首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
COMETS (1) Comets are among the most interesting and unpredictable bodies in the solar system. They are made of frozen gases
COMETS (1) Comets are among the most interesting and unpredictable bodies in the solar system. They are made of frozen gases
admin
2022-08-28
79
问题
COMETS
(1) Comets are among the most interesting and unpredictable bodies in the solar system. They are made of frozen gases (water vapor, ammonia, methane, carbon dioxide, and carbon monoxide) that hold together small pieces of rocky and metallic materials. Many comets travel in very elongated orbits that carry them far beyond Pluto. These long-period comets take hundreds of thousands of years to complete a single orbit around the Sun. However, a few short-period comets (those having an orbital period of less than 200 years), such as Halley’s Comet, make a regular encounter with the inner solar system.
(2) When a comet first becomes visible from Earth, it appears very small, but as it approaches the Sun, solar energy begins to vaporize the frozen gases, producing a glowing head called the coma. The size of the coma varies greatly from one comet to another. Extremely rare ones
exceed
the size of the Sun, but most approximate the size of Jupiter. Within the coma, a small glowing nucleus with a diameter of only a few kilometers can sometimes be detected. As comets approach the Sun, some develop a tail that extends for millions of kilometers. Despite the enormous size of their tails and comas, comets are relatively small members of the solar system.
(3) The observation that the tail of a comet points away from the Sun in a slightly curved manner led early astronomers to propose that the Sun has a repulsive force that, pushes the particles of the coma away, thereby forming the tail. Today, two solar forces are known to contribute to this formation. One, radiation pressure, pushes dust particles away from the coma. The second, known as solar wind, is responsible for moving the ionized gases, particularly carbon monoxide. Sometimes a single tail composed of both dust and ionized gases is produced, but often two tails—one of dust, the other, a blue streak of ionized gases—are observed.
(4) As a comet moves away from the Sun, the gases forming the coma recondense, the tail disappears, and the comet returns to distant space. Material that was blown from the coma to form the tail is lost from the comet forever. Consequently, it is believed that most comets cannot survive more than a few hundred close orbits of the Sun. Once all the gases are expelled, the remaining materials—a swarm of tiny metallic and stony particles—continue the orbit without a coma or a tail.
(5) Comets apparently originate in two regions of the outer solar system. Most short-period comets are thought to orbit beyond Neptune in a region called the Kuiper belt, in honor of the astronomer Gerald Kuiper. During the past decade over a hundred of these icy bodies have been discovered. Most Kuiper belt comets move in nearly circular orbits that lie roughly in the same plane as the planets. A chance collision between two comets, or the gravitational influence of one of the Jovian planets—Jupiter, Saturn, Uranus, and Neptune—may occasionally alter the orbit of a comet in these regions enough to send it to the inner solar system and into our view.
(6) Unlike short-period comets, long-period comets have elliptical orbits that are not confined to the plane of the solar system. These comets appear to be distributed in all directions from the Sun, forming a spherical shell around the solar system, called the Oort cloud, after the Dutch astronomer Jan Oort. Millions of comets are believed to orbit the Sun at distances greater than 10,000 times the Earth-Sun distance. The gravitational effect of a distant passing star is thought to send an occasional Oort cloud comet into a highly eccentric orbit that carries it toward the Sun. However, only a tiny portion of the Oort cloud comets have orbits that bring them into the inner solar system.
(7) The most famous short-period comet is Halley’s Comet, named after English astronomer Edmond Halley. [A] Its orbital period averages 76 years, and every one of its 30 appearances since 240 B.C. has been recorded by Chinese astronomers. [B] When seen in 1910, Halley’s Comet had developed a tail nearly 1.6 million kilometers (I million miles) long and was visible during daylight hours. [C] Its most recent approach occurred in 1986. [D]
According to paragraphs 5 and 6, compared to the orbits of short-period comets, the orbits of long-period comets are________.
选项
A、more circular
B、more likely to result in a comet’s entering the inner solar system
C、more likely to be affected by a passing star
D、more likely to lie in the same plane as the planets
答案
C
解析
本题属于推论题,定位在原文第5、6段,要求判断与短周期彗星的轨道相比,长周期彗星的轨道情况如何。根据第6段倒数第2句可知,一颗从远处经过的恒星的引力容易影响长周期彗星,将其送入高偏心轨道,对应C项“更容易受经过的恒星的影响”。A项“更圆”,第5段第4句提到,短周期彗星的轨道几乎都是圆形的,而第6段第1句提到,长周期彗星的轨道是椭圆形的,由此不难看出。A项错误。B项“更有可能使彗星进入内太阳系”,第5段最后一句指出,有多种因素能将短周期彗星送入内太阳系,而第6段最后一句表明,只有一小部分的长周期彗星能够进入太阳系,故B项也错误。D项“更有可能与行星处于同一平面”,第6段第1句指出,与短周期彗星不同,长周期彗星的椭圆形轨道并不一定与太阳系处于同一平面,D项错误。
转载请注明原文地址:https://kaotiyun.com/show/O7fO777K
0
托福(TOEFL)
相关试题推荐
WriteNOMORETHANTWOWORDSAND/ORANUMBERforeachanswer.MonarchButterfliesHibernationButterflyspeciesadoptdifferent
AsystemwasdevelopedtocontroltrafficcongestionontheM25motorway.Expertsuse【L5】________informationfromthemotorw
ENDANGEREDSPECIESAlthoughwecannotdoanythingabouttheplantsandanimalsthatarealready【31】________,wecandosomething
ChimpanzeebehavioursSpeciesWecanfindPanorPanTroglodytesinWestandCentralAfrica.TheBonoboorPanPaniscusare
ChimpanzeebehavioursSpeciesWecanfindPanorPanTroglodytesinWestandCentralAfrica.TheBonoboorPanPaniscusare
ChooseTWOlettersA-E.WhichTWOthingsmakethemuseumunusual?AtheguidesBtheeventsCtheanimalsDthebuildingsE
Whatdoesthepassagemainlydiscuss?WhichofthefollowingistrueaboutthehumandietpriortotheNeolithicperiod?
TheplanetNeptuneisabout30times______fromtheSunasEarthis.
"FourStagesofPlanetaryDevelopment"PlanetaryDevelopment→InourstudyoftheplanetEarth,wewillfindafour-sta
AThelargestoftheterrestrialBcarnivore,bearshavemassiveCbodies,moderate-sizedheads,andtinyDtails.
随机试题
胃短动脉
L3型急性淋巴细胞自血病的细胞学特征是
心为“五脏六腑之大主”的理论依据是
小儿4个月,人工喂养。平时易惊,多汗,睡眠少,近2日来咳嗽、低热,今晨突然双眼凝视,手足抽动。查体:枕后有乒乓球感。止抽后的处理是
感觉的非特异投射系统不能引起特定感觉的主要原因是
根据以下材料,回答以下问题。2009年1~4月,我国完成城镇固定资产投资为37082.30亿元,比去年同期增长30.5%,其中第一产业比去年同期增长82.1%,投资比重见下图:与去年同期相比,2009年1~4月,我国新增城镇固定资产
按照建筑给水、排水、供热及采暖管道工程的一般施工工序,在完成了管道安装之后,下一步应该进行的施工工序是()。
以下是某班级进行探究“馒头在口腔中的变化”实验的过程。要求:写出探究“馒头在口腔中的变化”的实验方案,并画出实验结果记录表。
组织行为塑造有四种方式:正强化指运用有价值的结果增加产生结果的这种行为重复出现的可能性;负强化指取消或避免不希望的结果;惩罚指处理厌恶的结果;自然消退指撤回或不给予强化的结果。根据上述定义,下列属于负强化的是()。
“32位微机”中的32位指的是()。
最新回复
(
0
)