Why are all the stars about the same size, as well as the moon and sun are about the same size?

Question

in viewing them of course.

Answer 1

The similarity in apparent size of sun and moon is because their discs present a similar angle to the eye measured in arc seconds. The moon is 400 times nearer to us than the sun and also 400 times smaller in diameter,

It is a bit like comparing a tennis ball in your hand to a football on the pitch when you are watching a game from the stands, It is a pure coincidence they look the same size,

Viewed from Jupiter (which ia 5 times as far from the sun as we are), the sun will look a lot smaller than it does from earth and one of Jupiter's moons which is about the same size as our moon (Io, say) will look much bigger to the Jovian eye than the Sun does,

Whether they are four light years away or 4 billion light years away, all stars are a single point of light to the human eye. simply because of the distances involved, Their actual sizes vary enormously

Compared to the Sun the 3 largest known stars are

VV Cephei 1900 Solar diameters
V354 Cephei 1520 Solar diameters
KW Sagitarii 1460 Solar diameters

Betelgeuse, a Red Giant in Orion, is 650 Solar diameters and if it were in our solar system that would mean its outer layers would engulf Jupiter, Brown dwarf stars are 8% of the Sun's mass in comparison.

Answer 2

Draw a circle around the moon on a piece of glass whilst your arm is fully extended. Compare this to the moon as it progresses across the sky. You will find that it doesn't change size (I know you all know this) even though it appears to. I am not saying to try this with the sun but if you did you would find a small difference in apparent size ( I think the questioner knows these bodies are different in size if you bothered to fully read the question). Now try this with headlights as they just come to the point where you can makew out that there are two. I think you will find this to be a similiar size as well. I think it is a property of eyes fully at infinity focus where an object far away is big enough to resolve some features with a high contrast to the surrounding field will appear to be about the size of the moon. The stars are so far away that no feature is available so there size to us is related to how bright/intense the point of light is. Try a blind with holes of variuos sizes at a distance with a light behind. If far enough away you will not see so much a difference in size as brightness.

Good question! Is the Sun and Moon's apparent size a coincidence? I think it more a syncronicity with our evolution perhaps but someone would have to ask the question.

Answer 3

With the stars, you're not actually seeing the star, but only the light it gives off. They're so far away that relative distances or sizes just don't matter to the naked eye. As for the sun and moon, they only appear to be the same size at certain times of the year and the day. The moon is much smaller than the sun, but is much closer.

Answer 4

the moon and the sun are not the same size, just because they look small doesnt mean that they actually are. Consider this, the moon is smaller than the earth and it would take i think a hundred or more earths to make up the same size as the sun. as for stars they vary in size.

Answer 5

Hi. You already have some good answers but here is a neat fact. The Moon has a diameter, as seen from Earth, of about 30 arc minutes (half a degree). The Sun is about the same. The Sun is actually about 400 times the size of the moon, but it is also 400 times as far away.

Answer 6

he means, why do they appear the same size.

The stars actually show no size. Even though they are actually suns, they are so far away that even under magnification they are still just points of light.

The sun and the moon appearing to be the same size, is sheer coincidence. The sun is 408 times the diameter but is about 408 times as far away, so they appear to us about the same size. This is why we get a fantastic solar eclipse, because when the moon passes directly in front of the sun, it covers it like putting a a black penny over a shiny one of the same size.

Answer 7

The stars appear all the same size because they are all bright points of light, at least from our point of view.

They actually vary quite a bit in size, but not in appearance, until you get much closer.

The sun and moon appear the same size, but this is by coincidence. A moon of a planet usually doesn't match the size of the sun.

Answer 8

It is just the effect of distance. The apparent size decreases with distance. The sun is really much larger than the moon, but much farther away. You can cover the sun with your hand because your hand appears larger as it's close to your face, and the moon can cover the sun in a solar eclipse.

The stars are various sizes, most of them much larger than the earth, many much larger than the sun. Again, they appear small because they are so far away--much farther than the sun is from the earth. They appear so small that you cannot make out any apparent detail--they just seem to be bright points.

Answer 9

This is just appearance. There is great variation in sizes of stars. Our Sol or Sun is a fairly average star. There are giant stars much bigger than it is, and dwarf stars much smaller than it is. Stars come in different colors. Red ones are cool. The hottest ones are white with a bluish tone. The Sun is much bigger than the Moon, but it is much more distant. These factors balance to make them appear to be about the same size. The Moon is 238,000 miles away, and the Sun's diistance is 93,000,000.

Answer 10

Look at the additional details. It says in veiwing them. The asker already knows that it LOOKS like it is the same size but really not.
They all look about the same size because they are so far away that it is pretty hard to tell if they are huge or small, but you can tell the difference from some because they are closer to Earth than other stars.