How do you find the parsecs and light-years away a star is from the parallax angle? For example, Sirius has a 0.379s parallax angle. How would you get the parsecs and light-years away?

1 Answer
Apr 30, 2016

3-sd approximations: 2.64 parsec = 8.65 ly = 544000 AU..


For your long-term-memory:

If #alpha# radian is the parsec angle,

the formula for distance = 1/#alpha# AU.

Here, #alpha#=(0.379/3600)(#pi#/180) radian.=1.8374 E-06 radian.

So, d=1/1.8374 AU=544000 AU.

Unit conversions:

In lu units, from AU units, d = 544000/62000 ly = 8.65 ly..

In parsec units, from AU units, d=544000/206265 parsec = 2.64 parsec.

All results are rounded to 3-sd.