Rooms of Hogwarts

Astronomy Tower

Answer: PULSAR

The crossword clues on the left and the pictures on the right all give clues that are halves of portmanteaus. Since the pictures on the right are already alphabetized, rearrange them to match the crossword clues, put the portmanteaus in the blanks.

COSTUME + PLAY = COSPLAY
CHANNEL + TUNNEL = CHUNNEL
BOMBAY + HOLLYWOOD = BOLLYWOOD
SPOON + FORK = SPORK
GAY + RADAR = GAYDAR
TOFU + TURKEY = TOFURKEY
POSITIVE + ELECTRON = POSITRON
BRO + PONY = BRONY
WEB + LOG = BLOG
SMOKE + FOG = SMOG
SITUATIONAL + COMEDY = SITCOM
FRAPPE + CAPPUCCINO = FRAPPUCCINO
LABRADOR + POODLE = LABRADOODLE

The highlighted letters spell PULSATING STAR, so the answer is PULSAR.