Press Releases 2006

ESO PR Photo 18a/06

Planetary System Around HD 69830 (Artist's Impression)

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The HARPS measurement reveal the presence of three planets with masses between 10 and 18 Earth masses around HD 69830, a rather normal star slightly less massive than the Sun. The planets' mean distance are 0.08, 0.19, and 0.63 the mean distance between the Earth and the Sun. From previous observations, it seems that there exists also an asteroid belt, whose location is unknown. It could either lie between the two outermost planets, or farther from its parent star than 0.8 the mean Earth-Sun distance.

ESO PR Photo 18b/06

Planetary System Around HD 69830 (Artist's Impression)

[Preview - JPEG: 473 x 400 pix - 22k]
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[HiRes - TIFF: 3000 x 2536 pix - 23M]

This image is taken from a point of view inside the asteroid belt, which is assumed here to lie between the two outermost planets.

ESO PR Photo 18c/06

Radial Velocity Measurements of HD 69830

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Measurements of the radial velocity of the star HD 69830 obtained by HARPS on the ESO 3.6m telescope at La Silla as a function of time, from November 2004 till February 2005 (a) and from mid-October 2005 till February 2006 (b). The two innermost planets are clearly revealed, while the presence of the third one becomes clear when removing the signal of the inner planets and binning the data points (one per observing run), as shown in (c). The lower parts of (a) and (b) show the residuals from the best fit indicated by the solid line.

ESO PR Photo 18d/06

Phase Folded Measurements of HD 69830

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The HARPS radial velocity measurements of HD 69830 are folded with the orbital periods of the three discovered planets: 8.67, 31.6 and 197 days, respectively. In each case, the contribution of the two other planets has been subtracted. The solid line shows the best fit to the measurements, corresponding to minimum masses of 10.2, 11.8 and 18.1 Earth masses. Note that the full span of the vertical axis is only 13 m/s! Error bars indicate the accuracy of the measurements. The integration time was 4 minutes on average for the first 18 measurements (shown as open dots), and was increased to 15 minutes for the remaining points (full dots). The latter measurements are therefore of much higher quality.

ESO PR Photo 18e/06

Formation Process of the Planetary System around HD 69830

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Illustration of the possible formation process and present day structure of the planetary system around HD 68930. The three planets form from embryos originally located at larger distances (dashed ellipses) than the present ones (indicated by solid ellipses at 0.07, 0.18 and 0.63 the mean Earth-Sun distance). The embryos of the inner and middle planets start interior to the ice line, so that these two planets build up from rocky planetesimals and gas. The two planets consist of a central rocky core (in brown) and an envelope of gas (in gray). The embryo of the outermost planet starts beyond the ice line, and the planet accumulates a large amount of ice at the beginning of its formation. The planet finally consists of a central rocky core (brown), surrounded by a shell of water (ice or liquid - in blue), and a quite massive gas envelope (gray).