Distances to Stars in Leo Worksheet

#### Fourteen Stars in the Constellation Leo

Star ID Star Name Spec.
Type
Lum. Class Apparent Mag. M from Spec.
Prllx
d from Spec.
Prllx
Measured Parallax
(arc sec)
d from Parallax
a Leo Regulus   V 1.36     0.038
b Leo Denebola A3 V 2.14 ~ 2 10 0.076 13
g1 Leo Al Geiba A*   III 2.14     0.036
d Leo Zozma A5 V 2.55 ~ 1 20 0.040 25
e Leo Ras Elased Australis   II 2.98     0.009
q Leo Chort   V 3.34     0.036
g2 Leo Al Geiba B*   III 3.39     0.036
z Leo Aldhafera F0 III 3.44 ~ 1 32 0.025 40
h Leo 30 Leonis A0 I 3.48 ~ -5 500 N/A **
o Leo Subra   V 3.52     0.034
r Leo   B1 I 3.85 ~ -6 900 N/A **
m Leo Ras Elased
Borealis
K2 III 3.88 ~ 2 25 0.025 40
s Leo   B9 V 4.05 ~ 2 25 0.017 59
R Leo ***   III 5 - 10 -1 to +4 160 N/A **
 * Visual Binary ** Distance is too far for a measurable parallax ***Variable Star M = absolute magnitude of the star Luminosity class symbols: V = dwarf, IV = subgiant, III = giant, II = luminous giant, I = supergiant.

1. As part of this exercise, you determined the distances to these stars based on the method of spectroscopic parallax. In your own words, summarize why the method is an important tool for astronomers.

2. Compare the two values for the distance to each of the seven stars. Do certain spectral types or luminosity classes lead to larger differences between the two values?

3. Comment on the accuracy of the spectroscopic parallax method vs the trigonometric parallax measurements.