Eclipsed by heat.
The faintest brush of feathers against her under belly alerted Celestia to the creature beneath her, and with a start she looked down to find twilight’s head poking out from between her front legs.

Twilight was nuzzling her horn and head into the taller alicorn’s chest fur, her eyes shut as she moved. Celestia, unsure of why such attention was being given lifted a leg cautiously. It was well known that her and twilight would hug and nuzzle occasionally…but the mare had never really pushed for physical contact like this.

thinking her student wanted a hug Celestia tried to wrap her hoff around the young mare’s neck,

Twilight’s leg lifted and quickly hooked around her old teacher’s hoof, stopping the action from moving further. her eyes barely opened and she looked up at the Sun, in all it’s glory. her wings opened and slowly wrapped themselves around the princess’ large white forelegs, whilst her back rubbed back and forth on the princess’ belly in a subtle but obvious attempt to cause friction.

“mmm….You’ve eclipsed me…Celestia..” Spoken from her lips, those words came out in the most sultry voice that Celestia had ever heard part from her student’s mouth. It all suddenly clicked.

The gentle nuzzling.

the bellyrubbing…

the blush on her student’s cheeks….

Celestia felt her wings suddenly snap open as realization dawned on her…Twilight was in heat.

She gulped and looked down as her former student hummed and brushed against her chest once more.

“..O-oh my…”