Absolute Magnitude - Blog Posts

Which star is the closest to us ?

I don't mean The Sun or Proxima Centauri, which are the closest stars, I mean in the image above, which star is the closest ?

Of course, I left out the names and the constellations on purpose, because when you look up in the night sky, unless you've got Stellarium (or similar) as an app on your phone, you're not going to see names and the lines which our ancestors made up for story telling.

Maybe it's the brightest one in the middle ? But then, how do you know if that's a massive star far away, or a smaller one really close ?

Thankfully, our orbit around the Sun is going to help us.

Parallax allows us to see which stars are closer and further based on how much they move between 6 months. This works great for the closer stars, but not so much the more distant ones and especially not the other galaxies, however there are other methods for finding which of them are closer, but for now, we're only interested in the closest stars, so simple maths and observations over a period of time can assist us.

Have you ever wondered what our Sun would look like in the night sky of another planet orbiting another star ? Truth is, when you look at those stars in that image above, almost all of them, the answer would be "You couldn't see it, it's not bright enough!"

Truth is, most of the stars we see in our night sky are larger and brighter than ours, at 32.5 light years our Star would be magnitude 4.83, just inside our naked eye ability.

The red square represents the upper image, zoomed out to better reflect what you could see with your naked eye. The tiny dot that the yellow arrow is pointed to, is the same brightness our Sun would be in the night sky of a planet 32.5 light years away.

Why 32.5 ? Well, the brightness of stars in the sky are ranked by Magnitude, the lower the number, the brighter, in fact, each integer is 2.5 times brighter than the one above it. What we see with our eyes we call Apparent Magnitude, but given some fun maths, we can take each star, pull it 10 parsecs (32.5 light years) from us, and imagine how bright it would be, this is known as the Absolute Magnitude.

Getting back to our original question, which was the closest, you'll already begin to understand the brightest stars are not necessarily the closest, using parallax we can really find out, and as some of you may have guessed already, it's the one you couldn't see with your naked eye.

Just 5.96 light years from us, but at apparent Mag 9.51 quite invisible to the naked eye. While the brightest Cebalrai was 81 light years, still close in terms of our Milky Way, but when you next look up, and see a sky full of stars, remember, you're only seeing the bright ones, there's thousands of times more quite close by, you simply cannot see.