HOW????? do they measure 1000 light years??

Question

I have a beautiful book of pictures taken in space and they have pictures of galaxies as far away as 1000 light years? Can anyone explain in layman's terms?? thanks all you scientists!!!!

Answer 1

easy answer its how far light can travel in one year, in empty space it is about 300,000 kilometers per second .

Answer 2

1000 x the speed of light travel in a year...

speed of light = 300,000 km/second

Answer 3

Light travels at about 186,282 miles per second.

That's more than 7 times around the earth in 1 second

multiply that by 3,600. That will give the distance covered in 1 hour.

=670,615,200 mph

if you multiply this by 24

= 16,094,764,800 ~ 16 billion miles per day or around the earth 643,790 times in 1 day

If you multiply this by 365 days

you would have the distance of 1 light year

This is 5,874,589,152,000 miles

Rounded this is 5.87 trillion miles

Multiply this by a thousand and you would have 5.87 quadrillion miles.

This is 5,874,589,152,000,000 / 25,000 = 234,983,350,000 revolutions around the earth in a 1,000 years.

If you were to take 234,983,350,000 golfs balls and place them in a cube in perfect alignment with each other, the side of the cube would be 10,167 feet long, and wide and high. This cube would have 6,170 (diameter of a golf ball being 1.68 inches) golfballs in alighnment on 1 side.   The number of golf balls inside this cube times the distance around the earth would equal the distance of a 1,000 light years.

See link for parsec explanation.  It basically say that qyou are able to use parallex methods to find the distance of stars beyond a certain distance by observing them 6 months apart when the earth has traveled 1/2 way around its orbit around the Sun.

Answer 4

parallax, cepheid variables, red shift, standard candles.

do a search.

Answer 5

Alot of astronomers will use what we call redshifts and blueshifts. These are due to the hubble constant, or the expansion of the universe. All of the objects are moving either away form us or towards us. Moving away from us will be redshift, becuase the light waves are actually changed due to the huge distance they have to travel, they will become redder (longer) and for blueshift, it is the other way around (blue=shorter). I don't know too much on the subject but here's a link:

http://en.wikipedia.org/wiki/Redshift

And here is a really cool website that has tons of astronomy stuff:

http://www.astronomycast.com/

Look under archive for the entire collection.

Answer 6

A light years represents the distance light travels in one year.   Light travels 5 trillion, 900 billion miles in a year and is usually rounded to 6 trillion miles to make it easier.  For the mileage of 1000 light years you have to multiply 1000 x 5,900,000,000,000.  For galaxies 13 billion miles away, that would be 5,900,000,000 000 x 13,000,000,000 for the mileage.  The closest star to us is 4.2 light years away which equals about 26 trillion miles away.

Answer 7

i have explained it before and trust me, you will fall asleep before i get to the good stuff.  My fault.

anyway... the simplest answer is this... if you had a way to measure how bright a light was shining on you, and someone shined the same light from twice as far... then someone with the same light from an unknown distance, do you think you could take a guess at how far away it was by how bright it was?

sure you could.

we can do that.

there is a class of stars that are always the same brightness, no matter how far away and we can measure how bright they are and figure out how far away they must be.

simple enough?

Answer 8

Space is huge, everything is a very long distance from us.

Instead of using miles or kilometers to describe these huge distances, scientists needed a more convenient measurement for astronomical distances.

Light travels at a known velocity - it is defined as exactly  299,792,458 metres per second.

Using that speed and defining a year (astronomically speaking) as the Julian year with a defined number of seconds in it, they came up with a "light year" - the distance light travels in one Earth year.

That distance works out to just over 9 trillion kilometers or just under 6 trillion miles.

So instead of saying that something is 9,000 trillion kilometers away, they can say its 1000 light years - 1000 is a lot easier for humans to understand than numbers will all those zeros and "illions" in them.

The light year also has the added bonus of telling you how long light takes to travel that distance - it takes light 1000 years to travel 1000 light years.

Answer 9

None of the *galaxies* is only 1000 light years away. Galaxies are HUGE collections of stars and are typically millions to billions of light years away. There *are* small clusters of stars inside our galaxy that are only 1000 light years away, though.

How do we measure these distances?

For close stars (within a few hundred light years), we use parallax: we look at where the star appears in the sky at one time and six months later (when the earth is at the opposite end of its orbit). The amount the star appears to shift is related to how far away it is.

For stars at medium distances, we use the data from closer stars to learn how their size and brightness and various aspects of their light are related. Then, when we see a star farther away, we can tell how bright it actually is. By comparing that to how bright it LOOKS, we can tell how far away it is.

For galaxies, we usually use some sort of standard candle: some star that we can tell how bright it actually is to compare to how bright it appears. Cepheid variables are good for this because the time it takes for them to vary in brightness is related to how bright they actually are. It is also possible to use certain types of supernova for more distant galaxies.