GRE阅读高频机经原文：SupernovaeObscurat by dust
<p> 30. <span word="Supernovae">Supernovae</span><span word="Obscuration">Obscuration</span> <span word="by">by</span> <span word="dust">dust</span></p><p> <span word="Recently">Recently</span>, <span word="significant">significant</span> <span word="progress">progress</span> <span word="has">has</span> <span word="been">been</span> <span word="made">made</span> <span word="by">by</span> <span word="using">using</span> <span word="Type">Type</span> <span word="Ia">Ia</span> <span word="supernovae">supernovae</span> <span word="as">as</span> ``<span word="standardizable">standardizable</span> <span word="candles">candles</span>. <span word="Supernovae">Supernovae</span> <span word="are">are</span> <span word="rare">rare</span> - <span word="perhaps">perhaps</span> <span word="a">a</span> <span word="few">few</span> <span word="per">per</span> <span word="century">century</span> <span word="in">in</span> <span word="a">a</span> <span word="Milky">Milky</span>-<span word="Way">Way</span>-<span word="sized">sized</span> <span word="galaxy">galaxy</span> - <span word="but">but</span> <span word="modern">modern</span> <span word="telescopes">telescopes</span> <span word="allow">allow</span> <span word="observers">observers</span> <span word="to">to</span> <span word="probe">probe</span> <span word="very">very</span> <span word="deeply">deeply</span> <span word="into">into</span> <span word="small">small</span> <span word="regions">regions</span> <span word="of">of</span> <span word="the">the</span> <span word="sky">sky</span>, <span word="covering">covering</span> <span word="a">a</span> <span word="very">very</span> <span word="large">large</span> <span word="number">number</span> <span word="of">of</span> <span word="galaxies">galaxies</span> <span word="in">in</span> <span word="a">a</span> <span word="single">single</span> <span word="observing">observing</span> <span word="run">run</span>. <span word="Supernovae">Supernovae</span> <span word="are">are</span> <span word="also">also</span> <span word="bright">bright</span>, <span word="and">and</span> <span word="Type">Type</span> <span word="Ias">Ias</span> <span word="in">in</span> <span word="particular">particular</span> <span word="all">all</span> <span word="seem">seem</span> <span word="to">to</span> <span word="be">be</span> <span word="of">of</span> <span word="nearly">nearly</span> <span word="uniform">uniform</span> <span word="intrinsic">intrinsic</span> <span word="luminosity">luminosity</span> <span word="They">They</span> <span word="can">can</span> <span word="therefore">therefore</span> <span word="be">be</span> <span word="detected">detected</span> <span word="at">at</span> <span word="high">high</span> <span word="redshifts">redshifts</span> , <span word="allowing">allowing</span> <span word="in">in</span> <span word="principle">principle</span> <span word="a">a</span> <span word="good">good</span> <span word="handle">handle</span> <span word="on">on</span> <span word="cosmological">cosmological</span> <span word="effects">effects</span> .</p><p> <span word="Obscuration">Obscuration</span> <span word="by">by</span> <span word="dust">dust</span> <span word="is">is</span> <span word="the">the</span> <span word="leading">leading</span> <span word="concern">concern</span> <span word="about">about</span> <span word="the">the</span> <span word="reliability">reliability</span> <span word="of">of</span> <span word="the">the</span> <span word="supernova">supernova</span> <span word="results">results</span>. <span word="Ordinary">Ordinary</span> <span word="astrophysical">astrophysical</span> <span word="dust">dust</span> <span word="does">does</span> <span word="not">not</span> <span word="obscure">obscure</span> <span word="equally">equally</span> <span word="at">at</span> <span word="all">all</span> <span word="wavelengths">wavelengths</span>, <span word="but">but</span> <span word="scatters">scatters</span> <span word="blue">blue</span> <span word="light">light</span> <span word="preferentially">preferentially</span>, <span word="leading">leading</span> <span word="to">to</span> <span word="the">the</span> <span word="well">well</span>-<span word="known">known</span> <span word="phenomenon">phenomenon</span> <span word="of">of</span> ``<span word="reddening">reddening</span>. <span word="Spectral">Spectral</span> <span word="measurements">measurements</span> <span word="by">by</span> <span word="the">the</span> <span word="two">two</span> <span word="supernova">supernova</span> <span word="teams">teams</span> <span word="reveal">reveal</span> <span word="a">a</span> <span word="negligible">negligible</span> <span word="amount">amount</span> <span word="of">of</span> <span word="reddening">reddening</span>, <span word="implying">implying</span> <span word="that">that</span> <span word="any">any</span> <span word="hypothetical">hypothetical</span> <span word="dust">dust</span> <span word="must">must</span> <span word="be">be</span> <span word="a">a</span> <span word="novel">novel</span> ``<span word="grey">grey</span> <span word="variety">variety</span>. <span word="This">This</span> <span word="possibility">possibility</span> <span word="has">has</span> <span word="been">been</span> <span word="investigated">investigated</span> <span word="by">by</span> <span word="a">a</span> <span word="number">number</span> <span word="of">of</span> <span word="authors">authors</span> . <span word="These">These</span> <span word="studies">studies</span> <span word="have">have</span> <span word="found">found</span> <span word="that">that</span> <span word="even">even</span> <span word="grey">grey</span> <span word="dust">dust</span> <span word="is">is</span> <span word="highly">highly</span> <span word="constrained">constrained</span> <span word="by">by</span> <span word="observations">observations</span>: <span word="first">first</span>, <span word="it">it</span> <span word="is">is</span> <span word="likely">likely</span> <span word="to">to</span> <span word="be">be</span> <span word="intergalactic">intergalactic</span> <span word="rather">rather</span> <span word="than">than</span> <span word="within">within</span> <span word="galaxies">galaxies</span>, <span word="or">or</span> <span word="it">it</span> <span word="would">would</span> <span word="lead">lead</span> <span word="to">to</span> <span word="additional">additional</span> <span word="dispersion">dispersion</span> <span word="in">in</span> <span word="the">the</span> <span word="magnitudes">magnitudes</span> <span word="of">of</span> <span word="the">the</span> <span word="supernovae">supernovae</span>; <span word="and">and</span> <span word="second">second</span>, <span word="intergalactic">intergalactic</span> <span word="dust">dust</span> <span word="would">would</span> <span word="absorb">absorb</span> <span word="ultraviolet">ultraviolet</span>/<span word="optical">optical</span> <span word="radiation">radiation</span> <span word="and">and</span> <span word="re">re</span>-<span word="emit">emit</span> <span word="it">it</span> <span word="at">at</span> <span word="far">far</span> <span word="infrared">infrared</span> <span word="wavelengths">wavelengths</span>, <span word="leading">leading</span> <span word="to">to</span> <span word="stringent">stringent</span> <span word="constraints">constraints</span> <span word="from">from</span> <span word="observations">observations</span> <span word="of">of</span> <span word="the">the</span> <span word="cosmological">cosmological</span> <span word="far">far</span>-<span word="infrared">infrared</span> <span word="background">background</span>. <span word="Thus">Thus</span>, <span word="while">while</span> <span word="the">the</span> <span word="possibility">possibility</span> <span word="of">of</span> <span word="obscuration">obscuration</span> <span word="has">has</span> <span word="not">not</span> <span word="been">been</span> <span word="entirely">entirely</span> <span word="eliminated">eliminated</span>, <span word="it">it</span> <span word="requires">requires</span> <span word="a">a</span> <span word="novel">novel</span> <span word="kind">kind</span> <span word="of">of</span> <span word="dust">dust</span> <span word="which">which</span> <span word="is">is</span> <span word="already">already</span> <span word="highly">highly</span> <span word="constrained">constrained</span> .</p>
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