Starting in 2009, astronomers have been discovering really cool objects out there (cool here meaning low-temperature, as well as really interesting), which they have called Y dwarfs. What distinguishes these brown dwarfs from others that astronomers have discovered?
A) they show absorption lines from the ammonia molecule in their spectra
B) they are hotter than other brown dwarfs
C) they orbit hundreds of nearby stars and are much more common than other brown dwarfs
D) they show strong evidence of helium in their spectra
E) they have much larger mass than other brown dwarfs

Question

Quizplus · Accepted Answer

Y dwarfs are distinguished by showing absorption lines from the ammonia molecule in their spectra, which is not seen in other types of brown dwarfs.

Starting in 2009, Astronomers Have Been Discovering Really Cool Objects