CSI star Marg Helgenberger celebrated her 50th birthday with a very special gift to herself — her own home!

The Emmy-winning actress — who plays forensic investigator Catherine Willows on CBS’ hit drama — has moved out of the house she shared with her longtime husband, actor Alan Rosenberg, to begin a new life, The ENQUIRER has learned exclusively.

“Marg hasn’t been happy for a long time, and as 50 approached she finally told Alan she wanted to start the second half of her life alone,” a close family friend told The ENQUIRER.

The strawberry blonde actress – who turned 50 on Nov. 16 – and Alan, 56, have been married since 1989. They have a son who turned 18 on Oct. 21.

“But both she and Alan love their son, and want to minimize any trauma the split would have on him. They’re excellent parents, but they just came to the decision that their lives together were no longer working.”

For all the details on Marg's move and the marriage bust-up, pick up the new issue of The Enquirer — on newsstands now!