1: Mapping the Night Sky

Lab Goals

As a result of this lab, you should be able to:

• Identify the location of a star in the sky using astronomical coordinates
• Use a starwheel to identify the constellation of different stars in the sky
• Predict the apparent magnitude of a star based on comparison stars

Equipment and Setup

This lab requires the following equipment:

• Planetarium (or Planetarium software)
• Starwheel
• Red lights / lasers (optional)

Submission Instructions

Submit a brief lab report that includes the following sections:

Background Information

We will begin our night sky learning journey by using our planetarium to simulate a starry sky in Hayward, CA. When the planetarium is on, please refrain from using cellphones, laptops, tablets, or any other device that produces light. We have special red flashlights that allow us to see without disrupting the dark adaptation of our eyes.

Lab Instructions

1. Choose a star in the sky. Do not point to it or give away its location.
2. Write instructions for how to locate that star.
3. Share your instructions with your group. Each member of the group should guess the location of your star.
4. Write down some ideas on how you could make the process of identifying each other’s star easier.
5. In collaboration with your partners, select a Focal Star that the entire group will use.
6. If you were to make a constellation out of the pattern of stars near the star you have chosen, what would it look like?
   1. Draw your imagined constellation below with a label to designate your focal star. Each group member may have a different response.

Background Information

We can identify the location of a star or a point in the sky by imagining a curved grid superimposed on the sky. Grids have two axes. For star locations, we can describe the Cardinal Direction of the star along the horizon and the Altitude of the star above the horizon. We can add precision to our cardinal directions by identifying 360 degrees around the horizon with our 0o point as North. This measurement is called Azimuth.

Lab Instructions

1. As a group: Identify the following for your group’s Focal Star:
   1. Cardinal direction: What direction should you face to see the star?
   2. Altitude: How high above the horizon is the star (in degrees)?
   3. Apparent brightness: Compare the brightness (Very bright, medium bright, dim) of your star to the brightest star you can see on the planetarium sky.
   4. Any other identifiers. Any other characteristics about the star or position that can help you identify the star?
2. Complete the table for 5 additional star choices agreed upon by your group. Choose stars that are not near each other in the sky.
3. Discuss the questions as a group, then respond in complete sentences:

1. Why are Cardinal Directions (Azimuth) and Altitude useful concepts for astronomical observation?
2. How else can astronomers communicate information about a star to help others locate the same star?

Results

Background Information

This activity involves the use of a Star Wheel. Your instructor will demonstrate how to set the starwheel to our latitude and local time and how to orient it correctly. Note: On a starwheel, constellations are labeled in all caps (URSA MAJOR). Some of the brightest stars in the constellations are labeled with only a capital first letter (Vega).

The apparent magnitude of a star indicates how bright the star looks to the naked eye. The magnitude scale we use today was first developed thousands of years ago by ancient Greek astronomers and has since been adapted into a logarithmic scale by modern astronomers. Adapting a more robust mathematical scale to ancient naked-eye observations yields a more functional but less intuitive scale. Negative magnitudes mean brighter stars!

The relative brightness of stars on your starwheel is represented by the size of the dot. Larger dots indicate brighter stars. The brightest star visible in our sky is Sirius (Mag -1.5). Some other bright stars that should be labeled on your starwheel are Arcturus (Mag 0), Vega (Mag 0), Deneb (1.25), and Antares (Mag 1). Fainter stars are not specifically named on your starwheel except for Polaris (Mag 2). The naked eye limit (the faintest magnitudes that can be seen with the naked eye in very dark skies) is about Magnitude 6.

Your starwheel may include a magnitude chart on the back (and a section titled "The First Magnitude Stars").

Lab Instructions

1. Keep the same stars and star numbers you used in the first table. Now, using your starwheel, identify the constellations of your 6 original stars.
   1. Is your star not on the starwheel? Reasons could be:
      1. It is too faint
      2. It is not a star! It could be a planet.
   2. If your star is not on the starwheel, give a constellation hypothesis based on general location and nearby stars.
2. Locate the stars mentioned in the Background section on your starwheel and compare their brightness and magnitudes to the stars on your table. Estimate an apparent magnitude for each of your 6 stars in the table (you don’t have to be exact, just give it a good guess).
3. Bonus Credit: If you have completed your two tables, and you are waiting for your classmates to catch up. You can choose 5 additional stars and, using the same steps 3-6 fill out this table.
4. Your instructor will put up the outline and the name of each constellation. Discuss the questions as a group, then respond in complete sentences:
   1. Were you correct for each of your six stars? Explain below any corrections that need to be made to your table (but do not change your original answers)
   2. What would you change about your process next time if you had 6 different stars? Explain the reasons for those changes.

Results