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The Warsaw Voice » The Polish Science Voice » February 23, 2012
Space Research
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Exploring Extrasolar Planets
February 23, 2012   
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A group of Polish astronomers—led by Prof. Andrzej Udalski, Prof. Marcin Kubiak, and Michał Szymański, Ph.D., from the Astronomical Observatory of the University of Warsaw—are busy conducting the Optical Gravitational Lensing Experiment (OGLE), which aims to explore planets outside our solar system, known as extrasolar planets or exoplanets.

The Polish astronomers lead the way in international research on gravitational microlensing.

In the course of the research, the gravitational microlensing method has helped identify a number of planets outside the solar system.

It turns out that when an object such as a planet circles around a star whose gravitational field works like a lens, the object may radically alter the shape of the curve illustrating changes in the star’s brightness, the astronomers say. In cases like these, the bell-shaped graph features extra peaks caused by the planet’s lensing effect.

The microlensing technique is extremely hard to use to detect planets and researchers need a lot of luck to succeed. To begin with, they need to regularly watch millions of stars in the hope that once in a while, the phenomenon occurs for one of them. For the time being, however, microlensing is the only way to detect very distant and lightweight planets.

Star gazing in Chile

The OGLE project team are using a dedicated 1.3-meter telescope at the Las Campanas Observatory in Chile connected to a CCD camera designed by Prof. Udalski. Combined with high-performance software written by Polish scientists, the equipment has made the Polish team the monopolists in the global research on gravitational microlensing.

One of the most interesting microlenses to have been discovered during the OGLE project to date is the OGLE-2006-BLG-109, which in March and April 2006 revealed highly intriguing changes in brightness. The only way to account for the changes was to propose the star was accompanied two planets, one with 0.71 times the mass of Jupiter on an orbit 2.3 astronomical units (a unit of length equal to the average distance between the Earth and the Sun) from its star and the other with 0.27 times the mass of Jupiter and located 4.6 astronomical units from the star.

The Polish scientists are the world leaders in extrasolar planet detection using methods other than gravitational microlensing. The OGLE team has also been using the highly efficient transit method, which has led to the discovery of several new planets with another several dozen awaiting confirmation.

Research on extrasolar planets has been a Polish specialty. The first extrasolar planetary system was discovered by Polish astronomer Prof. Aleksander Wolszczan. The gravitational microlensing method was invented by Prof. Bohdan Paczyński, who together with his student Shude Mao, proposed that it be used to search for exoplanets. The OGLE team put the method into action.

Poland’s Marcin Konacki, Ph.D., from the Astronomical Center of the Polish Academy of Sciences (PAN), has used the so-called transit method to discover a planet in the HD 188753 triple star system.
(A.O.)
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