February 21, 1901
At 11:00 p.m. Ida Watson '01, a Vassar senior, discovered a new star in Perseus—simultaneously, it appeared, with Dr. Thomas D. Anderson, a well-known amateur astronomer in Edinburgh, Scotland. The joint discovery of the first new star of the 20th century by a Scotsman and an American woman was noted in newspapers from New York and Philadelphia to Los Angeles, where the Los Angeles Herald reported Miss Watson "at once recognized it as a new star. In magnitude it was nearly as bright as Capella, the brilliant yellow star directly overhead in the early evening. The next observation...was made on February 25, when it had then diminished in brightness, being the same magnitude as Pollux. On the same evening the spectroscope...showed the spectrum to be continuous, crossed by broad lines, thus giving evidence of great outbursts of hydrogen and helium."
After graduation, Ida Watson stayed on at the Vassar observatory for postgraduate work and with her classmate Helen Swartz published their calculations of the maxima and minima of variable stars for 1902 in monthly installments in Popular Astronomy, an important journal for amateur observers of variable stars. Thomas David Anderson remained the discoverer of record of the nova, which continued to fade until, 11 years after its discovery, it was no longer visible to the naked eye.