Motalebi, F.Udry, S.Gillon, M.Lovis, C.Ségransan, D.Buchhave, L. A.Demory, B. O.Malavolta, L.Dressing, C. D.Sasselov, D.Rice, K.Charbonneau, D.Cameron, A. CollierLatham, D.Molinari, E.Pepe, F.Affer, L.Bonomo, A. S.Cosentino, R.Dumusque, X.Figueira, P.Fiorenzano, A. M.Gettel, S.Harutyunyan, A.Haywood, R. D.Johnson, J.Lopez, E.Lopez-Morales, M.Mayor, M.Micela, G.Mortier, A.Nascimbeni, V.Philips, D.Piotto, G.Pollacco, D.Queloz, D.Sozzetti, A.Vanderburg, A.Watson, C. A.2019-09-262015Motalebi, F., S. Udry, M. Gillon, C. Lovis, D. Ségransan, L. A. Buchhave, B. O. Demory, et al. 2015. “The HARPS-N Rocky Planet Search.” Astronomy & Astrophysics 584 (November): A72. https://doi.org/10.1051/0004-6361/201526822.0004-63611432-0746http://nrs.harvard.edu/urn-3:HUL.InstRepos:41412100We know now from radial velocity surveys and transit space missions that planets only a few times more massive than our Earth are frequent around solar-type stars. Fundamental questions about their formation history, physical properties, internal structure, and atmosphere composition are, however, still to be solved. We present here the detection of a system of four low-mass planets around the bright (V = 5.5) and close-by (6.5 pc) star HD219134. This is the first result of the Rocky Planet Search programme with HARPS-N on the Telescopio Nazionale Galileo in La Palma. The inner planet orbits the star in 3.0935 +/- 0.0003 days, on a quasi-circular orbit with a semi-major axis of 0.0382 +/- 0.0003AU. Spitzer observations allowed us to detect the transit of the planet in front of the star making HD219134 b the nearest known transiting planet to date. From the amplitude of the radial velocity variation (2.25 +/- 0.22 ms(-1)) and observed depth of the transit (359 +/- 38 ppm), the planet mass and radius are estimated to be 4.36 +/- 0.44 M-circle plus and 1.606 +/- 0.086 R-circle plus, leading to a mean density of 5.76 +/- 1.09 g cm(-3), suggesting a rocky composition. One additional planet with minimum-mass of 2.78 +/- 0.65 M-circle plus moves on a close-in, quasi-circular orbit with a period of 6.767 +/- 0.004 days. The third planet in the system has a period of 46.66 +/- 0.08 days and a minimum-mass of 8.94 +/- 1.13 M-circle plus, at 0.233 +/- 0.002AU from the star. Its eccentricity is 0.46 +/- 0.11. The period of this planet is close to the rotational period of the star estimated from variations of activity indicators (42.3 +/- 0.1 days). The planetary origin of the signal is, however, the preferred solution as no indication of variation at the corresponding frequency is observed for activity-sensitive parameters. Finally, a fourth additional longer-period planet of mass of 71 M-circle times orbits the star in 1842 days, on an eccentric orbit (e = 0.34 +/- 0.17) at a distance of 2.56AU.en-USJournal Article2019-09-2610.1051/0004-6361/201526822