Earth 2.0 கிரகத்தை எப்படி கண்டுபிடிப்பது | Exoplanet Discovery Mechanics?

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Planets may give themselves away when they pass in front of a star and dim some of its light. The passage of a planet between a star and Earth is called a "transit." If such a dimming is detected at regular intervals and lasts a fixed, repeated length of time, then it is very likely that another, dimmer object is orbiting the star. Some of these transiting objects might be small, dim stars (in which case the pair is called an eclipsing binary), but most of them are planets.

How much a star dims during a transit directly relates to the relative sizes of the star and the planet. A small planet transiting a large star will create only a slight dimming, while a large planet transiting a small star will have a more noticeable effect. The size of the host star can be known with considerable accuracy from its spectrum, and photometry therefore gives astronomers a good estimate of the orbiting planet's diameter, but not its mass. This makes photometry an excellent complement to the radial-velocity method, which allows an estimate (a lower limit) of a planet's mass, but provides no information on the planet's diameter. Using both methods, combining mass and diameter, scientists can calculate the planet's density. Density, in turn, can suggest whether a planet is rocky, gassy, or in between.
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