Would the size of the sun make any difference to the radiated temperature at a given point away from it?

Question

Its surprisingly hard to sum up a question like that in 110 characters!

Please read the whole thing so that you understand what I’m asking…

This is linked to a question I had about earth’s internal heat vs thermal radiation from the sun. Someone who answered that question made an interesting point about radiated heat traveling through space in that it will not loose energy over the distance as it will meet no resistance or be absorbed by any matter. The only reason the temperature reduces over a distance is that it spreads out (imagine a sphere getting bigger as it moves away from its source).

So, my question is really a maths question..

So comparing 2 suns, both identical temperatures, same physical properties, radiating heat at exactly the same rate etc… but one is half the size of the other. At a fixed point away from the surface, (say earths distance, 1AU) would you expect a difference in temperature?

Answer 1

Yes it would make a major difference to the heat ( or solar radiation, as you can deal with heat conversion in your own time i assume)  All bodies in space emit radiation dependant on there size. So a planet the size of jupiter will emit a greater amount of radiation than the much smaller Earth.  

    As we know the sun is much hotter than than both these objects and a great deal larger so will result in a higher 'solar luminosity'. A brief definition of a star ( and thus our sun) is a celestial body sustaining (or having sustained) nuclear fusion at its core.

   Now to answer the question, knowing that the greater the size of an object in space the greater its solar luminosity (and thus the amount of radiation emmited) and knowing that a star emits solar radiation ( and thus electromagnetic radiation) then yes the greater the size of the new sun then the greater the thermal influence on a nearby planet of the larger body.

Answer 2

Assuming this new sun is, as you say, exactly the same as our own except it is half the size (half the diameter), the amount of heat radiation produced per unit surface area would be the same. But, since the surface area is a quarter of the original area, that adds up to a quarter of the total original heat radiation.

Therefore, at any point in space away from the surface, you'd expect less radiation.

But in fact, this is not likely to happen, because such small stars tend to be cooler anyway, so the radiation would not only be less intense as previously described, but also at a longer wavelength (redder light, and less energy).

Answer 3

i would give u a seriouys answer if i underdtood d big words in dis question

Answer 4

For a start, they couldn't have the same physical properties. If one is half the size, mass, as the other, to achieve the same temperature it must be working harder, burning up quicker, to achieve the same temperature. As far as I know radiation obeys the inverses square law. Radiation is affected by gravity as well.

I would expect a lower level of radiation to be lower from the smaller star at any given distance.

This just my opinion.

Answer 5

The larger sun would radiate more heat.  The size of the disk would be greater for a larger sun at a given distance.

Answer 6

larger sun would radiate more temperature owing to fact it has a larger surface area hence a higher temperature reading at the same fixed distance .

Answer 7

I would say that the one with the smaller size, will have a lower temperature compared to the one with the bigger sun.

Reason being that the amount of radiant heat reaching the same point by the smaller sun would be lesser. This has something to do with the probability of the IR waves hitting this point.

Bigger sun would emit more rays, so its probability of hitting the point would be higher, consequently its temperaure will be higher as well.