Exoplanet LAB PDF

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Exoplanet lab...

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Extrasolar)Planets! Handout)&)Lab)Report) ! Name:!Javeria!Ijaz!

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Extrasolar)Planet)Transits! Background)Material) ! Last!semester,!for!the!first!time,!the!telescope!on!top!of!Research!Hall!here!at!GMU!observed!the!transit!of! an!exoplanet!across!a!star!in!a!distant!solar!system.!Students!are!using!the!telescope!on!every!clear!night!to! try!to!observe!more!of!these!events.!Some!of!them!have!turned!out!to!be!binary!star!systems,!but!others! are!actual!exoplanets.!These!observations!will!be!used!for!undergraduate!and!graduate!student!research! projects!designed!to!learn!more!about!these!distant!solar!systems.!In!this!lab!we!will!examine!some!of!the! data!taken!with!our!telescope!of!2!exoplanet!transits!and!use!it!to!better!understand!the!properties!of!the! planets!orbiting!these!distant!stars.!!

The!above!image!shows!how!the!amount!of!light!from!a!star!might!change!if!a!planet!passed!in!front!of!it,!a! transit.!This!light!curve!can!tell!astronomers!how!long!it!took!the!planet!to!pass!in!front!of!the!star,!and!by! measuring!the!time!between!transits!is!it!possible!to!find!other!things!such!as!the!period!of!the!planet’s! orbit.!!We!will!generate!light!curves!for!two!different!transiting!planets!and!examine!them!for!more! information!about!the!planets.!

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Part)I:)Looking)at)Star)Images) In!this!section!we!will!look!at!images!collected!with!the!GMU!site!and!look!at!how!we!can!measure!changes! in!brightness.!!If!it!is!not!installed!on!your!computer!go!to!the!web!site:! http://ds9.si.edu/site/Download.html!to!download!the!ds9!image!viewer.! ! 1. Load!the!WASP!33b!image!that!is!in!the!lab!folder!on!Blackboard.! ! 2. [3)points]!This!is!a!picture!taken!with!the!equivalent!of!a!digital!camera!mounted!on!the!GMU! telescope.!The!bright!white!dots!are!the!stars.!The!brightest!star!in!the!image!is!WASP!33.!Describe!the! image!that!you!see.!!You!can!adjust!the!zoom!to!see!the!whole!image!or!just!part!of!it.!!Identify!the! brightest!star!you!see.! ! a. There!are!5!stars!in!the!image,!four!of!them!are!almost!aligned!in!a!slanted!a!line,!and!there!is! one!star!on!the!left!of!the!line.!The!brightest!star!is!the!third!down!from!the!top!of!the!line! (WASP33).! ! 3. [3)points]!Left!click!and!drag!to!form!a!small!circle.!Move!the!circle!so!that!it!is!centered!on!the! brightest!star.!Click!on!the!circle!(four!squares!will!appear!around!it)!and!then!under!the!region!menu! go!to!get!information.!From!the!window!that!opens,!under!the!analysis!menu!go!to!statistics.!In!the! window!that!opens!you!will!see!information!about!the!area!inside!your!circle.!!Record!the!information! for!star!below.! a. SUM:)8062724.9! b. ERORR:)2839.4938! c. AREA:)1773! d. MEAN:)4547.5042! ! 4. [6)points]!When!you!are!finished!with!WASP!33,!move!the!circle!to!the!bright!star!above!and!to!the! right!of!WASP!33!and!record!the!values!for!that!star.!Do!the!same!thing!for!one!more!star.! ! Star! Sum! Error! Area! Mean! STAR!ABOVE!! 6176226! 2485.2014! 4104! 1504.9284! STAR!TO!THE! 4029049.9! 2007.2493! 1774! 2271.1668! RIGHT! STAR!3! 5174705.2! 2274.7978! 5255! 984.7203! ! 5. [4)points]!The!relative!brightness!of!the!target!star!you!is!its!brightness!divided!by!the!sum!of!the! brightness!values!of!the!comparison!stars!(stars!2!and!3!in!this!case):! ! Relative!brightness!=!(Brightness!target!star)/(Brightness!comp1!+!Brightness!comp2+…)! ! What!is!the!brightness!of!the!target!star!relative!to!the!comparison!stars?! (8062724.9)/(6176226+4029049.9+5174705.2)=0.52423503! ! 6. [4)points]!Why!do!you!think!you!might!want!to!use!more!than!one!comparison!star?! a. We!use!more!than!one!comparison!star!in!order!to!get!a!more!accurate!measurement!for!the! target!star.!This!also!accounts!for!a!better!average!and!allows!room!for!any!disparities!between!

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the!distances!of!the!stars!and!target!stars.!It’s!better!to!get!a!relative!brightness!of!a!target!star! compared!to!the!numerous!and!various!different!luminosities!of!the!different!stars!in!the!sky.!! ! Part)II:)Plotting)some)GMU)transit)data) ! In!your!lab!folder!there!are!2!files,!WASP33b_Table.xlsx!and!HD189733b_Table.xlsx!(both!excel!files).!Open! these!files!in!excel.!The!first!column!is!the!date!in!the!format!of!something!called!the!Julian!date!which!is! the!number!of!days!since!noon!on!January!1,!4713!BC.!To!make!plots!of!the!brightness!variation!over!time:! ! [10)points])for)the)following)3)steps:) • Highlight!the!first!2!columns!of!data!(date!and!brightness!of!the!star)!and!make!a!scatter!plot!such! that!the!date!is!on!the!x-axis!and!the!brightness!on!the!y-axis.!! • Add!error!bars!to!the!data!points!by!clicking!on!the!points!and!then!on!chart!layout.!Under!error! bars!you!can!choose!error!bar!options!and!“custom”!which!will!allow!you!to!select!the!third!column! as!the!positive!AND!negative!error!bars!for!the!y-axis!errors.!! • Once!you!create!the!error!bars!x-error!bars!will!also!appear.!Click!on!the!end!of!one!of!the!x-axis! error!bars!and!change!the!fixed!value!to!0!–!there!is!no!error!on!the!date!at!which!the!data!were! taken,!only!an!uncertainty!in!the!brightness!of!the!source.!! ! 1. [3)points]!Note!that!the!relative!brightness!values!for!the!light!curve!are!found!just!found!them!in!Part! I.!!!How!often!was!a!new!image!taken!to!make!the!light!curve!for!this!transit?! a. Every!.05!julian!days.!! ! 2. [3)points]!Describe!the!light!curve!(which!we!call!the!plot!of!brightness!versus!time!for!the!star)!for! WASP!33.! a. The!graph!starts!to!make!a!U-shape,!with!a!high!value!in!the!beginning!and!starts!to!dip!down! incrementally.!It!begins!to!climb!back!up!but!at!a!slower!rate!than!when!it!first!dipped!down.! (table!is!inserted!below).!!

Brightness!v.!Time!for!Star!(WASP33) 0.675 0.67

Brightness

0.665 0.66 0.655 0.65 0.645 0.64 0.635 56600.44 56600.46 56600.48 56600.5 56600.52 56600.54 56600.56 56600.58 56600.6 56600.62 56600.64

Time

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! 3. [5)points]!Repeat!with!the!second!table!and!describe!the!light!curve!for!HD!189733.! a. The!shape!of!the!data!starts!at!a!relatively!constant!place!and!begins!to!dip!down!dramatically! around!0.825!JD.!It!continues!to!dip!until!it!creates!a!U!shape.!!

Brightness!v!Time!for!Star!(HD189733b) 0.84 0.835

Brightness

0.83 0.825 0.82 0.815 0.81 0.805 0.8 56535.55

56535.6

56535.65

56535.7

56535.75

56535.8

Time

! ! 4. [4)points]!Compare!and!contrast!the!two!light!curves.!! a. The!two!charts!vary!considerably!although!they!have!similar!factors.!The!time!each!photo!was! taken!is!the!same—each!are!0.05!JD!apart.!As!far!as!brightness!they!are!both!relatively!in!the! same!range!as!well.!However,!their!light!curves!are!completely!different.!HD189733b!has!a! more!definite!U!shape!to!it!and!has!a!greater!range!of!brightness!over!time.!Whereas!WASP33! is!a!more!abstract!U!shape!that!stays!varies!a!lot!slowly!over!time.)! ! 5. [6)points]!Examine!the!light!curves!and!fill!out!the!table!below:! ! Source! Maximum! Minimum! Transit! Transit! Transit! Noise!Level! Brightness! Brightness! Depth! Duration! Duration! (days)! (hours)! WASP!33! 0.67133! 0.642048! 0.029285! 1!! 2!hr.!45!mins! ! HD!189733! 0.031703! 1! 1!hr.!15!mins! 0.11! 0.834416! 0.802713! ! 6. [4)points]!Why!is!the!maximum!brightness!not!1.0!in!these!light!curves?!! a. The!brightness!is!never!at!1.0!or!rather!100%!because!these!light!curves!are!eclipsing!binaries.! These!types!of!light!curves!spend!a!lot!of!their!time!unocculated,!meaning!that!they!will!spend! most!of!their!time!near!maximum!brightness!(1.0),!punctuated!by!two!sharp!dips,!or!rather!the! transit.!! ! ! !

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7. [4)points]!Why!do!we!see!a!decrease!in!the!brightness!of!these!stars!over!time?!! a. A!star!can!shine!for!a!very!long!time!as!it!continues!to!grow.!Eventually!it!will!stop!producing! any!light!at!all!and!this!is!determined!by!the!size!of!the!star.!! ! Part)III:)Comparing)with)transit)simulations) ! In!general!when!we!study!exoplanet!transits!we!have!information!about!the!star!around!which!the!planets! are!orbiting.!This!information!is!obtained!by!taking!spectra!of!the!stars.!For!this!part!of!the!lab!you!are! going!to!combine!the!information!that!you!have!about!the!star!(given!below)!and!the!planet!(measured! from!the!light!curve!in!the!last!section)!to!try!to!simulate!the!light!curve.!The!ability!to!simulate!the! measured!curve!provides!information!about!the!properties!of!the!planet.!Use!the!simulator!from!the!last! time:! ! http://astro.unl.edu/naap/esp/animations/transitSimulator.html! ! For!HD!189733!you!know!that!the!mass!of!the!star!is!0.8!times!the!mass!of!the!sun!and!the!exoplanet!has!a! period!of!2.2!days.!! ! 8. [4)points]!How!do!you!think!the!exoplanet!period!is!determined?! a. The!orbital!period!is!determined!through!Kepler’s!third!law!and!requires!the!planet’s!semimajor!axis,!and!the!(stellar)!mass.!! ! 9. [5)points]!Set!the!simulator!to!Option!A!and!then!adjust!the!stellar!mass!and!noise!level.!Show!both!the! theoretical!curve!and!the!simulated!measurements.!What!values!(related!to!the!transit!observation)!are! you!going!to!try!to!match!to!learn!more!about!this!planet! a. I!need!to!try!to!match!radius!of!the!planetary!object!and!its!semi-major!axis.! ! 10. [2)points]!Which!properties!are!you!going!to!change!to!try!to!match!the!parameters!from!the!previous! question?!! a. The!mass!of!the!planetary!object!and!the!semi-major!axis.!! ! 11. [2)points]!What!changes!as!you!change!the!semi-major!axis!(the!distance!between!the!planet!and!the! star)?!! a. As!I!change!the!semi-major!axis,!the!gray!points!on!the!graph!change.!! ! 12. [2)points]!What!changes!as!you!change!the!radius!of!the!planet?! a. As!I!change!the!radius,!the!blue!line!(the!theoretical!light!curve)!flattens!as!it!decreases!and!dips! lower!as!it!increases.!! ! 13. [2)points]!What!changes!as!you!change!the!mass!of!the!planet?!! a. The!gray!points!once!again!move!around,!but!stay!pretty!constant!on!the!blue!line.!! ! 14. [5)points]!Try!to!get!the!closest!match!that!you!can!to!the!transit!data!for!HD18933.!You!can!assume! that!the!inclination!is!90°.!Include!here!a!screen!shot!of!your!closest!match!to!the!parameters!of!this! planet.!How!close!were!you!able!to!get?!Which!properties!of!the!planet!are!the!most!uncertain?!! a. I’m!not!exactly!sure!how!close!I!was!able!to!get,!but!I!tried!to!match!the!noise!level!as!accurate! as!I!could.!Additionally,!I!matched!the!stellar!mass!and!was!able!to!get!close!to!the!2.2!orbital! period!of!the!star.!I!didn’t!quite!match!up!with!the!eclipse!(transit)!time!of!the!star.!I!think!the!

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hardest!values!to!match!were!the!planet!properties.!I!honestly!just!toggled!them!around!until!I! found!something!close!to!the!shape/values!I!was!looking!for.!!

! ! 15. )[5)points])The!web!page:!http://exoplanets.org/detail/HD_189733_b!has!a!full!description!of!the! properties!of!this!star-planet!system.!What!happens!when!you!enter!these!star/planet!numbers!into! the!simulator?!Do!you!get!closer!to!the!observed!transit!properties?!Discuss.!!!! a. When!I!entered!the!actual!values!from!the!table!I!found!that!I!got!a!completely!different!graph! from!the!one!I!made!with!the!observed!values.!The!graph!didn’t!have!as!sharp!of!a!dip!as!the! one!I!created!from!Excel.!As!I!was!entering!the!values,!the!blue!line!started!to!flatten!out! considerably.!! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! ! !

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WASP)33)is)a)star)that)is)1.495)times)the)mass)of)the)sun)with)a)period)of)1.2)days.)) 16. [5)points]!As!with!HD!189733,!try!to!get!the!closest!match!that!you!can!to!the!transit!data.!You!can! assume!that!the!inclination!is!90°.!Include!here!a!screen!shot!of!your!closest!match!to!the!parameters! of!this!planet.!How!close!were!you!able!to!get?!Which!properties!of!the!planet!are!the!most!uncertain?!! a. As!with!HD189733,!the!most!uncertain!aspects!of!the!planet!are!its!mass,!eccentricity,!and! semi-major!axis.!That!being!said,!I!tried!to!get!as!close!as!I!could!to!the!graph!I!made!earlier! with!the!observed!data.!!

! ! 17. [5)points]!The!full!data!are!available!for!WASP!33b!at!http://exoplanets.org/detail/WASP-33_b.!What! happens!when!you!enter!these!star/planet!numbers!into!the!simulator?!Do!you!get!closer!to!the! observed!transit!properties?!Discuss.!!!! a. Strangely!enough,!as!I!entered!the!data!from!the!link!the!transit!similar!pulled!up!a!graph!that! was!very!similar!to!the!one!that!I!created!with!the!observed!data.!The!period!was!almost! exactly!to!what!I!had!found!in!the!graph!at!2.44!hour!transit!for!a!1.22!day!orbit.!The!stars!(aka! the!gray!dots)!also!resembled!the!points!on!the!graph!from!Excel!and!the!blue!line!was!similar! to!the!shape!in!that!graph!as!well.!As!I!would!enter!the!numbers!into!the!simulator,!especially! the!planetary!properties—I!found!the!simulator!to!reflect!the!observed!data!a!lot! better/accurately.!! ! 18. [4)points]!What!questions!do!you!still!have!about!how!we!find!and!measure!the!basic!properties!of! exoplanets?! ! a. Is!the!transit!method!the!best!way!to!find!exoplanets!or!is!the!Doppler!shift!method!better?! Which!one!deals!with!a!constraint!to!the!mass?!Other!than!that,!I!don’t!really!have!any!other! questions!regarding!the!discovery!and!measurement!of!the!basic!properties!of!the! exoplanets—but!rather!have!more!pressing!questions!about!the!necessity!of!it.!If!we!examine! these!planets,!wouldn’t!it!be!better!to!determine!their!potential!for!exobiology?!! !

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