# Problem Understanding A Main Sequence Question:

1. Aug 14, 2012

### jguy

Hello, all, I am an adult college student and I'm having a terrible time "understanding" a particular astronomy question. I do not ask that any of you answer the question, but I am asking that maybe some of you can re-structure the original question so that I may have a clue as to what's expected?
Here is the question: "Tell what single stellar physical property the Main Sequence is a sequence of."

There are several properties like spectral types and luminosities -- so I'm not sure what the intent of the professor with this inquiry. Again, please don't answer the question. I want to "think it through" myself -- I've been stumpped by this for the last 2 days. Any help would be most graciously appreciated.

J.

2. Aug 14, 2012

### mathman

Stars on the main sequence have a direct correlation between color and brightness, ranging from red dwarfs to blue giants. White dwarfs and red giants are off sequence.

The underlying physics is that main sequence stars are hydrogen burning, the others are not.

3. Aug 14, 2012

### Chronos

There is indeed a single, simple property that defines all other properties of a main sequence star. So, you might ask yourself what determines the color and brightness of a star?

4. Aug 14, 2012

### onomatomanic

I agree with ^, that seems to be what the question is aiming for.

If so, I'd have phrased it as something like "which single stellar physical property determines primarily where on the Main Sequence a given star is located?"

At face value, the question doesn't really make sense to me. The Main Sequence is a region in a two-dimensional phase space, saying that it is "a sequence of [a] physical property" is at best semantically vague and at worst nonsensical, IMO.

5. Aug 14, 2012

### jguy

Thank you all for the comments! Onomatomanic, I defiantly understand your position with regard to the question. I seriously and directly "cut-n-pasted" that question right from the assignment! I was at a loss - I have reviewed the magnitude class and the H-R diagram as well as the interrelated properties spectra reveals, but really couldn't cope with the question's intent. This is a "distance Ed" class, one where I am physically located on one side of my country and the professor is in another. Thus, communications can be misconstrued from time to time. I personally thank you all for taking time from your busy lives to entertain a disparate individual!