Homework Help: astronomy

Posted by rohit on Monday, April 30, 2007 at 1:44am.

Arcturus is about half as hot as the Sun but is about 100 times more luminous. What is its radius campared to the sun.

If Arcturus is half as hot, it radiates (1/2)^4 = 1/16 as much as the sun PER UNIT AREA. But since it radiates 100 times more totally, it must have 1600 times the area of the sun. That means it must have sqrt 1600 = 40 times the radius, since radius is proportional to the square root of area

No one has answered this question yet.

Answer this Question

Related Questions

astronomy - Arcturus is about half as hot as the Sun but is about 100 times more...
astronomy - 1. The radius of the Sun is 7 X 10^5 kilometers. Use powers of ten ...
Astronomy - When the Sun ends up as a white dwarf, billions of years from now, ...
Astronomy - If we assume the Sun is made totally out of hydrogen, how many ...
science - Suppose that you can just barely see a certain star that is at a ...
math - The mass of Mars is about 421x10^20 metric tons. The mass of the sun is ...
algebra word problem - The mass of Saturn is about 5.688 10^23 metric tons. The ...
astronomy - Assume that the mass of a sun-like star is 2.50 x 10^5 Earth masses ...
Astronomy - Mass of the Sun = 1.989 x 10^30 kg Mass of Hydrogen Atom = 1.00794 ...
Physics - Our sun rotates in a circular orbit about the center of the Milky Way ...

For Further Reading

First Name:
School Subject:
Answer: