When I was little and watched the sky I saw only three or four stars, the brightest. I felt lucky to have stars bright enough to shine above the city sky. So I asked what was special to those stars to shine more than others. It was a question
which found no easy answer. That is, I imagined the stars as lanterns floating in space. I took the flashlight from my house, lit it and went away to see it as a dot. My flashlight did not shine much so far. But when I was going closer and closer to the eye, my pupil is contracted until it was even able to dazzle. That is, the distance should also stars shine less. Does that mean that the stars that shine in the sky are the closest to us? Not necessarily.
In the television sets have a very large outbreaks, much more powerful than my little flashlight. If you placed a these foci at the same distance to my flashlight, it is clear that the focus of much television shine, dazzling even from afar. Then go! Reached a dead end. How would I know if the sky's brightest stars are nearest stars shine brighter or because they emit more light than others.
Wait. . . Maybe when I was a kid I could not know, but now. I know calculate the distance to the stars (see entry 7 this blog). So actually I also know how powerful the star lights. I know what its intrinsic brightness.
So, what think? If we calculate the intrinsic brightness of all stars by correcting the distance factor, what we see? What all the stars shine like and some we see intrinsically brighter only because they are closer? Or really not all stars emit the same amount of light? I do not know that you will have responded but the second option is correct: not all the same issue.
And what might have stars that are brighter than others? Let's see if I know the answer ... Think ... As the stars shine by virtue of being hot (entry 8 see this blog), surely the stars that are brighter are those hotter, right?
Do you remember how you know the temperature of a star ? Well, if we look at how dependent the intrinsic brightness temperature we have the following figure:
Hertzprung-Russell Diagram. This diagram shows that stars some
temperature can not have any intrinsic brightness.
Most are concentrated in a line diagonally across the diagram,
although there stars outside the main sequence.
In this figure we painted in vertical brightness of the stars, which emit, and the horizontal axis the temperature (with the coolest stars on the right and the hottest on the left).
see that, indeed, the hottest stars emit more than the coldest in general, but not always. There are some cool stars (ie red) to shine much (top right of Figure 2.7). How can it be?
That I was not so difficult to imagine. I just imagined what would happen if many lanterns hung out weaklings like mine and put them all together. If you compare the combined light of all lanterns brighten sure that the focus of television that dazzled me. For example, the TV screen or computer, is composed of many small lights (or LED pixels, depends on TV) that together can even illuminate the dining room of my house when I see a scary movie with the lights off, but that one does not illuminate much of anything.
I'm not saying that those cool stars that shine brighter than the hottest stars are actually many close together. Stars but are simply larger (more surface station) and so bright as the hottest but smaller. So to know the size of a star is enough to see how much light is emitted, and knowing the temperature, and we have your size.
And oddly enough, this method to determine the size of the stars from that glitters is inherently easier than the direct method, ie, watching the star under high magnification and measure its size. The latter method itself that is used to measure the size of planets and nearby stars, distant stars but we need many more increases to distinguish such things off and know their size, which is difficult to achieve.
One last hope left for us to measure the size of those distant stars without the help of its luminosity. And that hope goes through that is part of an eclipsing binary system. A binary system is two stars that revolve around each other. If they are called eclipsing aligned with Earth, so that when one goes against the other, that an eclipse. During these eclipses, the amount of light they receive is lower (or higher depending on whether the star that eclipses are less bright or brighter than the other). Looking at what does the eclipse, ie the time a star takes to move ahead of the other, you can know the size of the stars if you know the distance to the system. Ingenious, no?
Measuring so it takes a star to pass in front of another in a dual
we know the size of the stars of the system.
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