Activities

Observing Projects

  1. Use a telescope with an aperture of at least 20 cm (8 in.) to observe the Seyfert Galaxy NGC 1068 (also known as M77). Located in the constellation Cetus (the Whale), this galaxy is most easily seen from September through January. The epoch 2000 coordinates are R.A. = 2h 2.7m and Decl. = −0° 01′. Sketch what you see. Is the galaxy’s nucleus diffuse or starlike? How does this compare with other galaxies you have observed?

  2. Use a telescope with an aperture of at least 20 cm (8 in.) to observe the two companions of the Andromeda Galaxy, M32 and M110. Both are small elliptical galaxies, but only M32 is suspected of harboring a supermassive black hole. They are located on opposite sides of the Andromeda Galaxy and are most easily seen from September through January. The epoch 2000 coordinates are

    Galaxy Right ascension Declination
    M32 (NGC 221) 0h 42.7m +40° 52′
    M110 (NGC 205) 0 40.4 +41 41

    Make a sketch of each galaxy. Can you see any obvious difference in the appearance of these galaxies? How does this difference correlate with what you know about these galaxies?

  3. If you have access to a telescope with an aperture of at least 30 cm (12 in.), you should definitely observe the Sombrero Galaxy, M104, which is suspected to have a supermassive black hole at its center. It is located in Virgo and can most easily be seen from March through July. The epoch 2000 coordinates are R.A. = 12h 40.0m and Decl. −11° 37′. Make a sketch of the galaxy. Can you see the dust lane? How does the nucleus of M104 compare with the centers of other galaxies you have observed?

  4. If you have access to a telescope with an aperture of at least 30 cm (12 in.), observe M87 and compare it with the other two giant elliptical galaxies, M84 and M86, that dominate the central regions of the Virgo cluster. If you have access to the Starry Night program, use it to help you plan your observations. The epoch 2000 coordinates are:

    Galaxy Right ascension Declination
    M84 (NGC 4374) 12h 25.1m +12° 53′
    M86 (NGC 4406) 12 26.2 +12 57
    M87 (NGC 4486) 12 30.8 +12 24
  5. If you have access to a telescope with an aperture of at least 40 cm (16 in.), you might try to observe the brightest-appearing quasar, 3C 273, which has an apparent magnitude of nearly +13. It is located in Virgo at coordinates R.A. = 12h 29m 07s and Decl. +2° 3′ 8″.

  6. Energetic jets of material moving at relativistic speeds are observed to be blasting outward in opposite directions from the centers of many active galaxies. These are thought to be projected at right angles to the accretion disks of supermassive black holes at the centers of these galaxies. Use the Starry Night program to examine an example of one of these energetic jets in the vicinity of the galaxy M87. Select Favourites > Explorations > Atlas to view the sky from the center of a transparent Earth. Use the Find facility to locate M87 and Zoom in to a field of view of about 25 arc minutes. (a) What type of galaxy is M87? (b) Place the cursor over the galaxy, right-click to open the dropdown menu, click on Show Info, and obtain the distance to M87 from the Position in Space layer in the Info pane. What is the distance of M87 from the Earth? (c) Click on the Options tab, expand the Deep Space layer, and ensure that the Hubble Images are switched On. A high-resolution Hubble Space Telescope image of M87 is shown in the view, offset from the galaxy position to the upper right to avoid confusion, close to the position of the star HIP61051. Position the cursor over this image, right-click to open the dropdown list, and Centre on this image. Zoom in to a field of view of about 1 arcminute to view one of the jets emanating from the galaxy. Use the angular separation tool to measure the angular extent of this jet. What is this angle? (d) What is the projected length of this jet into space? (Hint: Use the small-angle equation, the distance to the galaxy, and the measured angle, remembering that 1 radian = 2.06 × 105 arcseconds). (e) Click on Favourites > Explorations > Milky Way Galaxy and use the location scroller to move the simulated image of the Milky Way Galaxy to imagine how such a jet would appear to us from Earth if our Galaxy were to produce a jet like that from M87. The Sun is about 26,000 ly from the galactic center. Calculate how far across our sky this jet would extend if it were perpendicular to the galactic plane, again using the small-angle approximation.

  7. Use the Starry Night program to examine a very distant pair of quasars. Most quasars are starlike in appearance but their spectra show very large redshifts. If these redshifts are cosmological (i.e., caused by the expansion of the universe), then quasars obey Hubble’s law, and their large redshifts show that they must be very far away. Since they appear bright in our sky, they must be very luminous, with outputs equivalent to that of billions and even trillions of Suns. They are part of a group of objects known as active galactic nuclei. The source of energy output of these very luminous objects is probably a supermassive black hole at the object’s center. Select Favourites > Explorations > Quasar Pair and Zoom in to a field of view about 30 arcseconds wide. Open the Info pane for this pair of quasars and note the Distance from observer from the Position in Space layer. (a) What is the distance from Earth of these quasars? (b) Using a Hubble constant of 73 km/s/Mpc, calculate the expected recessional velocity of this quasar pair. (Note: 1 pc = 3.26 ly) (c) What is the ratio of the recessional velocity of these quasars to the speed of light?

Collaborative Exercises

  1. Make a labeled sketch clearly showing how the spectrum of 3C 273, shown in Figure 24-3, would be different if the object were moving toward us at the same velocity. Compare your sketch to that of another group and resolve any inconsistencies.

  2. Two dramatic images of M87 are shown in Figure 24-8. Invent an imaginary scenario that would be analogous to a local dance club where two pictures would show different aspects of the event and write a description of each. Be sure to include a description of how this is analogous to the images in Figure 24-8.