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Difference in HR diagram clusters

The main difference is due to the age of the cluster. In our Galaxy the globular clusters are old ($>10^{10}$ years) and as a result the main sequence turn-off is down at something like $0.9 M_{\...
ProfRob's user avatar
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5 votes
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How can red supergiants be cooler than dwarfs of the same spectral type?

The HR diagram has many forms. There is no one to one relationship between temperature, colour and spectral type that is true for stars of all surface gravities and metallicities. Spectral type ...
ProfRob's user avatar
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4 votes
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Redshift to calculate age of stars

The redshift that is referred to is not a Doppler redshift, but a cosmological redshift. The difference is that the former is caused by the source moving through space, while the latter is caused by ...
pela's user avatar
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4 votes

When exactly does a sub giant become a red giant?

The straightforward definition is in terms of where a star lies on its evolutionary track in the HR diagram (see below). The subgiant branch stars are those which have exhausted their hydrogen core ...
ProfRob's user avatar
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4 votes
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HR diagram x-axis (color) and redshift?

The short answer is that the redshift of stars that are close enough to put into H-R diagrams (or "color magnitude diagrams", if we're being precise, given that you're talking about using ...
Peter Erwin's user avatar
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4 votes
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How does the stellar evolution for low and intermediate mass stars differ?

Where does the evolution actually stop? Is the Helium Core Flash the last thing a Sun-like stars experiences or does it in fact follow the rest of the tractory? Stars with masses below about 2 solar ...
Warrick's user avatar
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4 votes
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Is there a general way to plot the evolutionary track of a star on HR diagram?

One nice resource is the Digital demo room. You can choose the masses of the stars, their metallicity, and it creates a movie where you can see the evolution of those stars in the HR diagram. It's ...
Prallax's user avatar
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3 votes
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Is a branch on HR diagram a line formed by stars in the same evolutionary phase, or the evolutionary track of an individual star?

The answer is: both, but for different contexts. The HR diagram is used to display the properties of observed stars. A point on the diagram represents a star with a certain effective temperature and ...
Daddy Kropotkin's user avatar
3 votes

How can red supergiants be cooler than dwarfs of the same spectral type?

For this, its important to understand how temperature increases in a star. Inside a stellar core, there are two forces that are balancing each other out to keep the star in equilibrium. The core ...
Aryan Bansal's user avatar
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3 votes
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Is there a stellar database that indicates how long ago stars in our Galaxy formed?

There isn't really a database as you request. Finding the ages of stars is difficult. Only one star has an accurately known age - the Sun. That comes from radioisotope dating of meteorites. For other ...
ProfRob's user avatar
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3 votes
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How can you determine the distance of a star using the magnitude equation?

This is all absolutely true (pun intended). Finding absolute magnitudes is hard. For many types of star, we don't really know their absolute magnitude and so we don't really know their distance. For ...
James K's user avatar
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3 votes

When exactly does a sub giant become a red giant?

Let's walk through the stages of post-main sequence evolution. For reference, the images, and much of the content is being pulled from An Introduction to Modern Astrophysics by Carroll and Ostlie. I'...
zephyr's user avatar
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3 votes

Why do post main sequence stars enter the red giants branch?

If your question is why the star starts moving up the red giant branch, it's in essence because of the behaviour of the surface opacity and the development of a substantial convective envelope in ...
Warrick's user avatar
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3 votes

Why is the track of the subgiant stage almost horizontal on the HR diagram?

I will replace the previous answer to focus on the "subgiant" branch prior to red giant, rather than the pre-main-sequence or the "horizontal branch" of core helium fusion. Those are other times that ...
Ken G's user avatar
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3 votes
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How do you use Gaia Passbands to find Gbp-Grp Coordinates?

You should multiply your spectrum by the filter response function, integrate to get a flux and then turn that into a magnitude using a published zero-point flux (i.e. the flux that defines a magnitude ...
ProfRob's user avatar
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2 votes

Estimating a star's radius, temperature, and luminosity based on its mass

You could plot $L$ vs $T$ and compare your model result to the measured/estimated $L$ and $T$ of main sequence stars? You have not explained or labelled what your diagram is, but it isn't $L$ ...
ProfRob's user avatar
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2 votes

Locating a star cluster on a Hertzsprung-Russell diagram with other color index

With an absolute magnitude of zero and a colour (any colour) of zero, your stars are around spectral type A0 (by definition). The only thing that can confuse this is reddening/extinction. If there is ...
ProfRob's user avatar
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2 votes

Creating an HR diagram from tabulated stellar data

With the Gaia Data Release 2, you can plot an HR diagram with a few million stars. From the Gaia website : The data can be accessed in the search tab, where you can specify the columns you want to ...
usernumber's user avatar
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2 votes

Why does the Gaia color-magnitude diagram have this shape?

Try plotting absolute G magnitude (i.e. corrected for the fact tthat all the stars are at different distances) on the y-axis.
ProfRob's user avatar
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2 votes

Difference in HR diagram clusters

So, @ProfRob's answer is absolutely amazing and covers the bulk of star-cluster properties that I could think of. Nevertheless, since the question specifically asked for HR diagrams of open vs. ...
guilimberg's user avatar
2 votes
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Variables in the Instability Strip

You can, in fact, differentiate between the crossings of the instability strip in certain types of variable stars. There have been quite a few evolutionary models devoted to this, and many, as well as ...
HDE 226868's user avatar
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2 votes
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Is there a formula to calculate any star mass from Luminosity, Radius, and/or Temperature (K)?

I think the issue you are going to have here is that the position of a star in the HR diagram - which amounts to saying what the (2 dimensional) spectral type is - does not just depend on its mass. ...
ProfRob's user avatar
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2 votes

What would the HR diagram look like if the axes were scaled linearly instead of logarithmically?

What would the HR diagram look like if the axes were scaled linearly instead of logarithmically? This is a partial answer: Not so good. If things are well separated for clarity in a log-log plot, ...
uhoh's user avatar
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2 votes
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Unusual amount of white dwarfs in star clusters in my analysis

You don't have a horizontal branch, which would have an absolute magnitude of $\sim 2$ and you don't have a massive population of white dwarfs, which have a sequence that parallels the main sequence ...
ProfRob's user avatar
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1 vote

Graphing the evolution of stars on an HR diagram with timesteps

There is a rich variety of types of stellar evolution models. The modern model of a star is the spherically symmetric quasi-static gas assumed to be in local thermodynamic equilibrium (Chandrasekhar, ...
Daddy Kropotkin's user avatar
1 vote

Position of a star on the HR diagram

Firstly, a HR diagram is not the same thing as a CMD. A HR diagram is luminosity (or absolute bolometric magnitude) against effective temperature or a reliable proxy for effective temperature. ...
ProfRob's user avatar
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