Activities

Observing Project

Observing tips and tools

Meteors: Informative details concerning upcoming meteor showers appear on the Web sites for Sky & Telescope and Astronomy magazines.

Comets: Because astronomers discover dozens of comets each year, there is usually a comet visible somewhere in the sky. Unfortunately, they are often quite dim, and you will need to have access to a moderately large telescope (at least 35 cm, or 14 in.). You can get up-to-date information from the Minor Planet Center Web site. Also, if there is an especially bright comet in the sky, useful information about it might be found at the Web sites for Sky & Telescope and Astronomy magazines.

Asteroids: At opposition, some of the largest asteroids are bright enough to be seen through a modest telescope. Check the Minor Planet Center Web site to see if any bright asteroids are near opposition. If so, check the current issue as well as the most recent January issue of Sky & Telescope magazine for a star chart showing the asteroid’s path among the constellations. You will need such a chart to distinguish the asteroid from background stars. Also, you can locate Ceres, Pallas, Juno, and Vesta using the Starry Night program if you have access.

  1. Make arrangements to view a meteor shower. Table 15-1 lists the dates of major meteor showers. Choose a shower that will occur near the time of a new moon. Set your alarm clock for the early morning hours (1 to 3 a.m.). Get comfortable in a reclining chair or lie on your back so that you can view a large portion of the sky. Record how long you observe, how many meteors you see, and what location in the sky they seem to come from. How well does your observed hourly rate agree with published estimates, such as those in Table 15-1? Is the radiant of the meteor shower apparent from your observations?

  2. If a comet is visible with a telescope at your disposal, make arrangements to view it. Can you distinguish the comet from background stars? Can you see its coma? Can you see a tail?

  3. Make arrangements to view an asteroid. Observe the asteroid on at least two occasions, separated by a few days. On each night, draw a star chart of the objects in your telescope’s field of view. Has the position of one starlike object shifted between observing sessions? Does the position of the moving object agree with the path plotted on published star charts? Do you feel confident that you have in fact seen the asteroid?

  4. Use Starry Night to explore some of the dwarf planets of the solar system. Select Favourites > Explorations > Dwarf Planets from the menu. This view, from a position in space about 97 AU from the Sun shows Neptune’s orbit as well as the orbits of several dwarf planets. Right-click (Ctrl-click on a Mac) on the Sun and select Centre from the contextual menu. (a) Do the dwarf planets revolve about the Sun in the same or opposite direction as the planets? (b) Use the location scroller to adjust the view so that the plane of Neptune’s orbit appears edge-on. How do the orbital planes of the dwarf planets compare to those of the planets?

  5. Use Starry Night to locate the largest asteroid Ceres, now designated a dwarf planet, and to examine the asteroid belt. Select Favourites > Explorations > Asteroids. The view shows the orbits of the major planets and of the dwarf planet Ceres, centered on the Sun from a distance just beyond the orbit of Jupiter, at about 5.3 AU. Numerous asteroids are represented by the bright green dots. Use the location scroller to examine the extent of the asteroid belt and observe the orbits of some of the asteroids from different perspectives, particularly along the plane of the ecliptic and perpendicular to the plane of the ecliptic. (a) In which region of the solar system is the major concentration of asteroids? (b) How would you describe the plane of Ceres’s orbit relative to the plane of the ecliptic? (c) Look for asteroids whose motion brings them within Earth’s orbit. If you find such an asteroid, click the Stop button and use the HUD to identify it. You can display an asteroid’s orbit by right-clicking on the asteroid (Ctrl-click on a Mac) to open the contextual menu and selecting Orbit. Use the location scroller to study the asteroid’s orbit. Are the orbits of these asteroids generally in the plane of the ecliptic?

  6. Use Starry Night to observe the motions of two smaller objects in the solar system, the dwarf planet Ceres and the minor planet Pallas, both members of the asteroid belt, as seen from Earth. Open Favourites > Explorations > Atlas to view the sky from the center of a transparent Earth. Select View > Ecliptic Guides > The Ecliptic from the menu and set the Time Flow Rate to 1 sidereal day. Open the Find pane, type the name Ceres in the search box, and press the Enter key to center the view on this dwarf planet. Click the Play button and observe the motion of Ceres over the course of at least 2 years of simulated time. (a) Describe how Ceres moves. (b) How can you tell that Ceres orbits the Sun in the same direction as the planets? (c) Return to the Find pane, type the name Pallas in the search box and press the Enter key to center the view on this minor planet. Watch the motion of Pallas in the sky for at least 2 years of simulated time. (d) How does the motion of Pallas compare with that of Ceres? (e) Which object’s orbit is more steeply inclined to the plane of Earth’s orbit? How can you tell? (f) One distinguishing feature that identifies a dwarf planet from a minor planet is its shape. A dwarf planet is approximately spherical in shape whereas a minor planet is more irregular. Find and zoom in on each of the above objects in turn. Which object has the more irregular shape? (g) Find the objects Juno and Iris. On the basis of the above criterion, what is the classification of each of these objects, dwarf planet or minor planet?

  7. Use Starry Night to observe a comet. (a) Select Favourites > Explorations > Hale-Bopp. From the appearance of this comet, predict the direction of the Sun relative to the comet and explain how you made your prediction. Use the hand tool to find the Sun in the view to verify your hypothesis. (b) Select File > Revert from the menu. From the appearance of the comet, can you predict what its motion will be in the future against the background stars? Click the Play button to see if your prediction was correct.

  8. Use Starry Night to study the motion of two comets. (a) Open Favourites > Explorations > Hyakutake to observe Comet Hyakutake from space as it approaches the inner solar system. Click the Play button and observe the comet as time progresses. Allow time to continue and observe the approach of a second comet, Hale-Bopp. To repeat the animation, select File > Revert from the menu and, if you wish, decrease the Time Flow Rate to observe the motion of the comet more closely. Use the location scroller to gain different perspectives on the motion of both comets. Describe what you see. Is each comet’s orbit in about the same plane as the orbits of the inner planets, or is it steeply inclined to that plane? (Hint: You can stop Time Flow and right-click on each comet in turn and click on Orbit in the dropdown menu to display each comet’s orbit.) How does the comet’s speed vary as it moves along its orbit? During which part of the orbit is the tail visible? In what direction does the tail point? (b) Select Favourites > Explorations > Atlas from the menu. Set the date in the toolbar to January 1, 1995. Open the Find pane and enter Hyakutake in the search box to center the view on the comet. Change the Time Flow Rate to 1 sidereal day and click the Play button. Observe the comet’s motion for at least 2 years of simulated time. Describe the motion, and explain why it is more complicated than the motion you observed in part (a). (c) Click the Now button in the toolbar. Set the time step to 1 lunar m, and click the Play button. Comet Hyakutake is currently moving almost directly away from the Sun and so, as seen from the Sun, its position on the celestial sphere should not change. Is this what you see in Starry Night? Explain your observation. (Hint: You are observing from Earth, not the Sun.)

  9. Use Starry Night to examine the regions of the solar system where comets originate. Open Favourites > Explorations > Oort cloud. The view is centered on the Sun and shows the orbits of the major planets as well as the inner and outer boundaries of the region in the solar system in which the Kuiper belt is found. (a) What type of comets originates from this belt? (b) Use the location scroller to view the boundaries of the Kuiper belt region. The inner boundary corresponds approximately to the orbit of which major planet? (c) Beyond the Kuiper belt lies the Oort cloud. Use the Increase current elevation button to move farther from the Sun until you encounter the boundary of the Oort cloud. What type of comet arises from this region of the solar system?