ECLIPSING PLANETS - and we collect only the light from the...

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ECLIPSING PLANETS Another method that has come unto use recently is based on the time variation of the total light from a star-planet system. This works when the plane of the planet's orbit is along the line from the star to the viewer. (In the figure below the orbit is in a plane perpendicular to the paper.) At the time of (a) the planet is to the right of the star and the light we collect is the total of star + planet. (The assumption is that we cannot see the two separate objects, but only collect a certain total quantity of light from that direction in space.) The planet's light is really reflected starlight. Only the half of the planet facing toward the star is lit (just as when we see a half moon). At (b) the planet has gone behind the star
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Unformatted text preview: and we collect only the light from the star. The graph shows that the quantity of light is reduced. At (c) the planet comes out at the left, and we collect the total star + planet light again. At (d) the planet is in front of the star. The planet is dark, and a part of the starlight is blocked (eclipsed). So the light in (d) is less than the light in (a) and (c), as shown in the graph. FIG. 5 This kind of graph is called a "light curve." From it astronomers can deduce various properties of the planet, including its diameter, but not its mass. The eclipsing technique is now being employed by a dedicated satellite-based telescope, launched in 2010, to study a large sample of 156,000 stars....
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