Notable Exoplanet Discoveries to Know for Exoplanetary Science

Notable exoplanet discoveries have transformed our understanding of the universe. From the first confirmed exoplanet around a Sun-like star to potentially habitable worlds, these findings challenge existing theories and open new avenues for exploring life beyond Earth.

1. 51 Pegasi b (first confirmed exoplanet orbiting a Sun-like star)

   • Discovered in 1995, marking the first detection of an exoplanet around a star similar to our Sun.
   • Its discovery challenged existing theories about planet formation and migration.
   • The planet is a "hot Jupiter," with a short orbital period of about 4.2 days.

2. HD 209458 b (first transiting exoplanet)

   • Discovered in 1999, it was the first exoplanet observed to transit its host star.
   • The transit method allowed astronomers to measure the planet's size and atmospheric composition.
   • It has a significant atmosphere, with evidence of water vapor detected.

3. Kepler-16b (first circumbinary planet)

   • Discovered in 2011, it orbits two stars, making it the first confirmed circumbinary planet.
   • Its discovery provided insights into the dynamics of planetary systems with multiple stars.
   • The planet is similar in size to Saturn and is located in the Kepler-16 system.

4. Gliese 581g (potentially habitable exoplanet, though controversial)

   • Discovered in 2010, it is located in the habitable zone of its star, raising the possibility of liquid water.
   • Its existence sparked debate regarding its actual detection and habitability.
   • The planet's mass suggests it could be rocky, similar to Earth.

5. TRAPPIST-1 system (seven Earth-sized planets)

   • Discovered in 2017, this system contains seven Earth-sized exoplanets, three of which are in the habitable zone.
   • The close proximity of the planets allows for comparative studies of their atmospheres and potential habitability.
   • The system's star is an ultra-cool dwarf, which influences the planets' climates.

6. Proxima Centauri b (nearest potentially habitable exoplanet)

   • Discovered in 2016, it orbits Proxima Centauri, the closest star to the Sun.
   • Located in the habitable zone, it raises interest for future studies on habitability and potential life.
   • Its proximity makes it a prime target for future exploration missions.

7. HR 8799 system (first directly imaged multi-planet system)

   • Discovered in 2008, it is the first system where multiple exoplanets were directly imaged.
   • The system contains four gas giant planets, providing insights into planetary formation and evolution.
   • Direct imaging allows for the study of the planets' atmospheres and compositions.

8. PSR B1257+12 system (first confirmed exoplanets, orbiting a pulsar)

   • Discovered in 1992, it was the first confirmed detection of exoplanets, orbiting a pulsar.
   • The system includes three planets, showcasing the diversity of planetary systems.
   • Its discovery expanded the understanding of planet formation in extreme environments.

9. Kepler-452b (Earth-like planet in habitable zone of Sun-like star)

   • Discovered in 2015, it is often referred to as "Earth's cousin" due to its similarities.
   • Located in the habitable zone of a star similar to the Sun, it raises interest in potential habitability.
   • The planet's size and distance from its star suggest conditions that could support liquid water.

10. HD 189733 b (first exoplanet with detected atmospheric composition)

    • Discovered in 2005, it was the first exoplanet where the atmospheric composition was analyzed.
    • Observations revealed the presence of water, methane, and carbon dioxide in its atmosphere.
    • The planet is a hot Jupiter, with extreme weather conditions, including high-speed winds.