Ordinary Galaxy Hints at Less Ordinary Matter

Ordinary Galaxy Hints at Less Ordinary Matter

first_imgAn alien civilization curious about the lifestyle of humans shouldn’t limit itself to studying celebrities. Likewise, for astronomers interested in the early universe, focusing on just the flashiest quasars–the luminous cores of active galaxies–might lead to skewed results. But so far these have been the only objects in the distant universe bright enough for detailed spectroscopic studies. Now, three Italian astronomers have recorded the spectrum of light emitted by a “normal” galaxy some 12 billion light-years away. Their results suggest that current estimates of the amount of ordinary matter in the universe may be too high.Sandra Savaglio of the Observatory of Rome and Nino Panagia and Paolo Padovani of the Space Telescope Science Institute used the UVES spectrograph at the European Very Large Telescope in Chile to observe a galaxy known as cB58. Getting a high-resolution spectrum was possible thanks to a fortunate trick of nature: The light of the distant object is magnified 50 times by the gravity of a galaxy cluster halfway between the Earth and cB58. In the spectrum, the team found evidence of a large concentration of neutral hydrogen clouds close to the galaxy, indicating the presence of a giant cluster of embryonic galaxies.If clouds of hydrogen also cluster around quasars–which convert all nearby neutral hydrogen to invisible ionized gas–then quasars must have ionized more hydrogen than astronomers had assumed, Savaglio says. This, in turn, means that the universe’s diffuse background of ultraviolet radiation plays a smaller role in the ionization process. But calculations of the amount of ionized hydrogen in intergalactic space depend on the ionization rate for the background radiation, and a lower ionization rate would mean less ionized hydrogen.Sign up for our daily newsletterGet more great content like this delivered right to you!Country *AfghanistanAland IslandsAlbaniaAlgeriaAndorraAngolaAnguillaAntarcticaAntigua and BarbudaArgentinaArmeniaArubaAustraliaAustriaAzerbaijanBahamasBahrainBangladeshBarbadosBelarusBelgiumBelizeBeninBermudaBhutanBolivia, Plurinational State ofBonaire, Sint Eustatius and SabaBosnia and HerzegovinaBotswanaBouvet IslandBrazilBritish Indian Ocean TerritoryBrunei DarussalamBulgariaBurkina FasoBurundiCambodiaCameroonCanadaCape VerdeCayman IslandsCentral African RepublicChadChileChinaChristmas IslandCocos (Keeling) IslandsColombiaComorosCongoCongo, The Democratic Republic of theCook IslandsCosta RicaCote D’IvoireCroatiaCubaCuraçaoCyprusCzech RepublicDenmarkDjiboutiDominicaDominican RepublicEcuadorEgyptEl SalvadorEquatorial GuineaEritreaEstoniaEthiopiaFalkland Islands (Malvinas)Faroe IslandsFijiFinlandFranceFrench GuianaFrench PolynesiaFrench Southern TerritoriesGabonGambiaGeorgiaGermanyGhanaGibraltarGreeceGreenlandGrenadaGuadeloupeGuatemalaGuernseyGuineaGuinea-BissauGuyanaHaitiHeard Island and Mcdonald IslandsHoly See (Vatican City State)HondurasHong KongHungaryIcelandIndiaIndonesiaIran, Islamic Republic ofIraqIrelandIsle of ManIsraelItalyJamaicaJapanJerseyJordanKazakhstanKenyaKiribatiKorea, Democratic People’s Republic ofKorea, Republic ofKuwaitKyrgyzstanLao People’s Democratic RepublicLatviaLebanonLesothoLiberiaLibyan Arab JamahiriyaLiechtensteinLithuaniaLuxembourgMacaoMacedonia, The Former Yugoslav Republic ofMadagascarMalawiMalaysiaMaldivesMaliMaltaMartiniqueMauritaniaMauritiusMayotteMexicoMoldova, Republic ofMonacoMongoliaMontenegroMontserratMoroccoMozambiqueMyanmarNamibiaNauruNepalNetherlandsNew CaledoniaNew ZealandNicaraguaNigerNigeriaNiueNorfolk IslandNorwayOmanPakistanPalestinianPanamaPapua New GuineaParaguayPeruPhilippinesPitcairnPolandPortugalQatarReunionRomaniaRussian FederationRWANDASaint Barthélemy Saint Helena, Ascension and Tristan da CunhaSaint Kitts and NevisSaint LuciaSaint Martin (French part)Saint Pierre and MiquelonSaint Vincent and the GrenadinesSamoaSan MarinoSao Tome and PrincipeSaudi ArabiaSenegalSerbiaSeychellesSierra LeoneSingaporeSint Maarten (Dutch part)SlovakiaSloveniaSolomon IslandsSomaliaSouth AfricaSouth Georgia and the South Sandwich IslandsSouth SudanSpainSri LankaSudanSurinameSvalbard and Jan MayenSwazilandSwedenSwitzerlandSyrian Arab RepublicTaiwanTajikistanTanzania, United Republic ofThailandTimor-LesteTogoTokelauTongaTrinidad and TobagoTunisiaTurkeyTurkmenistanTurks and Caicos IslandsTuvaluUgandaUkraineUnited Arab EmiratesUnited KingdomUnited StatesUruguayUzbekistanVanuatuVenezuela, Bolivarian Republic ofVietnamVirgin Islands, BritishWallis and FutunaWestern SaharaYemenZambiaZimbabweI also wish to receive emails from AAAS/Science and Science advertisers, including information on products, services and special offers which may include but are not limited to news, careers information & upcoming events.Required fields are included by an asterisk(*)Koen Kuijken of the University of Groningen, the Netherlands, says the results by Savaglio and her colleagues suggest that astronomers have overestimated the total amount of baryonic matter–“normal” matter, consisting of atoms. “It would change the balance of baryonic versus dark [nonbaryonic] matter, and all models of the formation of stars, galaxies, and heavy elements,” he says. “But this would need much more data to be confirmed. We should be cautious and wait to see if the same result is confirmed in other lines of sight.”Related sitesPaper by Savaglio et al.European Southern Observatory Web sitelast_img

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