灯塔阅读 - Astronomers spot repeating radio burst patterns from deep space - 太空垃圾：是时候给宇宙来一场大扫除了

Posted 2022-10-18 Bupt_Luke

Astronomers have spent six years watching an unknown object a million, billion light years away explode again and again. They still don't know what's expelling the violent bursts of energy, but one team thinks they've figured out at least when the extragalactic pyrotechnics are likely to go off. If they're right, the object will be shooting out flares all summer long—potentially providing a string of new hints to one of the greatest mysteries in modern astronomy. "Every pulse is telling you something new,"says Kaustubh Rajwade, an astronomer at the University of Manchester in the UK who helped uncover the new pattern. "If we had stopped at 10 pulses, we wouldn't have seen this." 

In the late 2000s and early 2010s astronomers began to notice flashes of radio waves dotting the sky. Each speck marked a potentially catastrophic outpouring of energy on par with what the sun produces over decades but compressed into a few thousandths of a second. Whatever was causing the Fast Radio Bursts (FRBs), as they came to be called, must be some of the universe's most dramatic explosions. Theorists let their imaginations run wild, considering distant supernovae, neutron star collisions, and even alien spacecraft. Then came the repeat acts. In 2015, astrophysicists picked up ten additional FRBs from a point in deep space that had first flashed in 2012. That object, whatever it was, had apparently survived to burst again. And again. And again. Radio telescopes racked up dozens, and then hundreds of detections from this prolific emitter. It flashed seemingly at random, sometimes giving off back-to-back flickers just tenths of a second apart, and sometimes spacing its bursts out by days or even months. Nearly twenty of the roughly hundred known FRB sources have since revealed themselves to be "repeaters," most of which were discovered in the last year by astronomers working with the Canadian Hydrogen Intensity Mapping Experiment (CHIME) telescope. 

Of that group, the CHIME collaboration observed just one source flashing with a detectable pattern, a sixteen-day cycle of alternating active and quiet periods. Theorists hungry for concrete information seized the figure, suggesting that 16 days might match the wobbling of a magnetized neutron star as it spins, the bursts becoming visible when it points toward Earth. Now Rajwade and his collaborators have detected a second possible pattern, this time in the original 2012 repeater. They detailed their findings in May in the Monthly Notices of the Royal Astronomical Society. 

The team devoted as much time as they could get on the Lovell Telescope in the UK to staring at the original repeater, which amounted to about 120 hours scattered sporadically over four years. During those precious hours, the repeater gave off 32 brief bursts, enough for the pattern of behavior to become clear when Rajwade analyzed it last fall. "I just basically plotted my data," he says, "and immediately the pattern came out visually." 

After gathering 250 additional flashes from published data spanning six years, Rajwade felt confident he had enough evidence to make the case that the repeater acted regularly. The source flashes at random times for 90 days straight, he calculated, then goes silent for 67 days. Next the cycle repeats—making for a 157-day period overall. The source should have switched on for three months of bursting, the group predicts, on June 2.  

But the finding remains unconfirmed for now. Due to telescope maintenance and fierce competition for observing time, the group's 120 hours of observing happened to fall largely during periods when they now understand the repeater to have been "switched on," possibly throwing off their results. They'll need regularly spaced follow-up observations to see if the source truly keeps to their inferred timetable.  

Other FRB researchers share her enthusiasm for the work ahead. "It's really exciting stuff and it's good for the global community to push forward on this," says Emmanuel Fonseca, an astronomer at McGill University and member of the CHIME collaboration. "These sorts of discoveries really restrict things to the point where we might someday have a solid picture for what these things are."The lengthy 157-day period (as opposed to the other repeater's 16-day cycle) offers a new clue as to what could be emitting the bursts, hinting at something slower than the wild spinning and wobbling of a lone neutron star. "It becomes difficult to explain this intrinsically," Gourdji says. 

第 1 题细节理解
A ：They found that an unknown object a million, billion light years away explode again and again.
B ：They found that what's expelling the violent bursts of energy when the extragalactic pyrotechnics go off.
C ：They found that the answer of the mystery is that object will be shooting out flares all summer long in our galaxy.
D ：They found that more than ten pulses can help human uncover new secrets of the universe.

解析：题目询问，根据第一段，天文学家发现了什么？定位到第一段开头第一句话表示，天文学家花了6年时间观察一个在百万到十亿光年之外的未知物体一次又一次的爆炸。和A选项“他们发现了一个未知的天体在百万到十亿光年之外反复爆炸”相同，故A正确；B选项“他们发现当银河系外的烟火离开的时候就知道了什么是驱逐暴力的能量爆发”，原文则表示，他们仍然不知道什么是驱逐暴力的能量爆发，但这个团队认为他们已经至少发现在银河系外的烟火很可能离开，故该项错误；C选项“他们发现了奥秘的答案就在于这个天体将在整个夏天都在发射耀斑”，原文说，如果他们是对的，这个天体将在整个夏天都在发射耀斑——这可能为现代天文学中最大的谜团之一提供了一系列新的线索。也就是说这只是猜想，而不是一经发现的事实，故不选；D选项“他们发现超过十个脉冲就可以帮助人类了解到宇宙的奥秘”，原文说的是英国曼彻斯特大学的天文学家Kaustubh帮助发现了这个新模式，他说:“每个脉冲都在告诉你一些新的东西。”“如果我们停止在10次脉冲，我们不会看到这个。”但并不是说超过十次脉冲就可以一定有什么收获，强调的是天文学家的不懈努力，故属于夸大事实，不能选。因此正确答案是A。

第 2 题细节理解
A ：It is a technology which helps astronomers notice flashes of radio waves dotting the sky.
B ：It is a phenomenon which leads to dramatic energy slants and explosions in the universe.
C ：It is a radio telescope which can get hundreds of detections from this prolific emitter.
D ：It is a repeater which gives off back-to-back flickers just tenths of a second apart.

解析：题目询问，从文章中我们知道什么是FRB？定位到文中第二段，给出了FRB的定义，它的全称是“Fast Radio Bursts”，接着解释这是一种宇宙中最剧烈的爆炸现象，能将微粒压缩到千分之一秒，在进行巨大的爆炸，所以B选项“它是一种能引发宇宙中剧烈的能量倾斜和爆炸”，因此B选项正确；A选项“它是可以帮助天文学家注意到无线电波的闪光点缀天空的技术”，开头是提到了但是FRB并不是一种技术；C选项“它是一个射电望远镜，可以从这个多产的发射器获得数百个探测结果”。原文是说射电望远镜观察到了这种现象，但FRB本身不射电望远镜，故不选；D选项“它是一种中继器，只相隔十分之一秒发出背对背闪烁”。原文是说“在大约100个已知的FRB源中，有将近20个都是‘中继器’，其中大部分是去年由天文学家在加拿大氢强度映射实验(CHIME)望远镜下发现的。”可以知道它本身是被观察的现象不是一个中继器，是一个形象的比喻说法，故也不能选。因此正确答案是B。

第 3 题推理判断
A ：they speculated the repeater had a regular pattern of action based on the data
B ：they spent a lot of time observing and collecting data before reaching a conclusion
C ：they had sufficient evidence to support the conclusion without the need for further observation
D ：they faced greater competitive pressure because of fewer instrument resources

解析：题目询问，从团队的经历中我们可以推断出的内容不包括什么？定位到文中第四、五和六段，A选项“他们根据数据推测出中继器有自己的行动规律”，定位到第五段第一句话，拉杰韦德在收集了长达6年的公开数据中额外的250次闪光后，确信他有足够的证据来证明中继者定期行动。也就是说他们推测出中继器有自己的行动规律，故该选项正确；B选项“他们在得出结论之前花了很长时间去观察岔河收集数据”，定位到第四段开头表示，这个团队在英国的洛弗尔望远镜上花了尽可能多的时间盯着原来的中继器，在四年的时间里，他们花了大约120个小时，偶尔地散在一起。可以看出团队花了很长时间做这个研究，故该选项正确；C选项“他们有足够的证据支撑它们的结论而不需要进一步的观察”，第六段该发现目前并未得到证实，是因为望远镜的维护和观测时间的激烈竞争使他们没有足够的时间去进行更多的观察活动，所以需要进一步的观察，故该选项错误；D选项“他们在更少仪器资源的使用上面临更大的竞争压力”，“Due to telescope maintenance and fierce competition for observing time, the group's 120 hours of observing happened to fall largely during periods when they now understand the repeater to have been "switched on," possibly throwing off their results.”与该选项是同义替换，故正确。题目中要选择不正确的，故选择C选项。

第 4 题观点目的
A ：Positive.
B ：Negative.
C ：Reserved.
D ：Objective.

解析：题目询问，Emmanuel Fonseca对于此项研究的态度是什么？定位到倒数第一段，段落中Emmanuel Fonseca说：“这真的是令人兴奋的事情，对全球社会推进这一进程很有好处。”可见，她是非常赞同这项研究和这项研究成果对于人类进步的非凡意义的，因此A积极的正确。B消极的、C保守的和D客观的均不是正确选项。