这颗彗星从何而来
巴黎天文台天体物理学家尼古拉·比韦（ Nicolas Biver） 表示，这颗彗星直径据估算约为1公里，散发绿光，可能来自太阳系外围的“奥尔特云”，可能在此次造访后“被永久逐出太阳系”。
The comet was believed to have come from the Oort Cloud, a theorized vast sphere surrounding the solar system that is home to mysterious icy objects.
这颗彗星可能来自于“奥尔特云”，这片巨大区域位于太阳系外围，是神秘的冰冻天体的家园。
The comet was believed to have come from the Oort Cloud, a theorized vast sphere surrounding the solar system that is home to mysterious icy objects.
这颗彗星可能来自于“奥尔特云”，这片巨大区域位于太阳系外围，是神秘的冰冻天体的家园。
“奥尔特云”是太阳系距我们最遥远的区域。即使是“奥尔特云”中距太阳最近的天体，也被认为比“柯伊伯带”中的任何天体远许多倍。
The Oort Cloud is the most distant region of our solar system. Even the nearest objects in the Oort Cloud are thought to be many times farther from the Sun than the outer reaches of the Kuiper Belt.
Kuiper Belt：柯伊伯带 位于太阳系的海王星轨道（距离太阳约30天文单位）外侧，在黄道面附近的天体密集圆盘状区域。
The Oort Cloud is the most distant region of our solar system. Even the nearest objects in the Oort Cloud are thought to be many times farther from the Sun than the outer reaches of the Kuiper Belt.
Kuiper Belt：柯伊伯带 位于太阳系的海王星轨道（距离太阳约30天文单位）外侧，在黄道面附近的天体密集圆盘状区域。
这颗彗星外观有何特点
据比韦介绍，这颗彗星由冰和尘埃组成，散发出绿色的光环，估计直径约为一公里。相比上一颗肉眼可见的“新智慧星”（NEOWISE），即将造访地球的C/2022 E3 (ZTF) 体积小得多。
Made of ice and dust and emitting a greenish aura, the comet is estimated to have a diameter of around a kilometer, said Nicolas Biver. That makes it significantly smaller than NEOWISE, the last comet visible with an unaided eye.
aura /ˈɔːrə/ n. 光环，氛围
Made of ice and dust and emitting a greenish aura, the comet is estimated to have a diameter of around a kilometer, said Nicolas Biver. That makes it significantly smaller than NEOWISE, the last comet visible with an unaided eye.
aura /ˈɔːrə/ n. 光环，氛围
此前最近的一颗肉眼可见、影响力比较大的彗星是1997年的海尔波普彗星。
彗星（comet）是什么
2020年7月23日，在英国英格兰威尔特郡的巨石阵，新智彗星划过天际
图源：新华社
Comets are frozen leftovers from the formation of the solar system composed of dust, rock, and ices. As they orbit closer to the Sun, they heat up and spew gases and dust into a glowing head that can be larger than a planet. This material forms a tail that stretches millions of miles.
彗星是由尘埃、岩石和冰组成的太阳系形成的冰冻残留物。当接近太阳时，它们会被加热并开始释气和尘埃，变成一个比行星还大的发光体，尘埃和气体形成一条延伸数百万英里的尾巴。
Comets are frozen leftovers from the formation of the solar system composed of dust, rock, and ices. As they orbit closer to the Sun, they heat up and spew gases and dust into a glowing head that can be larger than a planet. This material forms a tail that stretches millions of miles.
彗星是由尘埃、岩石和冰组成的太阳系形成的冰冻残留物。当接近太阳时，它们会被加热并开始释气和尘埃，变成一个比行星还大的发光体，尘埃和气体形成一条延伸数百万英里的尾巴。
BBC旗下的《仰望夜空》（Sky at Night）杂志称，这颗彗星不会带来“新智慧星”出现时的惊艳瞬间，也没有长长的彗星尾巴。相反，C/2022 E3（ZTF）看起来更像是天空中的一块污迹，就像有人用手指蘸了粉笔灰，然后在黑板上擦了一下。
It’s important to say straight from the start that C/2022 E3 (ZTF) will not repeat the memorable show NEOWISE gave us. A long misty NEOWISE-like tail is unlikely too.
Instead C/2022 E3 (ZTF) will more likely look like a smudgein the sky, like someone has dipped their finger in chalk dust and dabbed it on a blackboard.
smudge /smʌdʒ/ n. 污点，污迹
It’s important to say straight from the start that C/2022 E3 (ZTF) will not repeat the memorable show NEOWISE gave us. A long misty NEOWISE-like tail is unlikely too.
Instead C/2022 E3 (ZTF) will more likely look like a smudgein the sky, like someone has dipped their finger in chalk dust and dabbed it on a blackboard.
smudge /smʌdʒ/ n. 污点，污迹
何时观测最佳
尽管此次彗星将在2月初通过近地点时亮度最高，但届时满月可能影响观测。比韦建议，北半球最佳观测时间为1月最后一周，“我们可能收获一个惊喜，彗星亮度可能是预期的两倍”。
美国加州理工学院物理学教授、兹威基瞬态研究设施研究员托马斯·普林斯（Thomas Prince）表示，另一个不错的观测时间是2月10日，那时这颗彗星将经过火星附近。
The new moon during the weekend of January 21-22 offers a good chance for stargazers, Biver said. Another opportunity to locate the comet in the sky will come on February 10, when it passes close to Mars, said Thomas Prince, a physics professor at the California Institute of Technology who works at the Zwicky Transient Facility.
The new moon during the weekend of January 21-22 offers a good chance for stargazers, Biver said. Another opportunity to locate the comet in the sky will come on February 10, when it passes close to Mars, said Thomas Prince, a physics professor at the California Institute of Technology who works at the Zwicky Transient Facility.
图源：NASA
据记载，彗星上一次经过地球是在旧石器时代晚期，当时尼安德特人依然存在。普林斯预计，这颗彗星下一次造访太阳系内部预计在5万年后。
The last time the comet passed Earth was during the Upper Paleolithic period, when Neanderthals still roamed Earth. Prince said the comet's next visit to the inner solar system was expected in another 50,000 years.
Paleolithic period：旧石器时代
Neanderthal：尼安德特人
The last time the comet passed Earth was during the Upper Paleolithic period, when Neanderthals still roamed Earth. Prince said the comet's next visit to the inner solar system was expected in another 50,000 years.
Paleolithic period：旧石器时代
Neanderthal：尼安德特人
无论如何，这位“罕见的访客”都将为我们提供关于“太阳系居民”前所未有的信息。
Notes
太阳系 solar system
行星 planet
彗星 comet
小行星 asteroid
矮行星 dwarf planet
冥王星 Pluto
水星 Mercury
金星 Venus
地球 Earth
火星 Mars
木星 Jupiter
土星 Saturn
天王星 Uranus
海王星 Neptune
来源：新华社 AFP Sky at Night Magazine NASA返回搜狐，查看更多