新华社洛杉矶11月19日电（记者谭晶晶）美国航天局19日公布了由其探测器和空间望远镜拍摄的"星际 访客"——彗星3I/ATLAS的一批最新图像。这颗彗星预计将于12月19日前后飞掠地球，届时它与地球的 最近距离约2.7亿公里，约为地日距离的两倍。 研究人员认为，3I/ATLAS起源于太阳系外的一个恒星系统，在形成后被抛入星际空间，在数百万至数 十亿年的时间里一直在漂流，最近才进入太阳系。 这颗彗星的命名蕴藏着其"身份密码"。其中"ATLAS"代表它的发现者ATLAS研究团队；字母"I"代表"星 际"，说明它是来自太阳系外的天体；数字"3"表示它是第三个被确认的来自星际空间的天体。（完） 今年7月1日，美航天局资助的位于智利的"小行星撞击地球最后警报系统"（ATLAS）巡天望远镜首次发 现该天体。这是迄今被观测到的第三个造访太阳系的星际天体。此后，美航天局已有12台探测设备拍摄 到它，包括哈勃空间望远镜、詹姆斯·韦布空间望远镜、火星探测器等。随着该天体继续穿越太阳系， 预计还会有更多航天器继续捕捉其影像。 据介绍，今年秋季，彗星3I/ATLAS从距离火星约3000万公里处飞掠。当时美航天局3个火星探测器对其 进 ...

Core Insights - The COSMOS-Web project has released the largest cosmic map and observational data to date, based on data collected by the James Webb Space Telescope (JWST), covering over 780,000 galaxies and spanning 13.5 billion years, which represents 98% of the universe's history [1][2] - The goal of the research team is to create an unprecedented ultra-deep wide-angle image of the universe, with the COSMOS-Web image being equivalent to a mural of approximately 4 meters in length and over 15 square meters in area, significantly larger than the Hubble Space Telescope's deep field image [1] - JWST has discovered a number of ancient galaxies far exceeding expectations, finding ten times more galaxies than previously predicted within the first 500 million years after the universe's birth, along with supermassive black holes that were undetectable during the Hubble era [2] Data and Accessibility - The released data includes not only ultra-deep space images but also a detailed galaxy catalog, which is made available to researchers worldwide [3]

Core Findings - An international team led by astronomer Nikku Madhusudhan from Cambridge University has published findings in the Astrophysical Journal Letters, indicating the discovery of the "strongest evidence" for potential life activity outside the solar system in the atmosphere of exoplanet K2-18b, located approximately 124 light-years away from Earth [1][2] - The atmosphere of K2-18b contains chemical signatures of dimethyl sulfide (DMS) and dimethyl disulfide (DMDS), which are associated with biological processes on Earth [1][2] - This research utilized the James Webb Space Telescope (JWST) to analyze the starlight passing through the planet's atmosphere, revealing the presence of these complex organic molecules, which are more intricate than methane [1][2] Exoplanet Characteristics - K2-18b is one of the most common types of exoplanets discovered, with a mass approximately 8.6 times that of Earth and a volume about 2.6 times larger, situated within the habitable zone [2] - Previous studies using the Hubble Space Telescope suggested that K2-18b's atmosphere was rich in water vapor, although later analyses indicated that the observed water vapor might actually be methane [2] - The recent study confirmed the presence of methane and carbon dioxide in K2-18b's atmosphere and proposed the existence of dimethyl sulfide for the first time, achieving a detection confidence level of 3.4, which is considered a significant threshold in astronomical observations [2] Scientific Debate - There is skepticism among some researchers regarding the findings, with concerns about potential noise interference in the observational data and the possibility that reported features could be statistical fluctuations [3] - Alternative models could explain the observed data, and some scientists suggest that K2-18b may resemble a gaseous planet like Neptune, potentially lacking a solid surface [3] - The origin of dimethyl sulfide is also debated, with some experts proposing that it could arise from non-biological processes or even from interstellar medium [3] Future Exploration - The search for extraterrestrial life continues to be a significant focus, with various countries developing plans for exoplanet exploration, including China's Tianling Plan and the U.S. Habitable Worlds Observatory project [4] - Advancements in astronomical telescopes, atmospheric modeling, and astrobiology are expected to enhance the understanding of potential life signals in the universe [4]