Yet another study has disproved the existence of two Earth-like planets “discovered” outside our solar system that could potentially host liquid water, and therefore possibly life. While it disproves this theory, it may also have uncovered a way to make detecting new planets easier.
When the discovery of Gliese 581 g was announced in 2010, there was much excitement because it was in the habitable zone of its red dwarf star – the “Goldilocks region – not too hot nor too cold – where liquid water and life could possibly exist. The planet appeared to be 1.2 to 1.4 times larger than planet Earth, and thought to have a rocky surface.
Another planet in the system, Gliese 581 d, announced in 2007, was on the edge of the habitable zone.
“They were very high value targets if they were real,” said Paul Robertson, a postdoctoral researcher at Penn state University and the lead author of the new study, published this week in Science.
“But unfortunately we found out that they weren’t.”
The two Earth-like planets have caused much controversy since they were discovered using a method that looks for small changes in the color of a star’s light caused by the tug of the planet’s gravity.
Robertson says this is due to the planets having very low masses, if they indeed exist.
“And their signals are so small that just a very small tweak in how you analyze the data can make the difference to whether you see one planet or the other.”
Several studies have argued the planet’s existence, based on different methods of analyzing the signals and ways of trying to sharpen them up. Among them was one by Phil Gregory, professor emeritus at the University of British Columbia. Another study by a Swiss team using additional data, caused the scientists who discovered Gliese 581 g, Steve Vogt of the University of California Santa Cruz and Paul Butler of the Carnegie Institution for Science in Washington D.C., to publish a new paper in 2012 criticizing the team’s analysis and attempting to reaffirm the existence of Gliese 581 g with their own analysis.
Robertson said that he and his colleagues were not intentionally trying to disprove the existence of Gliese 581 g but to find a way to sharpen the small signals from planets and make them more visible by correcting the activity of the star, which can also cause small shifts in color of a star’s light.