NASA space probe ‘phones home’ in landmark mission to solar system’s edge 最遠距離最近觀測 「新視野號」新年喜報平安

Sun, Jan 06, 2019 - Page 9

NASA’s New Horizons explorer successfully “phoned home” on Tuesday after a journey to the most distant world ever explored by humankind, a frozen rock at the edge of the solar system that scientists hope will uncover secrets to its creation. The nuclear-powered space probe has traveled 6.4 billion km to come within 3,540km of Ultima Thule, an apparently peanut-shaped, 32-km-long space rock in the uncharted heart of the Kuiper Belt. The belt is a ring of icy celestial bodies just outside Neptune’s orbit.

Engineers at Johns Hopkins Applied Physics Laboratory in Maryland cheered when the spacecraft’s first signals came through the NASA Deep Space Network at 10:28am EST. “We have a healthy spacecraft,” Mission Operations Manager Alice Bowman declared. The spacecraft will ping back more detailed images and data from Thule in the coming days, NASA said.

Launched in January 2006, New Horizons embarked on its 6.4 billion km journey toward the solar system’s edge to study the dwarf planet Pluto and its five moons. “Last night, overnight, the US spacecraft New Horizons conducted the farthest exploration in the history of humankind, and did so spectacularly,” New Horizons principle investigator Alan Stern told a news conference at the Johns Hopkins facility in Laurel, Maryland.

An image of Thule, sent overnight and barely more detailed than previous images, deepens the mystery of whether Thule is a single rock shaped like an asymmetrical peanut or actually two rocks orbiting each other, “blurred together because of their proximity,” Stern said.

During a 2015 fly-by, the probe found Pluto to be slightly larger than previously thought. In March, it revealed methane-rich dunes on the icy dwarf planet’s surface. Now 1.6 billion km beyond Pluto for its second mission into the Kuiper Belt, New Horizons will study the makeup of Ultima Thule’s atmosphere and terrain in a months-long study to seek clues about the formation of the solar system and its planets. Scientists had not discovered Ultima Thule when the probe was launched, according to NASA, making the mission unique in that respect. In 2014, astronomers found Thule using the Hubble Space Telescope and the following year selected it for New Horizon’s extended mission.

As the probe flies 3,540km above Thule’s surface, scientists hope it will detect the chemical composition of its atmosphere and terrain in what NASA says will be the closest observation of a body so remote. “We are straining the capabilities of this spacecraft, and by tomorrow we’ll know how we did,” Stern told reporters on Monday. “There are no second chances for New Horizons.”

While the mission marks the farthest close encounter of an object within our solar system, NASA’s Voyager 1 and 2, a pair of deep-space probes launched in 1977, have reached greater distances on a mission to survey extrasolar bodies. Both probes are still operational.

(Reuters)

美國國家航空暨太空總署的「新視野號」太空船於週二成功打通電話向地球報平安。這趟長途旅程造訪了一顆位於太陽系邊緣的冰封岩石,是人類迄今探索過最遙遠的星體,科學家盼望能藉此揭開太陽系的創造之謎。這艘核子動力的太空探測船已航行六十四億公里,來到距離「終極遠境」三千五百四十公里處。「終極遠境」是一顆形似花生、長三十二公里的太空岩石,位於人類未曾探索過的古柏帶中心,古柏帶則是一圈環繞在海王星運行軌道外側的結冰天體。

美東時間早上十點二十八分,太空船的第一批訊號透過美國太空總署的「深太空通訊網」傳回地球,守候在馬里蘭州約翰霍普金斯大學應用物理實驗室的工程師們紛紛歡呼。任務執行主管艾莉斯‧鮑曼隨即宣布:「我們的太空船健康狀況良好。」美國太空總署也表示,在接下來的幾天內,這艘太空船還會繼續從「終極遠境」傳回更多詳細的影像與資料。

「新視野號」太空船發射於二○○六年一月,就此展開這趟飛向太陽系邊緣、距地球六十四億公里遠的長途旅程,為的是研究矮行星「冥王星」及其五顆衛星。應用物理實驗室由約翰霍普金斯大學設立於馬里蘭州的勞瑞爾市,在該研究機構舉行的記者會中,「新視野號」首席科家學艾倫‧史登表示:「昨晚,就在一夜之間,美國太空船『新視野號』執行了人類歷史上最遠的探測任務,而且此回行動讓人讚嘆不已。」

這次徹夜傳回的「終極遠境」影像僅比先前的影像稍微清晰一點,遂加深了「終極遠境」的神秘謎團,令人好奇它究竟是形似不對稱花生的單一岩石星體,還是如史登所言,實際上是兩顆互相繞行彼此的岩石星體,「因為太過相鄰而模糊不清」。

在二○一五年的飛掠任務中,探測船發現冥王星比人們之前認為的還要稍大一些。該年三月,探測船更揭露出這顆冰冷矮行星表面有一片富含甲烷的沙丘。為了執行第二次古柏帶探勘任務,「新視野號」現已飛離冥王星十六億公里遠,將在長達數月的調查任務中研究「終極遠境」的大氣組成和地貌,以期找出形成太陽系和其行星的線索。美國太空總署表示,科學家在探測船發射當時,尚未發現「終極遠境」的存在,讓任務就此層面而言更具獨特性。二○一四年,天文學家利用哈伯太空望遠鏡發現「終極遠境」,遂於隔年選擇此星體作為「新視野號」的延伸任務目標。

隨著探測船飛到距離「終極遠境」表面三千五百四十公里的上空,科學家希望它能偵測出該星體大氣層的化學成份組成和地貌。美國太空總署表示,這項將會是目前對於遙遠天體的最近距離觀測。史登週一時向記者表示:「我們正在把這台太空船的性能伸展到極限,到明天我們就會知道成果如何。」他也指出:「『新視野號』不會再有第二次機會。」

這項任務標誌著我們對太陽系內最遙遠星體的最近距離觀察,不過美國太空總署的「旅行家一號」和「旅行家二號」──於一九七七年發射的一組深太空探測船──目前已經抵達更遠的距離,任務是調查外太陽系天體。兩台探測船目前仍在運行中。

(台北時報章厚明譯)