Kepler stares at about 160,000 stars continuously ò?? we donò??t change targets because we donò??t want to miss a transit that might last only 10 hours and occur only once per year. Half a percent of 160,000 stars is 800 stars, so you might think that this is about how many transiting planets with Earth-sized orbits Kepler should find. But nothing is simple when working at such high precision; we must consider several important factors.
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