Two stars with spectral class G2V are observed to have apparent magnitudes of V=

Question

Two stars with spectral class G2V are observed to have apparent magnitudes of V=17.65 and V=14.8. While both stars have good spectra, neither has a reliable parallax and neither is associated with a star cluster. G2V stars have absolute magnitude of MV=4.8. (a) How can we distinguish these G2V stars from more luminous G2IV and G2III stars using their observed properties? (b) Are the stars closer or further than 10 pc? You must explain your reasoning. (c) If both stars have an absolute magnitude of Mv= 4.8, what are their distances in pc?

Explanation / Answer

a)    We can distinguish them by their apparent magnitudes V . Thus, their luminousity can be determined from more luminous G2IV and G2III stars .

b) Stars are further than 10 pc . This is determined by their absolute magnitude of MV = 4.8 .

c)   Their distances are 15.4 pc and 18.2 pc .

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