首页
登录
职称英语
That large regions of the galaxy can be influenced by the formation
That large regions of the galaxy can be influenced by the formation
游客
2025-02-22
9
管理
问题
That large regions of the galaxy can be influenced by the formation of
massive stars in a few localized regions requires that star formation somehow be
coordinated over long periods of time. The process commences with a single O-
Line type star or a cluster of such stars in a giant molecular cloud, around which
(5) stellar radiation, winds and explosions carve a modest cavity from of the
surrounding interstellar medium, concomitantly destroying the progenitor
cloud. Perchance this disturbance triggers star formation in a nearby cloud, and
so on, until the interstellar medium in this corner of the galaxy resembles Swiss
cheese, composed of what theorists have recently begun to refer to as bubbles,
(10) or superbubbles, one of the most exciting discoveries in astrophysics in years.
Within a hot bubble, the sun has revealed itself in x-rays emitted by highly
ionized trace ions such as oxygen and at some point in the process of its
formation, nearby bubbles commence to overlap, coalescing into a superbubble.
The energy from more and more O-type stars feeds this expanding superbubble
(15) until its natural buoyancy stretches it from the midplane up toward the halo,
forming a chimney-the superbubble thus becomes a pathway for hot interior
gas to spread into the upper reaches of the galactic atmosphere, producing a
widespread corona. Far from its source of energy, the coronal gas slowly starts
to cool and condense into clouds. Over cons, these clouds fall back to the
(20) galaxy’s mid-plane, completing the fountain-like cycle and replenishing the
galactic disk with cool clouds from which star formation begins anew.
Star formation often occurs in sporadic but intense bursts, but in the Milky
Way the competing feedback effects almost balance out, so that stars form at an
unhurried pace-just 10 per year on average, except in some galaxies where
(25) positive feedback has gained the upper hand. 20 million to 50 million years ago,
star formation in the central parts of M82 began running out of control. Our
galaxy, too, may have had sporadic bursts, and the way these starbursts occur,
and what turns them off must be tied to the complex relation between stars and
the tenuous atmosphere from which they precipitate.
(30) Progress will be made in this complicated subject as astronomers continue
to study how the medium is cycled through stars, through the different phases
of the medium, and between the disk and the halo. Observations of other
galaxies give astronomers a bird’ s-eye view of the interstellar goings-on, and
answer such a critical question as whether stars are really the main source of
(35) power for the interstellar medium. The loop above the Cassiopeia superbubble
looks uncomfortably similar to the prominences that arch above the surface of
the sun, prominences which owe much to the magnetic field in the solar
atmosphere, and scientists have begun to wonder if magnetic activity dominates
our galaxy’s atmosphere. [br] Which of the following, if true, would most seriously undermine the validity of the model of star formation that is presented in the passage?
选项
A、A star is discovered that emits lower levels of trace ions than those discovered by x-rays of our galaxy’s sun.
B、A section of the universe is discovered to lack both stars and any sort of interstellar medium.
C、A galaxy is discovered with a negative rate of star formation.
D、In one corner of the galaxy, coronal gas is discovered to rarify as it becomes cooler.
E、A superbubble is found of equal mass to the galaxy surrounding it.
答案
D
解析
转载请注明原文地址:https://tihaiku.com/zcyy/3968493.html
相关试题推荐
Thatlargeregionsofthegalaxycanbeinfluencedbytheformation
Thatlargeregionsofthegalaxycanbeinfluencedbytheformation
Thatlargeregionsofthegalaxycanbeinfluencedbytheformation
Thatlargeregionsofthegalaxycanbeinfluencedbytheformation
Thatlargeregionsofthegalaxycanbeinfluencedbytheformation
Diseaseisafluidconceptinfluencedbysocietalandculturalatti
Diseaseisafluidconceptinfluencedbysocietalandculturalatti
BeforeGibson,populardiscoursesurroundingtheInformationAgeof
BeforeGibson,populardiscoursesurroundingtheInformationAgeof
BeforeGibson,populardiscoursesurroundingtheInformationAgeof
随机试题
HowtoBeanExpertI.Backgroundinformationaboutthe
1.题目∶二年级《大象的耳朵》片段教学 2.内容: 大象有一对大耳朵,像扇子
在结构化分析方法中,用于对功能建模的(49)描述数据在系统中流动和处理的过程,它
克黄长石A.6T5f B.6PfH C.P6fH D.6PH
清除率A.t1/2=0.693/k B.MRT C.V=X0/C0 D.A
有关结核病的病原学及发病机制叙述正确的是A.结核杆菌属分支杆菌具有抗碱性 B.
高处作业应一律使用工具袋。较大的工具()。(A)应用绳拴在牢固的构件上
计算机辅助教学属于下列教学策略中的( )。A、个别化教学 B、情境教学 C
向日本出口家用微波炉(检验检疫类别为L.M/N),报检时须提交单据包括()。
女,50岁。腹部阵发性胀痛1天,呕吐为胃内容物,近3个月来有时腹胀,大便带黏液无
最新回复
(
0
)