Since celestials come from space they are not required to eat, drink or sleep.

However, they do need to meditate  to re-attune their connection to the universe and to reflect and contemplate on existence and reality itself. After meditating, you get advantage on wisdom and intelligence checks for the next two hours. They only need to meditate or pray for 4 hours, Doing so equates to a full 8 hours rest or addressed as a long rest.

Your "eyes" know no such concept as darkness, merely an absence of the light.

While containing inspiration or similar boosts, a dim light emits from you 10ft in every direction

Being isolated for eons with nothing to do but think made you wise. You gain +1 to your wisdom and intelligence score.

Because you have been alive since the very first moment of existence, you know a thing or two. Gain proficiency in three skills.

You can speak telepathically with any creature within 60 feet of you. This creature must know at least 1 language.

This allows them to increase or decrease the force of gravity in their immediate vicinity. (200ft) 

You can take the gravity from a 60 foot area sphere surrounding you, creating near weightlessness in that area, and can either gain advantage on all strength and constitution rolls for 1 hour or create a 15ft dense gravity area where all in it must roll a dexterity saving throw and get at least a 14, on a success nothing happens but on a fail they are stunned for up to three turns and must get a 12 or higher on a strength check in order to be able to escape. You can use this power once per long rest. 

You can use your gravity in a way that grants you the same powers as telekinesis. You can use this power three times per long rest.

Space Celestials can change their matter to look like the most average combination of a planets species