Page numbers refer to the 1995 Edition of the Seeds textbook.
A star at a distance of 40 pc is seen to be a binary, with a separation of 0.1 arcsec and an orbital period of 6 years. What is the semimajor axis of the orbit in AU and what is the sum of the masses of the two stars (M_1 + M_2) in units of the Sun's mass Msun?
Assuming the two stars of the binary system have equal masses and luminosities, and are on the main sequence, use the mass-luminosity relation to determine their luminosity relative to the Sun's luminosity Lsun. What is the absolute visual magnitude M_v of these stars? What would you predict the apparent visual magnitude of these stars to be given the distance?
If an H II region (ionized hydrogen) in the interstellar medium at a temperature of 10000 K is in pressure equilibrium with a cloud of H I (neutral atomic hydrogen) at a temperature of 100 K, what can you say about the relative densities of the two regions?
Using the Einstein mass-energy relation E = m c^2, calculate how much energy (in Joules) conversion of 1 kg of matter to energy would give. Compare this to the luminosity of the Sun. How many kilograms of matter need to be converted every second to produce the luminosity of the Sun? If the entire mass of the Earth were to be converted into energy, how long would it power the Sun at this luminosity?
Find the amount of mass converted to energy in nuclear fusion of hydrogen to form helium (p.190), and compute the fraction of the total mass of the four hydrogen nuclei (before fusion) that is converted. How much energy would a kilogram of hydrogen produce through fusion? How many kilograms of hydrogen need to be ``burned'' in fusion reactions to furnish the luminosity of the Sun? How long could the Sun sustain its current luminosity using all of its hydrogen to form helium?
Be sure to visit the DRL rooftop Student's Observatory on a clear Monday or Thursday night, or the Flower & Cook observatory during one of the bi-weekly Wednesday field trips (next one scheduled Wed March 20).
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Steven T. Myers - Last revised 18Mar96