# What does this symbol $\odot$ mean?

While reading through a physics textbook, I came across the use of sub-scripted ☉s.

Here's the context:

Stars between 0.5M and 10M will evolve into red giants...

I'm assuming it's to do with the life-span of a star; however, I don't know exactly how.

I searched google/wikipedia however it simply stated it represented the sun

• solar mass – AccidentalFourierTransform Nov 20 '16 at 17:28
• I really don't understand why this was down-voted. – Tobi Nov 20 '16 at 17:31
• I didnt downvote, but I guess the reason is that you didnt really show any research effort. – AccidentalFourierTransform Nov 20 '16 at 17:32
• And what you found when you searched is exactly right and the answer to your question. – dmckee --- ex-moderator kitten Nov 20 '16 at 17:57
• I do not at all believe that this symbol is not defined in the textbook previous to its use. At worst, there will be a table at the very beginning of the book. – Kyle Kanos Nov 20 '16 at 18:27

The symbol in question, $\odot$, usually denotes the Sun. The solar mass, $M_\odot$, is often used as a unit of mass in astronomical/astrophysical texts. Another example is the solar luminosity, $L_\odot$.
• Just in case it's not clear, "solar mass" and "mass of the Sun" mean exactly the same thing, represented by the symbol $M_\odot$. – Viktor Toth Nov 20 '16 at 17:50