By Zara Woodcock Model Helena Christensen looked out of this world as she showed off her ageless beauty in a new social media post. The 55-year-old star took to her Instagram to post a carousel of pictures from her birthday celebrations – which fell on Christmas Day. She captioned the photos: “Birthday chills with my family.” In one snap, Helena looked happy as she posed on the ladder as she climbed out of the river she was swimming in. She rocked a light pink one-piece swimsuit with black and blue detailing. Her bright lipstick still perfectly sat on her face as she showed off her pearly whit…