A New Planet in the Outer Solar System?

Transcription

1 A New Planet in the Outer Solar System? Michael Migo Mueller Rijksuniversiteit Groningen, Kapteyn Astronomical InsDtute 6th Quantum Universe Symposium Groningen March 2016

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5 Planets move rela-ve to stars: ἀστήρ πλανήτης ~ wandering star

6 5 planets are visible to the naked eye February 5, Photo by Greg Hogan

7 5 planets are visible to the naked eye February 5, Photo by Greg Hogan

8 Pre Copernicus:

9 Post Copernicus: Planeten Saturn Jupiter Mercury Venus Mars Earth 1 AU

10 Post Copernicus: Planeten Saturn Jupiter Mercury Venus Mars Earth 1 AU ~ 1.5e27 fm

11 First discovery of a planet: William Herschel discovers Uranus (1781) Herschel was actually studying stellar parallax, found a moving object ( comet ) serendipitously.

12 First discovery of a planet: William Herschel discovers Uranus (1781) Herschel was actually studying stellar parallax, found a moving object ( comet ) serendipitously. Previous observers had seen Uranus, but failed to recognize its apparent mo-on (or resolvable size).

13 Uranus Saturn Jupiter

14 Enter classical mechanics / perturbadon theory : Laplace and Lagrange pioneer what we now call perturba-on theory to explain planetary mo-on.

15 Enter classical mechanics / perturbadon theory : Laplace and Lagrange pioneer what we now call perturba-on theory to explain planetary mo-on.

16 1840s: problems with Uranus Le Verrier: mismatch between Uranus predicted and observed posi-ons. Solu-on: add an extra planet! Predicts posi-on and mass of new planet. U. Le Verrier

17 1846: Urbain Le Verrier predicts a planet. Johann Galle discovers it within hours of receiving Le Verrier s le`er within a degree of the predicted posidon J. Galle, Sternwarte Berlin U. Le Verrier, obs. Paris

18 1846: Urbain Le Verrier predicts a planet. Johann Galle discovers it within hours of receiving Le Verrier s le`er within a degree of the predicted posidon J. Galle, Sternwarte Berlin U. Le Verrier, obs. Paris

19 Neptune Uranus Saturn Jupiter

20 Mercury s perihelion precession Leading order (secular) perturba-on theory: Interac-on term doesn t depend on angular variables à argument of perihelion changes at constant rate (apsis precession) U. Le Verrier

21 Mercury s perihelion precession Le Verrier (1859): mismatch between predicted and observed perihelion precession of Mercury Venus: ~280 /100yr Jupiter: ~150 /100yr Other planets: ~100 /100yr Total predicted: ~530 /100yr Observed: ~570 /100yr Is there another planet interior to Mercury? U. Le Verrier

22 Mercury s perihelion precession Le Verrier (1859): mismatch between predicted and observed perihelion precession of Mercury Venus: ~280 /100yr Jupiter: ~150 /100yr Other planets: ~100 /100yr Total predicted: ~530 /100yr Observed: ~570 /100yr Is there another planet interior to Mercury? NO! U. Le Verrier

23 Mercury s perihelion precession Le Verrier (1859): mismatch between predicted and observed perihelion precession of Mercury Venus: ~280 /100yr Jupiter: ~150 /100yr Other planets: ~100 /100yr Total predicted: ~530 /100yr Observed: ~570 /100yr General RelaDvity explains the small discrepancy.

24 Mercury s perihelion precession Le Verrier (1859): mismatch between predicted and observed perihelion precession of Mercury Venus: ~280 /100yr Jupiter: ~150 /100yr Other planets: ~100 /100yr Total predicted: ~530 /100yr Observed: ~570 /100yr General RelaDvity explains the small discrepancy.

25 Another outer planet? Small residuals in posidons of Uranus and Neptune. Percival Lowell Lowell Observatory, Flagstaff

26 1930: Clyde Tombaugh discovers Pluto Clyde Tombaugh: 23 years Pluto Neptun

27 M. Standish, 1993: new mass measurement of Neptune (by Voyager) explains orbits of Uranus and Neptune. Pluto is not needed (yet present) Pluto s exponendal mass loss Lowell s predic-on At discovery First diameter measurement Discovery of moon Charon

28 M. Standish, 1993: new mass measurement of Neptune (by Voyager) explains orbits of Uranus and Neptune. Pluto is not needed (yet present) Pluto s exponendal mass loss Lowell s predic-on At discovery First diameter measurement Discovery of moon Charon

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30 2016: discovery of a new planet adverdzed in press. Batygin & Brown, 2016 Frequently referred to as Planet X, we ll call it P9. M. Brown K. Batygin

31 M. Brown K. Batygin

32 2016: discovery of a new planet adverdzed in press. Batygin & Brown, 2016 M. Brown K. Batygin

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36 Sedna has siblings! (on similarly detached orbits) Sedna et al. (green) display conspicuous clustering. Perihelion precession should randomize orbits, this happens in Kuiper belt (red) AU

37 Also, same orientadon reladve to eclipdc plane. Above eclip-c Below eclip-c

38 Also, same orientadon reladve to eclipdc plane. Likelihood of both things happening coincidentally: 0.007% ~ 3.8σ

39 Batygin & Brown: A new distant planet stabilizes these orbits (and destabilizes others).

40 N- body simuladons over 4 Gyr: t=- 4.0E9 yr

41 N- body simuladons over 4 Gyr: t=- 3.0E9 yr

42 N- body simuladons over 4 Gyr: t=- 2.0E9 yr

43 N- body simuladons over 4 Gyr: t= now

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45 What do we know about Planet 9? We have not seen it, yet.

46 What do we know about Planet 9? We have not seen it, yet. We do know where to look, and the search is on!

47 What do we know about Planet 9? We have not seen it, yet. We do know where to look, and the search is on! Orbit Perihelion ~ 200 AU Aphelion ~ 1,200 AU Period 10,000 20,000 yr InclinaDon ~ 20 deg (!) Mass 5 10 * Earth ~ 0.5 * Neptune ComposiDon Ice giant?

48 How come we haven t seen it, yet? aphelion perihelion Bright ç è faint P9 isn t pardcularly faint, but the sky is big. Orbital phase unknown! Near perihelion, we d probably have seen P9. But it could easily be hiding elsewhere. Even at aphelion, P9 is easily detectable with dedicated telescope obs.

49 xkcd.com/1633

50 The search is on! Two strategies Direct detecdon of P9; survey of orbit should take ~5 yr Try and find more Sednas (similar or dissimilar orbits?)

51 Conclusions It s hard to make predicdons, especially about the future (a`ributed to Niels Bohr) 1846, Neptune: right predicdon, planet found. 1930, Pluto: wrong predicdon, found something unexpected. 2016, P9: convincing predicdon. The planet, if it exists, should be found in the next few years. Telescope Dme well spent. If P9 exists: why? A highly inclined, detached planet is difficult to fit in. If not: how else can we explain Sednas? It stays interesdng!