WHEN YOU'RE a famous genealogist, it makes for great cocktail-party chatter once people find out what you do. The questions pour in, since practically everyone wants help uncovering their family's roots.

Haddonfield resident Megan Smolenyak Smolenyak (yes, that's really her name) mostly has been able to exist just under the radar, so to speak, despite being a world-renowned genealogical sleuth. That has changed now that she has traced the roots of first lady Michelle Obama.

Smolenyak's latest research, which landed her on the front page of the New York Times earlier this month, revealed that besides having black ancestry, Obama also has at least one white ancestor, presumably that of a former slave owner.

Two years ago, Smolenyak unearthed links between President Obama and his maternal ancestors to a fishing village in Ireland. (It turns out that the president is distant cousins with actor Brad Pitt.) At a time when the nation's first black president is being besieged with death threats and attacks, some racially motivated, Smolenyak's findings about the first family are a poignant reminder of just how intermingled the races in America really are.

"It's part of what it is to be an American, to have a mixed background," she told me last week.

"Mathematically, we are supposedly all 50th cousins or closer. If you go back far enough, we are all from Africa and we are all cousins. Genealogy helps people wrap their brains around that," Smolenyak said. "I really do think that even if you knew you were 10th cousins with someone, you would treat them a little bit different. I can roll into a town in Ireland and knock on the door of any business with my surname [on the door] and wind up going to lunch with them. Talk to anybody who has ever done a family reunion or gone back to the old country."

Her research for the Times traced Michelle Obama's ancestors to a slave girl named Melvinia who gave birth to a biracial son.

Ever since the Times story broke, Smolenyak's phones have been ringing with calls from around the world.

"This has turned into a 'This Is Your Life' for me. I have heard from people from all facets of my life," she said. "I have heard from people from India and Spain. A lot with Ireland. Ireland always obsesses with this. Irish love to claim their own. I know this because I'm half Irish myself. They love it when someone of accomplishments claims to be part Irish."

Smolenyak, who famously discovered that relatives of black activist Rev. Al Sharpton's were once owned by those of the late GOP Sen. Strom Thurmond of South Carolina, began unraveling the first lady's ancestry around the time of the presidential Inauguration at the request of the Times. After reporters there finished their article, Smolenyak kept digging. She says it felt as if Melvinia Shields, the illiterate slave girl, was calling to her, as was Melvinia's son Dolphus T. Shields.

"I just started marching backwards in time through [Michelle Obama's] entire roots. I just kept chipping away steadily over nine months. It was like I was doing it full time. I started online with the basic records like Census records, draft records . . . Pretty soon, I was into courthouse records," Smolenyak recalled. "I went a little light on her father's branch, her Robinsons' branch. Her mother, Marian Robinson, is a Shields by birth. My own mother is a Shields . . . that was enough for me to feel a little sense of affinity."

The chief family historian for Ancestry.com and the head of her own Internet start-up, Roots

Television.com, Smolenyak hardly has time to waste poking around in strangers' backgrounds. I asked if she'd been motivated to delve in Michelle's background because of the possibility that she might be a distant relation to the first lady.

"I knew from the beginning that if we were related, it would be back in the old country," said Smolenyak, adding that she had done it between breaks from other work. "It was like my treat. My super treat is to work on my own roots."

Smolenyak became fascinated with the subject of genealogy when she was just 11 and a schoolteacher assigned a class project for students to discover the origin of their surnames. That experience fueled her curiosity, Who were her relatives? What was their family history?

"I turned into this twisted kid saving her allowance for death certificates," she said, laughing. "I wanted to be 16, so I could get into the National Archives."

A self-described Army brat, Smolenyak moved frequently but claims Washington, D.C., as her home. Her mother's family lived in Jersey City, while her dad's was in New York City. She and her husband moved here from Williamsburg, Va., five years ago. She met Brian Smolenyak, who works in logistics for Pinnacle, while researching her family's roots - hence the Megan Smolenyak Smolenyak name.

"It took me a long time to find another Smolenyak," she said, laughing.

After tiring of a career as a marketing consultant, Smolenyak took a month off to decide what to do with the next phase of her life. While vacationing on a beach, she got a call from NBC's "Today Show" to come on air and discuss genealogy. (Smolenyak is a second cousin to Jack Ford, who used to work for the show.)

She also was invited to be a lead investigator on a short-lived PBS show called "Ancestors." Smolenyak compiled information not used by the show into her first book, which was called "In Search of Our Ancestors."

Three more genealogy books followed, as did an Army contract in which she helps trace unaccounted-for deceased soldiers. She once helped Chris Haley, a nephew of "Roots" author Alex Haley, use DNA to document his family's Scottish ancestry. A fifth book, with basic advice for searching your family's roots, is scheduled for release by Penguin/Viking later this year.

As for the first lady, Smolenyak admits to being a tad sheepish about all of her sleuthing. So as to not invade Michelle's privacy, she stuck to public records. The Times also conducted some of its own research.

The political ramifications could wind up being helpful should Obama run for re-election, since people love claiming folks as their own.

"She winds up having roots in every Southern state except for Florida, Texas and Arkansas," she said of the first lady. "It's a story of the Great Migration. She has five different branches that went to Chicago."

Will Smolenyak do more? President Obama's paternal line in Kenya is ripe for exploring.

"I don't want them to feel I'm ancestrally stalking."

Megan Smolenyak will chat online today from noon to 1 p.m. Click www.go.philly.com/hotbutton.