Luminosity of different star types

[ajtribick]

Ok, a few questions:

1. How does Celestia calculate the luminosity of a star based on the information provided, and is the displayed value the visual or the total luminosity of the star?

2. Is there any info on how luminosity is related to star spectral type (including luminosity class).

I ask because I'm slightly suspicious of distant stars which appear to have high luminosities but have luminosity class V (dwarf) in the database. I'm guessing that this means the luminosity class code for these stars isn't available in the Hipparcos database and class V is used by default.

It might be interesting to see what the calculated luminosity suggests the actual luminosity class code is.

[granthutchison]

1. How does Celestia calculate the luminosity of a star based on the information provided, and is the displayed value the visual or the total luminosity of the star?

Apparent visual magnitude and measured parallax are recorded in Hipparcos, so the visual luminosity is calculated from these.

2. Is there any info on how luminosity is related to star spectral type (including luminosity class).

Sure - you should be able to find any number of tables online.

I ask because I'm slightly suspicious of distant stars which appear to have high luminosities but have luminosity class V (dwarf) in the database. I'm guessing that this means the luminosity class code for these stars isn't available in the Hipparcos database and class V is used by default.

There's also the problem that there are many anomalously low parallaxes in Hipparcos, which push a star out to an excessive distance and so require a high luminosity to account for the known apparent magnitude. Most of the problems I've run into with excessive luminosity in Celestia (and correspondingly unphysically large radii) have been in this category.

Grant