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科学家们正试图查明来自外太空的神秘信号的来源

Have you ever looked up at the sky and wondered if there were aliens looking down upon you? Have you ever turned your radio to a specific frequency and picked up mysterious signals that appeared to be coming from far away? This phenomenon has been observed by many scientists. Scientists and researchers have frequently observed strange signals coming from the far-off cosmos. Are these signals from aliens or is there a more logical and reasonable explanation? Let's find out. 

Fast radio bursts and mysterious signals 

Astronomers commonly detect what is known as fast radio bursts, or FRBs, as they search for signs of celestial objects. FRBs commonly last only a few thousandths of a second and usually have fairly irregular patterns. The sources of FRBs are difficult to precisely track down and locate. Since they can come at irregular intervals and from virtually any part of the sky, they take some serious astronomical skill to track down and pinpoint. Once astronomers do track down and isolate a given FRB, that's when the fun begins. What may at first appear to be seemingly random bursts of radio-signals, is often found to be regularly-occurring pulses. Using large and complex radio telescopes, astronomers are able to lock onto specific radio signals and determine their regularity, often anywhere from a few hours to many months.  

How researchers specifically isolate FRBs 

Astronomers use the radio telescopes to find, measure, and record many of these fast radio bursts. Radio telescopes have to be absolutely massive to pick up the faint signals coming from various galaxies in the universe. This often means that their dishes are partially fixed in place, allowing the dish to be moved through only a limited angle from the zenith. For the most part, this is good enough to pick up repeating signals on a regular basis, but it takes a decent degree of luck, and being in the right place at the right time in reference to where the dish is pointing. Once a repeating FRB is isolated by one telescope, though, astronomers can work together to use other radio telescopes to hone in on the exact source galaxy and learn more about the signal. Astronomers believe that sources for FRBs include neutron stars, supernovae, black holes, or other sources of electromagnetic radiation.  

All of that said, it's all still speculation. Most of the fast radio bursts detected to date have only appeared once. They are also impossible to predict, which makes them extremely difficult to trace. To date, only three have had their origin traced to a specific galaxy. 

Recent signals from space 

Then, last year, a repeating FRB was found by astronomers and tracked back to its source galaxy. This source, however, has proven to be rather interesting. The source of the signal is a spiral galaxy some 500 million light-years away, which makes it the closest source of FRBs that we have recorded. The signal itself is coming from a region that is just seven light-years wide. Astronomer Kenzie Nimmo of the University of Amsterdam, in the Netherlands, said this about the FRB they found: "This object's location is radically different from that of not only the previously located repeating FRB but also all previously studied FRBs. This blurs the differences between repeating and non-repeating fast radio bursts. It may be that FRBs are produced in a large zoo of locations across the Universe and just require some specific conditions to be visible." 

Astronomers have also begun finding more fast radio bursts that repeat at regular intervals; a strange phenomenon. The Canadian Hydrogen Intensity Mapping Experiment telescope, or CHIME, has played a pivotal role in finding many of these repeating FRBs. The CHIME was used to find nine new repeating FRBs in the last year, almost doubling the number of known repeaters found up to that point. The spiral galaxy where many of these repeating FRBs had their origins was dubbed with the catchy name of SDSS J015800.28+654253.0. Scientists are still unsure of the causes for the repeating FRBs but are hopeful that the discovery of more FRBs will help shed some light on the mystery. For now, FRBs will remain mysterious radio waves that propagate from distant galaxies, but we're getting better at finding them, and also determining what's creating them. 

Who knows, maybe someday soon we'll get a radio wave signal from outer space that has been deliberately sent and has some type of translatable or discernible pattern. Regardless, the research surrounding FRBs is helping astrophysicists to learn more about the universe. 

第 1 题细节理解
A ：Fast radio bursts last a very short duration.
B ：Fast radio bursts usually have fairly irregular patterns.
C ：Fast radio bursts are no way to locate.
D ：Fast radio bursts can come at irregular intervals.

解析：题目询问，关于快速无线电脉冲，下列哪一项信息是不正确的？通过题干定位到第三段，文章表明“FRBs commonly last only a few thousandths of a second and usually have fairly irregular patterns”，选项A中“very short duration”对应原文“a few thousandths of a second”，正确；选项B与原文严格对应，正确。选项C原文表述为“The sources of FRBs are difficult to precisely track down and locate”，很难去定位并不代表不能定位，C错误。选项D对应原文“Since they can come at irregular intervals”，正确。所以正确答案为C。

第 2 题细节理解
A ：The massive cosmos.
B ：The neutron stars.
C ：The supernovae.
D ：The black holes.

解析：题目询问，从天文学家的角度来看，下列哪一项可能不是FRBs的来源？通过题干定位到第五段最后一句，文章表明“Astronomers believe that sources for FRBs include neutron stars, supernovae, black holes, or other sources of electromagnetic radiation”即天文学家认为，FRBs的来源包括中子星、超新星、黑洞或其他电磁辐射的来源。可知选项A，巨大的宇宙，未提及。

第 3 题推理判断
A ：turn on light
B ：uncover
C ：lighten
D ：cover

解析：题目询问，第九段中“shed light on”是什么意思？该段中含有该词的句子为“Scientists are still unsure of the causes for the repeating FRBs but are hopeful that the discovery of more FRBs will help shed some light on the mystery”即，科学家们仍不确定重复FRBs的原因，但希望更多FRBs的发现将有助于“shed light on”这个谜团。句中含有表述转折的逻辑关系词“but”，可知逗号前后表达相反的含义，逗号前后分别表达现在和将来：现在不能确定原因，但却有望在将来“解开”谜题，可知选项B，正确。选项A，开灯；选项C，减轻；选项D，掩盖，均错误。

第 4 题观点目的
A ：To prove that aliens exist in the cosmos.
B ：To make aliens work for mankind.
C ：To track them down and locate them.
D ：To help astrophysicists to learn more about the universe.

解析：题目询问，根据这篇文章，科学家研究FRBs的来源的最终目的是什么？一般来说，观点和目的会在文章的开头或结尾表明，该篇文章的观点目的体现在结尾做后一句话“Regardless, the research surrounding FRBs is helping astrophysicists to learn more about the universe”即无论如何，围绕FRBs的研究正在帮助天体物理学家更多地了解宇宙，可知选项D最为贴切。选项ABC最终的目的都是为了选项D。