Sandra Bullock enjoyed an early 50th birthday celebration at a cowboy bar on Thursday (24.07.14).

The 'Gravity' actress reached the milestone age on Saturday (26.07.14), but began her festivities early by heading to the Million Dollar Cowboy Bar in Jackson Hole, Wyoming, with a group of female pals to listen to country group Southern Soul Allstars.

A source said: ''There were probably six to ten women in the group. It appeared to be a ladies night. They just came in to listen to the band.''

Though the group - which included Chelsea Handler - didn't seem to be dancing, they all had a great time.

The onlooker added to E! News: ''It was pretty low key. They all had one drink...and were all dressed casually.

''Sandra looked radiant, beautiful and was very sweet. It looked like she was having a blast.''

Sandra and Chelsea have been close friends for years, and on Saturday night, the 'Chelsea Lately' host posted a picture on Instagram of a group of women in a cheeky pose, with one of the group showing off her thong-clad butt, though it is unclear as to her identity.

While the picture was captioned ''Birthday girls'', the 'Blind Side' actress - who has a four-year-old son, Louis - can't be seen in the Instagram picture.