J.Sturner

T.Ghosh-AreciboObservatory

Venerable Radio Telescope Sets New Standard for

Universal Constant

α

Oneofthemostfundamentalconstantsinphysics,alpha,describeshowchargedpar?clesinteractwithelectromagne?cfields.

Itsvalueisn’tderivedfromanydeepertheory,yetitiscrucialtounderstandingthenatureofatomicandmolecularspectra,andindeedtheirforma?onitself.Forexample,ifitsvaluewastwiceasbig,atoms

woulddecaytwiceasfast.

Butisalphatrulyconstant?

•  Quasarsprovidelightfromtheremotepast.•  Travelingtous,thelightcrossgascloudsproducing

absorp?onlines.•  TheselinesareredshiFed.•  Toiden?fytheselines,variousra?osarecompared

withtheirlaboratoryvalues..•  Smalldeparturesfromthepresent-daylaboratory

resultsareanalyzedasapossiblesystema?ceffectduetoavaria?onoffundamentalconstants.

•  ValuesderivedfromKeck(lowervalue~10Billionyearsago)andVLTobserva?onsareincontradic?on(Webbetal.2001,Phys.Rev.LeV.87,091301,&Molaroetal.2008,EPJSpecialTopics,163,173)

Alphaoverthecosmicepoch:ContradictoryresultfromopAcalspectroscopy

AreciboResult:QuasarsseenthroughcloudsofOHcansetbeVerlimitson

anychangeofalphaOH

3000000000lightyears

OH1720M

Hz

1612MHz•  Arecibodetected3-billion-year-old

radiowavesfromaquasar,PKS1413+135,veiledbyacloudofhydroxyl(OH)molecules.

•  Thespectralproper?esofOHarewellknownfromlaboratorymeasurements.

•  Forthissource,the1612MHzlineisseeninabsorp?onwhilethe1720MHzlineisinemission.

•  Thetwolinescompletelycanceleachother.Adifferentvalueofalphaattheepochofthisobject(i.e.3billionyearsago)wouldimplyashiFbetweenthetwolines.Weseenone.

A125-HOURARECIBOINTEGRATION

Alphahaschangedatmostby1.3partsinamillionin3billionyears

•  Theresultisthemostaccuratees?mateofvaria?onofthefinestructureconstantsofar.

•  Moreaccurateresult,reachingfurtherbackin?mewouldrequirefindingmoredistantquasarsthatarealsoveiledbyanOH(orafewotherwell-studied)molecularcloud.

•  Webbet.al.(2011,Phys.Rev.LeV.,107,191101)reportedspa?alvaria?onofalphawhichneedsindependentverifica?on.

Formoreinforma?on,contact<tghosh@usra.edu>

l  Arecibo result: At 2σ significance, [∆α/α] < 1.3 × 10−6 (z < 0.25).

Areciboresult:At2σsignificance,[∆α/α]<1.3×10−6(z<0.25).