Re: [Phys-l] stellar distance measurement

[John Denker <jsd@av8n.com>]

On 05/20/2009 06:31 AM, mark.sylvester@spin.it wrote:
> How is the distance to a star like Antares measured? It's too far for
> trigonometrical parallax and not being a main sequence star is not a
> candidate for spectroscopic parallax... so how is it done?

1) Parallax works.

The Hipparcos astrometry satellite is good to 10% at 100 pc
   http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit1/distances.html


2) Antares is so big and so close that its diameter (!) can be
 measured by interferometry or occultation.  If you know the 
 diameter you don't need the HR diagram to get absolute brightness
 from color;  all you need is the black-body law.