Distances in Astronomy
How do we know the distance of the sun from the earth? Or that of the nearest galaxy to our own? This article introduces four methods that astronomers use to measure distances in space.
Much of our knowledge of astronomy is based on our ability to measure distances in space. Knowing astronomical distances helps us understand, among other things, how stars, star clusters, nebulae, galaxies are distributed in space; or, how bright they truly are as opposed to how bright they appear to us. However, given the scale of this task, estimating distances to objects in outer space is not a trivial task.
Over time, astronomers have come up with some really interesting ways to pin down distances to stars in our own as well as other galaxies. These include:
- Trigonometric parallax: this technique is useful in estimating distances to stars within a few 100 light-years from us (see Box 1).
- Observations of variable stars: this technique is useful in estimating distances to variable stars, or star clusters with variable stars, in our own as well as neighbouring galaxies (see Box 2).
- Observations of standard candles in the dark: this technique is useful in estimating distances to galaxies in which supernova explosions (standard candles) are underway (see Box 3).
- Estimation of the velocity with which galaxies are receding from us: this technique is useful in estimating distances of galaxies that are >100 million light-years away (see Box 4).