typing star between brackets in text

Question

Suppose I write a post that contains equations that I like to refer back to later, like this:

$$3^2 + 4^2 = 5^2 \qquad (*)$$ $$3^3 + 4^3 + 5^3 = 6^3 \qquad (**)$$ $$3^4 + 4^4 + 5^4 + 6^4 = 7^4 \qquad (***)$$

In spite of the well known truth of ( * ) and the lesser known but equally valid truth of ( ** ) we have that equation ( *** ) is patently false.

You may note that I put some extra spaces between the stars and the brackets, because otherwise the sentence becomes garbled by Markup:

In spite of the well known truth of () and the lesser known but equally valid truth of () we have that equation () is patently false.

(If you click the edit button you will see that the above weird looking sentence is typed just as you would naively do on a type writer)

My question is twofold:

1. How can I get ( * ) without the extra spaces?
2. In real life I found that sometimes everything works out just fine without me doing anything special, see e.g. my latest post here. (Update: and the bracket-star-bracket just two lines down in this very question(?!?)) But then at some other places in the same post I had the same problem as above and needed the extra spaces. So my second question is: how is this possible? What is going on here? What determines if I can type (*) or not? It seems arbitrary but it can't be, right?

Answer 1

Q1. With \tags and \labels:

 $$3^2 + 4^2 = 5^2  \tag{$*$}\label{1}$$
 $$3^3 + 4^3 + 5^3 = 6^3 \tag{$**$}\label{2}$$
 $$3^4 + 4^4 + 5^4 + 6^4 = 7^4 \tag{$***$}\label{3}$$ 
 
 In spite of the well known truth of \eqref{1} and the lesser known but equally valid
 truth of \eqref{2} we have that equation \eqref{3} is patently false.

$$3^2 + 4^2 = 5^2 \tag{$*$}\label{1}$$ $$3^3 + 4^3 + 5^3 = 6^3 \tag{$**$}\label{2}$$ $$3^4 + 4^4 + 5^4 + 6^4 = 7^4 \tag{$***$}\label{3}$$

In spite of the well known truth of \eqref{1} and the lesser known but equally valid truth of \eqref{2} we have that equation \eqref{3} is patently false.

Q2: The reason is that * is used to render Markdown. Specifically, it makes text italic, bold or italic and bold (*italic*, **bold** or ***italic and bold***) If you want to use *, you can type \*, or (to make it fit with what you are referring to) $*$.