![]() That distance (line AB in Figure (Links to an external site.)) is called the baseline. You set up two observing stations some distance apart. Suppose you are trying to measure the distance to a tree across a deep river ( Figure (Links to an external site.)). Let’s see how surveyors take advantage of the same idea. In order to see the shift of an object a city block or more from you, your eyes would need to be spread apart a lot farther. ![]() This is because our depth perception fails for objects more than a few tens of meters away. If your arms were made of rubber, you could stretch the pen far enough away from your eyes that the shift would become imperceptible. Your brain automatically performs such comparisons and gives you a pretty good sense of how far away things in your immediate neighborhood are. If you play with moving the pen for a while, you will notice that the farther away you hold it, the less it seems to shift. Now hold the pen at arm’s length: the shift is less. Note how the pen seems to shift relative to objects across the room. Look at it first with one eye (closing the other) and then switch eyes. To see what we mean, take a pen and hold it a few inches in front of your face. You therefore view the world from two different vantage points, and it is this dual perspective that allows you to get a general sense of how far away objects are. As you are pleased to discover every morning when you look in the mirror, your two eyes are located some distance apart. Even so, we can, in principle, survey distances to the stars using the same technique that a civil engineer employs to survey the distance to an inaccessible mountain or tree-the method of triangulation.Ī practical example of triangulation is your own depth perception. 1 (Links to an external site.) The nearest star, however, is hundreds of thousands of AU from Earth. As this is written in 2016, Voyager 1 is 134 AU from the Sun. For example, our Voyager 1 probe, which was launched in 1977, has now traveled farther from Earth than any other spacecraft. It is an enormous step to go from the planets to the stars. Discuss astronomers’ efforts to study the stars closest to the Sun.Explain why space-based satellites deliver more precise distances than ground-based methods.Understand the concept of triangulating distances to distant objects, including stars.To do this, you will construct a simple tool called an astrolabe.īy the end of this section, you will be able to: In the lab activity, you will calculate the height of an object using the same mathematical techniques involved in stellar parallax. (Click "Next" at the bottom of this page). Once you understand these ideas, you may proceed to the lab activity by proceeding the the Lab Activity part of this module. The Background information on this page will help you to understand the concept of parallax and how it is used to determine distances in astronomy.
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