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# Sirius A

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Sirius A

 Problem Sirius A (Alpha Canis Majoris) is close enough to Earth for accurate parallax measurement of its distance. This knowledge enables an accurate determination of its luminosity. Calculate its (A) mass, (B) radius, and (C) effective temperature, assuming (correctly) that it is a Main Sequence star with mass near that of the Sun. (Data are from Liebert et al., 2005).   Hints:   Use the equations and data given below

Data

Distance to Sirius in Parsecs

 (2.1)

Luminosity of Sirius in Units of Solar Luminosity

 (2.2)

Solution

A)

Calculate the mass of Sirius in solar masses.

 (4.1.1)

 (4.1.2)

The estimated mass, 2.24 solar masses, is reasonably close to the accepted figure of 2.02 solar masses.

B)

 (4.2.1)

The estimated radius, 1.81 times that of the Sun, is reasonably close to the accepted figure of 1.711.

C. Calculate the effective temperature of Sirius in kelvins.

 (4.2.2)

The estimated effective temperature at the surface, 9645 K, is reasonably close to the accepted figure of 9940 K.

 References -------------------------------------------------------------------   Liebert, J., Young, P., Arnett, D., Holberg, B. and Williams, K. (2005). The Age and Progenitor Mass of Sirius B. Astrophysical Journal, 630, 1, L69-L72.