This animation shows planets believed to orbit the red dwarf star Gliese 581. These detections, made with the Doppler technique, were published in scientific papers from 2004 to 2014 and put some of the claimed planets in or near the star's habitable zone, where it might be possible for life as we know it to exist.
Blue indicates detections of candidate planets in the just-right region inside or near the habitable zone, where liquid water could exist. Orange indicates detections in the too-hot region that is too close to the star. Green indicates detections in the too-cold region farther away from the star and outside the habitable zone.
New research led by astronomers at Penn State University and published in the journal Science has disproved the existence of two of these controversial "Goldilocks planets," showing, instead, that the signals resulted from magnetic activity of the star, not from an orbiting planet. The three planets shown in the 2014 frames of this animation are the only ones that the study found to be actual planets, while the other two detections result from the star's own activity signals.
The size of each planet in this figure corresponds to its minimum mass. Some simplifications have been made for illustrative purposes. The refereed literature provides a complete history of the scientific publications relevant to this star and its planets.
The background image is a composite photo of our sun taken by Alan Friedman. The left side of the sun is seen through a filter that allows the camera to see wavelengths of light only in the deep-blue range, while the right side is seen through a filter that blocks all wavelengths except those in the red range. While the blue region is traditionally used to detect a star's activity, this study used the red region of the light spectrum.