Gliese 581d was discovered in the year 2009 and the scientists believed that its rocky surface probably had the potential for harboring liquid water and microbial life. Scientists across the globe are trying to spot Earth-like planets in the universe which orbit parent stars in the habitable or “Goldilocks zone” that offer appropriate temperatures for the presence of liquid water as well as life, and Gliese 581d, when discovered, was thought to be one such exoplanet.
Scientists believed that the planet was about twice the size of Earth with gravity about twice that of the Earth. A very small frequency shift of light from the parent star known as Doppler shift helped in the discovery of the planet as it moved in front of the star. However, last year a group of astronomers from Pennsylvania State University suggested that the activity of the parent star around which Gliese 581d was thought to be orbiting was interfering and could have imitated the signal from the orbiting planet, which implies that the orbiting planet might not be existent. According to the team, the noisy data was obtained due to the Doppler shift which indicated that the planet was there.
Recently another scientist named Guillem Anglada-Escudé has suggested that the members of the scientific community must be more careful about such claims. Guillem Anglada-Escudé opines that the planet exists, orbiting the star in question. The scientist also remarked that the statement of the researchers from Pennsylvania State University was too strong and if the team was correct, there would be a need to change the methods used for detecting planets by some ground-based observatories. Guillem Anglada-Escudé commented “The existence (or not) of GJ 581d is significant because it was the first Earth-like planet discovered in the ‘Goldilocks’-zone around another star and it is a benchmark case for the Doppler technique.” The study has been published in the journal Science.