1. DEPARTMENT OF PHYSICS AND ASTRONOMY Extra-solar planets Dr. Matt Burleigh

2. A brief history of extra-solar planets In the 16th century the Italian philosopher Giordano Bruno said that the fixed stars are really suns like our own, with planets going round themIn the 16th century the Italian philosopher Giordano Bruno said that the fixed stars are really suns like our own, with planets going round them 1991 Radio astronomers Alex Wolszczan & Dale Frail discovered planets around a pulsar PSR1257+121991 Radio astronomers Alex Wolszczan & Dale Frail discovered planets around a pulsar PSR1257+12 –Variations in arrival times of pulses suggests presence of three or more planets –Planets probably formed from debris left after supernova explosion 1995 Planet found around nearby Sun-like star 51 Peg by Swiss astronomers Michel Mayor & Didier Queloz using the “Doppler Wobble” method1995 Planet found around nearby Sun-like star 51 Peg by Swiss astronomers Michel Mayor & Didier Queloz using the “Doppler Wobble” method –Most successful detection method by far, but other methods like transits are now very successful –573 exoplanets found to date

3. Dr. Matt Burleigh Planet Hunting: The Radial Velocity Technique (“Doppler Wobble”) (“Doppler Wobble”) (“Doppler Wobble”) Star + planet orbit common centre of gravity Star + planet orbit common centre of gravity As star moves towards observer, wavelength of light shortens (is blue- shifted) As star moves towards observer, wavelength of light shortens (is blue- shifted) Light red-shifted as star moves away Light red-shifted as star moves away 523 planets detected by Doppler Wobble inc. 52 multiple systems

4. Dr. Matt Burleigh Planet Hunting 2: Transits Transits

5. Dr. Matt Burleigh Transits The depth of the transit is simply the ratio of the planetary and stellar disk areas: The depth of the transit is simply the ratio of the planetary and stellar disk areas: –  R p 2 /  R * 2 = (R p / R * ) 2 – so we can measure the planet’s radius But the probability of a transit is very low: only 1 in >10,000 stars has a transiting planet

6. Dr. Matt Burleigh Super WASP Wide Angle Search for Planets (by transit method)Wide Angle Search for Planets (by transit method) First telescope located in La Palma, second in South AfricaFirst telescope located in La Palma, second in South Africa Operations started May 2004Operations started May 2004 Data stored and processed at LeicesterData stored and processed at Leicester >50 new planets detected by WASP>50 new planets detected by WASP –144 by transit experiments in total www.superwasp.orgwww.superwasp.orgwww.superwasp.org www.wasp.le.ac.ukwww.wasp.le.ac.ukwww.wasp.le.ac.uk

7. Dr. Matt Burleigh Super WASP SuperWASP monitors about 1/4 of the sky from each siteSuperWASP monitors about 1/4 of the sky from each site That means millions of stars, every night!That means millions of stars, every night!

8. Dr. Matt Burleigh “Hot Jupiter” planets Doppler Wobble and transit surveys find many gas giants in orbits of 2-4 daysDoppler Wobble and transit surveys find many gas giants in orbits of 2-4 days –cf Mercury’s orbit is 80 days Surveys are biased towards finding themSurveys are biased towards finding them –Larger Doppler Wobble signal –Greater probability of transit These planets are heated to >1000 o F on “day” sideThese planets are heated to >1000 o F on “day” side –And are “tidally locked” like the Moon –Causes extreme weather conditions Must have formed much farther away from star and migrated inwardsMust have formed much farther away from star and migrated inwards –Environment too hot for dust and ice to form

9. Dr. Matt Burleigh Planet Hunting 3: Direct Imaging In 2008 3 planets imaged around the star HR8799In 2008 3 planets imaged around the star HR8799 130 light years away (40pc)130 light years away (40pc) Three planets at 24, 38 and 68AU separationThree planets at 24, 38 and 68AU separation –In comparison, Jupiter is at 5AU and Neptune at 30AU Masses of 7Mjup, 10Mjup and 10MjupMasses of 7Mjup, 10Mjup and 10Mjup

10. Dr. Matt Burleigh Fomalhaut (alpha Piscis Austrini) One of the brightest stars in the sky (southern hemisphere)One of the brightest stars in the sky (southern hemisphere) There is a dust disk around FomalhautThere is a dust disk around Fomalhaut Sub-mm image taken from James Clarke Maxwell telescope on HawaiiSub-mm image taken from James Clarke Maxwell telescope on Hawaii Disk has a hole in centre like a doughnutDisk has a hole in centre like a doughnut Part of disk appears to be perturbedPart of disk appears to be perturbed Is there a giant planet orbiting Fomalhaut?Is there a giant planet orbiting Fomalhaut?

11. Dr. Matt Burleigh Fomalhaut (alpha Piscis Austrini) 2M jup planet imaged inside disk 2M jup planet imaged inside disk 200Myr old 200Myr old Like early solar system Like early solar system

12. Dr. Matt Burleigh Direct 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? WDs are 1,000-10,000 times fainter than Sun-like starsWDs are 1,000-10,000 times fainter than Sun-like stars – contrast problem reduced Over 100 WD within 20pcOver 100 WD within 20pc – At 10pc a separation of 100AU = 10” on sky At Leicester we are searching for planets around nearby WD with 8m telescopes and the Spitzer space telescope At Leicester we are searching for planets around nearby WD with 8m telescopes and the Spitzer space telescope

13. Dr. Matt Burleigh The end of our solar system -4000 -2000 0 Solar Radii

14. Dr. Matt Burleigh Spitzer 4.5micron image GJ3483 (LTT3059 / WD0808-661) I am the white dwarf I maybe a planet… or a brown dwarf 130” / 2500AU

15. Dr. Matt Burleigh What we know about extra-solar planets 573 planets now found573 planets now found 69 multiple systems69 multiple systems 144 transiting planets144 transiting planets Unexpected population with periods of 1-4 days: “hot Jupiters”Unexpected population with periods of 1-4 days: “hot Jupiters” Planet with orbits like Jupiter discovered (eg 55 Cancri d)Planet with orbits like Jupiter discovered (eg 55 Cancri d) Smallest planet: CoRoT-7b - 1.7R earthSmallest planet: CoRoT-7b - 1.7R earth

16. Dr. Matt Burleigh Extra-solar planet masses Mass distribution peaks at 1-2 x mass of JupiterMass distribution peaks at 1-2 x mass of Jupiter Lowest mass planet so far: 5.5xM EarthLowest mass planet so far: 5.5xM Earth

17. Dr. Matt Burleigh Results of the Planet Hunting surveys Of 2000 stars surveyedOf 2000 stars surveyed –5% have gas giants between 0.02AU and 5AU –10% may have gas giants in wider orbits –<1% have Hot Jupiters How many have Earths…..?How many have Earths…..?

18. Dr. Matt Burleigh Hunting for Earth-like planets Jupiter Earth

19. Dr. Matt Burleigh Planet population predictions Small planets expected to be very common Observations Population Synthesis ?

20. Dr. Matt Burleigh Towards other Earths TelescopeMethodDate Corot (Fr) Transits2007 Kepler (NASA) Transits2008 GAIA (ESA) Astrometry2013 SIM (NASA) Astrometry 2015 (?) Plato (ESA) Transits2018 Darwin (ESA) Imaging 2025+ (?) 39m E-ELT Imaging2019

21. Dr. Matt Burleigh Next Generation Transit Survey Queen’s University Belfast, University of Leicester, University of Warwick, Observatoire de Genève

22. Dr. Matt Burleigh NGTS Prototype La Palma 2010

23. Dr. Matt Burleigh Early NGTS v SuperWASP

24. Dr. Matt Burleigh NGTS – Site Requires an excellent photometric siteRequires an excellent photometric site ESO STC recently approved construction at ParanalESO STC recently approved construction at Paranal –Near to VISTA –Status as official ESO project

25. Dr. Matt BurleighKepler 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 star in a one year orbitAims to find an Earth around a Sun-like star 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…

26. Dr. Matt Burleigh Small planets from the Kepler faint star sample Borucki et al 2010 Kepler size distribution compared to that from the exoplanet encyclopedia. NB Faint star results not confirmable Frequency of different sized planets as a function of orbital period.

27. Dr. Matt Burleigh Towards 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 star’s spectral type (ie temperature)Changes in extent and distance from star according to star’s spectral type (ie temperature)

28. Dr. Matt Burleigh Towards Other Earths: Biomarkers So we find a planet with the same mass as Earth, and in the habitable zone:So we find a planet with the same mass as Earth, and in the habitable zone: –How can we tell it harbours life? Search for biomarkersSearch for biomarkers –Water –Ozone –Albedo

29. Dr. Matt Burleigh Recommended reading Wikipedia Extra-Solar PlanetsWikipedia Extra-Solar PlanetsWikipedia Extra-Solar PlanetsWikipedia Extra-Solar Planets NASA JPL PlanetQuestNASA JPL PlanetQuestNASA JPL PlanetQuestNASA JPL PlanetQuest University of California Planet SearchUniversity of California Planet SearchUniversity of California Planet SearchUniversity of California Planet Search Extra-Solar Planets EncyclopaediaExtra-Solar Planets EncyclopaediaExtra-Solar Planets EncyclopaediaExtra-Solar Planets Encyclopaedia SuperWASPSuperWASPSuperWASP KeplerKeplerKepler