OGLE-2003-BLG-235/MOA 2003-BLG-53 was a gravitational microlensing event which occurred in the constellation of Sagittarius during July 2003. The event was observed both as part of the Optical Gravitational Lensing Experiment (OGLE) and by the Microlensing Observations in Astrophysics group (MOA), hence the double designation.

The source star in the gravitational lens is a main sequence star of spectral type G located around 8.8 kiloparsecs (29,000 light years) away in the galactic bulge. The lens star is an orange dwarf star of spectral type K, which is accompanied by a giant planet.

Lens system

OGLE-2003-BLG-235L/MOA-2003-BLG-53L is the lens star. In 2004, analysis of the light curve produced as it passed in front of the source star allowed detection of an exoplanet orbiting the star with a mass 0.0039 times that of the host star (this would put it in the jovian mass range). The star was originally assumed to be a red dwarf star, since they are the most common type of star in the galaxy.

By 2006, the source and lens star had moved far enough apart (as viewed from Earth) that their light could be separated. Observations by the Hubble Space Telescope revealed that in fact the lens star was actually brighter and less red than expected, matching the expected spectra for a K dwarf of about 0.63 solar masses, more massive than the average star in the galaxy. This enables an estimate of the distance to the lens star, which puts it at around 5.8 kiloparsecs (19,000 light years) away.


OGLE-2003-BLG-235Lb is an extrasolar planet discovered in 2004 by the OGLE and MOA collaborations. Its high mass indicates that it is most probably a gas giant planet similar to Jupiter. It is located around 4.3 AU away from its parent star.


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