生命が存在する可能性のある太陽系外惑星(An exoplanet that could host life)


生命の痕跡を探すのに適した、地球質量の希少な岩石質惑星を発見 Astronomers find rare Earth-mass rocky planet suitable for the search for signs of life

2023-02-03 マックス・プランク研究所



M矮星周辺の系外惑星を探索する「CARMENES」、ウルフ1069 b:近傍の超低質量星のハビタブルゾーンにある地球質量の惑星 The CARMENES search for exoplanets around M dwarfs, Wolf 1069 b: Earth-mass planet in the habitable zone of a nearby, very low-mass star

D. Kossakowski, M. Kürster, T. Trifonov, Th. Henning, J. Kemmer, J. A. Caballero, R. Burn, S. Sabotta, J. S. Crouse, T. J. Fauchez, E. Nagel, A. Kaminski, E. Herrero, E. Rodríguez, E. González-Álvarez, A. Quirrenbach, P. J. Amado, I. Ribas, A. Reiners, J. Aceituno, V. J. S. Béjar, D. Baroch, S. T. Bastelberger, P. Chaturvedi, C. Cifuentes, S. Dreizler, S. V. Jeffers, R. Kopparapu, M. Lafarga, M. J. López-González, S. Martí n-Ruiz, D. Montes, J. C. Morales, E. Pallé, A. Pavlov, S. Pedraz, V. Perdelwitz, M. Pérez-Torres, M. Perger, S. Reffert, C. Rodríguez López, M. Schlecker, P. Schöfer, A. Schweitzer, Y. Shan, A. Shields, S. Stock, E. Wolf, M. R. Zapatero Osorio, M. Zechmeister
Astronomy & Astrophysics  accepted: 21 December 2022


We present the discovery of an Earth-mass planet (Mbsini=1.36±0.21M⊕) on a 15.6d orbit of a relatively nearby (d∼9.6pc) and low-mass (0.167±0.011M⊙) M5.0V star, Wolf 1069. Sitting at a separation of 0.0672±0.0014au away from the host star puts Wolf 1069b in the habitable zone (HZ), receiving an incident flux of S=0.652±0.029S⊕. The planetary signal was detected using telluric-corrected radial-velocity (RV) data from the CARMENES spectrograph, amounting to a total of 262 spectroscopic observations covering almost four years. There are additional long-period signals in the RVs, one of which we attribute to the stellar rotation period. This is possible thanks to our photometric analysis including new, well-sampled monitoring campaigns undergone with the OSN and TJO facilities that supplement archival photometry (i.e., from MEarth and SuperWASP), and this yielded an updated rotational period range of Prot=150−170d, with a likely value at 169.3+3.7−3.6d. The stellar activity indicators provided by the CARMENES spectra likewise demonstrate evidence for the slow rotation period, though not as accurately due to possible factors such as signal aliasing or spot evolution. Our detectability limits indicate that additional planets more massive than one Earth mass with orbital periods of less than 10 days can be ruled out, suggesting that perhaps Wolf 1069 b had a violent formation history. This planet is also the 6th closest Earth-mass planet situated in the conservative HZ, after Proxima Centauri b, GJ 1061d, Teegarden’s Star c, and GJ 1002 b and c. Despite not transiting, Wolf 1069b is nonetheless a very promising target for future three-dimensional climate models to investigate various habitability cases as well as for sub-ms−1 RV campaigns to search for potential inner sub-Earth-mass planets in order to test planet formation theories.