Yes, WELKINS is a Scrabble word!

Letter values in Scrabble US: W 4, E 1, L 1, K 5, I 1, N 1, S 1.

Is it a valid word?

WELKINS is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

the apparent surface of the imaginary sphere on which celestial bodies appear to be projected

Also: celestial sphere, vault of heaven.