The Real Final Frontier
Don: You know what amazes me? Voyager!
Yaël: Me too! Did you see the one were seventh of nine gets a face-lift?
D: I don't mean that TV show. I mean the real thing --- the Voyager spacecraft launched by NASA twenty-six years ago. For years this probe sent back amazing pictures of the outer planets in our solar system before sailing off into space. Now, Voyager is ninety times as far from the sun as we are, and is about to reach the Termination Shock.
Y: The Termination Shock? You sure this isn't a sci-fi?
D: Not at all. The Termination Shock is one of two proposed boundaries to our solar system. You can say that the solar system ends with Pluto. Astrophysicists, however, think of the solar system as extending farther out to include two less obvious, but just as real, outer edges.
One is the Termination Shock, where the charged particles blown out by the sun–and known as the “solar wind”–slow down abruptly, thanks to the pressure from other charged particles coming from deep space. Beyond that is the edge of the Heliosphere, which is where the solar wind finally ends.
The Voyager probe is just now crossing the Termination Shock. In another fifteen years or so it will pass the outer edge of the Heliosphere–a human-made object moving for the first time in history into true interstellar space. It’s an awesome thought.
Y: That is cool!
真正的邊界
Don: 你知道是什么東西讓我大開(kāi)眼界嗎?Voyager!
Yaël: 我也是呢。你看到被做了大幅度改造的那一期了嗎?
D: 我說(shuō)的不是電視節(jié)目,是真的東西——美國(guó)航空航天局(NASA)26年前發(fā)射的旅行者號(hào)探測(cè)器。在飛出太陽(yáng)系之前,數(shù)年來(lái),旅行者號(hào)不斷地傳回太陽(yáng)系內(nèi)讓人嘆為觀止的圖片。現(xiàn)在,旅行者號(hào)距離地球非常遙遠(yuǎn),相當(dāng)于地球與太陽(yáng)距離的90倍,快要達(dá)到太陽(yáng)系的終點(diǎn)(Termination Shock)了。
Y: 極限?你確定這不是在講科幻故事?
D: 完全不是。Termination Shock是人類(lèi)提出的太陽(yáng)系的兩個(gè)邊界點(diǎn)之一。你可以說(shuō)太陽(yáng)系的邊界是冥王星。然而,我們的天文物理學(xué)家們認(rèn)為,太陽(yáng)系不斷向外外延伸至兩個(gè)不是很明顯但是確確實(shí)實(shí)存在的邊界點(diǎn)。
一個(gè)就是我們的Termination Shock,由于深層空間內(nèi)射出的帶電粒子流所形成的氣壓的作用,太陽(yáng)所射出的離子體帶電粒子流——也就是我們所熟知的“太陽(yáng)風(fēng)”——在這里驟然減速。除此之外,另外一個(gè)就是日光層的的邊緣,太陽(yáng)風(fēng)最終會(huì)在這里完全停下來(lái)。
旅行者號(hào)探測(cè)器現(xiàn)在正在穿越Termination Shock。再過(guò)15年左右,旅行者號(hào)將會(huì)穿過(guò)更外圍的日光層,成為史上首個(gè)進(jìn)入星際空間的人造物體。這真的太讓人驚嘆了!
Y: 真的很酷呢!