Los Angeles, Dec 14 (TIWN / IANS) The "Guardians of the Galaxy" star Chris Pratt made his love for girlfriend Katherine Schwarzenegger public on her birthday.

He took to Instagram on Thursday to wish Katherine happy birthday. He shared a collage of intimate photographs of the two, which include Schwarzenegger giving Pratt a pedicure and both wearing face masks.

"Happy birthday Chief! Your smile lights up the room. I've cherished our time together," Pratt wrote alongside the collage, which marked the first time he has shared a photo of the two together, reports etonline.com.

"Thrilled God put you in my life. Thankful for the laughs, kisses, talks, hikes, love and care."

On Wednesday, a source said that the two, who were first spotted together in June, are in a "serious relationship and everything is going well", yet Pratt isn't rushing to get engaged anytime soon.

"Chris just finalised his divorce from Anna (Faris) a couple months ago, and he's happy with just dating Katherine for now. The couple has a lot of fun together and is fully involved in one another's life," the source said.

While they have remained out of the public eye, they have been spotted attending church, going to dinners and even hanging out with her star father Arnold and brother Patrick.