How many letters does the top answer for “a constellation in the southern hemisphere near the south celestial pole” have?

The most common answer is hydrus (6 letters).

Crossword clue: a constellation in the southern hemisphere near the south celestial pole

1 answer found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

hydrus 6 letters wn-def

a constellation in the southern hemisphere near the south celestial pole