An Astronomer's Guide to the Galaxy

October 1, 2014 5:26 PM

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An Astronomer's Guide to the Galaxy

Measuring distances in astronomy is notoriously difficult. Indeed, a quick glance at the night's sky reveals only a two-dimensional image, with no depth information. Yet, knowledge of precise distances is crucial, since that's the only way to determine the true, intrinsic luminosity of an object, from the apparent one, measured by our telescopes. The determination of distances therefore constitutes a major component of almost every astronomical study, whether that involves the evolution of stars or the accelerating expansion of the universe.

The most direct and precise method to measure distances is using trigonometric parallaxes (Figure 1). This method is based on the fact that as the Earth orbits the Sun, relatively nearby stars appear to move against the more distant stellar background. By measuring the angle associated with this app...

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