A huge cosmic object could force astronomers to rethink what a moon is– www.scientificamerican.com
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EXCERPT:
When is a moon not a moon? That’s the riddle raised by a new study, and the solution appears to be “when it’s a planet.” Or maybe the answer is vice versa.
Such are the strange semantic questions raised by studies of CD-35 2722 B, a brown dwarf with about 30 times the mass of Jupiter that’s orbiting a small star that is some 73 light-years from Earth in the system CD-35 2722. The brown dwarf appears to have its own satellite, much like Earth has the moon, albeit one almost as big as the largest planet in our solar system. While astronomers have discovered thousands of exoplanets, CD-35 2722 may be the first star system found that exhibits this three-tiered “star, brown dwarf, satellite” hierarchy.
Earlier observations of CD-35 2722 B, taken at the W. M. Keck Observatory in Hawaii, had shown hints of an exomoon—a type of object that has yet to be definitively found—but the data weren’t conclusive. To settle the matter, Kevin Hoy, a Ph.D. student at the Institute of Astrophysical Studies in Santiago, Chile, turned to the European Southern Observatory’s more powerful Very Large Telescope (VLT) and its CRIRES+ instrument on a mountaintop in the high Chilean desert.
