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Astron. Astrophys. 353, L33-L36 (2000)

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Letter to the Editor

An extrasolar giant planet in an Earth-like orbit *

Precise radial velocities of the young star [FORMULA] Horologii = HR 810

M. Kürster 1, M. Endl 1,2, S. Els 1,3, A.P. Hatzes 4, W.D. Cochran 4, S. Döbereiner 5 and K. Dennerl 5

1 European Southern Observatory, Casilla 19001, Vitacura, Santiago 19, Chile
2 Universität Wien, Institut für Astronomie, Türkenschanzstrasse 17, 1180 Wien, Austria
3 Universität Heidelberg, Institut für Theoretische Astrophysik, Tiergartenstrasse 15, 69121 Heidelberg, Germany
4 The University of Texas at Austin, McDonald Observatory, Austin, TX 78712-1083, USA
5 Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstrasse, 85748 Garching, Germany

Received 19 October 1999 / Accepted 7 December 1999


We present 5 1/2 years of radial velocity (RV) monitoring with the ESO CES of the young (ZAMS) G0V star [FORMULA] Hor. We find a Keplerian signal with a period of 320.1 d indicative of an orbiting planet with minimum mass [FORMULA]. With an eccentricity of 0.161 and a semi-major axis of 0.925 AU this object moves in the most Earth-like orbit found so far among extrasolar planets. [FORMULA] Hor is the youngest star with a known planet. In addition to the planetary signal we find an excess RV scatter of [FORMULA] rms exceeding our measurement precision of [FORMULA] and probably due to stellar activity.

Key words: stars: planetary systems – stars: individual: Hor – stars: rotation – techniques: radial velocities

* Based on observations collected at the European Southern Observatory, La Silla

Send offprint requests to: M. Kürster (mkurster@eso.org)

© European Southern Observatory (ESO) 2000

Online publication: January 18, 2000