Irish constellation

My 5-year-old was stargazing last night.
"Mummy?" she says.
"Mmmmm," I replied, sleepily snuggled up to the warmth of the dozing toddler.
"When I grow up, I think I might be an astronaut," she says, "and visit other worlds."
"Do you, love?" I say. "What other worlds do you want to visit? Mars, maybe?"
"No," she muses, "much farther than that. I think I will visit planets near stars a long, long way away."
The 7-year-old interjects, "You can't do that, they haven't found out how to bend space and time yet!" she declaims. G and I raise eyebrows at each other.
The 5-year-old frowns at her sister. "Well, they will, then I will go visit O'Brien!"
Ummmm...
"O'Brien, love?" I say. "Is that a star name that you've made up?"
"NO, Mummy!" in exasperation. "O'Brien! You know, with the belt?"
Trying not to chortle out loud, her father says, "I think that's O-RION, E."
"Oh," she says, "alright then. Well, there. And Cirrus the cloud star, too."
"Sir-IUS?" I guess.
"Yes!"
I was awaiting the next stellar mondegreen with interest when she nicked off to play dolls with her sister instead.