地球上最新的一顆小衛(wèi)星將在明天離開(kāi)我們之前運(yùn)行最后一圈

地球上最新的一顆小衛(wèi)星將在明天離開(kāi)我們之前運(yùn)行最后一圈

Last September, astronomers discovered 2020 SO, a small near-Earth object approaching our planet. In November, it was temporarily captured by Earth's gravity and spent a brief spell in close orbit, becoming what is known as a "mini-moon". But now its time with us has ended and on February 2, it will break free and return to its orbit around the Sun.

去年9月，天文學(xué)家發(fā)現(xiàn)了2020年，一個(gè)小型近地天體正在接近我們的星球。去年11月，它被地球引力暫時(shí)捕獲，在近軌道上停留了一段時(shí)間，成為了所謂的“迷你月亮”。但現(xiàn)在它與我們?cè)谝黄鸬臅r(shí)間已經(jīng)結(jié)束，2月2日，它將掙脫束縛，返回繞太陽(yáng)運(yùn)行的軌道。

But first, mini-moon 2020 SO will make one final close approach to us at roughly 220,000 kilometers (140,000 miles) from Earth, just over halfway between Earth and the Moon.

但首先，迷你月球2020年將在距離地球約22萬(wàn)公里(14萬(wàn)英里)的地方最后一次接近我們，距離地球和月球的一半多一點(diǎn)。

Temporary satellites are fairly common. Small asteroids are captured for a brief time before going about their business away from Earth. But since the first detections of 2020 SO, researchers suspected that the new mini-moon was not in fact a natural object, but artificial.

臨時(shí)衛(wèi)星相當(dāng)普遍。小小行星在離開(kāi)地球之前會(huì)被捕獲一小段時(shí)間。但自從2020年第一次探測(cè)到這顆衛(wèi)星以來(lái)，研究人員懷疑這顆新的迷你月亮實(shí)際上不是一個(gè)自然物體，而是人造的。

Dr Alfredo Carpineti

It had a low relative velocity compared to Earth and sunlight significantly affected its orbit, a clear way to distinguish between natural and artificial small bodies in the proximity of Earth.

與地球相比，它的相對(duì)速度較低，陽(yáng)光明顯影響它的軌道，這是區(qū)分靠近地球的自然小天體和人造小天體的明確方法。

Light can be interpreted as a wave and as a particle. When we consider these particles, the photons, we are looking at massless particles that carry momentum, which means they can push things about. This is how solar sails work. In the case of 2020 SO, having a large surface area and a relatively light mass, led to the body showing an acceleration that could not be explained with gravity.

光既可以解釋為波，也可以解釋為粒子。當(dāng)我們考慮這些粒子，光子時(shí)，我們看到的是無(wú)質(zhì)量的帶有動(dòng)量的粒子，這意味著它們可以推動(dòng)物體。這就是太陽(yáng)帆的工作原理。在2020年的例子中，由于表面積大，質(zhì)量相對(duì)較輕，導(dǎo)致物體呈現(xiàn)出重力無(wú)法解釋的加速度。

"Solar radiation pressure is a non-gravitational force that is caused by light photons emitted by the Sun hitting a natural or artificial object," Davide Farnocchia, a navigation engineer at JPL who analyzed 2020 SO's trajectory for the Center for Near-Earth Object Studies (CNEOS), explained back in November. "The resulting acceleration on the object depends on the so-called area-to-mass ratio, which is greater for small and light, low-density objects."

“太陽(yáng)輻射壓力是一種非重力力，是由太陽(yáng)發(fā)射的光子撞擊自然或人造物體引起的，”噴氣推進(jìn)實(shí)驗(yàn)室的導(dǎo)航工程師戴維·法諾奇亞在11月解釋說(shuō)，他為近地天體研究中心分析了2020年的軌道。“物體產(chǎn)生的加速度取決于所謂的面積質(zhì)量比，這對(duì)于小、輕、低密度的物體來(lái)說(shuō)更大。”

This was an important piece of evidence suggesting 2020 SO was human-made, but another came from a detailed projection of its orbital parameters into the distant past. The object has gotten close to our planet several times, but in 1966 it was so close that it could have actually originated from Earth. In fact, it matched the launch of NASA's lunar lander.

這是一個(gè)重要的證據(jù)，表明2020年是人造的，但另一個(gè)證據(jù)來(lái)自對(duì)它的軌道參數(shù)對(duì)遙遠(yuǎn)過(guò)去的詳細(xì)預(yù)測(cè)。該天體曾多次接近地球，但在1966年，它離地球如此之近，以至于它實(shí)際上可能起源于地球。事實(shí)上，它與美國(guó)國(guó)家航空航天局(NASA)發(fā)射的月球著陸器相匹配。

"One of the possible paths for 2020 SO brought the object very close to Earth and the Moon in late September 1966," said CNEOS Director Paul Chodas. "It was like a eureka moment when a quick check of launch dates for lunar missions showed a match with the Surveyor 2 mission."

CNEOS主任保羅·喬達(dá)斯說(shuō):“2020年的一條可能路徑是在1966年9月下旬使這顆天體非常接近地球和月球。”“當(dāng)對(duì)月球發(fā)射日期的快速檢查顯示與‘勘測(cè)者2號(hào)’的任務(wù)匹配時(shí)，這就像是一個(gè)頓悟的時(shí)刻。”

Observations in December, after its first close passage, revealed that it was made of stainless steel, confirming that it was indeed an old piece of the Surveyor 2 Centaur rocket's upper stage, launched on September 20, 1966.

在它第一次近距離飛行后，12月的觀測(cè)顯示它是由不銹鋼制成的，證實(shí)它確實(shí)是1966年9月20日發(fā)射的“勘測(cè)者2號(hào)”半人馬座火箭上一級(jí)的舊部件。

After tomorrow’s close passage, the piece of rocket will go back into deep space but it will continue to visit us over the next few decades despite staying millions of kilometers away from us.

在明天的近距離飛行后，這塊火箭碎片將返回深空，但它將在未來(lái)幾十年繼續(xù)訪問(wèn)我們，盡管它距離我們數(shù)百萬(wàn)公里。