At rest hydrogen has a spectral line at 149nm. If this line is observed at 144 nm for the star proxima how fast is proxima moving in km/s

A Type Ia supernova is observed and achieves an apparent magnitude of m = 19.89 at peak brightness. The absolute magnitudes of Type Ia supernovae at peak brightness are known to be M=−19. Determine the distance to the supernovae in units of Mpc.

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A main sequence star of mass 25 M⊙has a luminosity of approximately 80,000 L⊙. a. At what rate DOES MASS VANISH as H is fused to He in the star’s core? Note: When we say “mass vanish '' what we really mean is “gets converted into energy and leaves the star as light”. Note: approximate answer: 3.55 E14 kg/s b. At what rate is H converted into He? To do this you need to take into account that for every kg of hydrogen burned, only 0.7% gets converted into energy while the rest turns into helium. Approximate answer = 5E16 kg/s c. Assuming that only the 10% of the star’s mass in the central regions will get hot enough for fusion, calculate the main sequence lifetime of the star. Put your answer in years, and compare it to the lifetime of the Sun. It should be much, much shorter. Approximate answer: 30 million years.