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Event typeExoplanet Edit this on Wikidata
ConstellationAndromeda Edit this on Wikidata
Right ascension 00h 44m 20.89s[1]
Declination+41° 28′ 44.6″[1]
Distance2,185,247.73 ly (670,000 pc)[2]

PA-99-N2 is a microlensing event detected in the direction of the Andromeda Galaxy in 1999.


One possibility for the event is that a star in the disk of M31 gravitationally lensed a red giant also in the disk. The lensing star would have a mass between 0.02 M and 3.6 M with the most likely value near 0.5 M. In this case the lens profile makes it likely that the star has a planet.[2][3]

Possible exoplanet[edit]

The possible exoplanet would have a mass of 6.34 Jupiter mass. If confirmed, it would be the first exoplanet found in another galaxy.[4]

The PA-99-N2 planetary system[2]
(in order from star)
Mass Semimajor axis
Orbital period
Eccentricity Inclination Radius
b (unconfirmed) 6.34 MJ


  1. ^ a b "MEGA-ML 7". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 3 June 2018.
  2. ^ a b c "The Extrasolar Planet Encyclopaedia — PA-99-N2 b". Retrieved 2017-07-30.
  3. ^ Ingrosso, G.; Paolis, F. DE; Novati, S. Calchi; Jetzer, PH.; Nucita, A. A.; Zakharov, A. F. (2012). "Detection of Exoplanets in M31 with Pixel-Lensing: The Event Pa-99-N2 Case". The Twelfth Marcel Grossmann Meeting. The Twelfth Marcel Grossmann Meeting: on Recent Developments in Theoretical and Experimental General Relativity. p. 2191. arXiv:1001.2105. Bibcode:2012mgm..conf.2191I. doi:10.1142/9789814374552_0433. ISBN 978-981-4374-51-4.
  4. ^ An, Jin H.; Evans, N. W.; Kerins, E.; Baillon, P.; Calchi Novati, S.; Carr, B. J.; Creze, M.; Giraud‐Heraud, Y.; Gould, A.; Hewett, P.; Jetzer, Ph.; Kaplan, J.; Paulin‐Henriksson, S.; Smartt, S. J.; Tsapras, Y.; Valls‐Gabaud, D. (February 2004). "The Anomaly in the Candidate Microlensing Event PA‐99‐N2". The Astrophysical Journal. 601 (2): 845–857. arXiv:astro-ph/0310457. Bibcode:2004ApJ...601..845A. doi:10.1086/380820.