Date of the discovery: 31 October 2019

Short Description: Kojima-1Lb is an exoplanet discovered by an Japanese amateur astronomer, called Tadashi Kojima. The exoplanet was discovered with the microlensing method. This is when a star moves in front of another star and lenses the light of the background star. Sometimes the brightening caused by the star comes with a second smaller brightening caused by planets orbiting the star. Usually microlensing exoplanets are very far away, but this one is quite close, in a less crowded region and could be studied in the future with other techniques. It is an exoplanet larger than Neptune on the snow line of the star. It orbits the star, which is less massive than our sun, at 1.1 au (astronomical units = earth-sun distance).

Amateur Astronomer(s): Tadashi Kojima

Researchers in the discovery paper: Fukui, A.; Suzuki, D.; Koshimoto, N.; Bachelet, E.; Vanmunster, T.; Storey, D.; Maehara, H.; Yanagisawa, K.; Yamada, T.; Yonehara, A.; Hirano, T.; Bennett, D. P.; Bozza, V.; Mawet, D.; Penny, M. T.; Awiphan, S.; Oksanen, A.; Heintz, T. M.; Oberst, T. E.; Béjar, V. J. S. Casasayas-Barris, N.; Chen, G.; Crouzet, N.; Hidalgo, D.; Klagyivik, P.; Murgas, F.; Narita, N.; Palle, E.; Parviainen, H.; Watanabe, N.; Kusakabe, N.; Mori, M.; Terada, Y.; de Leon, J. P.; Hernandez, A.; Luque, R.; Monelli, M.; Montañes-Rodriguez, P.; Prieto-Arranz, J.; Murata, K. L.; Shugarov, S.; Kubota, Y.; Otsuki, C.; Shionoya, A.; Nishiumi, T.; Nishide, A.; Fukagawa, M.; Onodera, K.; Villanueva, S., Jr.; Street, R. A.; Tsapras, Y.; Hundertmark, M.; Kuzuhara, M.; Fujita, M.; Beichman, C.; Beaulieu, J. -P.; Alonso, R.; Reichart, D. E.; Kawai, N.; Tamura, M.

Link to paper in ADS: https://ui.adsabs.harvard.edu/abs/2019AJ….158..206F/abstract

SIMBAD page: http://simbad.u-strasbg.fr/simbad/sim-id?Ident=%4012340127&Name=NAME%20Kojima-1&submit=submit

Telescopes involved: Equipment by Kojima: Canon EOS 6D + 135-mm f3.2 lens and many professional telescopes over the world

Figrue 1 of the paper, showing the microlensing event
Other pages:

sky and telescope: https://www.skyandtelescope.com/astronomy-news/amateur-neptune-snow-line/

Credit for the header image: T. Kojima / AAVSO

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