In 1995, astronomy changed dramatically when scientists found a planet orbiting a Sun-like star. In that year, astronomers found a planet orbiting a Sun-like star known as 51 Pegasi at an estimated distance of about 50 light-years away from Earth. 51 Pegasi b, as the planet came to be called, was an extraordinary discovery. It was a gigantic planet that orbited its star every 4.2 days.Until then, astronomers had largely used our solar system as the main model for studying planetary systems. For years, scientists thought gas giants had to orbit far from their parent stars because of the intense heat. However, the discovery of 51 Pegasi b turned this notion on its head by revealing that nature could create other ways of structuring planetary systems, involving massive planets very close to their parent stars.Challenging the planetary modelThe finding forced scientists to rethink long-held assumptions. As described by the European Space Agency, the planet 51 Pegasi b is about half as massive as Jupiter but orbits its sun much nearer than Mercury orbits the sun of the earth. Explaining such a phenomenon was not an easy task for scientists during those times.Scientists realized that planets could exist in forms unlike those in our solar system. In other words, the Solar System would no longer be the sole model for understanding planetary systems.This discovery was made through the radial velocity technique, which is also known as the wobble technique. According to the information available on the NASA Universe Exploration website of the National Aeronautics and Space Administration, no visual sighting of the planet was made. Instead, astronomers relied on the slight wobbles in the star’s movements induced by the planet’s gravitational force. The technique became crucial for finding many planets and is now one of astronomy’s most important methods.
The radial velocity method to detect exoplanet is based on the detection of variations in the velocity of the central star, due to the changing direction of the gravitational pull from an (unseen) exoplanet as it orbits the star. Image Credit: Wikimedia Commons
Discovery of the hot JupitersThe European team announced 51 Pegasi b in October 1995, and astronomers at Lick Observatory verified it a week later. Such a fast verification contributed to the reception of this sensational discovery as a breakthrough.This discovery helped establish the category of planets now known as hot Jupiters. They are gas giants that orbit very close to their stars and experience intense radiation and heat. The discovery of hot Jupiters suggested that planetary formation and migration theories needed major revision.New Era for AstronomyThe discovery depended on the star 51 Pegasi. Because it is a Sun-like star, the discovery invited comparisons with our own solar system. And if a planet such as this could be found circling a sun-like star, it meant that the cosmos was much more varied than initially thought.The planet prompted a major shift in scientific thinking. As pointed out by the European Space Agency, it marked the actual birth of a whole new science field of exoplanets. It helped turn the search for exoplanets into a rapidly developing branch of science. It suggested that our solar system is only one of many possible planetary configurations.
