluster.
    2. Column 4 ("Con") contains the name of the constellation where the globular cluster is found.
    3. The remaining columns are not necessary for this project, but you may find them interesting. Some simple text searches online or an introductory astronomy text book can help you figure out their significance. The abbreviations refer to:
      1. RA, Dec (2000): right ascension and declination for epoch 2000.0
      2. R_Sun, R_gc: distance from our Sun and the Galactic Center in thousands of light years (kly)
      3. m_v: apparent visual magnitude
      4. dim: apparent dimension in arc minutes



 M    NGC/IC  ID/Name/Crossref     Con               RA  (2000)     DEC     R_Sun   R_gc   m_v   dim
                                                                                     
         104   47 Tuc, Lac I.1      Tucana           00:24:05.2  -72:04:51   14.7   24.1   3.95  50.0 
         288   H 6.20               Sculptor         00:52:47.5  -26:35:24   28.7   39.1   8.09  13.0
         362   Dun 62               Tucana           01:03:14.3  -70:50:54   27.7   30.3   6.40  14.0
               Whiting 1            Cetus            02:02:56.8  -03:15:10                        1.2
        1261   Dun 337              Horologium       03:12:15.3  -55:13:01   53.5   59.4   8.29   6.6
               Pal 1                Cepheus          03:33:23.0  +79:34:50   35.6   55.4  13.18   2.8
               AM 1, E 1            Horologium       03:55:02.7  -49:36:52  397.6  401.8  15.72   0.5
               Eridanus             Eridanus         04:24:44.5  -21:11:13  294.2  310.5  14.70   1.0
               Pal 2                Auriga           04:46:05.9  +31:22:51   90.0  115.5  13.04   2.2
        1851   Dun 508              Columba          05:14:06.3  -40:02:50   39.5   54.5   7.14  12.0
M 79    1904                        Lepus            05:24:10.6  -24:31:27   42.1   61.3   7.73   9.6
        2298   Dun 578              Puppis           06:48:59.2  -36:00:19   34.9   51.2   9.29   5.0
        2419   H 1.218              Lynx             07:38:08.5  +38:52:55  274.6  298.4  10.39   4.6
               Koposov 2            Gemini           07:58:17.0  +26:15:18  130
               Pyxis                Pyxis            09:07:57.8  -37:13:17  129.4  135.9  12.90   4.0
        2808   Dun 265              Carina           09:12:02.6  -64:51:47   31.2   36.2   6.20  14.0
               E 3                  Chamaeleon       09:20:59.3  -77:16:57   14.0   24.8  11.35  10:
               Pal 3                Sextans          10:05:31.4  +00:04:17  302.3  312.8  14.26   1.6
               Segue 1              Leo              10:07:04    +12:47:30   75.0         14.7    4.5
        3201   Dun 445              Vela             10:17:36.8  -46:24:40   16.3   29.0   6.75  20.0
               Pal 4                Ursa Major       11:29:16.8  +28:58:25  356.2  364.6  14.20   1.3
               Koposov 1            Virgo            11:59:18.5  +12:15:36  160
        4147   H 1.19               Coma Berenices   12:10:06.2  +18:32:31   62.9   69.5  10.32   4.4
        4372                        Musca            12:25:45.4  -72:39:33   18.9   23.2   7.24   5.0
               Rup 106              Centaurus        12:38:40.2  -51:09:01   69.1   60.3  10.90   2.0
M 68    4590                        Hydra            12:39:28.0  -26:44:34   33.3   32.9   7.84  11.0
        4833   Lac I.4, Dun 164     Musca            12:59:35.0  -70:52:29   21.2   22.8   6.91  14.0
M 53    5024                        Coma Berenices   13:12:55.3  +18:10:09   58.0   59.6   7.61  13.0
        5053   H 6.7                Coma Berenices   13:16:27.0  +17:41:53   53.5   55.1   9.47  10.0
        5139   Omega Cen, Lac I.5   Centaurus        13:26:45.9  -47:28:37   17.3   20.9   3.68  55.0
M  3    5272                        CVn              13:42:11.2  +28:22:32   33.9   39.8   6.19  18.0
        5286   Dun 388              Centaurus        13:46:26.5  -51:22:24   35.9   27.4   7.34  11.0
               AM 4                 Hydra            13:56:21.2  -27:10:04   97.5   83.2  15.90   3.0
        5466   H 6.9                Boötes           14:05:27.3  +28:32:04   51.8   52.8   9.04   9.0
        5634   H 1.70               Vir              14:29:37.3  -05:58:35   82.2   69.1   9.47   5.5
        5694   H 2.196              Hydra            14:39:36.5  -26:32:18  113.2   94.9  10.17   4.3
       I4499                        Apus             15:00:18.5  -82:12:49   61.6   51.2   9.76   8.0
        5824                        Lupus            15:03:58.5  -33:04:04  104.4   84.1   9.09   7.4
               Pal 5                SerCp            15:16:05.3  -00:06:41   75.7   60.7  11.75   8.0
        5897   H 6.8, H 6.19        Libra            15:17:24.5  -21:00:37   40.4   23.8   8.53  11.0
M  5    5904                        SerCp            15:18:33.8  +02:04:58   24.5   20.2   5.65  23.0
        5927   Dun 389              Lupus            15:28:00.5  -50:40:22   24.8   14.7   8.01   6.0
        5946                        Norma            15:35:28.5  -50:39:34   34.6   18.9   9.61   3.0
               BH 176               Norma            15:39:07.3  -50:03:02   50.9   31.6  14.00   3.0
        5986   Dun 552              Lupus            15:46:03.5  -37:47:10   33.9   15.7   7.52   9.6
               Lynga 7              Norma            16:11:03.0  -55:18:52   23.5    2.5
               Pal 14, AvdB         Hercules         16:11:04.9  +14:57:29  241.0  225.0  14.74   2.5
M 80    6093                        Scorpius         16:17:02.5  -22:58:30   32.6   12.4   7.33  10.0
M  4    6121   Lac I.9              Scorpius         16:23:35.5  -26:31:31    7.2   19.2   5.63  36.0
        6101   Dun 68               Apus             16:25:48.6  -72:12:06   49.9   36.2   9.16   5.0
        6144   H 6.10               Scorpius         16:27:14.1  -26:01:29   27.7    8.5   9.01   7.4
        6139   Dun 536              Scorpius         16:27:40.4  -38:50:56   32.9   11.7   8.99   8.2
               Terzan 3             Scorpius         16:28:40.1  -35:21:13   24.5    7.8  12.00   3.0
M 107   6171   H 6.40               Ophiuchus        16:32:31.9  -13:03:13   20.9   10.8   7.93  13.0
               1636-283,ESO452-SC11 Scorpius         16:39:25.5  -28:23:52   25.4    6.5  12.00   1.2
M 13    6205                        Hercules         16:41:41.5  +36:27:37   25.1   28.4   5.78  20.0
        6229   H 4.50               Hercules         16:46:58.9  +47:31:40   99.1   96.8   9.39   4.5
M 12    6218                        Ophiuchus        16:47:14.5  -01:56:52   16.0   14.7   6.70  16.0
               FSR 1735, 2MASS-GC03 Ara              16:52:10.6  -47:03:29   29.7   10.4          0.8
        6235   H 2.584              Ophiuchus        16:53:25.4  -22:10:38   37.2   13.4   9.97   5.0
M 10    6254                        Ophiuchus        16:57:08.9  -04:05:58   14.4   15.0   6.60  20.0
        6256                        Scorpius         16:59:32.6  -37:07:17   27.4    5.9  11.29   4.1
               Pal 15               Ophiuchus        17:00:02.4  -00:32:31  145.5  123.6  14.00   3.0
M 62    6266   Dun 627              Ophiuchus        17:01:12.6  -30:06:44   22.5    5.5   6.45  15.0
M 19    6273                        Ophiuchus        17:02:37.7  -26:16:05   28.0    5.2   6.77  17.0
        6284   H 6.11               Ophiuchus        17:04:28.8  -24:45:53   49.9   24.8   8.83   6.2
        6287   H 2.195              Ophiuchus        17:05:09.4  -22:42:29   30.3    6.8   9.35   4.8
        6293   H 6.12               Ophiuchus        17:10:10.4  -26:34:54   28.7    4.6   8.22   8.2
        6304   H 1.147              Ophiuchus        17:14:32.5  -29:27:44   19.6    7.2   8.22   8.0
        6316   H 1.45               Ophiuchus        17:16:37.4  -28:08:24   35.9   10.4   8.43   5.4
M 92    6341                        Hercules         17:17:07.3  +43:08:11   26.7   31.3   6.44  14.0
        6325                        Ophiuchus        17:17:59.2  -23:45:57   26.1    3.6  10.33   4.1
M  9    6333                        Ophiuchus        17:19:11.8  -18:30:59   25.8    5.5   7.72  12.0
        6342   H 1.149              Ophiuchus        17:21:10.2  -19:35:14   28.0    5.5   9.66   4.4
        6356   H 1.48               Ophiuchus        17:23:35.0  -17:48:47   49.6   24.8   8.25  10.0
        6355   H 1.46               Ophiuchus        17:23:58.6  -26:21:13   31.0    5.9   9.14   4.2
        6352   Dun 417              Ara              17:25:29.2  -48:25:22   18.6   10.8   7.96   9.0
       I1257                        Ophiuchus        17:27:08.5  -07:05:35   81.5   58.4  13.10   5.0 
               Terzan 2, HP 3       Scorpius         17:27:33.4  -30:48:08   28.4    2.9  14.29   0.6
        6366                        Ophiuchus        17:27:44.3  -05:04:36   11.7   16.3   9.20  13.0
               Terzan 4, HP 4       Scorpius         17:30:38.9  -31:35:44   29.7    4.2  16.00   0.7 
               HP 1, BH 229         Ophiuchus        17:31:05.2  -29:58:54   46.0   19.9  11.59   1.2
        6362   Dun 225              Ara              17:31:54.8  -67:02:53   24.8   16.6   7.73  15.0
               Liller 1             Scorpius         17:33:24.5  -33:23:20   34.2    8.5  16.77  12.6
        6380   Ton 1                Scorpius         17:34:28.0  -39:04:09   34.9   10.4  11.31   3.6
               FSR 1767             Scorpius         17:35:43    -36:21:28    4.9   18.6             
               Terzan 1, HP 2       Scorpius         17:35:47.8  -30:28:11   18.3    8.2  15.90   2.4
               Ton 2, Pismis 26     Scorpius         17:36:10.5  -38:33:12   26.4    4.6  12.24   2.2
        6388   Dun 457              Scorpius         17:36:17.0  -44:44:06   32.6   10.4   6.72  10.4
M 14    6402                        Ophiuchus        17:37:36.1  -03:14:45   30.3   13.4   7.59  11.0
        6401   H 1.44               Ophiuchus        17:38:36.9  -23:54:32   34.2    8.8   9.45   4.8
        6397   Lac III.11, Dun 366  Ara              17:40:41.3  -53:40:25    7.5   19.6   5.73  31.0
               Pal 6                Ophiuchus        17:43:42.2  -26:13:21   19.2    7.2  11.55   1.2
        6426   H 2.587              Ophiuchus        17:44:54.7  +03:10:13   67.5   47.6  11.01   4.2
               Djorg 1              Scorpius         17:47:28.3  -33:03:56   39.1   13.4  13.60      
               Terzan 5, Terzan 11  Sagittarius      17:48:04.9  -24:48:45   33.6    7.8  13.85   2.4
        6440   H 1.150              Sagittarius      17:48:52.6  -20:21:34   27.4    4.2   9.20   4.4
        6441   Dun 557              Scorpius         17:50:12.9  -37:03:04   38.1   12.7   7.15   9.6
               Terzan 6, HP 5       Scorpius         17:50:46.4  -31:16:31   31.0    5.2  13.85   1.4
        6453                        Scorpius         17:50:51.8  -34:35:55   31.3    5.9  10.08   7.6
               UKS 1, UKS 1751-241  Sagittarius      17:54:27.2  -24:08:43   27.1    2.6  17.29   2.0
        6496   Dun 460              Scorpius         17:59:02.0  -44:15:54   37.5   14.0   8.54   5.6
               Terzan 9             Sagittarius      18:01:38.8  -26:50:23   21.2    5.2  16.00   0.2
               Djorg 2, E456-SC38   Sagittarius      18:01:49.1  -27:49:33   21.9    4.6   9.90   9.9
        6517   H 2.199              Ophiuchus        18:01:50.6  -08:57:32   35.2   14.0  10.23   4.0
               Terzan 10            Sagittarius      18:02:57.4  -26:04:00   18.6    7.8  14.90   1.5
        6522   H 1.49               Sagittarius      18:03:34.1  -30:02:02   25.4    2.0   8.27   9.4
        6535                        SerCd            18:03:50.7  -00:17:49   22.2   12.7  10.47   3.4
        6528   H 2.200              Sagittarius      18:04:49.6  -30:03:21   25.8    2.0   9.60   5.0
        6539                        SerCd            18:04:49.8  -07:35:09   27.4   10.1   9.33   7.9
        6540   H 2.198, Djorg 3     Sagittarius      18:06:08.6  -27:45:55   12.1   14.4   9.30   1.5
        6544   H 2.197              Sagittarius      18:07:20.6  -24:59:51    8.8   17.3   7.77   9.2
        6541   Dun 473              Corona Austrina  18:08:02.2  -43:42:20   22.8    7.2   6.30  15.0
               2MASS-GC01           Sagittarius      18:08:21.8  -19:49:47   11.7   14.7          3.3
               ESO 280-SC06         Ara              18:09:06    -46:25:24   70.7   46.6          1.5
        6553   H 4.12               Sagittarius      18:09:15.6  -25:54:28   19.6    7.2   8.06   9.2
               2MASS-GC02           Sagittarius      18:09:36.5  -20:46:44   13.0   13.4          1.9
        6558                        Sagittarius      18:10:18.4  -31:45:49   24.1    3.3   9.26   4.2
       I1276   Pal 7                SerCd            18:10:44.2  -07:12:27   17.6   12.1  10.34   8.0
               Terzan 12            Sagittarius      18:12:15.8  -22:44:31   15.7   11.1  15.63   1.0
        6569   H 2.201, Dun 619     Sagittarius      18:13:38.9  -31:49:35   34.9    9.5   8.55   6.4
               AL 3                 Sagittarius      18:14:05.7  -28:38:08                        1.3
        6584   Dun 376              Telescopium      18:18:37.7  -52:12:54   43.7   22.8   8.27   6.6
        6624   H 1.50               Sagittarius      18:23:40.5  -30:21:40   25.8    3.9   7.87   8.8
M 28    6626   Lac I.11             Sagittarius      18:24:32.9  -24:52:12   18.3    8.8   6.79  11.2
        6638   H 1.51               Sagittarius      18:30:56.2  -25:29:47   31.2    7.5   9.02   7.3
M 69    6637   Lac I.12, Dun 613    Sagittarius      18:31:23.2  -32:20:53   29.7    6.2   7.64   9.8
        6642   H 2.205              Sagittarius      18:31:54.3  -23:28:35   27.4    5.5   9.13   5.8
        6652                        Sagittarius      18:35:45.7  -32:59:25   32.9    9.1   8.62   6.0
M 22    6656                        Sagittarius      18:36:24.2  -23:54:12   10.4   16.0   5.10  32.0
               Pal 8                Sagittarius      18:41:29.9  -19:49:33   42.1   18.3  11.02   5.2
M 70    6681   Dun 614              Sagittarius      18:43:12.7  -32:17:31   29.4    6.8   7.87   8.0
               GLIMPSE-C01          Aquila           18:48:49.7  -01:29:50   10-17
        6712   H 1.47               Scutum           18:53:04.3  -08:42:22   22.5   11.4   8.10   9.8
M 54    6715   Dun 624              Sagittarius      18:55:03.3  -30:28:42   87.3   62.6   7.60  12.0
        6717   H 3.143, Pal 9       Sagittarius      18:55:06.2  -22:42:03   23.1    7.8   9.28   5.4
        6723   Dun 573              Sagittarius      18:59:33.2  -36:37:54   28.4    8.4   7.01  13.0
        6749   Berkeley 42          Aquila           19:05:15.3  +01:54:03   25.8   16.3  12.44   4.0
        6752   Dun 295              Pavo             19:10:51.8  -59:58:55   13.0   17.0   5.40  29.0
        6760                        Aquila           19:11:12.1  +01:01:50   24.1   15.7   8.88   9.6
M 56    6779                        Lyra             19:16:35.5  +30:11:05   32.9   31.6   8.27   8.8
               Terzan 7             Sagittarius      19:17:43.7  -34:39:27   75.7   52.2  12.00   1.2
               Pal 10               Sagitta          19:18:02.1  +18:34:18   19.2   20.9  13.22   4.0
               Arp 2                Sagittarius      19:28:44.1  -30:21:14   93.3   69.8  12.30   2.3
M 55    6809   Lac I.14, Dun 620    Sagittarius      19:39:59.4  -30:57:44   17.3   12.7   6.32  19.0
               Terzan 8             Sagittarius      19:41:45.0  -34:00:01   84.8   62.3  12.40   3.5
               Pal 11               Aquila           19:45:14.4  -08:00:26   42.4   25.8   9.80  10.0
M 71    6838                        Sagitta          19:53:46.1  +18:46:42   13.0   21.9   8.19   7.2
M 75    6864                        Sagittarius      20:06:04.8  -21:55:17   67.5   47.6   8.52   6.8
        6934   H 1.103              Delphinus        20:34:11.6  +07:24:15   51.2   41.7   8.83   7.1
M 72    6981                        Aquarius         20:53:27.9  -12:32:13   55.4   42.1   9.27   6.6
        7006   H 1.52               Delphinus        21:01:29.5  +16:11:15  135.4  126.5  10.56   3.6
M 15    7078                        Pegasus          21:29:58.3  +12:10:01   33.6   33.9   6.20  18.0
M  2    7089                        Aquarius         21:33:29.3  -00:49:23   37.5   33.9   6.47  16.0
M 30    7099                        Capricornus      21:40:22.0  -23:10:45   26.1   23.2   7.19  12.0
               Pal 12, Cap Dwarf    Capricornus      21:46:38.8  -21:15:03   62.3   51.9  11.99   2.9
               Pal 13               Pegasus          23:06:44.4  +12:46:19   84.1   87.0  13.80   0.7
        7492   H 3.558              Aquarius         23:08:26.7  -15:36:41   84.1   81.2  11.29   4.2


Table 1: List of all known globular clusters in the Milky Way. This table is reproduced from data available as of June 30, 2010 at http://seds.org/messier/xtra/supp/mw_gc.html#harris. See Bibliography.



  1. Count how many globular clusters are in each constellation.
    1. NGC104 is the first globular cluster in the list. It is seen in the constellation Tucana.
    2. Make a data table in your lab notebook, add the constellation Tucana, and put NGC104 next to it.
    3. Repeat the process for each globular cluster. Add a new line in your data table for each constellation, but if a cluster is in a constellation that you already have in your list, put the cluster's name on that line instead of on a new one.
    4. Count the number of globular clusters you found in each constellation and record the numbers in another column in your data table. Note: Every entry in the data table is a globular cluster—some begin with "M," but most are names, numbers or codes. With a little patience you can easily sort all of the entries by constellation.
  2. Identify the three constellations with the most globular clusters seen in them.
  3. Now go to http://earth.google.com and click "Download Google Earth."
    1. Click "Agree and Download."
    2. Once the file has been downloaded, install the program.
    3. Open the Google Earth program.
  4. Set up Google Earth in Sky Mode.
    1. At the top, click "View," then "Explore," then select "Sky."
    2. On the left-hand side of the window, you should see "Layers."
    3. Uncheck every item, except "Imagery" and "Backyard Astronomy."
    4. Click the arrow next to "Backyard Astronomy."
    5. Uncheck every item except "Constellations."
  5. Try to become familiar with the Google Earth navigation controls by panning around and zooming in and out, using the controls located in the top right corner of the screen.
  6. Notice the bright band that stretches across the sky. This is the disk of our Milky Way galaxy!
  7. Find the three constellations that contain the most globular clusters, which you identified in step 4.
    1. On the left-hand side is a search bar; type in the name of the first constellation.
    2. Repeat for the other two constellations.
    3. Zoom out and pan the sky until you can see all three constellations at once.
  8. Are the three constellations near each other? Most of the Milky Way's globular clusters should be in the direction of the center of the galaxy. Where do you think the center of the galaxy is?
  9. In the search bar, type "Galactic Center" to find the true center of the galaxy. How close was your guess?
  10. Try going back and using three other constellations with fewer globular clusters to predict the center of the galaxy. Is this second prediction more or less accurate (meaning closer or farther away from the true center of the galaxy) than the first one? Based on your results, do you think the distribution of stars really does increase as you approach the center of the galaxy?
    1. For your project display board, you can create a table or graph showing how the accuracy of your prediction changed as you used sets of constellations with fewer and fewer globular clusters to create those predictions.

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Variations

  • Find the distribution of globular clusters in the Milky Way by plotting their locations using Google Earth.

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