1. How Far To The Stars? By Vanessa Soto

2. Giovanni Cassini First astronomer to observe stellar parallax of Mars.
He sent Jean Richer to French Guyana while he stayed in Paris. They both made simultaneous observations of Mars.

3. Parallax
Hold your finger a few inches in front of your face. Close your right eye and observe what your finger is in front of on the distant background. Do the same for your left eye.
The apparent shift of your finger against the background is parallax.

4. Stellar Parallax
The small annual shifts in a star’s apparent position which is caused by the Earth’s motion around the sun.

5. Parallax Formula D is the distance from the Earth to the object in pc.
P is the parallax angle.
PC is parsec, the distance to an object with a parallax angle of 1 arc second.

6. Parsec to Light-years
There are 3.26 light-years in one parsec. The parallax formula will give us the distance in parsecs so we have to use the formula PCx3.26 to get the distance in light-years.

7. Distance to the Stars D=1/P Sirius 0.379 1/.379 D=2.64 8.60 0.772
Celestial Bodies
Parallax Angle
D=1/P
D=PC
Convert
Light-years
Sirius
0.379
1/.379
D=2.64
2.64x3.26
8.60
Proxima Centauri
0.772
1/.772
D=1.30
1.30x3.26
4.24
Vega
0.125
1/.125
D=8
8x3.26
26.08
Altair
0.2
1/.2
D=5
5x3.26
16.3
Moon
0.5
1/.5
D=2
2x3.26
6.52

8. The End