3. The star Sorius appears to be about ten times brighter than Deneb. Yet scientists have found that Deneb gives off much more light than Sirius. Why is this?
4. Why is a light year (distance light travels in a year) a useful unit for measuring distance to stars?
at least answering 1 would be helpful, thanks in advance!!!
2007-12-18 10:56:24 · 9 answers · asked by B Y 1 in Science & Mathematics ➔ Astronomy & Space
Notice how street lights that are close by appear much brighter that street lights miles away even though they are all about the same brightness?
Well same thing with stars. If two stars are each giving off the same amount of light, then the closer one will appear much brighter.
Yes, the stars are all at different distances from us. They also give off different amounts of light.
Sirius is very close, being 8.6 light years away. Whereas Deneb is about 5000 lightyears away (exact distance unknown). So even if Deneb gives off more light than Sirius, it is much farther away so it appears dimmer in the sky.
A light year is a measure of distance. It is the distance that light travels in a year.
I like to think of it this way: It takes light 12 hours to travel across our solar system from one side to the other. Sirius is about 8.6 light years away, so it takes light 8.6 years to travel from Sirius to us. Since 8.6 years is about 3139 days or about 6000 half days, then Sirius is about 6000 solar system diameters away. In other words if the solar system was modelled as a flat disk a foot across, then Sirius would be over a mile away!
2007-12-18 11:24:49 · answer #1 · answered by Quadrillian 7 · 0⤊ 0⤋
Sirius is only 8.6 light years away. Deneb is over 3200. Sirius only appears brighter because it's closer.
Light years are a useful unit because the distances between stars is so great. A large measurement unit saves us from having to write something like 364,889,000,000,000,000 miles from Earth.
2007-12-18 23:20:22 · answer #2 · answered by Anonymous · 0⤊ 0⤋
3. This is just a guess, but maybe Sirius is closer to earth than Deneb and so it appears brighter to us.
4. Light years are easier to use because measurements and calculations often require working with very large numbers.
Example: The nearest star to earth is 4 light years away, so instead of writing 1 thousand billion meters away, you use light years.
2007-12-18 19:09:25 · answer #3 · answered by Anonymous · 0⤊ 0⤋
3. I would say that the reason Sorius is appears brighter is because it is closer to the earth than Deneb, thus causing it to have a relatively more bright appearance.
4. A light year is useful because the universe is so huge, using a large number like a light year makes it easier to quantify distances
2007-12-18 19:07:50 · answer #4 · answered by Anonymous · 0⤊ 0⤋
Sirius is 9 ly away, Deneb is 1500. Deneb is actually several 00 times as bright as the sun. A way to describe how bright a star is, is to refer to its absolute magnitude, that is how bright it is at a distance of 32 ly. The sun would be 4.6, Sirius would be about 2.8, Deneb would be -7 and would cast clear shadows.
(visible mag Venus -4.6, Moon -14, Sun -26)
As has been said, the universe is so large that you need a large unit as a basis. Actually, the unit used is the parsec which is 3.26 ly. Why 3.26? I dunno that one. Even so, distances are measured in Megaparsecs.
2007-12-18 19:25:46 · answer #5 · answered by RobRoy 3 · 0⤊ 0⤋
If they are that easy, why don't you do them yourself?
Deneb is farther away than Sirius. Lots farther away.
Measuring distances in light years produces manageable numbers, and has physical significance: that's how long the light took to get to us.
Addendum: a parsec is the distance where the parallax of an object is one second of arc across Earth's orbit (PARallax of one SECond). You can run the numbers to verify that this is 3.26 light years - and see that even the Alpha Centauri system has a parallax of less than 1 second.
2007-12-18 19:22:02 · answer #6 · answered by laurahal42 6 · 0⤊ 0⤋
Representating the distance in light years not only tells us the distance but also the instance when the light was emitted from the star. A star which is 2 light years away had emitted the light 2 years before the actual moment when your are seeing it and may not be in existance at this moment.
2007-12-18 19:08:53 · answer #7 · answered by Debashis P 2 · 0⤊ 0⤋
3. I'm pretty sure that the scientists will always have different anwsers and will have different facts.
4. If it takes a stars light more than one year to travle then you know that it's farther away then the one in front of it.
2007-12-18 20:57:44 · answer #8 · answered by Anonymous · 0⤊ 0⤋
3. Maybe Deneb is a lot lot farther away?
4. because stars are really far apart lol
2007-12-18 18:58:49 · answer #9 · answered by Anonymous · 0⤊ 1⤋