Post on 08-Aug-2020
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).