Free Astronomy Magazine January-February 2020

26 JANUARY-FEBRUARY 2020 EXOPLANETS Between 2004 and 2007, when BD +20 307 was still considered a single star, astron- omers observed it in the infrared with highly sensitive instruments − including Keck and Gemini North in Hawaii, as well as the Spitzer space telescope. The data collected showed the existence of a large disk of dusty debris around the star. The disk appeared unusually warm and, therefore, was brilliant in the infrared, but its presence and its temperature could only be explained by assuming that the star was extremely young, perhaps just a few million years old. In fact, it is normal to observe disks of debris and dust around younger stars, as their planetary system is still in for- mation. Only after tens or hundreds of mil- lions of years, that scattered material runs out after being raked up by the formed planets, consumed by the star, confined to the periphery of the system, or dispersed by stellar radiation pressure. A fantasy illus- tration of a protoplanetary disk. These types of structures are transitory and usually remain observable until the complete for- mation of a plan- etary system. [ESO/L. Calçada]