Patsy Tombaugh, the woman who looked after the world her husband discovered, passed away Thursday at the age of 99 in Las Cruces, N.M., after a series of health problems.

She was the widow of astronomer Clyde Tombaugh, who found Pluto in 1930. After Clyde's death in 1997, Patsy took on the job of keeping Pluto in the spotlight, during a time when more worlds were being discovered on the solar system's edge. She was a guest of honor at the 2006 launch of New Horizons, NASA's mission to Pluto, and was in tears at liftoff. When Pluto was reclassified as a dwarf planet later that year, few people took it harder than Patsy. "I don't know just how you handle it," she told reporters. "It kind of sounds like I just lost my job."

But she didn't: Patsy continued to promote Pluto's planethood, sitting in the public gallery when the New Mexico House of Representatives passed a resolution creating "Pluto Planet Day." When I visited her in 2009, she had a feeling that people would still be talking about Pluto long after she was gone. "It looks like we're going to have to keep on discussing this," she told me.

Patsy is survived by her son, Alden; her daughter, Annette Tombaugh-Sitze; five grandchildren, nine great-grandchildren and one great-great-grandchild. A memorial service is scheduled Feb. 12 at the Unitarian Universalist Church of Las Cruces, where a stained-glass window already serves as a tribute to the Tombaughs.