A G0 III star with a mass of about 1 M⊙ sits on the horizontal branch. Horizontal branch stars are in the helium-burning phase of stellar evolution. For this process, 3He→C +energy If the star has a luminosity of 100 L⊙, estimate the size of this star assuming it has a temperature of 6000 K. What is the thermal time scale (time for the star to radiate away all its potential energy) if only 10% of the star’s mass is in the form of helium?

A G0 III star with a mass of about 1 M⊙ sits on the horizontal branch. Horizontal branch stars are in the helium-burning phase of stellar evolution. For this process, 3He→C +energy If the star has a luminosity of 100 L⊙, estimate the size of this star assuming it has a temperature of 6000 K. What is the thermal time scale (time for the star to radiate away all its potential energy) if only 10% of the star’s mass is in the form of helium?

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Many of the bright stars in the night sky are highly luminous normal blue stars (such as Acrux), and others are blue giants (such as Rigel) or red giants (such as Betelgeuse). Generally, such stars have a luminosity of 103 to 105 times that of our Sun! Ignoring any effects from our atmosphere, how bright would a star with a luminosity of 8380 solar luminosities be if it were located 620 light years from Earth? (You will need to convert some values.) W/m² For comparison, if you were 1 meter from a regular 100 W light bulb, the brightness would be 7.96 W/ m². (Since stars are not this bright, your answer should be considerably less!) Kind of amazing you can see these things, isn't it?
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