A Constellation’s “Feathers” and “Hair” actually work like tendrils/tentacles.
They have full control on them and yes, when they are trying to frighten someone you can say they go SHOOM and show them fully. The shorter ones on their skin which you can consider small feathers are often against the skin and flat but they can totally fluff up to show extreme emotions. ( FLOOF FOR POWER)
This is the main reason most constellations have long ‘hair’ except of Teo, Teo got his cut by someone when he fell to Earth. Without them Teo lacks a lot of his skills in combat and daily life and is the reason he took his weapon in the first place.
Someone feeds him though.

Another use for their tendrils is for feeding, they feed off rocks (meteors and gems are a buffet for them )  and minerals and use them to crush them into smaller pieces so they can fit on their mouths.

A Constellation ill or hungry is unable to move them whatsoever and their color turns somewhat dim. In extreme illness their feathers and hair fall off which often causes them to starve until they die. It is rare, these things are very very old and they cannot catch your common flu.