1. DEPARTMENT OF PHYSICS AND ASTRONOMY 3677 Life in the Universe: Extra-solar planets Dr. Matt Burleigh www.star.le.ac.uk/mrb1/lectures.html

2. Dr. Matt Burleigh 3677: Life in the Universe Course outline Lecture 1Lecture 1 –Definition of a planet –A little history –Pulsar planets –Doppler “wobble” (radial velocity) technique Lecture 2Lecture 2 –Transiting planets –Transit search projects –Detecting the atmospheres of transiting planets: secondary eclipses & transmission spectroscopy –Transit timing variations

3. Dr. Matt Burleigh 3677: Life in the Universe Course outline Lecture 3Lecture 3 –Microlensing –Direct Imaging –Other methods: astrometry, eclipse timing –Planets around evolved stars Lecture 4Lecture 4 –Statistics: mass and orbital distributions, incidence of solar systems, etc. –Hot Jupiters –Super-Earths –Planetary formation –Planetary atmospheres –The host stars

4. Dr. Matt Burleigh 3677: Life in the Universe Course outline Lecture 5Lecture 5 –The quest for an Earth-like planet –Habitable zones –Results from the Kepler mission How common are rocky planets?How common are rocky planets? Amazing solar systemsAmazing solar systems –Biomarkers –Future telescopes and space missions

5. Dr. Matt Burleigh 3677: Life in the Universe Useful web sites Extra-solar planets encyclopaedia: exoplanets.euExtra-solar planets encyclopaedia: exoplanets.euExtra-solar planets encyclopaedia: exoplanets.euExtra-solar planets encyclopaedia: exoplanets.eu Exoplanet Data Explorer (California Planet Survey): exoplanets.orgExoplanet Data Explorer (California Planet Survey): exoplanets.orgExoplanet Data Explorer (California Planet Survey): exoplanets.orgExoplanet Data Explorer (California Planet Survey): exoplanets.org NASA exoplanet archive: exoplanetarchive.ipac.caltech.eduNASA exoplanet archive: exoplanetarchive.ipac.caltech.eduNASA exoplanet archive: exoplanetarchive.ipac.caltech.eduNASA exoplanet archive: exoplanetarchive.ipac.caltech.edu Planet hunters (Zooniverse): www.planethunters.orgPlanet hunters (Zooniverse): www.planethunters.orgPlanet hunters (Zooniverse): www.planethunters.orgPlanet hunters (Zooniverse): www.planethunters.org Kepler mission: kepler.nasa.govKepler mission: kepler.nasa.govKepler mission: kepler.nasa.govKepler mission: kepler.nasa.gov Next Generation Transit Survey: www.ngtransits.orgNext Generation Transit Survey: www.ngtransits.orgNext Generation Transit Survey: www.ngtransits.orgNext Generation Transit Survey: www.ngtransits.org

6. Dr. Matt Burleigh 3677: Life in the Universe Useful books Extrasolar planets & Astrobiology: Caleb A. ScharfExtrasolar planets & Astrobiology: Caleb A. Scharf Extrasolar planets: the search for new worlds: Stuart ClarkExtrasolar planets: the search for new worlds: Stuart Clark Transiting Exoplanets: Carole A. HaswellTransiting Exoplanets: Carole A. Haswell The Exoplanet Handbook: Michael PerrymanThe Exoplanet Handbook: Michael Perryman An Introduction to Astrobiology: Iain Gilmore & Mark SephtonAn Introduction to Astrobiology: Iain Gilmore & Mark Sephton Life in the Universe: Bennett & ShostakLife in the Universe: Bennett & Shostak

7. Dr. Matt Burleigh 3677: Life in the Universe Useful numbers R Sun = 6.995x10 8 mR Sun = 6.995x10 8 m R jup = 6.9961x10 7 m ~ 0.1R SunR jup = 6.9961x10 7 m ~ 0.1R Sun R nep = 2.4622x10 7 m ~ 4R earthR nep = 2.4622x10 7 m ~ 4R earth R earth = 6.371x10 6 m ~ 0.1R jup ~ 0.01R SunR earth = 6.371x10 6 m ~ 0.1R jup ~ 0.01R Sun M Sun = 1.989x10 30 kgM Sun = 1.989x10 30 kg M jup = 1.898x10 27 kg ~ 0.001M Sun = 317.8M earthM jup = 1.898x10 27 kg ~ 0.001M Sun = 317.8M earth M nep = 1.02x10 26 kg ~ 5x10 -5 M Sun ~ 0.05M jup = 17.15M earthM nep = 1.02x10 26 kg ~ 5x10 -5 M Sun ~ 0.05M jup = 17.15M earth M earth = 5.97x10 24 kg = 3x10 -6 M Sun = 3.14x10 -3 M jupM earth = 5.97x10 24 kg = 3x10 -6 M Sun = 3.14x10 -3 M jup 1AU = 1.496x10 11 m1AU = 1.496x10 11 m 1 day = 86400s1 day = 86400s

8. Dr. Matt Burleigh 3677: Life in the Universe What is a planet? International Astronomical Union definition –International Astronomical Union definition – –An object orbiting a star –Too small for dueterium fusion to occur Less than 13 times the mass of JupiterLess than 13 times the mass of Jupiter –Formation mechanism? Forms from a circumstellar disk of dust and gas around a young starForms from a circumstellar disk of dust and gas around a young star –Lower mass limit – IAU decided that Pluto should be downgraded!

9. Dr. Matt Burleigh 3677: Life in the Universe What is a planet? Above, left to right: limb of Sun, late M (red) dwarf, L brown dwarf, T brown dwarf, Jupiter. The coolest stars, old brown dwarfs and gas giant planets have the same radii!

10. Dr. Matt Burleigh 3677: Life in the Universe A brief history of extra-solar planets 16th century: the Italian philosopher Giordano Bruno said that the fixed stars are really suns like our own, with planets going round them16th century: the Italian philosopher Giordano Bruno said that the fixed stars are really suns like our own, with planets going round them 19 th Century: astronomers believed orbital anomalies in the binary star 70 Oph could be explained by an unseen planet, but later disproved19 th Century: astronomers believed orbital anomalies in the binary star 70 Oph could be explained by an unseen planet, but later disproved 1950s & 60s: Peter van de Kamp concluded that irregularities in the high proper motion of nearby Barnard’s Star were caused by a planet. Sadly, this too turned out to be erroneous.1950s & 60s: Peter van de Kamp concluded that irregularities in the high proper motion of nearby Barnard’s Star were caused by a planet. Sadly, this too turned out to be erroneous. late 1980s: Canadian Gordon Walker found tentative evidence for exoplanets using radial velocity method: but not confirmed until 2000s!late 1980s: Canadian Gordon Walker found tentative evidence for exoplanets using radial velocity method: but not confirmed until 2000s! 1991: Andrew Lyne & Setnam Shemar at Jodrell Bank claimed to have discovered a pulsar planet in orbit around PSR 1829-10, using pulsar timing variations. They withdrew the claim later that year due to an error in their calculations.1991: Andrew Lyne & Setnam Shemar at Jodrell Bank claimed to have discovered a pulsar planet in orbit around PSR 1829-10, using pulsar timing variations. They withdrew the claim later that year due to an error in their calculations. New York Times 16 th April 1963

11. Dr. Matt Burleigh 3677: Life in the Universe A brief history of extra-solar planets 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 >1700 exoplanets confirmed to date by all methods>1700 exoplanets confirmed to date by all methods –Kepler has several thousand more candidates

12. Dr. Matt Burleigh 3677: Life in the Universe Blue: radial velocity, Green: transiting, Red: microlensing, Orange: direct imaging, Yellow: pulsar timing

13. Dr. Matt Burleigh 3677: Life in the Universe

15. Pulsar planets Pulsars are neutron stars that emit radio pulses every ~second as they spinPulsars are neutron stars that emit radio pulses every ~second as they spin –More stable and accurate than an atomic clock If a planet accompanies the pulsar, then the pulsar will orbit the centre of mass of the systemIf a planet accompanies the pulsar, then the pulsar will orbit the centre of mass of the system –The pulses will then arrive earlier or later than expected Radio observations have found a dozen or so such “pulsar planets”Radio observations have found a dozen or so such “pulsar planets” –Wolszczan & Frail’s discovery of PSR1257+12’s planets in 1991 at Arecibo in Puerto Rico were the first confirmed exoplanets – PSR1257+12’s planets are all ~Earth mass or smaller

16. Dr. Matt Burleigh 3677: Life in the Universe Pulsar planets Pulsars are created when a massive star (>8M sun ) explodes as a supernovaPulsars are created when a massive star (>8M sun ) explodes as a supernova –Their original planetary systems will not survive –Radio-detected planets thought to have formed from supernova debris –Planets will be bathed in high energy radiation from pulsar – no chance of life!

17. Dr. Matt Burleigh 3677: Life in the Universe 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 (blue-shifted) As star moves towards observer, wavelength of light shortens (blue-shifted) Light red-shifted as star moves away Light red-shifted as star moves away 517 planets detected by Doppler Wobble and many more transiting planets confirmed by this method

18. Dr. Matt Burleigh 3677: Life in the Universe Measuring Stellar Doppler shifts Method:Method: –Observe star’s spectrum through a cell of iodine gas –Iodine superimposes many lines on star’s spectrum –Measure wavelength (or velocity) of star’s lines relative to the iodine Measure:Measure: –  e = (   e ) / e = v r / c   observed wavelength, e =emitted wavelength

19. Dr. Matt Burleigh 3677: Life in the Universe M * from spectral type

20. Dr. Matt Burleigh 3677: Life in the Universe Doppler Wobble Method Since measure K (= v * sin i), not v * directly, only know mass in terms of the orbital inclination iSince measure K (= v * sin i), not v * directly, only know mass in terms of the orbital inclination i Therefore only know the planet’s minimum mass, M sin iTherefore only know the planet’s minimum mass, M sin i –If i=90 o (eclipsing or transiting) then know mass exactly i=90 0 Orbital plane i0i0i0i0

21. Dr. Matt Burleigh 3677: Life in the Universe Example: 51 Peg P= 4.15days = 4.15x86400s = 3.5856x10 5 sP= 4.15days = 4.15x86400s = 3.5856x10 5 s G5V star, M * =1.11M sun = 1.11x1.989x10 30 kg = 2.21x10 30 kgG5V star, M * =1.11M sun = 1.11x1.989x10 30 kg = 2.21x10 30 kg Find r = 0.052AU, v pl =1.37x10 5 ms -1 M pl sin i = 0.45M jupFind r = 0.052AU, v pl =1.37x10 5 ms -1 M pl sin i = 0.45M jup

22. Dr. Matt Burleigh 3677: Life in the Universe Above: eccentric orbit (e=0.93) Top right: 55 Cancri multiple-planet system (4, maybe 5 planets) Bottom right: 3 planet HD37124 system

23. Dr. Matt Burleigh 3677: Life in the Universe HARPS radial velocity spectrograph Built by Geneva Observatory First installed on ESO 3.6m at La Silla, Chile in 2002/3 Has found over 130 planets Precision 30cm/s – 1m/s Simultaneously observes star and a reference Thorium lamp through two separate fibres Highly stable optical bench, housed in sealed, thermally stable room Second HARPS installed on Italian Galileo telescope on la Palma 2012

24. Dr. Matt Burleigh 3677: Life in the Universe Doppler Wobble Method Precision of current surveys routinely <1m/sPrecision of current surveys routinely <1m/s –Jupiter causes Sun’s velocity to vary by 12.5m/s –All nearby, bright Sun-like stars are good targets Lots of lines in spectra, relatively inactiveLots of lines in spectra, relatively inactive –Smallest planet found by this method is ~1M earth : Alpha Cen Bb – nearest star system to us! –Most are Neptune size and larger Length of surveys limits distances planets have been found from starsLength of surveys limits distances planets have been found from stars –Earliest surveys started 1988 –Jupiter (5AU from Sun) takes 12 yrs to orbit Sun –Saturn takes 30 years Would be strongly hinted at but not yet completed one orbit since surveys beganWould be strongly hinted at but not yet completed one orbit since surveys began –Do not see planet directly

25. Dr. Matt Burleigh 3677: Life in the Universe Alpha Cen Bb Alpha Cen system is the nearest star system to us Alpha Cen B has been monitored by radial velocity method Very recent discovery of a rocky planet: Minimum mass 1.1xEarth Period 3.2 days Dumusque et al. 2012, Nature Thought: if Alpha Cen B has a rocky planet, do most stars have rocky planets?