Specht DPoleski RPenny MTKerins EMcDonald IChung-Uk LUdalski ABond IAShvartzvald YZang WStreet RAHogg DWGaudi BSBarclay TBarentsen GHowell SBMullally FHenderson CBBryson STCaldwell DAHaas MRVan Cleve JELarson KMcCalmont KPeterson CPutnam DRoss SPackard MReedy LAlbrow MDSun-Ju CJung YKGould AHan CKyu-Ha HYoon-Hyun RIn-Gu SYang HYee JCSang-Mok CDong-Jin KSeung-Lee KDong-Joo LLee YByeong-Gon PPogge RWSzymański MKSoszyński IUlaczyk KPietrukowicz PKozłowski SZSkowron JMróz PMao SFouqué PZhu WAbe FBarry RBennett DPBhattacharya AFukui AFujii HHirao YItow YKirikawa RKondo IKoshimoto NMatsubara YMatsumoto SMiyazaki SMuraki YOlmschenk GRanc COkamura ARattenbury NJSatoh YSumi TSuzuki DSilva SIToda TTristram PJVandorou AYama HBeichman CBryden GNovati SC2025-01-152025-01-152023-04-01Specht D, Poleski R, Penny MT, Kerins E, McDonald I, Chung-Uk L, Udalski A, Bond IA, Shvartzvald Y, Zang W, Street RA, Hogg DW, Gaudi BS, Barclay T, Barentsen G, Howell SB, Mullally F, Henderson CB, Bryson ST, Caldwell DA, Haas MR, Van Cleve JE, Larson K, McCalmont K, Peterson C, Putnam D, Ross S, Packard M, Reedy L, Albrow MD, Sun-Ju C, Jung YK, Gould A, Han C, Kyu-Ha H, Yoon-Hyun R, In-Gu S, Yang H, Yee JC, Sang-Mok C, Dong-Jin K, Seung-Lee K, Dong-Joo L, Lee Y, Byeong-Gon P, Pogge RW, Szymański MK, Soszyński I, Ulaczyk K, Pietrukowicz P, Kozłowski SZ, Skowron J, Mróz P, Mao S, Fouqué P, Zhu W, Abe F, Barry R, Bennett DP, Bhattacharya A, Fukui A, Fujii H, Hirao Y, Itow Y, Kirikawa R, Kondo I, Koshimoto N, Matsubara Y, Matsumoto S, Miyazaki S, Muraki Y, Olmschenk G, Ranc C, Okamura A, Rattenbury NJ, Satoh Y, Sumi T, Suzuki D, Silva SI, Toda T, Tristram PJ, Vandorou A, Yama H, Beichman C, Bryden G, Novati SC. (2023). Kepler K2 Campaign 9 – II. First space-based discovery of an exoplanet using microlensing. Monthly Notices of the Royal Astronomical Society. 520. 4. (pp. 6350-6366).0035-8711https://mro.massey.ac.nz/handle/10179/72376We present K2-2016-BLG-0005Lb, a densely sampled, planetary binary caustic-crossing microlensing event found from a blind search of data gathered from Campaign 9 of the Kepler K2 mission (K2C9). K2-2016-BLG-0005Lb is the first bound microlensing exoplanet discovered from space-based data. The event has caustic entry and exit points that are resolved in the K2C9 data, enabling the lens-source relative proper motion to be measured. We have fitted a binary microlens model to the Kepler data and to simultaneous observations from multiple ground-based surveys. Whilst the ground-based data only sparsely sample the binary caustic, they provide a clear detection of parallax that allows us to break completely the microlensing mass-position-velocity degeneracy and measure the planet’s mass directly. We find a host mass of 0.58 ± 0.04 M and a planetary mass of 1.1 ± 0.1 MJ. The system lies at a distance of 5.2 ± 0.2 kpc from Earth towards the Galactic bulge, more than twice the distance of the previous most distant planet found by Kepler. The sky-projected separation of the planet from its host is found to be 4.2 ± 0.3 au which, for circular orbits, deprojects to a host separation a = 4.4+−0149 au and orbital period P = 13+−29 yr. This makes K2-2016-BLG-0005Lb a close Jupiter analogue orbiting a low-mass host star. According to current planet formation models, this system is very close to the host mass threshold below which Jupiters are not expected to form. Upcoming space-based exoplanet microlensing surveys by NASA’s Nancy Grace Roman Space Telescope and, possibly, ESA’s Euclid mission, will provide demanding tests of current planet formation models.(c) The author/shttps://creativecommons.org/licenses/by/4.0/Journal article10.1093/mnras/stad2121365-2966CC BYjournal-article6350-6366