Free Astronomy Magazine January-February 2020

27 JANUARY-FEBRUARY 2020 EXOPLANETS However, the idea astronomers had about a young BD +20 307 turned out to be incor- rect at the beginning of 2008, when new observations of that star showed that in re- ality it was a binary system with an age of at least one billion years, if not even several billion years. At that point, it was evident that if the stars were surrounded by a dusty disk, that disk could only have been gener- ated by a relatively recent event, consider- ing that its temperature is around 420 K (almost 150° C), higher than the average for these structures. In the BD +20 307 system, the set of debris and dust that astronomers observed may have been generated solely through a couple of mechanisms: the colli- T he protoplan- etary disk sur- rounding the young star MWC 758. A similar structure was un- expectedly dis- covered around BD +20 307. [ALMA (ESO/ NAOJ/NRAO)/ Dong et al.]