Celestia Forums

I am trying to create IMHO the definitive Star Chart for all Stars, all the way from Wolf-Rayet Stars to Type L Stars, ranging in size from (O) Hypergiants to (VII) White Dwarfs (wd) (D). However, I am running into trouble filling in all the information for the Mass and Radius of the stars. To my knowledge, I don?€™t think anyone has ever attempted to Classify every Single Star type. I need people to look at this chart and Help me fill it out

I noticed that Celesita seems to have this list, or at least all the stars seem to be based upon some type of formula(s) to determine the Temperature, Radius. Is this information just pulled out of the star catalog, or is there some type of logic behind everything.

You can find the Star Chart at
http://vegastrike.sourceforge.net/users/mkruer/Celestia/Master_Star_Chart.xls

Thanks

Celestia has tables with some fundamental information on the various spectral types. The properties that come directly from tables are surface (photosphere) temperature, bolometric magnitude correction, and rotational period. Absolute magnitude is a per-star property. Other star properties such as radius are derived from the temperature, absolute magnitude, and bolometric correction. I'd be happy to provide the actual equations if you'd like them.

There are comments in celestia/src/celengine/star.cpp that give the source of some of the table data; most of it is from Lang's Astrophysical Data: Planets and Stars.

In Celestia 1.4.0, star definitions in .stc files may override the default values for their spectral type. This is important for properties such as rotation period which can only be very roughly estimated from the spectral type.

--Chris
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Thanks Chris, looking at the file it looks like you had/have the same problem that I am where if you are to use a more logarithmic scale for the data, what the scale says is the star type is not the same as what has been historically classified. As you mention in the file Sol is poorly classified as a G2V when it should me more of a G5V based upon the temperature.

Anyway back to my question, I noticed that you are using 3 arrays of 10 to define all the temperatures of a the star for a give spectra type, I guess my next question is which set to use? Or is each set for V, III, I type stars?

And yes if you have a general Equasion that can sum up most things that would be helpfull.

Thanks

Matt

http://cvs.sourceforge.net/viewcvs.py/celestia/celestia/src/celengine/star.cpp?view=markup

Chris, Just out of Curiosity, would you agree that Temperature, and Radius are, or should be the definitive characteristics defining all stars? Temperature is obvious for the spectral type. The reason why I say radius is that the Radius is the defining characteristic for the Size.

MKruer wrote:Chris, Just out of Curiosity, would you agree that Temperature, and Radius are, or should be the definitive characteristics defining all stars? Temperature is obvious for the spectral type. The reason why I say radius is that the Radius is the defining characteristic for the Size.

I think the primary "defining characteristic" of stars is mass - pretty much everything comes from that. Luminosity and Radius would be a close second. I don't think Temperature is that important really, at least not in practical terms - if people talk about stars (and how they affect planets around them) then the mass, luminosity and radius are the most important things.

Another parameter to keep in mind is Age, because that affects luminosity, radius, and temperature.

Evil Dr Ganymede wrote:

MKruer wrote:Chris, Just out of Curiosity, would you agree that Temperature, and Radius are, or should be the definitive characteristics defining all stars? Temperature is obvious for the spectral type. The reason why I say radius is that the Radius is the defining characteristic for the Size.

I think the primary "defining characteristic" of stars is mass - pretty much everything comes from that. Luminosity and Radius would be a close second. I don't think Temperature is that important really, at least not in practical terms - if people talk about stars (and how they affect planets around them) then the mass, luminosity and radius are the most important things.

While it's true that mass is the most fundamental property of a star, it's not a property that we can measure directly for most stars. Magnitude and color (from which we determine temperature) are much more easily measured, and that's why Celestia uses them as the fundamental properties.

chris wrote:

Evil Dr Ganymede wrote:

MKruer wrote:Chris, Just out of Curiosity, would you agree that Temperature, and Radius are, or should be the definitive characteristics defining all stars? Temperature is obvious for the spectral type. The reason why I say radius is that the Radius is the defining characteristic for the Size.

I think the primary "defining characteristic" of stars is mass - pretty much everything comes from that. Luminosity and Radius would be a close second. I don't think Temperature is that important really, at least not in practical terms - if people talk about stars (and how they affect planets around them) then the mass, luminosity and radius are the most important things.

While it's true that mass is the most fundamental property of a star, it's not a property that we can measure directly for most stars. Magnitude and color (from which we determine temperature) are much more easily measured, and that's why Celestia uses them as the fundamental properties.

Precisely

Bye Fridger

The other aspect about Mass in stars is that you can have 2 stars, both with the same mass, but one is 1 solar radius, the other is 100 solar radius. In addition, depending on where they are in their life cycle, they may change in their luminosity.

The problem I am having, and that others apparently have, is that there has never been anyone that has specified exactly what thermal ranges constitute what rating on the Hertzsprung-Russell Diagram

The more and more I look at the Hertzsprung-Russell Diagram, the more and more I am convinced that it need to be radically modified or a new superior system created. What I also find particularly annoying is that for different star masses, i.e. Giants (III), Supergiants (I), have different temperature from the Main sequence stars dwarf stars (V), yet it says it retains the same spectral type.

MKruer wrote:The more and more I look at the Hertzsprung-Russell Diagram, the more and more I am convinced that it need to be radically modified or a new superior system created. What I also find particularly annoying is that for different star masses, i.e. Giants (III), Supergiants (I), have different temperature from the Main sequence stars dwarf stars (V), yet it says it retains the same spectral type.

They don't. An M5 II should have the same surface temperature (roughly) as an M5 V or M5 III. A G2 V should have the same temperature as a G2 IV, or G2 III etc. That way you go from O to M as you look from left to right.

The LUMINOSITY of each size is different for a given surface temperature, because the giant stars are bigger than the dwarfs.

Mass doesn't factor into it directly - all the HR diagrams shows is Temperature vs Luminosity.

Evil Dr Ganymede wrote:

MKruer wrote:The more and more I look at the Hertzsprung-Russell Diagram, the more and more I am convinced that it need to be radically modified or a new superior system created. What I also find particularly annoying is that for different star masses, i.e. Giants (III), Supergiants (I), have different temperature from the Main sequence stars dwarf stars (V), yet it says it retains the same spectral type.

They don't. An M5 II should have the same surface temperature (roughly) as an M5 V or M5 III. A G2 V should have the same temperature as a G2 IV, or G2 III etc. That way you go from O to M as you look from left to right.

Exactly! Its the "roughly" part that is causing all the problems. The ?€?Roughly?€

[quote="MKruer"]Exactly! Its the "roughly" part that is causing all the problems. The ?€?Roughly?€

Did you take a look at the star chart that i made, to see if it is "correct"