How is the distance between two stars measured?

Answer 1

The distances to stars closer than about 150 light years can be measured directly by use of parallax. The position of the star against background stars is measured at times 1/2 year apart, and then it is a simple mathematical procedure to determine the distance (you have a side and two angles of a triangle--the angular distance the star appears to move at it's distance over 1/2 year equals 186 million miles-the diameter of the orbit of the earth).

Stars farther than that cannot be measured directly. But, by use of knowledge about how bright a star should be (on average) for it's spectral type (which loosely is governed by its mass) an estimate of its intrinsic brightness can be made, and then by looking at how bright it appears, it's distance can be estimated.

Cepheid variables are used, as well, but mostly to determine the distances to groups of stars and of other galaxies. Incidentally, the North Star (Polaris, or Alpha Ursa Minor) is a cepheid variable.

Novae and supernovae tend to have average intrinsic brightnesses, so their apparent brightness in, say, a distant galaxy, tells us (within limits) it's distance.

Red shift is used for objects outside our galaxy because the amount of red shift within our galaxy would be extremely small (it increases with distance) if it were not totally overcome by the gravity of the galaxy.

Answer 2

There are many different methods used to find stellar distances, but the earliest one used on the nearest stars involves the principle of parallax. Hold a pencil upright in front of your face at about arms length. Now blink each eye in succesion. You will see an apparent shift in position of the pencil against the background. That shift is parallax.

You will also find that the nearer the pencil, the greater the parallax. As distance increases, parallax is less apparent. The effect is dependent on both the distance to the object and the distance between your eyes.

To notice parallax in distant objects, your 'eyes' need to be further apart. Surveyors accomplish this with two different measurements, from each location of the simulated 'eyes'. Measuring the distance between these two 'eye' locations, and the amount of parallax shift, distance can be calculated.

For stellar distances, two 'eyes' on the earth are still not far enough apart to create an apparent shift. This is limited by the earth's diameter--8000 miles. So the two observation points used are from opposite sides of the earth's orbit around the Sun. Since we know the diameter of the earth's orbit, and that it travels from one side to the other every 6 months, a 'nearby' star's position shift from six months ago against a background of further stars can be measured. Using the same calculations that a surveyor on earth uses, the distance to the nearer stars can then also be determined.

Click the link below to know about the measurement of distances between stars. PLEASE READ THE WHOLE PAGE OF THE LINK GIVEN BELOW, TO COMPLETELY UNDERSTAND THE THEORY.
http://www.badastronomy.com/bitesize/parallax.html

Answer 3

We can approximate the vectors to the stars by measuring the "red shift" of the light coming from these stars. This only indicates the speed that the stars are moving relative to us. The distance from the earth is approximated based on this speed. The distance between these stars can be approximated by subtracting these measured vectors.

Answer 4

the distance between tow stars are measured in lightyear . Lightyear is a unit to measure distance . It is the distance travelled by light in a year.

Answer 5

In the early 1900s an astronomer named Henrietta Leavitt examined the relationship between the absolute magnitude and period of the variable stars known as Cepheid variables. She discovered that the period of the stars is directly proportional to their absolute magnitude. So, by determining the periods of these stars and thus their absolute magnitudes and comparing these with their apparent magnitude, the distance to the star can be determined. :) The unit used was light years.

Answer 6

The position of a star can be plotted against the background on different dates, the difference in position can then be used to determine the distance of the star given that we know how far we have moved in our orbit about the sun.

Answer 7

it is measured by lightyear