Max Planck Institute for Astronomy - Annual Report 2007

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22 II. Highlights radial velocity [m/s] radial velocity [m/s] 400 a 200 –200 –400 Fig. II.1.4: The radial velocity in the spectrum of TW Hydrae was measured over a total of 32 nights during the Spring of 2007: Its variation of 3.56 days is caused by the planet’s orbit. Rapid Planet Formation and Migration 0 400 200 0 –200 –400 b 0 February/ March 2007 0 5 10 15 Time [days] 60 65 70 75 Period = 3.65 days 0.5 1 Phase The discovery of the planet that has been named TW Hydrae b provides important new reference points for the theory of planetary formation. Until now, it was known from statistical analyses that the mean life-span of circumstellar disks is several tens of million years. This is thus the maximum available period of time for the creation of planets in the disk. The observation of TW Hya b provides for the first time a true upper limit for the required time span of planetary formation: It could not have lasted longer than eight to ten million years. Thus FEROS 2.2 m MPG/ESO April/May 2007 FEROS 2.2 m MPG/ESO February/March 2007 April/May 2007 1.5 2 TW Hya is an ideal touchstone for numeric models of planetary formation. For one, TW Hya b marks out the time frame for planetary formation. Simultaneously, the planet renews the question for theoreticians as to how such a massive body can orbit its central star at such a short distance. To date, there are several of these hot Jupiters among the known exoplanets. According to currently accepted theory, none of them was formed there: there is never enough material present near the star and, furthermore, it is too hot there. One therefore assumed that the planets formed in the further outlying, cool and dense regions of
the circumstellar disk. Subsequently, an exchange of the rotation impulse between the disk material and the planet leads to the latter slowly wandering in a spiral shaped orbit toward the central star. Computer simulations conducted at the MPIA have shown that a planet forming within five astronomical units from its central star will, within a few thousand years, open a void in the disk (Annual Report 2006, p. 27). At the same time it wanders inward. After a few tens of thousand years, it will have cut its distance to the star in half and doubled its mass, because during its migration it accretes the surrounding dust. Thus the decisive question: When and how does this wandering come to a halt? Is the reason for this the almost material free void at the disk’s center? TW Hydrae b’s orbit along the interior edge of the disk seems to support this hypothesis. Yet, this is not theoretically compelling. Whether additional braking effects – such as magnet fields or tidal forces – play a role, is currently a matter of research. In the final analysis an alternative theory is also being considered, according to which a planet is formed, like a star, through direct contraction and not through a gradual gathering of surrounding dust and gas. TW Hydrae b may in the future possibly provide further hints toward answers to these burning questions. An additional planet around HD 70573 MPIA’s astronomers were able to count a further success during their search program: they discovered a periodic Doppler shift with a period of 852 days at the 150 light year distant star HD 70573. Here too the bisector analysis showed no correlation with star activity signatures II.1 Youngest Extrasolar Planet Discovered in a Circumstellar Disk 23 so that, again, the likeliest explanation is a non-visible planet. Because in this case the orbital inclination is unknown, only a lower limit of 6.1 Jupiter masses can be indicated for its mass. Here one assumes that the mass of the star – a G dwarf – is 1.0 solar masses. HD 70573 is a member of the Hercules-Lyra Association, a local group estimated to be 200 million years old. An analysis of the stellar spectrum (equivalent width of the lithium line at 670.8 nm) yielded an age between 78 and 125 million years. Thus, this similarly aged planet is the second youngest known extrasolar planet after TW Hya b. The discovery of a planet at HD 70573 is significant also because this star is part of a sp i t z e r space telescope research program (sp i t z e r/Fe p s Legacy Program) examining the relationship between planets and older dust disks (so-called debris disks). Both of the described discoveries have shown that despite initial concerns, it is absolutely possible to prove that young stars have planets. This opens the door to completely new research inquiries into planetary formation. In addition to this program, the MPIA is now developing and building next generation observation instruments using other methods to track down extrasolar planets: direct imaging, astrometrical measurement of the apparent movement of the star in the sky, and the measurement of central star light intensity changes when the planet passes in front of it (transit photometry). Johny Setiawan, Thomas Henning, Ralf Launhardt, André Müller, Patrick Weise, Martin Kürster
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Page 5: Contents Preface ..................
Page 8 and 9: 6 I. General I. General I.1 Scienti
Page 10 and 11: 8 I. General Planet and Star Format
Page 12 and 13: 10 I. General plementary. Ground-ba
Page 14 and 15: 12 I. General High-fidelity imagers
Page 16 and 17: 14 I. General Fig. I.6: Foreseen de
Page 18 and 19: 16 I. General I.3 National and Inte
Page 20 and 21: 18 I. General Edinburgh, University
Page 22 and 23: 20 II. Highlights II.1 Youngest Ext
Page 26 and 27: 24 II. Highlights II.2 A Search for
Page 28 and 29: 26 II. Highlights F 1 [5] -2 0 2 4
Page 30 and 31: 28 II. Highlights Number of Planets
Page 32 and 33: 30 II. Highlights z [AU] z [AU] 1 0
Page 34 and 35: 32 II. Highlights t =0 T orb t =1 T
Page 36 and 37: 34 II. Highlights II.4 An Exoplanet
Page 38 and 39: 36 II. Highlights F / F 12m 4 3 2
Page 40 and 41: 38 II. Highlights the planet disapp
Page 42 and 43: 40 II. Highlights The Hercules Dwar
Page 44 and 45: 42 II. Highlights on the giant bran
Page 46 and 47: 44 II. Highlights II.6 Black Hole A
Page 48 and 49: 46 II. Highlights F [10 -23 W cm -
Page 50 and 51: 48 II. Highlights Flux [10 -23 W cm
Page 52 and 53: 50 II. Highlights Fig. II.7.2: A 22
Page 54 and 55: 52 II. Highlights i [mag] i [mag] 1
Page 56 and 57: 54 II. Highlights Follow-up Observa
Page 58 and 59: 56 II. Highlights II.8 Unique Galay
Page 60 and 61: 58 II. Highlights NGC5055 (M63) NGC
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Page 64 and 65: 62 II. Highlights be directly compa
Page 66 and 67: 64 III. Selected Research Areas III
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72 III. Selected Research Areas As
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74 III. Selected Research Areas a b
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76 III. Selected Research Areas Fig
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78 III. Selected Research Areas est
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80 III. Selected Research Areas tio
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82 III. Selected Research Areas mid
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84 III. Selected Research Areas for
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86 III. Selected Research Areas sio
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88 III. Selected Research Areas III
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90 III. Selected Research Areas mas
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92 IV. Instrumental Developments an
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100 IV. Instrumental Developments a
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118 V. People and Events Dr. Gerner
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120 V. People and Events Fig. V.2.2
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122 V. People and Events operated v
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124 V. People and Events Ludwig-Bie
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126 V. People and Events To interpr
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128 V. People and Events Within the
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130 V. People and Events Fig. V.5.1
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132 V. People and Events V.6 »A cl
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134 V. People and Events on through
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136 Staff Directors: Henning, Rix (
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138 Staff / Calar Alto / Department
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140 Teaching Activities / Service i
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142 Further Activities / Compatibil
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144 Cooperation with Industrial Com
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146 Conferences StageS workshop, MP
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148 Conferences Ralf Launhardt: Wor
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150 Conferences Anna Pasquali: ASU
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152 Publications Apai, D., A. Bik,
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154 Publications Chen, X. P., R. La
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156 Publications of an unusual dwar
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158 Publications Moreau, J. A. Peac
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160 Publications Pontoppidan, K. M.
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162 Publications Garching-Bonn Deep
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164 Publications Zirm, A. W., A. va
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166 Publications Linz, H., R. Klein
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168 Publications Güdel, M.: The su
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A656 Eppelheim Patrick- Henry- Sied
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Max Planck Institute for Astronomy - Annual Report 2007

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