Particle notation: What does the asterisk stand for? For instance, what's the difference between $\Sigma^0$ particles and $\Sigma^{0*}$ particles? I know they have the same quark configuration $sdu$, so how exactly are they different?
Some context: I'm reading the 2nd chapter of Halzen's Quarks and Leptons. I found the sigma baryons (with and without the asterisk) on Figure 2.8. More precisely, I found the $\Sigma$ particles on the spin 1/2 graph, and the $\Sigma^*$ particles on the spin 3/2 graph.
 A: In case of the $\Sigma$ particles the $^*$ means "excited" (i.e. having a higher energy, thus a higher rest mass). 
For other particles the $^*$ may have other meanings
(see the posted comments below).
According to Wikipedia "Sigma baryon":
The $\Sigma^{0*}$ baryon has total angular momentum $J=\frac{3}{2}$ and rest mass $1383\text{ MeV}/c^2$.
The $\Sigma^0$ baryon has total angular momentum $J=\frac{1}{2}$ and rest mass $1192\text{ MeV}/c^2$.  
Each quark ($u$, $d$ and $s$) has a spin angular momentum of $\frac{1}{2}$.
Grossly simplified you can imagine the particles like this:


*

*In the $\Sigma^{0*}$ baryon all 3 quarks are spinning in the same sense,
giving a total angular momentum of
$\frac{1}{2}+\frac{1}{2}+\frac{1}{2}=\frac{3}{2}$.

*In the $\Sigma^0$ baryon 2 quarks are spinning in one sense,
and 1 quark is spinning in the opposite sense,
giving a total angular momentum of
$\frac{1}{2}+\frac{1}{2}-\frac{1}{2}=\frac{1}{2}$.
Explaining why $\Sigma^{0*}$ has a higher energy than $\Sigma^0$
would be a more difficult story.
A: In the PDG notation, a star is not synonymous with an excited state. Yes, any state with a star is excited, but not all excited states have a star. It depends on the spin and parity.
From the PDG naming scheme for hadrons in the section on flavoured mesons:


  
*If the spin-parity is in the "normal" series, $J^P = 0^+, 1^-, 2^+,...$, a superscript "$^*$" is added.
  

In other words, the star tells you the parity is positive for even spin and negative for odd.
They don't seem to define rules for starred baryons, and the only one I can find is the $\Sigma_b^*$.
