Name: Partner(s): Day/Time: Version: plan

# Precession - Planetarium Activity

## Part 1: The Sky Now

Your GSI will show the sky at noon on May 1 of this year. She or he will also point out the Sun's position at the June Solstice.

1. In which constellation is the Sun?

2. In which constellation is the Sun at the June solstice?

3. The GSI will let the day and night proceed. Watch for the position of the North Celestial Pole. In which constellation is the pole? Enter the Declination of the pole in Table 1.

4. Find the constellations in Table 1 and enter their approximate Declinations and Altitudes in Table 1. If the constellation is below the horizon, enter "Below Horizon" for the Altitude.

## Part 2: The Sky in the Year 11,000 BC

Your GSI will show the sky at noon on May 1, 11,000 BC (13,000 years ago). She or he will also point out the Sun's position at the June Solstice.

1. In which constellation is the Sun?

2. In which constellation is the Sun at the June solstice?

3. The GSI will let the day and night proceed. Watch for the position of the North Celestial Pole. In which constellation is the pole? Enter the Declination of the pole in Table 1.

4. Find the constellations in Table 1 and enter their approximate Declinations and Altitudes in Table 1. If the constellation is below the horizon, enter "Below Horizon" for the Altitude.

Table 1: Object declination and altitude

### 11,000 BC

Declination Altitude Declination Altitude
North Celestial Pole
Ursa Minor

Corvus

Crux

## Concluding Questions

1. List the constellations that immediately circle the North Celestial Pole today:

List the constellations that immediately circled the North Celestial Pole in 11,000 BC, using your answer to Question 7:

Recall that circumpolar constellations are defined to be those that do not set below the horizon. Have the circumpolar constellations changed since 11,000 BC? Explain. Figure 4 in the Introduction may be helpful.

2. Did the coordinates of stars change between 11,000 BC and the present, in the equatorial coordinate system? Explain.

3. In the year AD 15,000, will the constellation Crux be visible from Ann Arbor? Explain.

4. In the year AD 15,000, will the Sun's path in the sky still follow the same zodiac constellations? Explain.

5. We say that Taurus is a winter constellation because it is in the evening sky in our (northern) winter. Based on your answers to Questions 1-2 and 5-6 in Parts 1 and 2 above, which zodiac constellation was in the winter evening sky in the year 11,000 BC? Figure 1 in the Introduction may be helpful.

updated: 1/19/10 by SAM & MSO