The Distance to the Hyades Cluster

### Table 1: Data and Distance for the 10 Marked Stars

Star Number
on Fig. 4
(km/sec)
Angle q Transverse
Velocity
(km/sec)
Proper Motion
(arcsec/year)
Distance (parsecs)
1 31.6     0.151
2 31.0     0.121
3 36.6     0.124
4 38.3     0.114
5 43.8     0.120
6 38.2     0.098
7 39.3     0.100
8 38.6     0.108
9 43.6     0.079
10 38.8     0.065
Average
Distance:
Error in
Distance:

1. Give two reasons why distances to individual stars vary from each other.

2. Could the distance to the Hyades be determined by annual parallax? Discuss.

3. Using criteria of your choice, what is the diameter of the Hyades in parsecs?

4. What is the mean distance in light years to the Hyades? What is the diameter of the Hyades in light years?

5. The Hipparcos satellite was able to measure the parallaxes of 200 Hyades stars very reliably. The distance to the Hyades's center of mass has been pinpointed at 46.34 +/- 0.27 parsecs, or 151 +/- 0.9 light years.
1. Compare your (albeit crude) results to the Hipparcos results.

2. Why is it significant that Hipparcos has parallaxes for so many stars?

3. What implication does this more accurate (and precise) measurement of the distance to the Hyades have for the size of the Universe?