If a marriage ended in separation, with no divorce papers being signed, is the marriage still legally in effect?

My husband and I have been married for 7 years. But he was previously married to another woman back in 1988 for a year. They separated then and have had no contact ever since. However, no divorce papers were filed, so is he still legally married to her? And is she entitled to alimony and/or back child support? And am I even legally married to him because of this horrible situation? Please tell me there is some law that says a marriage is nulled if the two parties have been separated for a certain amount of time.