Detecting Planets Via Transits That Produce a Dip in the Light Curve of a Star

In some instances, a planet can be detected by measuring the amount of light it blocks out from a distant star. It is similar to a solar eclipse, but with a much lessened effect. Usually, when a planet passes directly in front of a star, only about one percent of the light from the star is blocked out. Therefore, the detection must be very precise.

In order to make sure that the change in the amount of light isn't a glitch, the light is monitered over a long period of time. Since the period of the planet orbiting the sun is almost exactly constant, astronomers can estimate whether a planet is present by the light intensity line. This line shows the light intensity of a star at a given time. If a planet passes in front of the star and blocks out some light, then the line will have a drop in intensity for as long as the planet stays in front of the star.

Scientists use a photometer linked to a space telescope with a collecting area just of approximately 3 feet (1 meter). Then hey measure the minute changes in light coming from stars caused by what are known as "transits" of planets. Transits occur when planets in their orbits around their parent stars cross the line of sight between us and the star.

When a planet passes in front of a star, this is called a Transit

The Dip in light is quite small (about 1%)

Need to have precise data

Orbit causes the light intensity line to have a constant period

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