Radio signals from comet 12P/Pons-Brooks detected: Why it matters
What's the story
A team of astronomers from the Shanghai Astronomical Observatory, Chinese Academy of Sciences, has made significant findings. They have detected radio signals from the returning comet 12P/Pons-Brooks (12P) using the Tianma Radio Telescope. The study was published in Astronomy & Astrophysics. The researchers measured the water production rate during outburst activities and made the most distant detection of ammonia molecules in a Halley-type comet to date.
Insights
A look at comets
Comets are thought to be time capsules from the early solar system, containing a variety of icy components. These elements sublimate as they approach the Sun, leading to different cometary activities. The presence of volatile ices in comets suggests that they have not changed much since their formation. Studying these ices gives us important clues about the thermal and chemical conditions of our solar system 4.6 billion years ago.
Comet profile
About comet 12P/Pons-Brooks
Comet 12P is a Halley-type comet with an orbital period of about 71 years. Since its discovery in 1812, it has shown multiple outbursts during each return, an unusual behavior that is still not fully understood. During its 2024 return, Comet 12P again showed frequent outbursts as short-term spikes in overall brightness. These events often involve more gas being released from the nucleus, making them ideal for studying gas composition changes and understanding outburst mechanisms.
Research findings
Observations and calculations
From late 2023 to early 2024, the researchers used the Tianma Telescope to conduct L-band and K-band radio observations. They detected the 18-cm hydroxyl (OH) spectral line of Comet 12P in the L-band, a photodissociation product of water vapor. Using radiative transfer modeling, they calculated the water production rate and gas expansion velocity of Comet 12P before and after several outbursts.
Activity levels
First detection of ammonia in a Halley-type comet
At a heliocentric distance of 1 AU, Comet 12P can release over five tons of water vapor per second, more than most short-period comets and some long-period comets. This clearly shows that Comet 12P is highly active. During outbursts, its activity (using water as an example) can roughly double. The researchers also detected the ammonia molecules (NH3) in a Halley-type comet for the first time at radio wavelengths with three-sigma confidence.