BEVERLY HILLS, Calif. (AP) — When Nas became the first rapper invited to trace his family tree through the PBS series Finding Your Roots, he welcomed the opportunity.

But it hit him hard when he saw 1859 documentation of an ancestor being sold as a slave, he said during a panel discussion last week.

“First I was enraged when I looked at the bill of sale,” Nas said. “I was like, that guy that owned property owes me some cash. My people made him really wealthy, so maybe I should find his family and talk.”

The unearthed information made him think about his ancestors’ contribution to America, he said, “and now I’m on a mission to find out more.”

His family’s story is among those told on season two of Finding Your Roots, hosted by Harvard University scholar, author and filmmaker Henry Louis Gates Jr. and debuting Sept. 23.

The 10-part series that traces celebrities’ ancestry will focus on, among others, Ben Affleck, Jessica Alba, Tina Fey, Sting, Stephen King, Billie Jean King, Derek Jeter and chef Ming Tsai.

Others taking part include Courtney Vance, Khandi Alexander and writer and actress Anna Deavere Smith. They joined Nas and Gates on the Television Critics Association panel.

Research on each person begins with DNA testing of a saliva sample and eventually results in a detailed family history that Gates presents on-camera to the subject. “I feel like Santa Claus giving people a gift,” Gates said.

The results can be surprising. Alba’s background was traced to the ancient Mayans, while Affleck’s great-great-great-grandfather was among 19th-century spiritualists who claimed to connect Civil War dead with their grieving survivors, he said.

Gates, who has done a variety of PBS specials about African Americans and their history and experiences, recalled getting a letter from a white woman who accused him of racism for his singular focus.

“I thought white people had more access to knowledge about their family tree than we did,” said Gates, an African American.

But he realized that’s untrue and that people of every ethnicity share the same “cultural amnesia,” he said.

Nas was asked if his newfound knowledge could influence his music. Nothing is planned, he replied, “but I think in some way it will happen on its own.”