In nabbing exoplanets that are precariously close to their stars, astronomers have discovered a shortage of one type of alien world. It's a predicted class of Neptune-sized world that orbits just a few million miles from its star, much closer than the 93-million-mile distance between Earth and the Sun. Dubbed "hot Neptunes," these planets would have atmospheres that are heated to more than 1,700 degrees Fahrenheit (hot enough to melt silver).
However, the mysterious hot-Neptune deficiency suggests that these planets are rare, or, they were plentiful at one time, but have since disappeared. In... Read more