Experts argue that there might be an Earth-like planet relatively close to us (20 light-years away). GJ 581d, a planet first observed in 2009 in orbit around a Libra galaxy red dwarf called Gliese 581, became a subject for controversy last year, when Paul Robertson and his team of researchers challenged the assumption that there is actually a planet on that particular orbit, supporting the hypothesis that the data we receive about it is actually noise provoked by star-spots. Now, however, two scientists from Queen Mary University of London and University of Hertfordshire have reexamined the available data and reassessed the theory according to which this is indeed an earth-like planet. According to Guillem Anglada Escude and Mikko Tuomi, the two authors of the new study published last Friday in Science, the method employed by Robertson’s team (analysis of statistical significance using residual data statistics) led to incorrect conclusions, because noise cannot explain away the model’s increased complexity.
Supposing that the new article is in the right, GJ 581 d appears to be a habitable planet, situated in its star’s “Goldilocks zone” (the space interval around a star where solid planets with normal mass and atmospheric pressure can hold liquid water on the surface). It belongs to a category of celestial bodies known as super-Earths, which resemble out own planet but are a few times larger.
The planet was detected using observations of what scientists call the Doppler Effect (the change in Gliese 581’s light-hue towards blue when the orbiting planet is situated between its star and our point of observation, and towards red when the planet is at the other extremity of its orbit, farther from the Earth, a variation explained by the fact that the planet’s gravitational field slightly pulls the star in its direction).
The history of spotting planets outside our solar system is a recent one. The first two such celestial objects were observed in 1992, orbiting around a pulsar many light years away. In 1995, astrophysicists discovered 51 Pegasi, a planet orbiting a young star like our Sun. Among the hundreds of Earth-like planets discovered in the meanwhile, only a small fraction are situated in habitable zones.
image credit: Universe Today