Star Spectrum and the Discovery of Outer Planets

The spectrum of starlight shows patterns, because of the distinctive colors that different atoms radiate or absorb - carbon, sodium, etc. - that make up stars, and if a star moves away from us, its light budges to the right in the red region of the spectrum, compared to the light radiated by the same atoms in the laboratory, this is the famous Doppler Effect. In 1995, two astronomers at the Geneva Observatory, Michel Mayor and Didier Queloz, discovered that Doppler's displacement at 51 Pegasi (a nearby star similar to our Sun) rises and falls very slightly, although the star moves in a circle, approaches us and then retreats and then approaches again, so regularly, and the estimated speed indirectly is about fifty meters. They concluded that a planet about the size of Jupiter was orbiting the star, prompting it to orbit the center of mass of the entire system, and if the invisible planet had one-thousandth the mass of the star, the planet's rotational velocity would have been fifty kilometers per second, a thousand times faster than the star's motion. Jeffrey Marcy and Paul Butler, both of whom work in California, were the only known planetary hunters in the late 1990s whose instruments could record wavelengths of less than a fraction of 100 million, and so they measured the Doppler effect even when the velocities were one hundred millionth of the speed of light -- three meters per second -- and they found evidence for the existence of many planets. An Earth-like planet weighing a few hundred times less than Jupiter would make movements of a few centimetres per second, at which point the Doppler would be displaced to a fraction of ten billion parts, much less noticed and distinguished by the methods that discovered the large planets.1 - Dr. Martin Rees. (British Astronomers) — Source: Published on Facebook's "Braheen Center" page