These planets have an abundance of strange properties. The innermost world, GJ 15 A b, takes just 11 days to make a full orbit around the star – a "year" on this planet. It weighs in at three times the mass of Earth, qualifying it for the size category known as "super Earth." It's also super-heated, with an estimated surface temperature of 530 degrees Fahrenheit (276 Celsius). Its sister-world, GJ 15 A c, could hardly be more different. It's a gas giant 36 times the mass of Earth, and appears to have roughly a 20-year orbit around its cool and small parent star. While its temperature is not known, it's likely to be quite cold in this distant, possibly icy orbit, loosely comparable to the orbit of Saturn around our Sun.
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