We’ll start our tour of the night sky with perhaps the most recognizable asterism in the night sky, Orion’s Belt.
An asterism is a recognizable pattern of stars in the night sky. It may form part of an official constellation, or be composed of stars from more than one.
Orion’s belt is composed of three bright stars that appear aligned in the night sky- Alnitak, Alnilam, and Mintaka. If their names sound foreign, it because, like many of the bright stars in the night sky, astronomers use their Arabic names, as peoples of the ancient Middle East were very advanced in their study of the night sky.
* Alnitak – “the girdle” – a hot blue supergiant, 7 times wider than our sun, and 700 ly (light-years) from us. That means that it’s a sun, like our sun (only bigger), and that the light it shines in every direction takes 700 years to reach Earth, so you’re actually seeing what it looked like 700 years ago, back around the year 1300 AD.
* Alnilam – “string of pearls” – also a blue supergiant, Alnilam is 30 times wider than our sun, and 1,300 ly away from us. Alnilam looks like it’s sitting right next to Alnitak, but it’s actually twice as far away from us, far behind Alnitak.
* Mintaka – “the giant’s belt” -15x wider than our sun, it’s approximately 690 ly away from us.Original photo from https://en.wikipedia.org/wiki/File:Orion_Head_to_Toe_-_Reduced.jpg.