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

## 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 ...
- Science - One light year is about 9 trillion kilometers. Arcturus is a star that...
- Science 2 - One light year is about 9 trillion kilometers. Arcturus is a star ...
- Astronomy - If we assume the Sun is made totally out of hydrogen, how many ...
- Astronomy - When the Sun ends up as a white dwarf, billions of years from now, ...
- astronomy - A light bulb radiates most strongly at a wavelength of about 3000 ...
- physics - he sun radiates like a perfect blackbody with an emissivity of exactly...
- physics - The sun radiates like a perfect blackbody with an emissivity of ...
- Physics - The sun radiates like a perfect blackbody with an emissivity of ...

More Related Questions