Observing Projects
Using a telescope with an aperture of at least 30 cm (12 in.), observe as many of the spiral galaxies listed in the following table as you can. If you have a copy of the Starry Night™ program, use it to help determine when these galaxies can best be viewed. Many of these galaxies are members of the Virgo cluster, which can best be seen from March through June. Because all galaxies are quite faint, be sure to schedule your observations for a moonless night. The best view is obtained when a galaxy is near the meridian. While at the eyepiece, make a sketch of what you see. Can you distinguish any spiral structure? After completing your observations, compare your sketches with photographs found in an online catalog of Messier objects (the “M” in the galaxy designations stands for Messier).
700
| Spiral galaxy | Right ascension | Declination | Hubble type |
|---|---|---|---|
| M31 (NGC 224) | 0h 42.7m | +41° 16′ | Sb |
| M58 (NGC 4579) | 12 37.7 | +11 49 | Sb |
| M61 (NGC 4303) | 12 21.9 | +4 28 | Sc |
| M63 (NGC 5055) | 13 15.8 | +42 02 | Sb |
| M64 (NGC 4826) | 12 56.7 | +21 41 | Sb |
| M74 (NGC 628) | 1 36.7 | +15 47 | Sc |
| M83 (NGC 5236) | 13 37.0 | −29 52 | Sc |
| M88 (NGC 4501) | 12 32.0 | +14 25 | Sb |
| M90 (NGC 4569) | 12 36.8 | +13 10 | Sb |
| M91 (NGC 4548) | 12 35.4 | +14 30 | SBb |
| M94 (NGC 4736) | 12 50.9 | +41 07 | Sb |
| M98 (NGC 4192) | 12 13.8 | +14 54 | Sb |
| M99 (NGC 4254) | 12 18.8 | +14 25 | Sc |
| M100 (NGC 4321) | 12 22.9 | +15 49 | Sc |
| M101 (NGC 5457) | 14 03.2 | +54 21 | Sc |
| M104 (NGC 4594) | 12 40.0 | −11 37 | Sa |
| M108 (NGC 3556) | 11 11.5 | +55 40 | Sc |
| Note: The right ascensions and declinations are given for epoch 2000. | |||
Using a telescope with an aperture of at least 30 cm (12 in.), observe as many of the following elliptical galaxies as you can. Six of these galaxies are in the Virgo cluster, which is conveniently located in the evening sky from March through June. If you have a copy of the Starry Night™ program, use it to help determine when these galaxies can best be viewed. As in the previous exercise, be sure to schedule your observations for a moonless night, when the galaxies you wish to observe will be near the meridian. Do these elliptical galaxies differ in appearance from spiral galaxies?
| Right ascension | Elliptical galaxy | Declination | Hubble type |
|---|---|---|---|
| M49 (NGC 4472) | 12h 29.8m | +8° 009 | E4 |
| M59 (NGC 4621) | 12 42.0 | +11 39 | E3 |
| M60 (NGC 4649) | 12 43.7 | +11 33 | E1 |
| M84 (NGC 4374) | 12 25.1 | +12 53 | E1 |
| M86 (NGC 4406) | 12 26.2 | +12 57 | E3 |
| M89 (NGC 4552) | 12 35.7 | +12 33 | E0 |
| M110 (NGC 205) | 00 40.4 | +41 41 | E6 |
| Note: The right ascensions and declinations are given for epoch 2000. | |||
Using a telescope with an aperture of at least 30 cm (12 in.), observe as many of the following interacting galaxies as you can. If you have a copy of the Starry Night™ program, use it to help determine when these galaxies can best be viewed. As in the previous exercises, be sure to schedule your observations for a moonless night, when the galaxies you wish to observe will be near the meridian. While at the eyepiece, make a sketch of each galaxy. Can you distinguish hints of interplay among the galaxies? After completing your observations, compare your sketches with photographs found in an online catalog of Messier objects (the “M” in the galaxy designations stands for Messier).
| Interacting galaxies | Right ascension | Declination |
|---|---|---|
| M51 (NGC 5194) | 13h 29.9m | +47° 12′ |
| NGC 5195 | 13 30.0 | +47 16 |
| M65 (NGC 3623) | 11 18.9 | +13 05 |
| M66 (NGC 3627) | 11 20.2 | +12 59 |
| NGC 3628 | 11 20.3 | +13 36 |
| M81 (NGC 3031) | 9 55.6 | +69 04 |
| M82 (NGC 3034) | 9 55.8 | +69 41 |
| M95 (NGC 3351) | 10 44.0 | +11 42 |
| M96 (NGC 3368) | 10 46.8 | +11 49 |
| M105 (NGC 3379) | 10 47.8 | +12 35 |
| Note: The right ascensions and declinations are given for epoch 2000. | ||
Use Starry Night™ to visit a variety of galaxies and determine whether they are spiral, barred spiral, elliptical, or irregular. Click on Home to see the sky from your home location. Click on the Options tab, expand the Deep Space layer and click Off all images except Messier Objects and Bright NGC Objects. Type Ctrl-H (Cmd-H on a Mac) or select View > Hide Horizon from the menu to remove the horizon. Also select View > Hide Daylight to remove daylight from the view. Use the Find pane to visit each of the galaxies listed below. For each object, type its name in the search box of the Find pane and press the Enter key. (Hint: To go to the galaxy without slewing, press the spacebar.) (a) Use the Zoom buttons to examine each galaxy in detail and then classify it as a spiral (S), barred spiral (SB), elliptical (E), or irregular (Irr), and the subclassification of each galaxy (e.g., Sa, E5): M33, M58, M74, M81, M83, M94, M109, Large Magellanic Cloud, Small Magellanic Cloud, NGC1232, M84, M86, M59. (b) Use the Find pane and locate M51. What is the classification of this galaxy? (c) Examine this galaxy carefully and comment on anything unusual about its structure and/or its neighboring objects.
Clusters of galaxies contain different numbers and distributions of galaxies and harbor significant amounts of the mysterious dark matter. In this exercise you can use Starry Night™ to compare a few of these groupings and see the gravitational effect of dark matter. You can start by looking at one of the largest galaxy clusters, the Virgo cluster. Select Favourites > Explorations > Virgo Cluster-Milky Way from the menu. You are looking at this group of galaxies from a very large distance out in space, at about 66 Mly from the Sun. Our own Milky Way Galaxy is labeled at the bottom left of the view, across a void in space from this cluster. Use the location scroller to move around the Virgo cluster and consider its overall shape and its relationship to neighboring galaxies. (a) What is the general shape of the Virgo cluster? Zoom in toward this cluster until individual galaxies are shown and use the location scroller to help you to identify each classification of galaxy (elliptical, spiral and irregular) within the group. Select File > Revert to return to the original view and identify several other groups of galaxies. Select one or two clusters of galaxies in turn, move the cursor over a galaxy within the selected group, and right-click the mouse to open the object contextual menu and select the Highlight option to identify this group. You can select the Centre option to move the selected cluster to the center of the view and examine the cluster’s extent across space. Again, use the location scroller and Zoom in to examine this cluster from various viewpoints. (b) Describe the distribution of the galaxies within the cluster, compared to the distribution in the Virgo Cluster. For example, what are their shapes and relative sizes compared to Virgo and to each other? See if you can recognize the walls of galaxies surrounding large voids in space that link these concentrated regions of galaxies. (c) Click on the Home button to return to your sky. Click on the Find tab and ensure that the search box is empty. Click on the magnifying glass icon in the search box to open a dropdown list and click on Hubble Images. In the list of Hubble images, click on Gravitational Lens to center on this image of a cluster of galaxies known as CL0024+1654. Zoom in to a field of view of about 1 arcminute. This Hubble Space Telescope image shows a rich cluster of ordinary-looking yellowish galaxies surrounded by blue arcs of light. These are multiple images of a very distant galaxy, as seen through the gravitational “lens” of dark matter pervading the cluster of galaxies. The blue color of these images suggests that this distant galaxy is composed largely of young, blue stars. The distribution of this mysterious substance within galactic clusters can be inferred from these types of images of distant galaxies.
701
Collaborative Exercises
In the early twentieth century, there was considerable debate about the nature of spiral nebulae and their distance from us, but the debate was resolved by improvements in technology. As a group, list three issues that we, as a culture, did not understand in the past but understand today, and explain why we now have that understanding.
Even though there are billions of galaxies, there are not billions of different kinds. In fact, galaxies are classified according to their appearance. As a group, dig into your book bags and put all of the writing implements (pens, pencils, highlighters, and so on) you have in a central pile. Remember which ones are yours! Determine a classification scheme that sorts the writing implements into at least three to six piles. Write down the scheme and the number of items in each pile. Ask the group next to you to use your scheme and sort your materials. Correct any ambiguities before submitting your classification scheme.
Imagine your company, Astronomical Artistry, has been contracted by the local marching band to create a football half-time show about spiral galaxies. How exactly would you design the positions of the band members on the field to represent the different spiral galaxies of classes Sa, Sb, and Sc? Create two columns on your paper by drawing a line from top to bottom, drawing sketches in the left-hand column and writing a description of each sketch in the right-hand column. Also include what the band’s opening formation and final formation should be.