Leo Rising by Tricia Barr

TWELVE TEENS. ONE TASK. SAVE THE UNIVERSE.

As long as Cassandra controls her emotions, she’s okay. She just needs to focus—excel at school, sports, make her father proud…and suppress the anger that seethes within her.
Except there’s always been one person who gets under her skin, the girl Cassandra called her childhood best-friend in the loneliness of the orphanage. Now, when Cassandra can’t control her fury, she reveals her powers to Brielle. Powers that Cassandra has hidden for a reason.
The moment Cassandra grips her stone, the truth is undeniable. She’s a Zodiac Heir.
And she’s about to learn that evil is amassing. Dark matter is being manipulated and a wormhole has opened, releasing an asteroid heading straight for Earth. Tristan has foreseen the death and damage it could wreak.
Cassandra could be their most powerful weapon against Chardis yet. But first there are deep wounds to heal and relationships to be forged. Will the fledgling Zodiac Heir team be able to come together to save countless lives? Or will Cassandra’s anger prove to be the most dangerous power yet?