LOS ANGELES — By taking a fresh look at old data, an international team of astronomers has discovered a possible super-Earth planet relatively nearby that could potentially hold liquid water, scientists announced last week.
The research, released by the journal Astronomy & Astrophysics, used a novel technique to analyze previous measurements of a nearby star. The paper drew some praise even as other experts in the field expressed caution about the results.
The finding adds three planet candidates around the dwarf star HD 40307, about 42 light-years away. Combined with three others that were discovered in 2008, they bring the total to six. Five are clustered close to the star, nearer than Mercury's orbit around the sun.
But one of the three new finds lies far enough away to be in what's known as the habitable zone, where a planet could support liquid water — and perhaps life.
That candidate planet, dubbed HD 40307g, has seven times the mass of Earth, the scientists reported.
“It's likely that it's sufficient in mass that it does have an atmosphere," said co-author Hugh Jones, an astronomer at the University of Hertfordshire in England. “But we don't know."
It's difficult to draw extensive conclusions about such super-Earths because no such mid-range planet exists in our own solar system. But Jones did say that HD 40307g is far enough way from its star to be able to rotate freely and possibly have a proper night and day, making it even more likely to have an Earth-like climate. The closer-in planets are gravitationally locked into the star's motion, just as the moon is locked into Earth's, which is why we only see one side of it.
Although the planet appears somewhat closer to its star than Earth is to the sun, the dwarf star is also smaller and dimmer than the one at the center of our solar system.
Jones and his collaborators found the new planet by looking through old measurements collected by the 3.6-meter telescope at La Silla Observatory in Chile. They used a technique called the radial velocity method, which takes advantage of the Doppler effect.
The finding has yet to be confirmed by other analysis or observations. Not everyone is convinced this particular planet exists.
Francesco Pepe of the Geneva Observatory said his team already had seen the signals described in the new paper. In fact, they originally produced the data in question.
“These signals are, however, at the edge of detectability and some doubts remain(ed) on their planetary nature," Pepe wrote in an email. “It is our policy to exclude any possible other explanation and to collect sufficient data to confirm the (possible) additional planets."