1. Extra-Solar Planets Planetary Physics Summer Term 2006 Lecture 10

2. Extra-Solar Planets  Since October 1995, more than 180 planets have been detected around more than 150 stars like the Sun – why the sudden success?  None has been seen directly: all found by ‘wobble’ of parent star caused by orbiting planet – how?  None is yet like the Earth: most have masses between Neptune and Jupiter – why?

3. Extra-Solar Planets Definitions:  Star: > 0.08 solar masses (80 jupiter masses), powered by H fusion; formed by gravitational collapse, occur singly or in multiples  Brown Dwarf: 13 jup < mass < 80 jup, some initial D fusion, then fade; formation and occurrence as normal stars  Planet: < 13 jup, no nuclear power source; formed by accretion from protoplanetary disc left behind from formation of parent star

4. In these HST pictures we see disks around stars, but also jets of material being blown out again, especially in the lowest picture (the ‘Rotten Egg’ nebula). Planets form from the disks.

6. Extra-Solar Planets Methods of detection:  Astrometry - long history, no detections  Radial velocity surveys - very successful  Brightness variations –planet passes in front of star: drop in brightness –gravitational lensing of star by planet: increase in brightness - only way to detect earth-mass planets –both becoming effective for detection and study  Interferometry - ground and space missions

7. Extra-Solar Planets Astrometry:  Very precise measurements of position of parent star, relative to inertial frame, repeated over many years  Centre of mass of system (CoM) moves in straight line  If planet exists, star’s motion will have slight ‘wobble’ about CoM motion - can find size and period of orbit, and mass of planet  Massive planets in wide, long-period orbits give largest wobble; nearby stars are best, but effects still too small to measure with present equipment

8. Extra-Solar Planets Radial velocity surveys:  Very precise measurements of radial velocity of parent star – motion in line of sight from observer to star  Single star will have constant velocity, but if companions are present their orbital motions will be reflected in motion of star about centre of mass – look for periodic oscillations in radial velocity, using doppler effect

9. Extra-Solar Planets Limits of radial velocity measurements:  Can find period, eccentricity and M P sin i, where i is inclination of orbit to line of sight  Can not measure i : need transits for this  Motion largest for large masses, short periods  Limit set by oscillations in star’s size (2-3 m/s)  Earth mass in 1-yr orbit gives only 0.1 m/s

10. Extra-Solar Planets Gravitational lensing:  Parent star (‘lens’) focuses light of background star as it passes in front of it: Observer Star Lens (and planet)  Planet causes blip in slow light variation time

11. Extra-Solar Planets History I:  1950 - 1970: various false astrometric claims of Jupiter size companions, e.g. to Barnard’s star (van de Kamp)  1980s: pioneering radial velocity survey by Campbell & Walker - precision of 13 m/s, but no detections (small sample - only 21 stars)

12. Extra-Solar Planets History II:  Late 1980s, early 1990s: several large, high precision RV surveys began - Marcy & Butler (Lick), Mayor & Queloz (OHP), Cochran & Hatzes (McDonald)

13. Extra-Solar Planets 1995 October 6:  first extra-solar planet round a ‘normal’ star announced by Swiss team, Michel Mayor & Didier Queloz  (2 found earlier around a pulsar – but can’t be ‘normal’ planets)

14. Geoff Marcy and Paul Butler found this ‘wobble’ in the motion of the star 51 Pegasi, and were able to find a period of just over 4 days.

15. This shows the same observations, but now with all the different orbits superimposed to show the variation better.

16. Extra-Solar Planets What did we expect?  small mass planets (Earth-like) close to star: radiation should evaporate most abundant element, hydrogen, leaving small rocky planets  massive gaseous planets (Jupiter-like: mainly hydrogen) far enough out to avoid evaporation – so expect long periods  circular orbits, as in solar system  stars like the Sun

17. Extra-Solar Planets What did we find?  massive planets close to star!  no earth-like planets  many eccentric orbits!  stars generally richer in heavy elements (such as iron) than the Sun

18. Extra-Solar Planets Results for first 61 stars – later results confirm this trend

19. Extra-Solar Planets Update for 158 stars – red vertical line shows solar metallicity

20. The great majority of the planets are close to their star, although the systems with several planets do show a spread of distances

21. Extra-Solar Planets Current results (at 16/05/06):  188 planets with masses 0.017 M jup (~0.3M nep or ~5 Earth masses) to 17.4 M jup  ~50 ‘hot Jupiters’ (~Jupiter mass, close to star: a < 0.4 AU)  ~83 ‘Jupiter analogues’ (‘ice giants’) (~Jupiter mass, far from star: P > 1 yr)  ~98 ‘eccentric’ planets (high eccentricity orbits: e > 0.2)  18 systems with multiple planets

22. Three planets around Upsilon Andromedae: first ‘solar system’

23. Extra-Solar Planets 55 Cancri system, as seen from near outermost planet (~4 jup). Neptune-mass planet is the black dot very close to the star.

24. Extra-Solar Planets The first planet to be found round a red dwarf star, GJ 436. Its mass is about 21 earth masses, or just larger than Neptune.

25. Extra-Solar Planets The second lowest mass planet so far discovered: the innermost planet of Gliese 876, which also has two Jupiter-mass planets. The mass of this planet is 5.9 M Earth, less than half of Neptune. Semi-amplitude is 4.1 m/s! Radial velocity amplitude is ~6 m s -1 !

26. Extra-solar Planets Catalog Including Candidates to be confirmed (sorted by increasing mass) From the Extrasolar Planets Encyclopaedia http://www.obspm.fr/planets Extrasolar Planets Encyclopaedia Maintained by ©,1996 Jean Schneider Observatoire de Paris jean.schneider@obspm.fr ©,1996 Jean Schneider Update: 10 May 2001 ( Warning: As there is no clear consensus about the definition criteria of planets, `super-planets' and brown dwarfs (mass, formation,...), this Catalog includes only (with a few exceptions) objects lighter than 13 M Jup (no deuterium burning)). The Catalog below contains four tables (the objects are sorted for each by increasing mass of the lightest planet in the system): 1.Confirmed planets around main sequence stars 1.HD 83443 update 2 Nov. 00HD 83443 2.HD 16141 update 22 Nov. 00HD 16141 3.HD 168746 update 4 May 00HD 168746 4.HD 46375 update 29 Mar. 00HD 46375 5.HD 108147 update 4 May 00HD 108147 6.HD 75289 update 16 Apr. 01HD 75289 7.51 Peg update 16 Apr. 0151 Peg 8.BD -10 3166 update 27 Apr. 00BD -10 3166 9.HD 6434 update 22 Nov. 00HD 6434 10.HD 187123 update 6 Jul. 00HD 187123 11.HD 209458 update 25 Apr. 01HD 209458 12.upsilon And update 7 May. 01upsilon And 13.HD 192263 update 22 Nov. 00HD 192263 14.epsilon Eridani update 27 September 00epsilon Eridani 15.HD 38529 update 22 Nov. 00HD 38529 16.HD 179949 update 20 Apr. 01HD 179949 17.55 Cnc update 22 Nov. 0055 Cnc 18.HD 82943 update 10 May. 01HD 82943 19.HD 121504 update 21 August 00HD 121504 20.HD 37124 update 22 Nov. 00HD 37124 21.HD 130322 update 30 Mar. 00HD 130322 22.rho CrB update 6 Apr. 01rho CrB 23.HD 52265 update 22 Nov. 00HD 52265 24.HD 177830 update 22 Nov. 00HD 177830 25.HD 217107 update 6 Jul. 00HD 217107 26.HD 210277 update 22 Nov. 00HD 210277 27.HD 27442 update 16 Dec. 00HD 27442 28.16 Cyg B update 18 Jan. 0116 Cyg B 29.HD 74156 update 4 Apr. 01HD 74156 30.HD 134987 update 22 Nov. 00HD 134987 31.HD 160691 update 16 Dec. 00HD 160691 32.HD 19994 update 21 August 00HD 19994 33.Gliese 876 update 7 May. 01Gliese 876 34.HD 92788 update 22 Nov. 00HD 92788 35.HD 8574 update 4 Apr. 01HD 8574 36.HR810 update 22 Nov. 00HR810 37.47 Uma update 22 Nov. 0047 Uma 38.HD 12661 update 22 Nov. 00HD 12661 39.HD 169830 update 22 Nov. 00HD 169830 40.14 Her update 16 Apr. 0114 Her 41.GJ 3021 update 22 Nov. 00GJ 3021 42.HD 80606 update 4 Apr. 01HD 80606 43.HD 195019 update 22 Nov. 00HD 195019 44.HD 213240 update 4 Apr. 01HD 213240 45.Gl 86 update 22 Nov. 00Gl 86 46.tau Boo update 16 Dec. 00tau Boo 47.HD 50554 update 4 Apr. 01HD 50554 48.HD 190228 update 22 Nov. 00HD 190228 49.HD 168443 update 11 Jan. 01HD 168443 50.HD 222582 update 22 Nov. 00HD 222582 51.HD 28185 update 4 Apr. 01HD 28185 52.HD 178911 B update 4 Apr. 01HD 178911 B 53.HD 10697 update 22 Nov. 00HD 10697 54.70 Vir update 22 Nov. 0070 Vir 55.HD 106252 update 4 Apr. 01HD 106252 56.HD 89744 update 22 Nov. 00HD 89744 57.HD 141937 update 4 Apr. 01HD 141937 58.HD 114762 update 22 Nov. 00HD 114762 2.Confirmed planets around pulsars 1.PSR 1257+12 update 28 Mar. 01PSR 1257+12 2.PSR B1620-26 update 29 July 99PSR B1620-26 3.Disks (potentially protoplanetary or associated to planets) (sorted by distance to the Sun) 1.Beta Pictoris update 2 Sep. 98Beta Pictoris 2.L 1551 update 2 Oct. 98L 1551 3.BD +31 o 643 (disk; to be confirmed) update 10 mar. 97BD +31 o 643 4.Unconfirmed, doubtful, unpublished or invalidated objects. 1.W 3 (OH) update 28 Oct. 99W 3 (OH) 2.HR7875 update 15 Jul. 1998HR7875 3.Geminga (invalidated) update 8 Sep. 99Geminga 4.PSR 0329+54 (Very doubtful) update 28 Apr. 99PSR 0329+54 5.PSR 1828-11 (unpublished data)PSR 1828-11 6.Q0957+561 A (to be confirmed)Q0957+561 A 7.Lalande 21185 (data unpublished) update 5 dec. 97Lalande 21185 8.CM Dra (to be confirmed) update 25 mar. 00CM Dra 9.Alpha Tau (to be confirmed) update 4 Dec. 97Alpha Tau 10.TMR-1C (invalidated) update 3 Apr. 2000TMR-1C 11.98-BLG-35 (to be confirmed) update 7 mar. 200198-BLG-35 12.95-BLG-3 (to be confirmed) update 23 dec. 9695-BLG-3 13.97-BLG-41 (to be confirmed) update 4 nov. 9997-BLG-41 14.94-BLG-4 (to be confirmed) update 23 dec. 9694-BLG-4 5.21 stars with NO planet found (Walker et al.)NO planet found 1.- Confirmed planets (and/or brown dwarfs) (note 1: for planets detected by timing and radial velocity, only the product M x sini is known) 2.- Confirmed pulsar planets StarM[.sini] Jup. mass:(J) Earth mass:(E) (note 1) Semi- maj. Axis (AU) Period years(y) days(d) Ecc.Incli n. (deg) Radiu s (Earth rad.) PSR 1257+12 PSR 1257+12 ~ 300 pc 0.015 (E) 3.4 (E) 2.8 (E) ~ 100 (E) 0.19 0.36 0.47 ~ 40 25.34 (d) 66.54 (d) 98.22 (d) ~ 170 (y) 0.0 0.018 2 0.026 4 - -------- -------- PSR B1620- 26 PSR B1620- 26 3.8 kpc 1.2 < M.sini < 6.7 (J) 10 - 6461.8 - 389 (y) 0. - 0.5 -- 4.- Unconfirmed, doubtful or unpublished objects StarM[.sini] Jup. mass:(J) Earth mass:(E) (note 1) Semi-maj. Axis (AU) Period years(y) days(d) Ecc.Incli n. (deg) Radi us (Eart h rad.) HR7875 HR7875 25 pc F8V V = 5.12 0.69(J)-42.5 (d)0.429-- PSR 1828-11 PSR 1828-11 3.6 kpc 3 (E) 12 (E) 8 (E) 0.93 1.32 2.1 0.68 (y) 1.35 (y) 2.71 (y) ------ ------ ------ Q0957+56 1 Q0957+56 1 2.4 Gpc (z = 0.39) ~ a few (E) ----- Lal. 21185 Lal. 21185 2 pc M2 V = 7 0.9 (J) 1.6- 5.8 (y) 30 ? (y)--- CM Dra CM Dra 14.7 pc M4.5/M4. 5 V = 12.9 ------ Alpha Tau Alpha Tau 20 - 25 pc K5III V = 0.86 11 (J)1.3 - 1.4653.8 (d)0.182 #177 0.065 ?- TMR-1C TMR-1C ~130 pc V = ? 2- 3 (J) ?> 1,500> 40,000 (y) ??~1 R J 98-BLG- 35 98-BLG- 35 ~ 5 kpc ~ 0.4 - 1.5 (E) 1.5 or 2.3???- 95-BLG-3 95-BLG-3 ~ 5 kpc ~ 2 (J)> 5 - 10 ?---- 94-BLG-4 94-BLG-4 ~ 5 kpc ~ 5 (J)~ 1---- Beta Pic Beta Pic 18 pc A5V V = 3.8 -> 62000 (d)-< 1 o ~ 16 BD +31 o 643 BD +31 o 643 330 pc B5V, B5V V = 8.5, 8.5 diskrad. disk: 6,600 --< 10 o - W 3 (OH) W 3 (OH) 3 kpc pc O8 star V = ? 10 -4 ? (E)2,000?---- Back to the Extra-solar Planets Encyclopedia The majority of the planets found so far have orbital radii less than 1 AU: 40% of them are less than 0.4 AU, although there is a growing number with larger radius, including four ‘beyond Jupiter’. (log scale)

27. The majority of planets (~53%) still have masses between 1 and 8 Jupiter masses, but there is a growing number (~38%) with masses less than that of Jupiter (down to 0.017 jup ~5.4  ). But only lower limits are known without knowing i: needs transits. ‘Mass’ really means M sin i 10 with masses > 10 Mj

28. 7 November 1999: first-ever planetary transit observed for sun-like star HD 209458 by Henry, Marcy, Butler and Vogt

29. The radial velocity group of Marcy, Butler and Vogt found this evidence of a wobble in the motion of the star and alerted Greg Henry to observe its brightness.

31. This is the 0.8m Automatic Photoelectric Telescope of the Tennessee State University’s Fairborn Observatory in southern Arizona, which was used by Greg Henry to observe the planetary transit. An attempt to verify the result on November 14 was clouded out, but other groups later verified it.

32. Average of four HST transit observations

33. This is the light curve for the second transit to be detected, in July 2002. Nine transits are now known, four found (like this one) by a gravitational lensing survey. This planet is the second closest to its parent star so far (less than 5 solar radii away!).

34. Extra-Solar Planets The Future - I:  Continuing radial velocity searches (lower mass planets – now down to ~5 Earth masses; more multiple systems – now 18 known)  Transits – now 9 definite cases, and lensing surveys are producing many new candidates  Gravitational lensing proper – statistical only, but the best hope of detecting Earth- mass planets at Earth-like distances (~1AU)

35. Extra-Solar Planets The Future - II:  Direct imaging? Difficult from the ground  Space-based imaging (e.g. DARWIN)

36. An artist’s impression of the proposed 6-spacecraft Darwin mission, due to fly in about 2010. Each craft contains a large IR telescope, and they are spread over distances of 40 to 500 metres.

37. Extra-Solar Planets The Future - III:  Ground-based astrometry – very hard  Space-based astrometry (e.g. GAIA)

38. Due to fly about 2015

39. Extra-Solar Planets Where next? Who knows! THE END

40. Extra-Solar Planets