做好準備 近看木星極光
All Eyes (and Ears) on Jupiter
做好準備，近看木星極光！
As NASA’s Juno spacecraft closes in for its Monday arrival at Jupiter, many other eyes are also staring at the solar system’s largest planet.
美國宇航局(NASA)的“朱諾號”探測器將於週一抵達木星。隨着這一天的臨近，其他很多雙眼睛也在盯着太陽系最大的行星木星。
Data from about 25 observatories — including some of the largest on Earth, like the W. M. Keck Observatory in Hawaii, and in orbit around Earth, like the Hubble Space Telescope — will aid scientists in interpreting the data that Juno is expected to gather as it swoops close to the cloud tops of Jupiter over the next 20 months.
接下來的20個月裏，“朱諾號”預計會在從空中接近木星的表面雲層時收集相關數據。來自大約25個觀測點——包括地球上最大的一些天文臺，如位於夏威夷的W·M·凱克天文臺(W. M. Keck Observatory)，以及繞地軌道上的望遠鏡，如哈勃太空望遠鏡(Hubble Space Telescope)——的數據，將協助科學家對“朱諾號”收集到的數據進行解讀。
An ultraviolet image of the auroras at Jupiter’s north pole in May superimposed on top of an 2014 image made by the Hubble Space Telescope.
5月拍攝到的一幅木星北極的極光紫外圖像，疊映在哈勃太空望遠鏡2014年拍攝的一幅圖上。
It has taken Juno nearly five years to reach this point in its journey.
“朱諾號”用了近五年時間，纔到達這個位置。
“In just a few days, we’re about to arrive at Jupiter, and it’s hard to believe,” Scott Bolton, the mission’s principal investigator, said at a NASA news conference on Thursday.
“幾天後我們就要到達木星了，真是難以置信，”此次任務的首席研究員斯科特·博爾頓(Scott Bolton)週四在NASA的新聞發佈會上說。
Around last Friday, Juno crossed from interplanetary space into the magnetic bubble surrounding Jupiter that deflects the stream of particles from the sun known as the solar wind. “Inside that magnetosphere is Jupiter’s domain that’s filled with its particles,” Dr. Bolton said. “It has blocked out the sun’s particles.”
“朱諾號”於上週五前後穿過星際空間，進入包圍木星的磁泡。磁泡使來自太陽的粒子流，即太陽風發生偏轉。“那個磁力圈裏便是木星的領地，充滿了粒子，”博爾頓說。“它擋住了太陽的粒子。”
One of Juno’s instruments measures radio emissions from the charged particles, and those radio waves are easily converted into sound waves, which sharply changed in tone as the spacecraft crossed the “bow shock,” where Jupiter’s magnetic field plows through the solar wind.
“朱諾號”攜帶的其中一臺儀器，是用來測量帶電粒子的無線電發射的。那些無線電波容易被轉化成聲波。探測器穿過“弓形激波”，即木星的磁場費力地穿過太陽風時形成的激波時，聲波的音調發生鉅變。
“Just the sound of it can tell you it’s nontrivial to go into Jupiter,” Dr. Bolton said, as NASA released the recording of it.
“單是它的聲音就表明進入木星不簡單，”博爾頓在NASA公佈錄音時說。
A couple of days ago, the propulsion system was pressurized in preparation for the firing of the spacecraft’s engine, which will take 35 minutes on Monday. On Thursday, the last set of instructions before the arrival was sent to Juno.
幾天前，爲了準備探測器發動機在週一的點火，推進系統進行了加壓。點火過程將需要35分鐘。週四當天，抵達木星前的最後一組指令已被髮送給“朱諾號”。
“Then it’ll be hands-off from the team,” said Edward Hirst, the mission manager. “The spacecraft is on its own, and it’s designed to take care of itself.”
“然後就沒任務團隊的事了，”任務主管愛德華·赫斯特(Edward Hirst)說。“探測器獨自行動，設計時就考慮了它自行運轉的能力。”
When in orbit, Juno’s instruments will be able to peer deep into Jupiter, but only for a narrow swath. The faraway observations by telescopes will “fill in the blanks to get the big-picture story,” Leigh Fletcher, of the University of Leicester in England, said in an interview. “We’ll have the best observational data set of Jupiter that we’ve ever had.”
進入軌道後，“朱諾號”上的儀器將能深入探測木星，不過只能看到一小片地區。英格蘭萊斯特大學(University of Leicester)的利·弗萊徹(Leigh Fletcher)在接受採訪時表示，望遠鏡的遠距離觀察“將填補空白，讓我們有一個總體的瞭解。我們將獲得有史以來最好的木星觀測數據。”
This week, Dr. Fletcher and his colleagues released infrared photographs of Jupiter seemingly on fire. “You can see the internal glow of Jupiter coming out,” Dr. Fletcher said. “Those clouds are colder and are absorbing in the infrared.”
本週，弗萊徹博士和同事公佈了幾張紅外照片，照片上的木星像是着火了一樣。“能看到從木星內部散發出來的光，”弗萊徹說。“那些雲的溫度要低一些，正在吸收紅外線。”
Once Juno begins orbiting Jupiter, each time that the spacecraft zips in close, the team will take similar photographs using the European Southern Observatory’s Very Large Telescope in Chile “to place the Juno close-up observations in their broader spatial context.”
一旦“朱諾號”開始繞木星運轉，探測器每次接近木星時，任務團隊都會利用歐洲南方天文臺(European Southern Observatory)設在智利的甚大望遠鏡(Very Large Telescope)拍攝類似的照片，“將‘朱諾號’的近距離觀察置於更大範圍的空間背景中。”
For example, Dr. Fletcher said he wanted to piece together Juno’s measurements of ammonia and water — key constituents of Jupiter’s clouds — with the weather patterns seen in the Very Large Telescope pictures.
比如，弗萊徹說他希望把甚大望遠鏡觀測到的天氣規律，和“朱諾號”測量到的氨和水——木星雲層的關鍵成分——數據放在一起。
With Juno providing the first good look at Jupiter’s poles, Dr. Fletcher is curious as to whether huge hurricane-like storms rage, similar to what has been observed in Saturn’s polar regions. The auroras — glowing patterns powered by charged particles slamming into the atmosphere — might also affect the weather.
“朱諾號”將讓人們首次有機會好好觀察木星的兩極。弗萊徹博士想知道，是否會出現像颶風一樣的暴風雨，就像在土星的兩極地區觀察到的那樣。極光——帶電粒子撞向大氣層時產生的發光現象——可能也會影響天氣。
To gain more data on the auroras, the Hubble Space Telescope has been staring at Jupiter for 45 minutes every day for the past month. At Earth, auroras light up when solar wind particles slam into molecules of air near the polar regions. At Jupiter, the charged particles come mostly from a different source: the volcanos of Io. Jupiter’s powerful magnetic fields then accelerate the particles into the planet’s atmosphere.
過去一個月裏，爲了獲取更多有關極光的數據，哈勃太空望遠鏡每天都要盯着木星看45分鐘。在地球上，當太陽風粒子與兩極地區附近的大氣中的分子相撞時，會發生極光現象。在木星上，帶電粒子主要來自另一個來源：木衛一上面的火山。然後，木星強大的磁場促使粒子加速進入木星的大氣層。
At times, the auroras are subdued. At other times, they are “almost like fireworks going off in the ionosphere of Jupiter,” said Jonathan Nichols, a University of Leicester scientist who is leading the Hubble study.
有時候，極光頗爲柔和。但其他時候，它們“幾乎像是木星電離層裏燃放的煙花，”領導哈勃研究的萊斯特大學科學家喬納森·尼克爾斯(Jonathan Nichols)說。
One of the things that is unknown is how much the solar wind contributes to Jupiter’s auroras. “We’ll be working on that over the next few weeks and months,” Dr. Nichols said.
迄今尚待解答的其中一個問題是，太陽風對木星極光的影響有多大。“我們將在接下來的幾周和幾個月裏研究這個問題，”尼克爾斯說。
On Earth, auroras appear over an area about as large as the United States. Jupiter’s auroras, like everything else on Jupiter, are vastly larger, about as wide as five Earths.
在地球上，能看到極光的地區在面積上大約和美國相當。木星的極光區，就像木星上的所有事物一樣，都會大得多，大約相當於地球的五倍。
“But we’ve never been able to get up close and really observe these processes,” Fran Bagenal, a professor of astrophysical and planetary sciences at the University of Colorado and one of the mission scientists, said at the news conference. “So we can then compare them with what we see at Earth, what we seen at Saturn.”
“但我們一直無法接近並真正觀察這些過程，”科羅拉多大學(University of Colorado)研究天體物理和行星科學的教授、參與“朱諾號”探測任務的科學家之一弗蘭·巴格納爾(Fran Bagenal)在新聞發佈會上說。“因此，我們便能把它們和我們在地球和土星上看到的情況進行比較。”
Dr. Bagenal said scientists were curious about whether Jovian auroras were simply larger versions of Earth’s auroras. “Or do we have to really go back to the fundamental physics and work out what’s really going on here?” she asked.
巴格納爾表示，科學家好奇木星上的極光是否只是放大版的地球極光。“還是說我們必須真的回到基礎物理學，弄清楚它到底是怎麼回事？”她問道。
