垂死的恒星發(fā)出的光可以粉碎小行星

垂死的恒星發(fā)出的光可以粉碎小行星

Even stars that don’t end their lives in supernovae can spell catastrophe for the smallest members of their solar system. New research suggests that the light of dying stars is enough to pulverize asteroids located hundreds of times further than the Earth-Sun distance from their star.

即使是那些沒有在超新星中結(jié)束生命的恒星也會(huì)給太陽(yáng)系中最小的成員帶來(lái)災(zāi)難。新的研究表明，瀕死恒星發(fā)出的光足以粉碎距離其恒星數(shù)百倍于地球-太陽(yáng)距離的小行星。

The study, published in the Monthly Notices of the Royal Astronomical Society, looked at the consequence of the YORP effect in stellar systems. Named after the four scientists that contributed to the idea (Yarkovsky, O'Keefe, Radzievskii, and Paddack), the YORP effect is when an asteroid spins itself to death due to stellar radiation.

這項(xiàng)研究發(fā)表在《皇家天文學(xué)會(huì)月刊》上，研究了約普效應(yīng)對(duì)恒星系統(tǒng)的影響。“約普效應(yīng)”是以四位科學(xué)家的名字命名的，這四位科學(xué)家分別是:雅科夫斯基、奧基夫、拉濟(jì)耶夫斯基和帕達(dá)克。

Alfredo Carpineti

Starlight has a small but not zero momentum. As we have seen with the successful solar sail tests in the last decade or so, photons from the Sun can push objects around. When starlight hits an asteroid, it is absorbed, redistributed internally, and then reemitted at a different location.

星光有一個(gè)小但不是零的動(dòng)量。正如我們?cè)谶^去十年左右成功的太陽(yáng)帆試驗(yàn)中所看到的，來(lái)自太陽(yáng)的光子可以推動(dòng)物體。當(dāng)星光撞擊小行星時(shí)，它被吸收，在內(nèi)部重新分布，然后在不同的位置重新發(fā)射。

Asteroids are large piles of space rocks that often remain together due to weak gravity; however, they are not well mixed, so the heating from stellar radiation and the subsequent emissions are not balanced. This imbalance in the emissions produces a small torque. Over time and with the star getting brighter and brighter, the torque increases. Since the gravity exerted on the asteroids is too weak to counterbalance the forces pulling the asteroids apart, the space rocks become dust.

小行星是一大堆太空巖石，由于重力較弱，它們通常會(huì)保持在一起;然而，它們并沒有很好地混合在一起，因此恒星輻射產(chǎn)生的熱量和隨后的輻射并不平衡。這種排放的不平衡產(chǎn)生了一個(gè)小扭矩。隨著時(shí)間的推移，恒星變得越來(lái)越亮，扭矩也隨之增大。由于施加在小行星上的引力太弱，無(wú)法抵消把小行星拉開的力，太空巖石就變成了塵埃。

“When a typical star reaches the giant branch stage, its luminosity reaches a maximum of between 1,000 and 10,000 times the luminosity of our Sun. Then the star contracts down into an Earth-sized white dwarf very quickly, where its luminosity drops to levels below our Sun’s. Hence, the YORP effect is very important during the giant branch phase, but almost non-existent after the star has become a white dwarf,” lead author Dr Dimitri Veras, from the University of Warwick’s Astronomy and Astrophysics Group, said in a statement.

“當(dāng)一顆典型的恒星達(dá)到大分支階段時(shí)，它的光度最大達(dá)到太陽(yáng)光度的1000到10000倍。然后這顆恒星迅速收縮成地球大小的白矮星，其光度下降到低于太陽(yáng)的亮度。因此，約普效應(yīng)在大分支階段非常重要，但在恒星變成白矮星后幾乎不存在。華威大學(xué)天文和天體物理小組的首席作者迪米特里·維拉斯博士在一份聲明中說(shuō)。

The work provides insight into the future of our Solar System. In about 6 billion years, our Sun will have run out of fuel, shedding its outer layers and collapsing into a white dwarf. This will mean bye to the asteroid belt in record time.

這項(xiàng)工作為我們了解太陽(yáng)系的未來(lái)提供了視角。在大約60億年后，我們的太陽(yáng)將耗盡燃料，脫離它的外層，坍縮成一顆白矮星。這意味著小行星帶將在創(chuàng)紀(jì)錄的時(shí)間內(nèi)消失。

“For one solar-mass giant branch stars – like what our Sun will become – even exo-asteroid belt analogues will be effectively destroyed. The YORP effect in these systems is very violent and acts quickly, on the order of a million years. Not only will our own asteroid belt be destroyed, but it will be done quickly and violently. And due solely to the light from our Sun," said Dr Veras.

“對(duì)于一個(gè)太陽(yáng)質(zhì)量的巨型分支恒星——就像我們的太陽(yáng)將會(huì)變成的樣子——即使是外小行星帶的類似物也會(huì)被有效地摧毀。約珥普效應(yīng)在這些系統(tǒng)中非常強(qiáng)烈，而且作用迅速，大約有一百萬(wàn)年的時(shí)間。我們自己的小行星帶不僅會(huì)被摧毀，而且會(huì)被迅速而猛烈地摧毀。而這僅僅是由于來(lái)自太陽(yáng)的光。”維拉斯博士說(shuō)。

The simulations suggest that the size of the debris will plateau when objects are less than 100 meters (330 feet) across, as these often have quite high internal strength. The researchers think that by studying emissions from the asteroid debris around white dwarfs, it might be possible to gain insight into what the stellar system used to be like before the star died.

模擬表明，當(dāng)物體直徑小于100米(330英尺)時(shí)，碎片的大小將趨于平穩(wěn)，因?yàn)檫@些物體通常具有相當(dāng)高的內(nèi)部強(qiáng)度。研究人員認(rèn)為，通過研究白矮星周圍小行星碎片的排放，有可能了解恒星死亡前的恒星系統(tǒng)。