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2026 年 11 月 18 日，人类太空探索史将迎来一个标志性节点：NASA 旅行者 1 号探测器将在发射 49 年后，首次跨越距太阳一光日的距离——约 161 亿英里（约 259 亿公里）。这意味着，从太阳发出的光需要整整一天的时间才能追上这颗人类制造的最远飞行器。对于仍在深空网络支持下回传科学数据的旅行者双子而言，这不仅是一个距离刻度，更是行星际探测工程持续近半个世纪的见证。
175 年一遇的窗口：宏大之旅的起点
1977 年，NASA 抓住了太阳系四颗最大行星——木星、土星、天王星、海王星——约每 175 年才出现一次的特殊排列几何窗口，发射了旅行者 1 号和 2 号双子探测器。借助行星引力弹弓效应，两艘探测器共完成六次引力助推，逐一掠过气态与冰态巨行星，传回了木星大红斑、土星环细节、天王星与海王星及其卫星的近距离影像。这些观测成果直接为此后伽利略号木星轨道器、卡西尼号土星轨道器等雄心勃勃的任务奠定了基础。
1980 年代，两颗探测器在土星附近分道扬镳：旅行者 2 号继续飞向天王星和海王星，完成了至今唯一的冰巨星近距离造访；旅行者 1 号则调转相机，在告别内太阳系前拍摄了那张著名的“暗淡蓝点”——地球在 64 亿公里外仅是一粒悬浮在光束中的微尘。2012 年 8 月与 2018 年 11 月，两艘探测器先后穿越日球层顶——太阳风与星际介质交汇的边界，正式进入星际空间，成为迄今仅有的人造星际探测器。
【关键数据】
- 发射时间: 1977 年，利用 175 年一遇的行星排列窗口
- 一光日距离: 161 亿英里，约合 259 亿公里（2026 年 11 月 18 日跨越）
- 镀金唱片: 收录 55 种语言问候、27 首乐曲、116 张图像
- 铀-238 半衰期: 44.68 亿年，用于帮助外星文明推算唱片年代
- 日球层顶穿越: 旅行者 1 号 2012 年 8 月，旅行者 2 号 2018 年 11 月
一光日：用光丈量的深空刻度
许多人熟知“光年”，但“光分”“光日”这类单位衡量的同样是距离而非时间——光在真空中传播一分钟或一天所走过的路程。对深空探测而言，这是最直观的测距方式。目前，NASA 深空网络通过堪培拉站天线持续跟踪旅行者 1 号，其距离已达 258 亿公里。换算成通信延迟，地球发出的指令需要约一昼夜才能抵达探测器，这对任务测控提出了近乎极限的挑战，也解释了为何两艘探测器的每一次数据回传都弥足珍贵。
值得关注的还有探测器携带的那张金色唱片——一张 12 英寸铜质镀金唱片，封存着来自地球的声音与图像：55 种语言的问候、27 首乐曲、116 张图像，以及海浪、雷鸣、鸟鸣等自然之声。铝质唱片封套上蚀刻着太阳相对于 14 颗脉冲星的位置及播放说明，并电镀了一层超高纯度铀-238 同位素——其 44.68 亿年的半衰期，相当于为未来可能拾获它的文明提供了一枚天然“时钟”。
老化探测器的最后征程
两艘旅行者探测器的同位素热电电源正以每年约 4 瓦的速率衰减，NASA 已陆续关闭部分科学仪器以延长任务寿命。按现有电力水平估算，它们大约能在 2030 年代维持最低限度的科学运作。从长期看，即便通讯彻底中断，两艘探测器仍将以每秒约 17 公里的速度继续漂向银河系深处——旅行者 1 号将在约 4 万年后掠过鹿豹座方向的恒星邻域。
跨越一光日，是工程意义上的又一个坐标，也是人类探测器向星际深空延伸的最新刻度。在 6G、深空通信等技术加速演进的当下，旅行者任务所积累的超远距离测控经验，仍将为未来的星际探测任务提供不可替代的参照。49 年的漫长飞行提醒我们：最伟大的工程壮举，往往始于对一次罕见宇宙窗口的精准把握。
出处：November’s Night Sky Notes: Light-Day Away
英文原文2 min read November’s Night Sky Notes: Light-Day Away NASA’s Voyager mission took advantage of a once-every-175-year alignment of the outer planets for a grand tour of the solar system. The twin spacecraft revealed details about Jupiter, Saturn, Uranus and Neptune – using each planet’s gravity to send them on to the next destination. Voyager set the stage for such ambitious orbiter missions as Galileo to Jupiter and Cassini to Saturn. Today both Voyager spacecraft continue to return valuable science from the far reaches of our solar system. NASA/JPL-Caltech Twin Travelers In 1977, NASA launched twin spacecraft Voyager 1 and 2, taking advantage of a once-every-175-year planetary alignment of the four largest planets in our solar system: Jupiter, Saturn, Uranus, and Neptune. Using six gravity assists between them, this Grand Tour gave us up-close views of the gas and ice giants, including several moons. By the 1980s, the two probes went their separate ways at Saturn. As Voyager 2 continued toward Uranus and Neptune, Voyager 1 grabbed one more portrait of the solar system (excluding Mercury and Mars), including a final image of the pale blue dot we call home. The Golden Record Cover NASA/JPL-Caltech Playlist “Hello from the children of planet Earth.” Every good road trip needs some music to match. In this case, each craft carries the Golden Record , a 12-inch phonograph record with spoken greetings in 55 languages, 27 musical tracks, 116 images, and other sounds from Earth. Each record is protected by an outer cover featuring etchings showing our Sun’s location relative to 14 pulsars, along with instructions on how to play it. The design used various metals to protect the information encoded from space radiation: the record used copper and gold plating, and the cover used aluminum. The cover was electroplated with an ultra-pure sample of the isotope uranium-238. Uranium-238 has a half-life of 4.468 billion years. Are We There Yet? Did you know that a light-minute is a measure of distance, not time? In August 2012 and November 2018, Voyager 1 and 2 crossed the heliopause, the boundary where the Sun’s solar wind meets the interstellar medium. Using NASA’s Deep Space Network , Earth communicates with both spacecraft and tracks each on its journey. At the time of this article, the Canberra antenna tracked Voyager 1 at 25.80 billion km, or just over 16 billion miles. This graphic shows the position of NASA’s Voyager 1 and Voyager 2 probes, outside of the heliosphere, a protective bubble created by the Sun that extends well past the orbit of Pluto. NASA/JPL-Caltech On November 18, 2026, 49 years after its launch, Voyager 1 will cross the one-light-day mark, 16.1 billion miles from the Sun. You may have heard the term light-year in your favorite sci-fi movie or show, or when stargazing and referring to an object outside of our solar system. This video best demonstrates the different distances between the inner solar system, outer solar system, and beyond, using light measurements. Additionally, track each Voyager spacecraft here . You can get a real understanding of what a gravity assist might be like with our Gravity Assist activity and learn what it’s like to measure a “light minute” with our Measuring a Kid Minute activity guide!
