TNG Reveals the Carbon-Depleted Nature of the Comet C/2023 A3 before Perihelion

Spectroscopic data from Telescopio Nazionale Galileo confirm that comet C/2023 A3 (Tsuchinshan–ATLAS) is carbon-depleted, offering new insights into its early activity and molecular composition.

New observations carried out at Telescopio Nazionale Galileo shed light on the volatile composition of comet C/2023 A3.Based on data collected before the comet’s perihelion passage, the findings (published in Planetary and Space Science) confirm the comet’s carbon-depleted nature and provide new upper limits on the abundance of key volatile species such as C₂, C₃, and NH₂.

The observations were conducted on May 1, 2024, using the DOLORES, low-resolution spectrograph installed at the TNG. Despite the presence of a strong dust continuum that typically masks faint gas emissions, the team succeeded in detecting CN and measuring a production rate of (3.89 ± 0.21) × 10²⁵ molec/s, while placing stringent upper limits on other common cometary molecules such as C₂, C₃, and NH₂.

“Thanks to the sensitivity and reliability of the TNG and its instrumentation, we were able to observe the comet while it was still relatively far from the Sun, capturing its activity in an early stage and constraining its molecular composition before more intense outgassing processes took over” said Pamela Cambianica (INAF – Osservatorio Astronomico di Padova), lead author of the study.

The analysis confirmed that C/2023 A3 is carbon-chain depleted, with values of log[Q(C₂)/Q(CN)] < –0.48 and log[Q(C₃)/Q(CN)] < –1.10, in line with other members of the carbon-depleted comet family. The comet also exhibited a high dust production rate, as measured by an Afρ value of 4329 ± 56 cm, adding to the complexity of interpreting spectra from dust-rich environments.

This research underscores the crucial role of Telescopio Nazionale Galileo in advancing cometary science, especially through its ability to perform sensitive, early-phase spectroscopic observations of pristine Solar System bodies.

More details in the paper “Pre-perihelion observations of the carbon-depleted comet C/2023 A3 (Tsuchinshan-ATLAS). Insights into CN production and molecular upper limits.”

Planetary and Space Science, Volume 261, Article 106102. DOI: 10.1016/j.pss.2025.106102

Top panel. Gaussian fit to the CN emission band centered at 3881.68 Å in the comet’s spectrum. The black line represents the observed spectrum, the red line is the fitted Gaussian profile, the blue dashed line indicates the central wavelength, and the shaded area corresponds to the total flux under the curve. Bottom panel. Zoomed-in view of the CN emission band and its Gaussian fit. The detailed view highlights the agreement between the fitted Gaussian profile (red line) and the observed data (black line), with the shaded area representing the integrated flux. The central wavelength is marked by the blue dashed line.

Three color image of the comet C/2023 A3 Tsuchinshan-ATLAS taken with LRS@TNG during the night of October 22, 2024.

Fundación Galileo Galilei - INAF Telescopio Nazionale Galileo 28°45'14.4N 17°53'20.6W 2387.2m A.S.L.
Home General Info News Telescope & Instruments Observing Time Allocations & Schedules Publications Seminars Weather Webcam Outreach Gallery Links	TNG Reveals the Carbon-Depleted Nature of the Comet C/2023 A3 before Perihelion Spectroscopic data from Telescopio Nazionale Galileo confirm that comet C/2023 A3 (Tsuchinshan–ATLAS) is carbon-depleted, offering new insights into its early activity and molecular composition. New observations carried out at Telescopio Nazionale Galileo shed light on the volatile composition of comet C/2023 A3.Based on data collected before the comet’s perihelion passage, the findings (published in Planetary and Space Science) confirm the comet’s carbon-depleted nature and provide new upper limits on the abundance of key volatile species such as C₂, C₃, and NH₂. The observations were conducted on May 1, 2024, using the DOLORES, low-resolution spectrograph installed at the TNG. Despite the presence of a strong dust continuum that typically masks faint gas emissions, the team succeeded in detecting CN and measuring a production rate of (3.89 ± 0.21) × 10²⁵ molec/s, while placing stringent upper limits on other common cometary molecules such as C₂, C₃, and NH₂. “Thanks to the sensitivity and reliability of the TNG and its instrumentation, we were able to observe the comet while it was still relatively far from the Sun, capturing its activity in an early stage and constraining its molecular composition before more intense outgassing processes took over” said Pamela Cambianica (INAF – Osservatorio Astronomico di Padova), lead author of the study. The analysis confirmed that C/2023 A3 is carbon-chain depleted, with values of log[Q(C₂)/Q(CN)] < –0.48 and log[Q(C₃)/Q(CN)] < –1.10, in line with other members of the carbon-depleted comet family. The comet also exhibited a high dust production rate, as measured by an Afρ value of 4329 ± 56 cm, adding to the complexity of interpreting spectra from dust-rich environments. This research underscores the crucial role of Telescopio Nazionale Galileo in advancing cometary science, especially through its ability to perform sensitive, early-phase spectroscopic observations of pristine Solar System bodies. More details in the paper “Pre-perihelion observations of the carbon-depleted comet C/2023 A3 (Tsuchinshan-ATLAS). Insights into CN production and molecular upper limits.” Planetary and Space Science, Volume 261, Article 106102. DOI: 10.1016/j.pss.2025.106102 Top panel. Gaussian fit to the CN emission band centered at 3881.68 Å in the comet’s spectrum. The black line represents the observed spectrum, the red line is the fitted Gaussian profile, the blue dashed line indicates the central wavelength, and the shaded area corresponds to the total flux under the curve. Bottom panel. Zoomed-in view of the CN emission band and its Gaussian fit. The detailed view highlights the agreement between the fitted Gaussian profile (red line) and the observed data (black line), with the shaded area representing the integrated flux. The central wavelength is marked by the blue dashed line. Three color image of the comet C/2023 A3 Tsuchinshan-ATLAS taken with LRS@TNG during the night of October 22, 2024.
	Top ^ Home PDF Print Privacy