Rocky planets such as Earth are born through countless acts of violence—the collision and merging of many smaller bodies. A new study reveals that some planets continue to take a beating hundreds of millions of years after they've formed.
The evidence comes from an infrared survey of 266 youthful stars, revealing that 71 of them have disks of dusty debris. The disks are a sign that newborn planets are being clobbered by asteroids and that the asteroids—planet-formation leftovers—are banging together (SN: 10/9/04, p. 227: Planet Signs? Sifting a dusty disk) and making dust that glows at infrared wavelengths.