GRE閱讀高頻機經原文30：Supernovae&Obscuratbydust
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GRE閱讀高頻機經原文30：Supernovae&Obscurat by dust
Supernovae & Obscuration by dust
Recently, significant progress has been made by using Type Ia supernovae as ``standardizable candles''. Supernovae are rare - perhaps a few per century in a Milky-Way-sized galaxy - but modern telescopes allow observers to probe very deeply into small regions of the sky, covering a very large number of galaxies in a single observing run. Supernovae are also bright, and Type Ia's in particular all seem to be of nearly uniform intrinsic luminosity (absolute magnitude , typically comparable to the brightness of the entire host galaxy in which they appear)They can therefore be detected at high redshifts , allowing in principle a good handle on cosmological effects .
Obscuration by dust is the leading concern about the reliability of the supernova results. Ordinary astrophysical dust does not obscure equally at all wavelengths, but scatters blue light preferentially, leading to the well-known phenomenon of ``reddening''. Spectral measurements by the two supernova teams reveal a negligible amount of reddening, implying that any hypothetical dust must be a novel ``grey'' variety. This possibility has been investigated by a number of authors . These studies have found that even grey dust is highly constrained by observations: first, it is likely to be intergalactic rather than within galaxies, or it would lead to additional dispersion in the magnitudes of the supernovae; and second, intergalactic dust would absorb ultraviolet/optical radiation and re-emit it at far infrared wavelengths, leading to stringent constraints from observations of the cosmological far-infrared background. Thus, while the possibility of obscuration has not been entirely eliminated, it requires a novel kind of dust which is already highly constrained (and may be convincingly ruled out by further observations).
GRE詞彙精選之鄉村,田園
bucolic adj.鄉村的，牧羊的
rural adj.鄉村的
rustic adj.鄉村的，鄉土氣的
rusticate n.過鄉間生活
predial adj 土地的，鄉村的
campestral adj 田野的，農村的
paysage n 鄉村景色，風景
pastoral adj.田園生活的，寧靜的
eclogue n.田園詩，牧歌
idyll n.田園生活，田園詩
madrigal n.合唱曲，情詩，牧歌
boor n.舉止粗野的人，鄉下人
corny adj.平談無奇的，鄉巴佬的
yeoman n.自耕農，鄉下人
yokel n.鄉巴佬
bumpkin n 粗人，鄉巴佬
hillbilly n 鄉下人，鄉巴佬
GRE閱讀詞彙精選之演說
discourse n.演講，論述
disquisition n.長篇演講，專題論文
oration n.正式演說，演講
text n.(演講等)原文
oratory n 演講術，祈禱室，雄辯的演講
forum n.辯論的場所，講壇
podium n.講壇,指揮台
rostrum n 講壇
rostrum n 講壇,演講壇
elocution n.演說術
eloquent adj.雄辯的,演說動人的
extemporize v.即席演說
heroics n.裝腔作勢的演說或行爲
monologue n.獨白，個人長篇演說
screed n.冗長的演說，長篇大論的文章
diatribe n.(口頭或書面猛烈的)抨擊，抨擊性演說
harangue n.長篇演說
tirade n.長篇的攻擊性演說
valediction n.告別演說，告別詞
talkthon n 冗長的討論或演說
GRE閱讀詞彙精選之各種劑
analgesic n.鎮痛劑，adj.止痛的
anesthetic n.麻醉劑
antiseptic n.殺菌劑，adj 防腐的
astringent adj.止血的，收縮的 n.收縮劑，止血劑
catalyst n.催化劑，促使事情發展的因素
coagulant n.凝結劑
desiccant n.乾燥劑
detergent a.淨化的，n.清潔劑
disinfectant n.消毒劑
dose n.(藥)劑量，一劑
emollient n.潤膚劑
haemostat n.止血器，止血劑
leaven n.發酵劑，影響力v.發酵，影響或改變
lubricant n.潤滑劑
nebula n.星雲，噴霧劑
opiate n.安眠藥，鴉片製劑
overdose n.(藥物)過度劑量
pesticide n.殺蟲劑
placebo n.安慰劑
polish v.把…擦光亮n.上光劑,(態度等)優雅
preservative adj.n.防腐的,防腐劑
reagent n.試劑(導致化學反應)
sedative adj.n.(藥物)鎮靜的，鎮靜劑
solvent adj.有償債能力的，n.溶劑
stimulant n.興奮劑，刺激物
tranquillizer n.鎮定劑
styptic adj 止血的,n 止血劑
deodorant n 除臭劑，防臭藥
precipitant n 戀 劑，adj 突如其來的
obtundent adj 止痛的n 緩和劑
abrasive n 研磨劑a 研磨的
antihistamine n 抗組胺劑
inhibitor n 止氧劑
GRE閱讀高頻機經原文30：Supernovae&Obscurat by dust
