In: Physics
11b - Estimating Stars types
How would you go about estimating the size of the star called Betelgeuse using its absolute magnitude (-6) and its spectral class (M)? How many Sun's would it take to cross the diameter of Betelgeuse? The volume of Betelgeuse compared to the Sun. What about Rigel, a Blue Giant star? How does it compare to the Sun?
According to the question, the spectral type of the star Betelgeuse is M and its absolute magnitude is -6.
The spectral type M correspond to the surface temperature of 3000 K.
The relationship between absolute magnitude and luminosity is given by
where L* is the luminosity of a zero magnitude star (Vega).
Here the luminosity of Vega is 40.12 .
Again we know that,
Where L is luminosity, R is radius, T is absolute temperature.
Thus,
Thus, it would take approximately 751 Suns to cross Betelgeuse's Diameter.
Since , the volume of Betelgeuse will be times of the sun.
In case of a blue giant star, the radius is 5-10 times that of the Sun and the surface temperature is around 10000 K.
The estimated radius and Surface temperature of Rigel is 75 and 2