If you were outside on a clear June day in 2012, you may have seen Venusâ€™s silhouette as it passed exactly between Earth and the Sun. This phenomenon is called a â€œtransitâ€, and itâ€™s also a method that planet hunters like Lauren Weiss of the University of California, Berkeley use to find exoplanets.
"So we can see this phenomenon with exoplanets, too. We donâ€™t actually see the picture of the silhouette of the planet, but we can measure how much the starlight dims as the planet passes in front. And this very characteristic dimming tells us where the planet is, and how big it is compared to the star. And we see this transit happen multiple times before we declare that thereâ€™s a planet there."
Weiss says that thousands of exoplanets have been discovered with Kepler, a NASA space telescope designed to find habitable Earth-like planets in the Milky Way.
"Although its primary mission has ended, it has been revived in a mission called â€œK2â€ and is still finding new planets around other stars."
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