Question: How can you measure the distance to a star

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  1. There are 2 ways astronomers can measure the distance to a star, adn it all depends on how far away the star is. For stars that are pretty close to Earth (ie no further than 400 light years away) they can use a technique called triangulation.

    Triagulation relies on trigonometry (eww…maths). What they do is they look at the star one day, and then look at it again in six months time and compare the viewing angle. By comparing this angle they can calculate the distance (coincidently – this process of triangulation is also how your GPS works!)

    For starts that are further away there is no way to directly measure the distance so astronomers use something called ‘brightness measurements’. A stars colour spectrum is a good indicator of how far away it is (this was proven using stars that were within the measuring distance, so we have some data points we can prove). Its a little bit confusing, but astronomers can look at a distant star and work out what its colour spectrum is, this will tell them its brightness. Once they know the brightness they can compare the actual brightness to the brightness seen on Earth (so how dull/dim does the star look by the time the light has had to travel all that way) and use this info to calculate the distance to the star.


  2. There’s a fancy word for it: parallax! (could be the name of a diet pill)

    I think it’s best to watch this video on youtube (if your school has blocked youtube, watch it at home)

    but….turn off the volume. They have some aweful music playing in the background


  3. I like Kym’s answer to this, though I have to object to the “eww…maths” bit. šŸ™‚