Researchers and faculty from UC Berkeley and Stanford have identified a neutron star with the largest mass to date named PSR J0952-0607. The star has been deemed a “black widow” pulsar as it consumes gas from nearby companion stars.

According to Stanford physics professor Roger Romani, the pulsar was first observed in 2017 and is a neutron star on the cusp of becoming a black hole, making it the most “exotic matter” in the universe. According to a campus press release, the research was supported by NASA, the Christopher R. Redlich Fund, the Tabasgo Foundation and campus’s Miller Institute for Basic Research in Science.

“These bizarre and interesting objects give us a glimpse into really extreme physics that we can’t probe in any other way,” Romani said. “The sky is full of these opportunities to look beyond the horizon of today’s laboratories.”

Romani, who is also a member of the Kavli Institute for Particle Astrophysics and Cosmology, said he has been studying black widow stars with campus astronomy professor Alex Filippenko for more than a decade using NASA’s Fermi Gamma-ray Space Telescope. According to Filippenko, the Keck telescopes on Mauna Kea in Hawai’i are also used to obtain a series of spectra to measure the motion of the companion star orbiting the neutron star.

Campus researchers Thomas Brink and WeiKang Zheng were heavily involved in the collection of observations and software analysis, according to Brink. Thomas Brink joined the research group in 2016 and helped acquire raw data using the 10-meter Keck I telescope, while WeiKang Zheng acted as the primary observer every night.

Brink said he used software programs to calibrate the collected images and spectra for both professors to analyze.

“We typically only get to use the Keck telescopes a few times a year, so it’s always exciting and a little stressful as we try to maximize every single second each night,” Brink said in an email. “Working with all of them has been awesome!”

According to Romani, neutron stars are about 20,000 light-years away from Earth and consume up to 98% of their companion stars, leaving the rest as planetary mass that can be 20 times the mass of Jupiter.

Filippenko said neutron stars can have up to 2.35 times the mass of the Sun. Romani added that although neutron stars are “tremendous” gamma ray and X-ray producers, they are only 10 miles across and undetectable in visible light.

“It takes a honking big telescope to detect this planet thing,” Romani said. “I’m in the business of using telescopes as a way of peering into the laboratories of the heavens and trying to infer the laws of physics that we can’t yet really probe here on Earth.”