Our Sun, The Nearest Star
The sun turns 700,000,000 tons of hydrogen into 695,000,000 tons of helium every second by nuclear fusion. The remaining 5 tons is converted into energy. 400,000,000,000,000,000,000,000,000 watts
Distances to Other Stars
Distances are particularly easy to calculate if we use the parsec as our distance unit. In that case, the distance of a star in parsecs is:
D = 1/p
where D is the distance in pc and p is the parallax angle in seconds of arc. For example, Sirius has a parallax angle of 0.38 seconds of arc and thus its distance from the Earth is d = 1/0.38 = 2.6 pc = 8.6 LY. The nearest star (other than the Sun) is the alpha-Centauri system, which has a parallax of 0.76 seconds of arc, corresponding to a distance of 1.315 pc = 4.3 LY. Thus, all stars have parallax angles of less than one second of arc.
The Nearest Stars
How far away is Polaris? Where can I find reliable distances to nearby stars?
I am trying to find out the distance to the pole star. In one reference I found on the web 300 ly was the figure given while a second source gave 690 ly. My question for you is what is the distance and is there a > generally accepted reference available on line to get such information?
From: "Ask An Astronomer"
We now have an excellent way to find out the distances to (relatively) nearby stars: the Hipparcos catalog from a European space mission was released last summer. I checked the catalog for you and found that the distance to Polaris is 132 parsecs. There are 3.26 ly in one parsec, so the distance to Polaris is 430 ly. Polaris is a Cephied star, a type of variable star. That makes it tricky to get the distance from the brightness of the star. The Hipparcos satellite made a trigonometric measurement which is more secure. However, the measurement still has an uncertainty of plus or minus 100 ly, which is larger than one would like; the reason is because Polaris is so far away. It is near the limit of what Hipparcos could reach.