OGLE-TR-56 b: First Exoplanet Discovered via Transits

 An event called a transit takes place each time a planet traverses across its star during its orbital journey. As viewed from Earth, these transits become visible as consistent reductions in the star's luminosity due to the obstruction caused by the planetary disk. 

Transits serve as one of the foremost techniques for identifying exoplanets. The star's light intensity diminishes at regular intervals, mirroring the planet's revolution time, and follows a unique pattern that is easily identifiable. Nearly 4,000 exoplanets have been discovered through this method, with many attributed to the Kepler telescope.

The distinction of being the first planet discovered through transits goes to OGLE-TR-56 b, discovered in 2002. Prior to this, another exoplanet, Osiris, was observed transiting but had already been identified via the radial velocity method, so it doesn't count as a transit discovery.

OGLE-TR-56 b's discovery was made under the OGLE project. The announcement came in July 2002, and the following year it was confirmed after being observed using the radial velocity method. Orbiting an F-type star, OGLE-TR-56 b is situated 1,500 light-years away from Earth, making it the furthest known exoplanet at the time of its discovery.

OGLE-TR-56 b is categorized as a hot Jovian, essentially a gas giant slightly bigger than Jupiter, boasting a mass 1.4 times and a diameter 1.3 times that of Jupiter. With a semi-major axis of a mere 0.02 AU, it completes one revolution around its star in just 1.2 days. Given its status as a gas giant and its proximity to its star, OGLE-TR-56 b isn't capable of supporting life.

Source: NASA.