Question: My class and I are working on a class project about constellations so I was wondering if you could answer some of my questions. The first question that I have is what is a constellation. The second question that I have is what is the most popular constellation. The last question that I have for you is how they form and if there is a specific star that [is] in a constellation like a red giant. — Isabel
Answer: A constellation is a grouping of stars which form a pattern in the sky that is traditionally named after its apparent form or identified with a mythological figure. Modern use of constellations includes identification of general locations for stars and galaxies (i.e. the Andromeda Galaxy). As for which constellation is the most popular, I think that depends upon who you are asking. If you mean which constellation is the one that most people know about, I think that Andromeda might be a good answer, given its famous inhabitant, the Andromeda Galaxy (otherwise known as Messier 31). Regarding how constellations are formed, the fact is that they are not formed by any physical process, nor do the stars that make up a constellation generally have any association with each other. Constellations are usually just chance alignments of stars which appear to be near each other from our vantage point. Finally, yes there is at least one famous red giant star in a constellation. The constellation Taurus contains the red giant star Aldebaran. If you would like further information about the mythology associated with constellations, see my blog post on “Mythology and the Constellations”.