DEPARTMENT OF PHYSICS AND ASTRONOMY

Extra-solar planetsExtra-solar planets

Dr. Matt BurleighDr. Matt Burleigh

Dr. Matt Burleigh

A brief history of extra-solar planetsA brief history of extra-solar planets• In the 16th century the Italian philosopher In the 16th century the Italian philosopher

Giordano Bruno said that the fixed stars are Giordano Bruno said that the fixed stars are really suns like our own, with planets going really suns like our own, with planets going round themround them

• 1991 Radio astronomers Alex Wolszczan & Dale 1991 Radio astronomers Alex Wolszczan & Dale Frail discovered planets around a pulsar Frail discovered planets around a pulsar PSR1257+12PSR1257+12– Variations in arrival times of pulses suggests Variations in arrival times of pulses suggests

presence of three or more planetspresence of three or more planets– Planets probably formed from debris left after Planets probably formed from debris left after

supernova explosionsupernova explosion

• 1995 Planet found around nearby Sun-like star 1995 Planet found around nearby Sun-like star 51 Peg by Swiss astronomers Michel Mayor & 51 Peg by Swiss astronomers Michel Mayor & Didier Queloz using the Didier Queloz using the ““Doppler WobbleDoppler Wobble”” methodmethod– Most successful detection method by far, but Most successful detection method by far, but

other methods like transits are now very other methods like transits are now very successfulsuccessful

– 573 exoplanets found to date573 exoplanets found to date

Dr. Matt Burleigh

Planet Hunting: The Radial Velocity TechniquePlanet Hunting: The Radial Velocity Technique(“Doppler WobbleDoppler Wobble””))

• Star + planet Star + planet orbit common orbit common centre of gravitycentre of gravity

• As star moves As star moves towards observer, towards observer, wavelength of light wavelength of light shortens (is blue-shortens (is blue-shifted)shifted)

• Light red-shifted Light red-shifted as star moves as star moves awayaway

523 planets 523 planets detected by detected by Doppler Wobble Doppler Wobble inc. 52 multiple inc. 52 multiple systemssystems

Dr. Matt Burleigh

Planet Hunting 2: TransitsPlanet Hunting 2: Transits

Dr. Matt Burleigh

TransitsTransits

• The depth of the transit is simply the ratio of the The depth of the transit is simply the ratio of the planetary and stellar disk areas:planetary and stellar disk areas:

– RRpp22 / / RR**

2 2 = (R = (Rp p / R/ R**))22

– so we can measure the planetso we can measure the planet’’s radiuss radius

• But the probability of a transit is very low: only 1 in >10,000 stars has a transiting planet

Dr. Matt Burleigh

Super WASPSuper WASP

• Wide Angle Search for Planets (by Wide Angle Search for Planets (by transit method)transit method)

• First telescope located in La First telescope located in La Palma, second in South AfricaPalma, second in South Africa

• Operations started May 2004Operations started May 2004• Data stored and processed at Data stored and processed at

Leicester Leicester • >50 new planets detected by >50 new planets detected by

WASPWASP– 144 by transit experiments in total144 by transit experiments in total

• www.superwasp.orgwww.superwasp.org• www.wasp.le.ac.ukwww.wasp.le.ac.uk

Dr. Matt Burleigh

Super WASPSuper WASP

• SuperWASP monitors about 1/4 SuperWASP monitors about 1/4 of the sky from each siteof the sky from each site

• That means millions of stars, That means millions of stars, every night!every night!

Dr. Matt Burleigh

““Hot Jupiter” planetsHot Jupiter” planets• Doppler Wobble and transit surveys find many gas giants in Doppler Wobble and transit surveys find many gas giants in

orbits of 2-4 daysorbits of 2-4 days– cf Mercury’s orbit is 80 dayscf Mercury’s orbit is 80 days

• Surveys are Surveys are biasedbiased towards finding them towards finding them– Larger Doppler Wobble signalLarger Doppler Wobble signal– Greater probability of transitGreater probability of transit

• These planets are heated to >1000These planets are heated to >1000ooF on “day” sideF on “day” side– And are “tidally locked” like the MoonAnd are “tidally locked” like the Moon– Causes extreme weather conditionsCauses extreme weather conditions

• Must have formed much farther away from star and Must have formed much farther away from star and migratedmigrated inwardsinwards– Environment too hot for dust and ice to formEnvironment too hot for dust and ice to form

Dr. Matt Burleigh

Planet Hunting 3: Direct ImagingPlanet Hunting 3: Direct Imaging• In 2008 3 planets imaged In 2008 3 planets imaged

around the star HR8799around the star HR8799• 130 light years away (40pc)130 light years away (40pc)• Three planets at 24, 38 and Three planets at 24, 38 and

68AU separation68AU separation– In comparison, Jupiter is at In comparison, Jupiter is at

5AU and Neptune at 30AU5AU and Neptune at 30AU• Masses of 7Mjup, 10Mjup Masses of 7Mjup, 10Mjup

and 10Mjupand 10Mjup

Dr. Matt Burleigh

Fomalhaut (alpha Piscis Austrini)Fomalhaut (alpha Piscis Austrini)

• One of the brightest stars in the One of the brightest stars in the sky (southern hemisphere)sky (southern hemisphere)

• There is a dust disk around There is a dust disk around FomalhautFomalhaut

• Sub-mm image taken from Sub-mm image taken from James Clarke Maxwell telescope James Clarke Maxwell telescope on Hawaiion Hawaii

• Disk has a hole in centre like a Disk has a hole in centre like a doughnutdoughnut

• Part of disk appears to be Part of disk appears to be perturbedperturbed

• Is there a giant planet orbiting Is there a giant planet orbiting Fomalhaut?Fomalhaut?

Dr. Matt Burleigh

Fomalhaut (alpha Piscis Austrini)Fomalhaut (alpha Piscis Austrini)

• 2M2Mjupjup planet imaged planet imaged

inside disk inside disk

• 200Myr old200Myr old

• Like early solar Like early solar systemsystem

Dr. Matt Burleigh

Direct detection: White DwarfsDirect detection: White Dwarfs

• White dwarfs are the end state of stars like the SunWhite dwarfs are the end state of stars like the Sun– What will happen to the solar system in the future?What will happen to the solar system in the future?

• WDs are 1,000-10,000 times fainter than Sun-like WDs are 1,000-10,000 times fainter than Sun-like starsstars– contrast problem reducedcontrast problem reduced

• Over 100 WD within 20pcOver 100 WD within 20pc– At 10pc a separation of 100AU = 10At 10pc a separation of 100AU = 10”” on sky on sky

• At Leicester we are searching for planets around At Leicester we are searching for planets around nearby WD with 8m telescopes and the Spitzer nearby WD with 8m telescopes and the Spitzer space telescopespace telescope

Dr. Matt Burleigh

The end of our solar systemThe end of our solar system

Dr. Matt Burleigh

Spitzer 4.5micron imageSpitzer 4.5micron imageGJ3483 (LTT3059 / WD0808-661) GJ3483 (LTT3059 / WD0808-661)

I am the I am the white white dwarfdwarf

I maybe a planet… I maybe a planet… or a brown dwarf or a brown dwarf

130” / 130” / 2500AU2500AU

Dr. Matt Burleigh

What we know about What we know about

extra-solar planetsextra-solar planets • 573 planets now found573 planets now found• 69 multiple systems69 multiple systems• 144 transiting planets144 transiting planets• Unexpected population Unexpected population

with periods of 1-4 with periods of 1-4 days: days: ““hot Jupitershot Jupiters””

• Planet with orbits like Planet with orbits like Jupiter discovered (eg Jupiter discovered (eg 55 Cancri d)55 Cancri d)

• Smallest planet: Smallest planet: CoRoT-7b - 1.7RCoRoT-7b - 1.7Rearthearth

Dr. Matt Burleigh

Extra-solar planet masses Extra-solar planet masses

• Mass distribution Mass distribution peaks at 1-2 x mass peaks at 1-2 x mass of Jupiterof Jupiter

• Lowest mass planet Lowest mass planet so far: 5.5xMso far: 5.5xMEarthEarth

Dr. Matt Burleigh

Results of the Planet Hunting surveysResults of the Planet Hunting surveys

• Of 2000 stars surveyed Of 2000 stars surveyed – 5% have gas giants 5% have gas giants

between 0.02AU and 5AUbetween 0.02AU and 5AU– 10% may have gas giants 10% may have gas giants

in wider orbitsin wider orbits– <1% have Hot Jupiters<1% have Hot Jupiters

• How many have How many have Earths…..?Earths…..?

Dr. Matt Burleigh

Hunting for Earth-like planetsHunting for Earth-like planets

JupiterJupiter EarthEarth

Dr. Matt Burleigh

Planet population Planet population predictionspredictions

Small planets expected to be very commonSmall planets expected to be very common

ObservationsObservations Population Population SynthesisSynthesis??

Dr. Matt Burleigh

Towards other EarthsTowards other Earths

TelescopeTelescope MethodMethod DateDateCorot (Fr)Corot (Fr) TransitsTransits 20072007

Kepler (NASA)Kepler (NASA) TransitsTransits 20082008

GAIA (ESA)GAIA (ESA) AstrometryAstrometry 20132013

SIM (NASA)SIM (NASA) AstrometryAstrometry 2015 (?)2015 (?)

Plato (ESA)Plato (ESA) TransitsTransits 20182018

Darwin (ESA)Darwin (ESA) ImagingImaging 2025+ (?)2025+ (?)

39m E-ELT39m E-ELT ImagingImaging 20192019

Dr. Matt Burleigh

Next Generation Next Generation Transit SurveyTransit Survey

Queen’s University Belfast, University of Queen’s University Belfast, University of Leicester, University of Warwick, Observatoire Leicester, University of Warwick, Observatoire

de Genève de Genève

Dr. Matt Burleigh

NGTS Prototype La Palma 2010NGTS Prototype La Palma 2010

Dr. Matt Burleigh

Early NGTS v SuperWASP Early NGTS v SuperWASP

Dr. Matt Burleigh

NGTS – Site NGTS – Site

• Requires an excellent photometric Requires an excellent photometric sitesite

• ESO STC recently approved ESO STC recently approved construction at Paranalconstruction at Paranal– Near to VISTANear to VISTA– Status as official ESO projectStatus as official ESO project

Dr. Matt Burleigh

KeplerKepler

• Searching for Earths by transit methodSearching for Earths by transit method• Launched last year by NASALaunched last year by NASA• Aims to find an Earth around a Sun-like Aims to find an Earth around a Sun-like

star in a one year orbitstar in a one year orbit• Need three transits to confirmNeed three transits to confirm• So mission lasts at least three years…So mission lasts at least three years…

Dr. Matt Burleigh

Small planets from the Kepler Small planets from the Kepler faint star samplefaint star sample

Borucki et al 2010Borucki et al 2010Kepler size distribution Kepler size distribution compared to that from the compared to that from the exoplanet encyclopedia.exoplanet encyclopedia.

NB Faint star results not NB Faint star results not confirmableconfirmable

Frequency of different sized Frequency of different sized planets as a function of orbital planets as a function of orbital period.period.

Dr. Matt Burleigh

Towards Other Earths: Habitable ZonesTowards Other Earths: Habitable Zones

• Habitable zone defined as where liquid water existsHabitable zone defined as where liquid water exists• Changes in extent and distance from star according to Changes in extent and distance from star according to

starstar’’s spectral type (ie temperature)s spectral type (ie temperature)

Dr. Matt Burleigh

Towards Other Earths: BiomarkersTowards Other Earths: Biomarkers

• So we find a planet So we find a planet with the same mass as with the same mass as Earth, and in the Earth, and in the habitable zone:habitable zone:– How can we tell it How can we tell it

harbours life?harbours life?

• Search for biomarkersSearch for biomarkers– WaterWater– OzoneOzone– AlbedoAlbedo

Dr. Matt Burleigh

Recommended readingRecommended reading

• Wikipedia Extra-Solar PlanetsWikipedia Extra-Solar Planets

• NASA JPL PlanetQuestNASA JPL PlanetQuest

• University of California Planet SearchUniversity of California Planet Search

• Extra-Solar Planets Encyclopaedia Extra-Solar Planets Encyclopaedia

• SuperWASPSuperWASP

• KeplerKepler