It’s not just interstellar comet 3I/ATLAS that’s been catching the attention of scientists.
Comet 12P/Pons-Brooks, which was first discovered in 1812 and visits the Earth roughly every 71 years, has been found to be emanating intriguing radio signals.
As detailed in a new paper published in the journal Astronomy & Astrophysics, a team of astronomers led by the Shanghai Astronomical Observatory of the Chinese Academy of Sciences used data collected by the Tianma Radio Telescope during its latest approach to the Sun last year.
The comet is a Halley-type comet, meaning it’s an icy object that has an orbital period of anywhere between 20 and 200 years. Before 2024, its last closest pass was in 1954. Each time it’s come by for a visit, scientists have observed it giving off multiple outbursts of brightness and radio signals.
The mechanism behind these flareups remains mysterious, but in the radio signals observed by Tianma last year, the team detected a spike in the spectral line associated with hydroxyl, a free radical made up of a hydrogen and oxygen atom, which is the result of water vapor being broken down by the Sun’s radiation.
By simulating how the sunlight interacts with the comet’s surface, the team modeled how water production rates changed across each outburst, and determined it’s far more active than other Halley-type comets.
Measuring the components that comets are outgassing can give scientists an intriguing glimpse at the earliest days of the solar system, some 4.6 billion years ago. It could even help determine how the conditions came to be that allowed life to flourish on Earth.
During its 2024 approach, 12P became extremely bright as it neared the Sun. Using the Tianma to examine L-band and K-band radio waves, the researchers found that at a distance of one astronomical unit, or the average distance between the Earth and Sun, it released more than five tons of water vapor, which is far more material than other short- and long-period comets.
The observations also revealed ammonia molecules, the first time the organic compound has been detected in a Halley-type comet.
“The possible detection of [ammonia] during an outburst suggests possible connections between the subsurface volatile reservoir and the outburst mechanism,” the researchers concluded in their paper. “These results could further our understanding of the composition and activity of Halley-type comets.”
The research comes months after a team led by NASA Goddard Space Flight Center researcher Martin Cordiner found that 12P/Pons-Brooks contains water that’s almost identical to the stuff we have on Earth.
“Our new results provide the strongest evidence yet that at least some Halley-type comets carried water with the same isotopic signature as that found on Earth, supporting the idea that comets could have helped make our planet habitable,” Cordiner said in a statement earlier this year.
More on comets: Astronomer Suspects Mysterious Object Is Up to No Good While It’s Hidden Behind the Sun: “If You Want to Take a Vacation, Take It Before Then”
