Welcome to the first entry in my series on exoplanets based on NASA's Exoplanet Travel Bureau site. The site itself provides the gorgeous vintage travel posters and guided tours, but I wanted to do a deeper dive into these exoplanets.
51 Pegasi b is officially named Dimidium, but was unofficially dubbed "Bellerophon" by astronomer Geoffrey Marcy, who followed the convention of naming planets after Greek and Roman mythological figures (Bellerophon rode the winged horse Pegasus in Greek mythology).
It was the first exoplanet discovered orbiting a Sun-like star, 51 Pegasi, located approximately 50.9 light-years away from Earth in the constellation Pegasus. The discovery of 51 Pegasi b was announced in 1995 by Swiss astronomers Michel Mayor and Didier Queloz and it had a profound impact on our understanding of planetary systems beyond our solar system. It's classified as a "Hot Jupiter", which are gas giant planets similar in size and composition to Jupiter but with extremely close orbits to their parent stars. In the case of 51 Pegasi b, it orbits its host star at a distance of only about 4.2 million miles (about 6.8 million kilometers, or approximately 17.6 times the average distance between Earth and the Moon), completing an orbit in approximately 4.2 Earth days.
Its proximity to 51 Pegasi makes it subject to intense radiation and extreme temperatures. This close orbit was unexpected at the time of its discovery because it challenged existing theories of planetary formation. The discovery of the exoplanet 51 Pegasi b raised questions about how gas giants could form and migrate so close to their parent stars. Its existence challenged the traditional model of planetary formation, which suggested that gas giants should form farther from their stars and not migrate inward to such close orbits, and as such astronomers are revising their theories of planet formation.
51 Pegasi b was detected using the radial velocity method, also known as the Doppler spectroscopy technique. This method involves measuring the periodic changes in the star's spectral lines (dark or bright lines in an otherwise uniform and continuous spectrum) caused by the gravitational tug of an orbiting planet. These variations in the star's radial velocity indicated the presence of an unseen companion, which turned out to be the exoplanet. Since the discovery of 51 Pegasi b, thousands of exoplanets have been identified using this and other methods, including the transit method and direct imaging. It opened the door to further research into exoplanetary systems and has led to a deeper understanding of the diversity of planets in the universe.
Overall, 51 Pegasi b is a significant milestone in the history of astronomy, as it marked the beginning of the era of exoplanetary discoveries and revolutionized our understanding of planetary systems beyond our solar system.