天文學(xué)家在太陽系外發(fā)現(xiàn)了一群巖石

天文學(xué)家在太陽系外發(fā)現(xiàn)了一群巖石

Astronomers think they’ve found an entire population of asteroids originating from outside our solar system, according to a new paper.

根據(jù)一篇新論文，天文學(xué)家們認(rèn)為他們已經(jīng)發(fā)現(xiàn)了來自太陽系外的整個(gè)小行星群。

The objects at the centre of this investigation aren’t new discoveries. Called the Centaurs, they’re mysterious asteroids that orbit in the neighbourhood of Jupiter and beyond. These objects take highly inclined orbits relative to the plane of the rest of the planets, and in at least one case, orbit the “wrong” way relative to the rest of the solar system’s objects. By playing the laws of physics in reverse, scientists Fathi Namouni at the Université Côte d’Azur in France and Helena Morais at UNESP in Brazil found that 19 of these objects likely originated around another star.

這次調(diào)查的中心對象并不是新發(fā)現(xiàn)。它們被稱為半人馬座，是一種神秘的小行星，在木星附近或更遠(yuǎn)的地方運(yùn)行。這些天體的軌道相對于其他行星的平面高度傾斜，至少在一種情況下，它們的軌道相對于太陽系其他天體的方向是“錯(cuò)誤的”。法國科特迪瓦大學(xué)的科學(xué)家法特希·納穆尼和巴西聯(lián)合國環(huán)境規(guī)劃署的海倫娜·莫萊斯發(fā)現(xiàn)，通過顛倒物理學(xué)定律，其中19個(gè)天體可能起源于另一顆恒星。

Astronomers first spotted the object (514107) 2015 BZ509, now called Ka‘epaoka‘awela, in the Pan-STARRS survey in 2015. Analysis of this asteroid revealed something shocking: It was orbiting the wrong way around the solar system in a stable yet eccentric orbit near Jupiter, on a tilt relative to the rest of the planets.

天文學(xué)家在2015年的Pan-STARRS調(diào)查中首次發(fā)現(xiàn)了該天體(514107)BZ509，現(xiàn)在被稱為Ka 'epaoka 'awela。對這顆小行星的分析揭示了一件令人震驚的事情：它在木星附近以一種穩(wěn)定但偏心的軌道繞太陽系運(yùn)行，相對于其他行星呈傾斜狀態(tài)。

Morais and Namouni studied that object’s orbit, built a simulation, and played in reverse the behaviour of a million imaginary objects that fit Ka‘epaoka‘awela’s orbital parameters, each with slightly different properties within the margin of error of the original observations. Most of the simulated objects either crashed into the Sun or other planets or were ejected from the solar system, but both of these cases failed to produce sensical origin stories for the asteroids once they turned the arrow of time back forward, Namouni explained. The ones that did obey the laws of physics were stable since the founding of the solar system 4.5 billion years ago. The researchers interpreted their observations as the objects having been captured from elsewhere.

莫賴斯(Morais)和納莫尼(Namouni)研究了該物體的軌道，建立了一個(gè)模擬系統(tǒng)，并對符合Ka 'epaoka 'awela軌道參數(shù)的上百萬個(gè)虛擬物體的行為進(jìn)行了反向模擬，每個(gè)物體的屬性在原始觀測值的誤差范圍內(nèi)略有不同。納莫尼解釋說，大多數(shù)模擬的物體要么撞向太陽或其他行星，要么被拋出太陽系，但這兩種情況都沒有產(chǎn)生關(guān)于小行星起源的聳人聽聞的故事。那些遵守物理定律的行星自45億年前太陽系建立以來一直很穩(wěn)定。研究人員將他們的觀察解釋為這些物體是從其他地方捕獲的。

While some scientists doubted that conclusion, given that other explanations hadn’t been fully ruled out, Namouni and Morais continued on their search. They ran similar reverse-time simulations for other Centaurs and some objects past Neptune, specifically those forming more than a 60-degree angle between the planetary plane and their orbit. For 19 of these objects, not only did the stable orbits remain at the end of the simulations, but they took on orientations relative to the planets that could not be explained if these objects were formed in our solar system. The pair concluded that they’d found an entire population of objects captured from outside the solar system and published their results this week in the Monthly Notices of the Royal Astronomical Society.

盡管一些科學(xué)家對這一結(jié)論表示懷疑，因?yàn)槠渌慕忉屵€沒有被完全排除，但Namouni和Morais仍在繼續(xù)他們的研究。他們對其他人馬和海王星附近的一些物體進(jìn)行了類似的反向時(shí)間模擬，特別是那些在行星平面和軌道之間形成超過60度角的物體。對于其中的19個(gè)天體，不僅在模擬結(jié)束時(shí)它們的穩(wěn)定軌道仍然存在，而且它們的方向與行星有關(guān)，如果這些天體是在我們的太陽系中形成的，這些行星的方向是無法解釋的。他們得出的結(jié)論是，他們發(fā)現(xiàn)了太陽系外捕獲的所有天體，并于本周在《皇家天文學(xué)會月刊》上發(fā)表了他們的研究結(jié)果。

Namouni told Gizmodo that, despite the initial push back, he hasn’t seen peer-reviewed papers contradicting their 2018 results. But it’s always possible that some other explanation could correctly fit the team’s newest set of calculations – an interstellar origin is just one potential way to explain the data that they see. On the flip side, this is just a study of outliers. Who knows if other rocks from outside the solar system are lurking among the more familiar entities? After all, we’ve recently been visited by two comets from outside the solar system, one of which didn’t look too different from comets that originate inside the solar system.

Namouni告訴Gizmodo，盡管最初遭到了反對，但他還沒有看到同行評審的論文與2018年的結(jié)果相矛盾。但總有可能有其他的解釋能夠正確地符合該團(tuán)隊(duì)最新的計(jì)算結(jié)果——星際起源只是解釋他們所看到的數(shù)據(jù)的一種可能的方式。另一方面，這只是對異常值的研究。誰知道其他來自太陽系外的巖石是否潛伏在我們更熟悉的實(shí)體中呢?畢竟，最近有兩顆來自太陽系外的彗星造訪過我們，其中一顆看起來與來自太陽系內(nèi)部的彗星并無太大不同。

Interstellar objects stably orbiting inside of our own solar system would be an exciting find, of course. And if these Centaurs truly are from another star, then astronomers could learn about the composition of those distant systems by studying the Centaurs more closely – or maybe one day paying them a visit.

當(dāng)然，穩(wěn)定地在太陽系內(nèi)繞軌道運(yùn)行的星際物體將是一個(gè)令人興奮的發(fā)現(xiàn)。如果這些半人馬確實(shí)來自另一顆恒星，那么天文學(xué)家可以通過更仔細(xì)地研究這些人頭馬來了解這些遙遠(yuǎn)星系的組成——或者有一天拜訪他們。