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A super-Earth orbiting near the inner edge of the habitable zone around the M4.5 dwarf Ross 508

Harakawa, Hiroki and Takarada, Takuya and Kasagi, Yui and Hirano, Teruyuki and Kotani, Takayuki and Kuzuhara, Masayuki and Omiya, Masashi and Kawahara, Hajime and Fukui, Akihiko and Hori, Yasunori and Ishikawa, Hiroyuki Tako and Ogihara, Masahiro and Livingston, John and Brandt, Timothy D. and Currie, Thayne and Aoki, Wako and Beichman, Charles A. and Henning, Thomas and Hodapp, Klaus and Ishizuka, Masato and Izumiura, Hideyuki and Jacobson, Shane and Janson, Markus and Kambe, Eiji and Kodama, Takanori and Kokubo, Eiichiro and Konishi, Mihoko and Krishnamurthy, Vigneshwaran and Kudo, Tomoyuki and Kurokawa, Takashi and Kusakabe, Nobuhiko and Kwon, Jungmi and Matsumoto, Yuji and McElwain, Michael W. and Mitsui, Koyu and Nakagawa, Takao and Narita, Norio and Nishikawa, Jun and Nugroho, Stevanus K. and Serabyn, Eugene and Serizawa, Takuma and Takahashi, Aoi and Ueda, Akitoshi and Uyama, Taichi and Vievard, Sébastien and Wang, Ji and Wisniewski, John and Tamura, Motohide and Sato, Bun’ei (2022) A super-Earth orbiting near the inner edge of the habitable zone around the M4.5 dwarf Ross 508. Publications of the Astronomical Society of Japan, 74 (4). pp. 904-922. ISSN 0004-6264. doi:10.1093/pasj/psac044.

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We report the near-infrared radial velocity (RV) discovery of a super-Earth planet on a 10.77 d orbit around the M4.5 dwarf Ross 508 (J_(mag) = 9.1). Using precision RVs from the Subaru Telescope IRD (InfraRed Doppler) instrument, we derive a semi-amplitude of 3.92^(+0.60)_(−0.58) m s⁻¹⁠, corresponding to a planet with a minimum mass m sin i = 4.00^(+0.53)_(−0.55) M_⊕⁠. We find no evidence of significant signals at the detected period in spectroscopic stellar activity indicators or MEarth photometry. The planet, Ross 508 b, has a semi-major axis of 0.05366^(+0.00056)_(−0.00049) au. This gives an orbit-averaged insolation of ≈1.4 times the Earth’s value, placing Ross 508 b near the inner edge of its star’s habitable zone. We have explored the possibility that the planet has a high eccentricity and its host is accompanied by an additional unconfirmed companion on a wide orbit. Our discovery demonstrates that the near-infrared RV search can play a crucial role in finding a low-mass planet around cool M dwarfs like Ross 508.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Harakawa, Hiroki0000-0002-7972-0216
Hirano, Teruyuki0000-0003-3618-7535
Kotani, Takayuki0000-0001-6181-3142
Kuzuhara, Masayuki0000-0002-4677-9182
Omiya, Masashi0000-0002-5051-6027
Kawahara, Hajime0000-0003-3309-9134
Fukui, Akihiko0000-0002-4909-5763
Hori, Yasunori0000-0003-4676-0251
Ishikawa, Hiroyuki Tako0000-0001-6309-4380
Livingston, John0000-0002-4881-3620
Brandt, Timothy D.0000-0003-2630-8073
Currie, Thayne0000-0002-7405-3119
Aoki, Wako0000-0002-8975-6829
Beichman, Charles A.0000-0002-5627-5471
Hodapp, Klaus0000-0003-0786-2140
Janson, Markus0000-0001-8345-593X
Kodama, Takanori0000-0001-9032-5826
Konishi, Mihoko0000-0003-0114-0542
Krishnamurthy, Vigneshwaran0000-0003-2310-9415
Kudo, Tomoyuki0000-0002-9294-1793
Kusakabe, Nobuhiko0000-0001-9194-1268
Kwon, Jungmi0000-0003-2815-7774
Matsumoto, Yuji0000-0002-2383-1216
McElwain, Michael W.0000-0003-0241-8956
Nakagawa, Takao0000-0002-6660-9375
Narita, Norio0000-0001-8511-2981
Nishikawa, Jun0000-0001-9326-8134
Takahashi, Aoi0000-0003-3881-3202
Uyama, Taichi0000-0002-6879-3030
Vievard, Sébastien0000-0003-4018-2569
Wisniewski, John0000-0001-9209-1808
Tamura, Motohide0000-0002-6510-0681
Additional Information:© The Author(s) 2022. Published by Oxford University Press on behalf of the Astronomical Society of Japan. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited. Received: 06 March 2022. Accepted: 23 May 2022. Published: 30 June 2022. This research is based on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan. We are honored and grateful for the opportunity of observing the Universe from Maunakea, which has the cultural, historical, and natural significance in Hawaii. M.T. is supported by Japan Society for the Promotion of Science (JSPS) KAKENHI grant Nos. 18H05442, 15H02063, and 22000005. YH was partly supported by a Grant-in-Aid for Scientific Research on Innovative Areas (JSPS KAKENHI Grant Number 18H05439). This work is partly supported by JSPS KAKENHI Grant Numbers JP18H05439 and JP21K20388, Japan Science and Technology Agency (JST), Core Research for Evolutional Science and Technology (CREST) Grant Number JPMJCR1761, the Astrobiology Center of National Institutes of Natural Sciences (NINS) (Grant Number AB031010). This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France (Wenger et al. 2000). This research made use of Astropy,3 a community-developed core Python package for Astronomy (Astropy Collaboration 2013, 2018). This research has made use of the NASA Exoplanet Archive 〈〉, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. This research has made use of data obtained from or tools provided by the portal of The Extrasolar Planets Encyclopaedia. The corner (Foreman-Mackey 2016) Python module has been helpful to create the figures in this paper.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Japan Society for the Promotion of Science (JSPS)18H05442
Japan Society for the Promotion of Science (JSPS)15H02063
Japan Society for the Promotion of Science (JSPS)22000005
Japan Society for the Promotion of Science (JSPS)18H05439
Japan Society for the Promotion of Science (JSPS)JP18H05439
Japan Society for the Promotion of Science (JSPS)JP21K20388
Japan Science and Technology AgencyJPMJCR1761
National Institutes of Natural Sciences of JapanAB031010
Subject Keywords:infrared: planetary systems—planets and satellites: terrestrial planets—techniques: radial velocities
Issue or Number:4
Record Number:CaltechAUTHORS:20220802-743377000
Persistent URL:
Official Citation:Hiroki Harakawa, Takuya Takarada, Yui Kasagi, Teruyuki Hirano, Takayuki Kotani, Masayuki Kuzuhara, Masashi Omiya, Hajime Kawahara, Akihiko Fukui, Yasunori Hori, Hiroyuki Tako Ishikawa, Masahiro Ogihara, John Livingston, Timothy D Brandt, Thayne Currie, Wako Aoki, Charles A Beichman, Thomas Henning, Klaus Hodapp, Masato Ishizuka, Hideyuki Izumiura, Shane Jacobson, Markus Janson, Eiji Kambe, Takanori Kodama, Eiichiro Kokubo, Mihoko Konishi, Vigneshwaran Krishnamurthy, Tomoyuki Kudo, Takashi Kurokawa, Nobuhiko Kusakabe, Jungmi Kwon, Yuji Matsumoto, Michael W McElwain, Koyu Mitsui, Takao Nakagawa, Norio Narita, Jun Nishikawa, Stevanus K Nugroho, Eugene Serabyn, Takuma Serizawa, Aoi Takahashi, Akitoshi Ueda, Taichi Uyama, Sébastien Vievard, Ji Wang, John Wisniewski, Motohide Tamura, Bun’ei Sato, A super-Earth orbiting near the inner edge of the habitable zone around the M4.5 dwarf Ross 508, Publications of the Astronomical Society of Japan, Volume 74, Issue 4, August 2022, Pages 904–922,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:116024
Deposited By: George Porter
Deposited On:02 Aug 2022 19:56
Last Modified:17 Oct 2022 18:27

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