Chu Introduces Resolution to Mark Hubble’s 1923 Mount Wilson Discovery Above Pasadena

Rep. Judy Chu introduced a House resolution Monday, Oct. 5, honoring a 1923 observation at Mount Wilson Observatory above Pasadena that led to proof of a galaxy beyond the Milky Way, her office announced.

The measure expresses support for naming Oct. 5, 2026, “National Beyond the Milky Way Day.” It cites Carnegie Science, whose Observatories division is at 813 Santa Barbara St. in Pasadena. It places Mount Wilson Observatory “in the San Gabriel Mountains above Pasadena, California.” Chu introduced it on the date it would mark.

Under the resolution, the House would recognize the anniversary of the discovery of the universe beyond the Milky Way. It would commemorate the observation astronomer Edwin Hubble made during an observing run that began the night of Oct. 5, 1923. It would also honor Henrietta Swan Leavitt, a Harvard University astronomer. Her work on Cepheid variable stars gave astronomers a reliable way to measure distances in space.

The resolution urges schools, science groups, museums, observatories and communities across the United States to mark the milestone. It points to science, technology, engineering and mathematics education and public programs as ways to do so.

Reps. Zoe Lofgren, Sydney Kamlager-Dove and Ted Lieu, all of California, are co-sponsors, and Carnegie Science has endorsed the measure, Chu’s office said in a press release. Chu co-chairs the bipartisan Congressional Planetary Science Caucus.

“More than a century ago, right here in the San Gabriel Mountains, a groundbreaking discovery forever changed humanity’s understanding of our place in the universe,” Chu said in the release. “I’m proud to honor the scientists and institutions whose pioneering work made that discovery possible.”

“We are so grateful to Rep. Judy Chu for her tireless advocacy for science both here in Pasadena and nationwide,” Carnegie Science President John Mulchaey said in the release. Mulchaey, who is based in Pasadena, was named the institution’s 12th president in November 2024. He had spent a decade as director of the Observatories.

Hubble, a Carnegie astronomer, photographed the Andromeda Galaxy on the night of Oct. 5-6, 1923, with the 100-inch Hooker telescope at Mount Wilson, according to Carnegie Science. He first marked a star on the glass plate with an “N,” for nova. He later crossed that out and wrote “VAR!” after finding that the star varied in brightness like a Cepheid. The finding established that Andromeda was a galaxy separate from the Milky Way. Hubble reported his results to the American Astronomical Society on Jan. 1, 1925.

The plate, numbered H335H, is part of Carnegie’s plate archives. The archive’s vault is in the basement of the Observatories’ Santa Barbara Street office. It holds the second-largest collection of astronomical glass plates in the United States, according to Carnegie Science.

George Ellery Hale founded Mount Wilson Observatory in 1904 in the San Gabriel Mountains.

The resolution describes Carnegie Science as celebrating a significant institutional anniversary. The institution’s 125th anniversary is Jan. 29, 2027.