Eksoplaneettoja

Eksoplaneettoja, Finnish for exoplanets, are planets that orbit stars other than the Sun. The first convincing discovery of an exoplanet was announced in 1992, when astronomers detected a planet around the pulsar PSR B1257+12. The subsequent discovery of a planet orbiting the sun-like star 51 Pegasi in 1995 marked the beginning of a prolific field of exoplanetary science.

Exoplanets are detected by several indirect methods. The most prolific technique is the radial‑velocity method, which measures the tiny wobble a star exhibits due to the gravitational pull of an orbiting planet. Transit photometry, the method employed by missions such as Kepler and TESS, records the slight dimming of a star as a planet crosses its disk. Gravitational microlensing, direct imaging, and astrometry provide complementary data for certain systems.

To date, thousands of confirmed exoplanets have been catalogued. They exhibit a remarkable diversity: hot Jupiters orbiting within a few days of their host stars, super‑Earths with masses between Earth and Neptune, and Earth‑size planets located in the habitable zone where liquid water could exist. The Kepler mission alone has identified over two thousand planet candidates, many of which have been confirmed by follow‑up observations.

The study of exoplanets informs planetary formation theories and the potential for life beyond Earth. By comparing the architectures of other planetary systems with our own, scientists refine models of how disks of gas and dust evolve into complex arrangements of planets. Future observatories, such as the James Webb Space Telescope and the planned Extremely Large Telescopes, aim to analyze the atmospheres of rocky exoplanets, searching for biosignatures and further advancing our understanding of the cosmos.