The Summer Triangle is one of the skywatching treats of the season. Its stars are among the brightest in the night sky, so they’re visible even from light-polluted cities. And they bound a region that’s yielded more than a thousand confirmed exoplanets — planets orbiting stars other than the Sun. That’s mainly because that region of the sky was the target for Kepler, a planet-hunting space telescope. In four years of searching, it discovered more than 5,000 possible planets there. About a thousand have been confirmed, with the rest awaiting follow-up observations from the ground. Kepler’s list of discoveries includes the first Earth-size planet found in its star’s habitable zone — the distance from the star where temperatures are just right for liquid water. The list also includes star systems with as many as six planets, planets that orbit two stars, and planets that are so close to their stars that radiation is vaporizing their atmospheres; we’ll talk about a system with two of these
