Exoplanets and Free-Floating Planets

The search for and study of planets beyond the Solar System, known as exoplanets, is one of the fastest-growing fields of modern astronomy. For more than two decades, the OGLE project has played a strategic role in this area. Thanks to observations carried out with the Warsaw Telescope in Chile, OGLE scientists were among the first in the world to apply two groundbreaking methods for discovering exoplanets. One of these methods even enables the detection of so-called free-floating planets—objects not gravitationally bound to any star, wandering alone through the Milky Way.

The Transit Method

This method relies on detecting slight drops in a star’s brightness when a planet passes (transits) in front of it, blocking part of its disk. The first discovery using this technique—the planet OGLE-TR-56 b—was made in 2001 based on OGLE observational data. This achievement paved the way for the success of major space missions such as Kepler and TESS, which have applied this method extensively. The search for transiting planets within OGLE is still ongoing, with around 100 highly probable planetary candidates currently awaiting confirmation.

The Gravitational Microlensing Method

This method exploits the effect that occurs when the light of a distant background star is temporarily bent and magnified by the gravity of a star or planet lying in the foreground. It allows for the detection of low-mass planets located far from their parent stars. The Astronomical Observatory of the University of Warsaw is one of the world’s leading centers specializing in gravitational microlensing. The first discoveries using this method were made in 2003 as part of OGLE observations. So far, this technique has led to the detection of over 250 exoplanets.

This method also makes it possible to detect free-floating planets. Astronomers from the University of Warsaw showed that such objects are common in the Milky Way. Since they do not emit light, they cannot be found with traditional telescopic observations. By analyzing long-term observations of more than 50 million Milky Way stars, researchers discovered that free-floating planets with masses smaller than Neptune but greater than Earth are several times more numerous than stars in our Galaxy.