A newly discovered bright star has a luminosity of 78.4×1026 W. What is its temperature if it has a radius of ~1.2x106 km?

Astronomers use two basis properties of stars to classify them. These two properties are luminosity and surface temperature. Luminosity usually refers to the brightness of the star relative to the brightness of our sun. Astronomers will often use a star’s color to measure its temperature. Stars with low temperatures produce a reddish light while stars with high temperatures shine with a brilliant blue—white light. Surface temperatures of stars range from 3000o C to 50,000o C. When these surface temperatures are plotted against luminosity, the stars fall into groups. Using the data similar to what you will plot in this activity, Danish astronomer Ejnar Hertzsprung and United States astronomer Henry Norris Russell independently arrived at similar results in what is now commonly referred to as the HR Diagram. Procedures:1. Read the Background Information 2. On the graph paper provided. Place a number next to the star according to its luminosity and surface temperature listed in the data…

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.

A star has a peak output at 440 nm and has a luminosity of 3 solar luminosities.  What is its radius? (LS=3.826 X 1026 J/s)