Letter to the Editor

New constraints on Triton’s atmosphere from the 6 October 2022 stellar occultation

¹ Purple Mountain Observatory, Chinese Academy of Sciences, No. 10 Yuanhua Road, Nanjing 210033, PR China
e-mail: yuanye@pmo.ac.cn
² School of Astronomy and Space Science, University of Science and Technology of China, No. 96 Jinzhai Road, Hefei, Anhui 230026, PR China
³ Xinjiang Astronomical Observatory, Chinese Academy of Sciences, 150 Science 1-Street, Urumqi, Xinjiang 830011, PR China
⁴ Xingming Observatory, Urumqi, Xinjiang 830000, PR China
⁵ School of Landscape Architecture, Beijing Forestry University, 35 Qinghua E Rd, Haidian, Beijing 100083, PR China
⁶ Nanjing Institute of Astronomical Optics & Technology, Chinese Academy of Sciences, No. 188 Bancang Street, Nanjing 210042, PR China
⁷ CAS Key Laboratory of Astronomical Optics & Technology, Nanjing Institute of Astronomical Optics & Technology, Nanjing 210042, PR China
⁸ University of Chinese Academy of Sciences, No.1 Yanqihu East Rd, Huairou District, Beijing 101408, PR China
⁹ FuJian Astronomical Society, 3a-2303, phase 2, Shimao cuican Tiancheng, Jimei District, Xiamen, Fujian 361000, PR China
¹⁰ , Room 511-59, No. 28, Song Yang Yili, Fengxiang Street, Xiang’an District, Xiamen 361000, PR China
¹¹ Beijing Amateur Astronomer Sodality, Beijing 100000, PR China
¹² Dongguan Foreign Language School, No. 2 Hengtang Road, Dongguan, Guangdong 523413, PR China
¹³ Dongguan Science Museum, No. 38 Xinfen Road, Dongguan, Guangdong 523000, PR China
¹⁴ Amateur Astornomrs Association Of Maoming, Room 101-1,Unit 4 of Building 50, North Renmin Road, Maoming, Guangdong 525000, PR China
¹⁵ JiNan Amateur Astronomy Association, Jinan, Shandong 250000, PR China
¹⁶ Qixing Observatory, Jinan, Shandong 250000, PR China
¹⁷ College of Physics and Elctronic Engineering, Sichuan Normal University, No. 1819, Section 2, Chenglong Avenue, Longquan District, Chengdu 610101, PR China
¹⁸ Xiamen Minli Primary School, No. 1 Shengping Road, Xiamen, Fujian 361001, PR China
¹⁹ Duzhou Primary School, Shipai Town, Dongguan, Guangdong 523000, PR China
²⁰ School of Physics and Astronomy, Sun Yat-Sen University, No. 135, Xingang Xi Road, Guangzhou 510275, PR China
²¹ Foshan Xingkai Technology Co., Ltd, Foshan 528200, PR China
²² Dalian Bootes Astronomical Society, Dalian, Liaoning 116000, PR China
²³ BCTO, No. 5 Chaogui South Road, Foshan, Guangdong 528300, PR China
²⁴ XingYuan College, Ocean University of China, No. 238 Songling Road, Qindao, Shandong 266100, PR China
²⁵ Quzhou Astronomical Association, Quzhou, Zhejiang 324000, PR China
²⁶ Hunan Astronomical Association, Changsha, Hunan 410000, PR China
²⁷ Nanjing Amateur Astronomers Association, Nanjing 210000, PR China
²⁸ Shenzhen Astronomical Observatory, Tianwen Road, Shenzhen, Guangdong 518040, PR China
²⁹ Department of Space Sciences and Astronomy, Hebei Normal University, No. 20 Road East. 2nd Ring South, Shijiazhuang, Hebei 050024, PR China

Received: 1 November 2023
Accepted: 11 March 2024

Abstract

The atmosphere of Triton was probed directly by observing a ground-based stellar occultation on 6 October 2022. This rare event yielded 23 positive light curves collected from 13 separate observation stations contributing to our campaign. The significance of this event lies in its potential to directly validate the modest pressure fluctuation on Triton, a phenomenon not definitively verified by previous observations, including only five stellar occultations, and the Voyager 2 radio occultation in 1989. Using an approach consistent with a comparable study, we precisely determined a surface pressure of 14.07_−0.13^+0.21 μbar in 2022. This new pressure rules out any significant monotonic variation in pressure between 2017 and 2022 through direct observations, as it is in alignment with the 2017 value. Additionally, both the pressures in 2017 and 2022 align with the 1989 value. This provides further support for the conclusion drawn from the previous volatile transport model simulation, which is consistent with the observed alignment between the pressures in 1989 and 2017; that is to say, the pressure fluctuation is modest. Moreover, this conclusion suggests the existence of a northern polar cap extended down to at least 45°N–60°N and the presence of nitrogen between 30°S and 0°.