Scientists are surprised by the radio signals emitted by a comet

The interstellar comet 3I/ATLAS (an icy and stony celestial body with an elliptical orbit that creates a bright halo and luminous tail when it approaches the Sun due to the evaporation of surface materials) is not the only celestial body that has attracted the attention of scientists. Comet 12P/Pons-Brooks, which was first discovered in 1812 and approaches Earth approximately once every 71 years, has recently emitted interesting radio signals that have attracted the attention of astronomers. This discovery was made during the comet’s closest pass by the Sun last year and using Tianma radio telescope data by a team from the Shanghai Astronomical Observatory affiliated with the Chinese Academy of Sciences.

Comet 12P is Halley-type, that is, an icy body with an orbital period between 20 and 200 years. Before 2024, its last close pass was recorded in 1954, and on each return, scientists have observed numerous light bursts and radio signals from it.

The mechanism of these eruptions remains unknown, but in radio signals recorded by Tianma last year, the research team detected a sharp increase in the spectral line associated with hydroxyl, a free radical consisting of one hydrogen atom and one oxygen atom that results from the decomposition of water vapor by solar radiation.

By simulating how sunlight interacts with the comet’s surface, the researchers modeled how the rate of water production changes in each eruption and found that this comet is much more active than other Halley-type comets. Measuring the compounds ejected by comets can provide scientists with interesting insights into the early days of the solar system, about 4.6 billion years ago. These data may even help to understand the conditions that made life possible on Earth.

During the 2024 transit, Comet 12P became very bright as it approached the Sun. Using Tianma to examine L-band and K-band radio waves, the researchers found that at a distance of one astronomical unit (the average distance between the Earth and the Sun), this comet released more than five tons of water vapor, which is much more than other short- and long-period comets. The observations also revealed the presence of ammonia molecules, the first time this organic compound has been detected in a Halley-type comet.

The researchers wrote in their paper: “The possible identification of ammonia during an eruption probably indicates a connection between the subsurface fugitive reservoir and the eruption mechanism. These results can expand our understanding of the composition and activity of Halley-type comets.”

The research comes months after a team led by Martin Cordiner of NASA’s Goddard Space Flight Center announced that comet 12P/Pons-Brooks contained water that was nearly identical to water on Earth.

“Our new results provide the strongest evidence yet that at least some Halley-type comets carried water with an isotopic signature similar to Earth’s water, supporting the theory that comets played a role in making Earth habitable,” Cordiner said in a statement earlier this year.