How can a cool star be more luminous than a hot star?

How can a cool star be more luminous than a hot star? Examples please?



Oh and can you make this as easy to understand as possible please, im really having a difficult time understanding it :) ThanksHow can a cool star be more luminous than a hot star?Put VERY simplistically it's to do with size and distance from us [ earth ]. Example our sun is very small and cool compared to something like Sirius, but because we are very close to it we have the impression of it being very bright ! If I had a flashlight 5 ft. from you and someone had a powerful searchlight 20 miles away, my tiny flashlight would look brighter [ more luminous ] to you.How can a cool star be more luminous than a hot star?
Let's see. How do I put it into words that are simple to you? The hotter a star, the more energy will it be pouring out into space. However, in computing for the energy outflow of a star, you also have to consider its surface area which is directly proportional to the diameter of the star itself. Those two things will be necessary factors to know how much energy will a star pour out into space. Again, the total energy output we're talking about here is luminosity. So let's go to the examples. Rigel, first. Its temperature is about 11,000K and its radius about 70x that of the sun. The total luminosity is equal to 66,000 suns! Let's look at another star, Canopus. Its radius is about 65 suns. You may expect it to have the same luminosity, however, its temperature is lower at about 7,800K. The total luminosity of Canopus is only 15,000 suns. Why? The radii are near but why is the total luminosity so much different? Temperature. Let's look at another star, Betelgeuse. The temperature of this star is roughly 3,500K. We would be hoping for it to be less luminous but it is indeed the most luminous among the three, why? Because it is 1000x larger than the sun! See, there is so much relationship between the radii and temperatures of stars. If you change the numbers well enough, then you can come out with either a less luminous or a relatively more luminous star.How can a cool star be more luminous than a hot star?My theory is this... you've seen how light reflects off of the surface of water, well look into a pot full of room temp or cold water, and examine it for yourself under direct lighting. Take this same pot, and heat the water to just under a simmer, before it begins to bubble. The smoke dulls the sheen/gleam of the water's surface. multiply the temperature variation by a hundredth for the colder planets, and multiply it by a hundred for the warmer planets. picture space as a vaccum and how the smoke generated by/encircling the hot planets would be all the more dense because there's less oxygen present spacing out the debris/particles produced by the smoke. It has a slight dulling effect in combination with rising heat waves which impede, diffuse, and deflect the rays of the sun from hitting and radiating off of them and toward us.How can a cool star be more luminous than a hot star?
Well a cool star would be like our sun in comparison to a Blue Giant such as Rigel or Betelgeuse, you know the blue stars near Orion?



The glow and brightness would be a orangish-yellow instead of a hot-white color (since white heat is the hottest in the visible spectrum).How can a cool star be more luminous than a hot star?It really depends on how luminous is defined. Assuming Luminosity is energy radiated then there are dwarf stars neutron stars that are cool by our suns standards but can produce large pulse outputs of energy that are 20 yrs worth of energy produced by the sunHow can a cool star be more luminous than a hot star?
Hi. Simple. Luminosity is a function of diameter. A large red star (cool) radiates more energy than a a hot small star (like a white dwarf).How can a cool star be more luminous than a hot star?
Stefan-Boltzmann Law: L = k R^2 T^4

L1 = k R1^2 T1^4

L2 = k R2^2 T2^4

Suppose that: L2 %26gt; L1

L2/L1 %26gt; 1

(R2/R1)^2 (T2/T1)^4 %26gt; 1

R2 %26gt; R1 (T1/T2)^2
What would be brighter:

10.000 bulbs of light each 20 watt, or

10 bulbs of light each 100 watt.

....even the 100 watt lights are much hotter.