awakeIf you're curious, a parsec is about 3.26 light-years or 206,260 astronomical units, but those units are better for getting a mental picture of an star's distance rather than actually calculating it (or using modica of algebra, calculus, and physics to determine the intrinsic† properties of the star). But when you need to make that conversion you can just look it up or use something like WolframAlpha. Knowing those conversions is far, far less important than understanding where the parsec comes from (parallax of one arcsecond) and what it's good for. As always, a
† - An intrinsic property: This is a 100 watt light-bulb. (How "powerful" it is. This property is about the light-bulb itself.)
An extrinsic property: From 50 feet away, it looks about as bright as a candle would be at 4 feet. (How bright it looks. This property is dependent on the light bulb too, but it is also dependent on where the observer is located relative to the light bulb. If you know one property, you can determine the other.)
So what was Han Solo on about when he said the Millennium Falcon could make the Kessel Run in
But I actually wrote all that to give context to this: In an assignment question, I was asked to take a 1672 parallax measurement for the planet Mars and determine its distance from Earth at the time. Only this measurement was based on simultaneous observations taken from both sides of the Earth, so the arcseconds were subtending one Earth diameter, not the Earth-Sun distance! After calculating that Mars was about 6139 AU away and wondering what was up (it was really more like 0.5 AU), I discovered my error. But I was only off by about a factor of 11,800. I've done worse. ;-p