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Lecture 10

AS101 Lecture Notes - Lecture 10: Orbital Period, Gas Giant, Vb 10Premium


Department
Astronomy
Course Code
AS101
Professor
Ioannis John Haranas
Lecture
10

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AS101Lecture10SolarSystems,Stars,andExoplanets

Exoplanets
Firstsignofexoplanetswerediscoveredusingtimingsofpulsarstars
Themodulationsoftheirperiodscouldonlybeexplainedbythepresenceofsmall,planetary,
orbitingobjects
Littleattentionwasgiventothisdiscoveryaspulsarsaretoohostiletolifeorplanetaryformation
Directimaging:observingvisibleorinfraredlightproducedbyorreflectedfromtheexoplanet
Planetsreflectvisiblelightandgiveoffsomeoftheirintheinfraredrange
Theyaremuchdimmerthanthestarsthattheyorbit
Scientistsbloginfraredimagesofplanets.
Astrometry:measuringastar’schangeinposition

WobblingofStars
Thegravitationalpullofanorbitingplanetwillcausethestartowobbleinitsorbit
oTheorbitoftheotherplanetisunevenduetothe“wobble”
Planetsdon’tactuallyorbittheirsun
Theyorbitthecenterofmassofthesunplanetsystem
Astarwillwobbleduetoorbitingplanets
Astrometryrequiresprecisemeasurementsoverlongtimespans
Wobblemethodismoresuitablefornearbyandlowmassstars
Barnard’sStaristhesecondcloseststartoourSunandisfairlysmall,itisaperfectoneto
studyusingthismethod

PetervanderKamp
Apioneerinthesearchforextrasolarplanets
In1938hestartedtoleadagroupfromSproulObservatory
Itisagasgiant(aboutsixtimesJupiter’smass)calledVB10bandisabout20lightyearsaway
intheconstellationAquila

DopplerEffect
Measuringastar’schangesinradialvelocityusingtheDopplereffect
Rememberingthatastarwillwobbleduetoorbitingplanets
Ifitswobbling,thenitismovingawayfromussometimesandtowardusatothers
Whenitismovingaway,thewavelengthofthelightitemitsislengthened(redshifted)
Movingtoward,wavelengthoflightemittedisshortened(blueshifted)

Findingaplanet
RadialvelocitymethodswereusedbyMayorandQuelozin1995tofindthefirstextrasolar
planetaroundasuntypestar

PegasiSystem
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