# How many stars are in the constellation Canis Minor?

I've read Wikipedia and found a list of stars in Canis Minor, and counted the number of stars in the list. I came up with 56 stars, a surprising number. I did some more research and found that Canis Minor was just the two binary stars orbiting together: Procyon and Gomeisa. So I came to the conclusion that the answer could be found here somewhere. Please help and tell me how many stars the constellation Canis Minor is made of. Thank you.

• What is the point of knowing exactly how many stars are in the constellation? 'The most prominent' (or scientifically, those whose brightness is above a threshold) is enough. Dec 14, 2015 at 19:10

You possibly are confused by these two entries in Wikipedia (click on the quotations to go to the original distinct entries:

Canis Minor contains only two stars brighter than the fourth magnitude, Procyon (Alpha Canis Minoris), with a magnitude of 0.34, and Gomeisa (Beta Canis Minoris), with a magnitude of 2.9.

and

This is the list of [56] notable stars in the constellation Canis Minor, sorted by decreasing brightness.

The first statement is about stars brighter than the 4th magnitude, of which there are two, and not about all the others. Those two stars are NOT a binary. Procyon is 11 lightyears away and Gomeisa is 170 lightyears away. Procyon itself is a binary, but for the purpose of general observation is considered to be one star.

The second statement is about "notable stars", which is rather arbitrary. The list is 56 stars long, but in fact is one were to map every star visible to telescopes, there would be thousands.

Another quibble: What perchance is the exact area in the sky that is assigned to Canis Minor? This is not precisely defined. See below.

## ~~~~~~~~~~~~~~~~~~~~~~ and ~~~~~~~~~~~~~~~~~~~~~~

Note the completely different boundaries.

• The area of the sky that is covered by each constellation is in fact very precisely defined by the IAU: en.wikipedia.org/wiki/Constellation Dec 14, 2015 at 13:59

Aabaakawad's answer highlights an important aspect of any constellation: They are defined by a surface area on the sky, behind which many, many stars hide. In order to answer just how many stars, you'll have to ask "above which brightness threshold?".

I think you should accept his answer, but I have two comments:

1. "…if one were to map every star visible to telescopes, there would be thousands." Even inside the Milky Way, 'thousands' is a severe understatement. Canis Minor spans an area of 183 deg$^2$. Although this is one of the smallest constellations, it still corresponds to roughly 0.5% of the sky. And although the direction to Canis Minor is more or less away from the center of the Milky Way, with 100 billion stars in the Milky Way this is still millions of stars. But why stop in the Milky Way? If you continue your sightline, roughly $10^{20}$ stars lie within the observable Universe, of probably infinitely (!) many more outside.

2. The region, and hence the area, of Canis Minor and any other constellation is exactly defined by its coordinates on the sky, as shown by Aabaakawad's first figure. His second figure is from Johann Bode's Uranographia from 1801, at which time the boundaries weren't well-defined, but in 1930 the Belgian astronomer Eugène Delporte devised the modern boundaries (which at that time were along vertical and horizontal lines of right ascension and declination, but due to Earth's precession are becoming more and more skewed).