Alpha Centauri Bb

[10] The team made 459 observations of Alpha Centauri B's color spectrum over a four-year period, then used statistical filters to remove known sources of variance.

[2] The discovery was presented in the scientific journal Nature, with lead author Xavier Dumusque, a graduate student at the University of Porto.

The transformations filtered out other sources of radial-velocity variance, including effects of starspots, photospheric granulation and rotation, as well as interference from the neighboring star Alpha Centauri A.

[11][14] The final, derived radial-velocity measurements showed the periodic influence of the planet on the star, but were near the threshold of the HARPS instrument's sensory capabilities.

)[16] In October 2015, three years after the announcement of the initial finding, researchers from the University of Oxford published a paper entitled "Ghost in the Time Series", demonstrating flaws in the original analysis.

[8] Using the same data as Dumusque, the Oxford team found the signal was caused not by a planet, but instead was a mathematical artifact of the window function used to create the time series for the original observations.

An ESO artist's impression of the disproven planet Alpha Centauri Bb.
Doppler spectroscopy detects exoplanets by recording variations in the color of light coming from the host star. When a star moves towards Earth, its spectrum is blueshifted, and when it moves away from Earth it is redshifted. By regularly measuring the color spectrum of Alpha Centauri B, and deriving its radial velocity, astronomers deduced the gravitational influence of the planet.
This video shows an artist's rendition of a fly-through of the bright double star Alpha Centauri A and B. In the final sequence it closes in on Alpha Centauri B and a newly discovered planet comes into view. Despite this impressive visualization, the planet was later determined not to exist.