• Question: if the parallax angle to a near by star is two seconds of arc how far away is the star?

    Asked by to Kieren, Rowena, Roy on 20 Mar 2014. This question was also asked by .
    • Photo: Kieren Bradley

      Kieren Bradley answered on 20 Mar 2014:

      Unfortunately I never did a huge amount of astronomy, so I had a quick look to see how you calculate the answer and found this website:

      http://lcogt.net/spacebook/parallax-and-distance-measurement

      The fact you asked this question suggests you probably already know more about parallax and using it to measure distances than I do, but if you want to know more it looks quite a nice site to explain it. The answer is that d=1/p, in your case d=1/2, so the distance is 0.5 parsecs, or 1.5×10^16 m (15000000000000000 m) , which is 15 trillion kilometres away.

    • Photo: Rowena Fletcher-Wood

      Rowena Fletcher-Wood answered on 20 Mar 2014:

      I always have to draw diagrams to look at parallax… Interesting parallax fact – your eyes can only do it because they are a bit apart and look the same way (my husbands eyes look different ways so he can’t do parallax and depth perception at all!) but actually only ONE eye looks straight and the other follows it. This is your dominant eye. About 15% of people are left handed but about 40% of people are left eye dominant. I am right handed but left eyed.

      To test which eye is dominant hold out a finger pointing up as far away from you as you can reach and focus on it. very very slowly bring it towards yourself and it will move more towards one eye than the other! This is your dominant eye. When you do archery or shoot a gun, you use your dominant eye to aim – this means I use a left handed bow or rifle!

Comments