Celestia Forums

I am writing some code to generate systems based on the mass and luminosity of stars. I have the option of calculating the luminosity on either the absolute or bolometric magnitude. Which would be more suitable? What is the difference?

Also I am currently using the below table to find the mass given the spectralClass of a star.
I want to make this as accurate as I can so if anyone has any comments or links to similar tables that I could compare this to it would be much appreciated.

marc wrote:I have the option of calculating the luminosity on either the absolute or bolometric magnitude. Which would be more suitable? What is the difference?

They're two different concepts.
Bolometric magnitude is a measure of a star's total energy output - it contrasts with visual magnitude, which is a measure of its brightness in the visible spectrum only.
Absolute magnitude is a measure of a star's intrinsic brightness (given by its calculated brightness when viewed from a standard distance) - it contrasts with apparent magnitude, which is the brightness of the star as seen from its present distance. Apparent magnitude may be greater or less than absolute magnitude, depending on whether the star is closer or farther away than the standard distance.

So you can have absolute bolometric magnitude, absolute visual magnitude, apparent bolometric magnitude and apparent visual magnitude.

Celestia uses absolute and apparent visual magnitudes, and makes an internal conversion to bolometric magnitude when it calculates stellar radii.

(I apologize if some of the above is already familiar to you.)

Grant

Thanks Grant.
I was referring to absolute values, I didnt know about the visual part of it.

So is intrisic brightness just based on the visible spectrum?

marc wrote:So is intrisic brightness just based on the visible spectrum?

Sorry, I was using "brightness" in a way that was probably misleading. In common English usage, I guess "bright" would refer to just visible light, but astronomers talk about objects being, for instance, "radio bright" too, meaning that they have a high radiation output in that part of the spectrum. So by "bright" I intended to convey "radiating lots of energy" (so I probably should have just said that ).

So a low absolute magnitude indicates a high output of electromagnetic radiation - the adjective "bolometric" or "visual" is then required in order to specify whether you're talking about the overall radiation output, or just in the visual band.

Grant

You can use my excel table to generate random ( but real an accurate ) stars for the planetary systems

Here you will finf it in the astrotech section:

http://usuarios.lycos.es/darktemplars/Index.html


The project is much more advanced and now is capble to generate planets with mass, radius, axistilt, magnetic field, density and almost all physical paramemeter according to the last planetary formation theories, I am implementing binary and trinary systems in the planet generations and the Celestia code to make de scc file, I hope this will be usseful for you, if you want the planetary generator asl me:

j_omar7@hotmail.com

Unfortunately lycos.es is generating a "404: file not found" when I try to access the Excel and Celestia pages.

I have checked my page a minute ago and it is there, the files can be downloadand the images can be seen, if you still have thsi same problem please told me, if persist and you are interested I will send you the files





these are some screenshots, I hope you can see them

It seems to be working fine now.

Thanks!

Hi High Dark Templar,
I have already created a system generator which would create ssc files for all the stars in Celestia. It is based on a program called stargen, the theories behind it are somewhat old but it outputs a lot of information. (even what gases make up the atmosphere).
Here is the old thread on it, if you want to try it out download the version on the second page.
http://www.celestiaproject.net/forum/viewtopic ... sc&start=0
Because of the size problems with creating so many ssc files I have been learning some database programming and have been converting Celestia so it will read stars and planets from the database rather than from stars.dat and ssc files. Im working on this new system generator now.
I havn't had a close look at your spreadsheet yet, but if i find any useful formula would you mind if i used them?
Is it possible to make excel output to and format textfiles (ie create stc files)?

Excel can be used to make scc files using a curious method that i will explain in other post;I remember you that this spreadshets is only the begining, I have much more advenced it now but have a few problems with multiple orbits in binary systems.