Readers react to a dwarf planet’s odd ring, dry farming and more

Sizing up rings

The dwarf planet Quaoar sports a ring that lies outside the orb’s Roche limit, an invisible line beyond which rings aren’t thought to be stable, Lisa Grossman reported in “This dwarf planet hosts an odd ring” (SN: 3/11/23, p. 11).

Reader Henry Leonard wondered if it’s possible the ring isn’t so unusual, that p­erhaps Quaoar simply has an unexpectedly large mass, resulting in a large Roche limit.