Readers discuss Pluto’s planetary status, balding black holes and more

Viral buzz cut

The coronavirus razes cells’ hairlike cilia, which protect a person’s respiratory tract from foreign objects, Erin Garcia de Jesús reported in “How COVID-19 sabotages cells” (SN: 8/28/21, p. 18).

Reader Ron Kern asked if the mowed-down cilia can grow back.