How can scientists know how far an object is in space when the distance is billions of light years away?

Question

How are the scientists able to measure the distance of objects in space?

Answer 1

I know a lot of stars can be measured using trig. The earth goes around the sun and the star will appear at slightly different positions depending on what time of the year it is. We know the size of the earth's orbit around the sun and from observation we can determine the angle of different between us and the star and from that we can figure out the distance between us and the star.

Answer 2

There are quite a few ways actually.

The first that was measured is called parallax, where you use identify small shifts in a star's position as the earth moves around the Sun, and then use trig to figure out how far away it is. Unfortunately, since the angles involved are so tiny, this only works for stars very close to us.

Another way is to measure the star's apparent brightness m(magnitude) in a certain colour band, and then compare it to how bright a star of that type should be at a distance of 10 parsecs away from us. This is used for clusters of stars since there is some error involved in the measurements. You also require being able to distinguish one star from the next, so its not good for extra-galactic stars.

To measure distances to other galaxies, astronomers will look for stars called pulsating variable stars. These are stars that pulsate, getting brighter and softer in periodic fashion. They also have the property that their apparent luminosity is directly related to their period (which we can time). Once we have their apparent magnitude, we can calculate the distance using the same equation we used for #2.

There are other methods too. There's something called a main-sequence turn off point, where you graph something called a HR diagram for a collection of stars at a given distance, then compare it to the HR diagram for neighboring stars, and again you can read the luminosity difference off the graph and find distance that way. You can also look at Doppler shifting, and it keeps going.....

Answer 3

Measuring distances in astronomy is difficult: we cannot simply take a metre stick and pace out the distance to a star or galaxy. Instead we have to find indirect ways of estimating the distance, from other quantities which can be measured directly. A powerful method for estimating distances is the idea of a standard candle - i.e. a particular type of star whose intrinsic brightness is known, rather like knowing the wattage of a household light bulb. By comparing the intrinsic brightness (or luminosity) with how bright the star appears to be, one can estimate its distance. Two examples of standard candles commonly used by cosmologists to measure distances are Cepheids and Supernovae; together with measurements of galaxy redshifts, these distance estimates tell us a great deal about the distribution and motions of galaxies - and the dynamics of the Universe itself.

Answer 4

They have to figure out how bright it really is and then by measuring how dim it looks in our sky they can calculate the distance. The brightness is determined in a number of ways, some of which are more accurate than others. Some of those distance estimates are not very accurate.

For very distant galaxies the distance is related to how fast the galaxy is moving away, as measured by the red shift.

Answer 5

there are many different methods as noted above. it is important to note that all of these methods have regions of the scale where they overlap so that they can be calibrated with each other. the distance between the earth and sun is known very precisely from studies of solar system dynamics. stellar parallax distance measurement depends on the earth-sun distance. some of the 'standard candles' (variable stars and supernovae) are also within range of stellar parallax. some of the redshift measurements can be compared to standard candle measurements. in this way a sort of ladder of cosmic distance scales is formed.

Answer 6

They examine the red-shift, which tells them how fast the object is moving away. It's known as the Doppler effect. And they are also armed with very long tape-measures.

Answer 7

Generally, they use red shift. The faster something is moving away from us, the more it's light is shifted to the red end of the spectrum.
The amount it's shifted toward the red indicates it's speed; likewise, if we know the speed, we can extrapolate how far away something is (assuming we started at the same spot, and it's maintained a constant speed.)

Answer 8

they compare their wavelengths to determine if the objects are moving away or moving closer and then they compare at what stage in life such a ie. star would be... and then the compare it with known stars and their life spans... aNd basicallly its a long process of comparing things with things already known for sure to make an estimate... obviously something that is a 100 light years away might actually be 100 light years and 500000 meters away...

lol

:-)

Answer 9

Short answer: Doppler shifts and spectrometry (check them out on Wikipedia).

It's all about measuring the properties of light and comparing them to a baseline, typically our sun.

Answer 10

telescopes and satelites can send out mm wavelengths of light. if theres some kind of object in space, the light will be reflected back. that's how they track the source of gama rays. when theres a huge explosion, then they can tell how far away it is by measuring the reflected light off of other objects in space.
sorry if it doesn't make sense to you.