Researchers, including those of Indian-origin, have detected a methane-shrouded planet 100 light years away that resembles a young Jupiter and may hold water.
The planet, called 51 Eridani b, is only 20 million years old - a mere infant by astronomy standards and may hold the key to understanding how large planets form in the swirling accretion disks around stars.
It is the first planet detected by the Gemini Planet Imager, or GPI, which was designed to discover and analyse faint, young planets orbiting bright, nearby stars.
James Larkin, a University of California, Los Angeles (UCLA) professor of physics and astronomy and colleagues developed and built GPI's highly advanced spectrometer, which enabled the instrument to detect the presence of methane on 51 Eridani b.
It showed that the planet has the strongest concentration of methane ever detected on a planet outside the Milky Way - as well as the presence of water - which indicates that it's similar to planets in our solar system and should yield additional clues about how the planet formed.
The light from 51 Eridani b is very faint; its nearest star is 3 million times brighter, researchers said.
"Many of the exoplanets astronomers have imaged before have atmospheres that look like very cool stars. This one looks like a planet," said the project's lead investigator, Bruce Macintosh, a professor of physics at Stanford University's Kavli Institute.
The newly discovered planet orbits a little farther from its parent star than Saturn does from the Sun. It is roughly twice the mass of Jupiter.
Until now, the gas giant planets that have been directly detected have been much larger - five to 13 times Jupiter's mass, researchers, said.
The scientists reported that 51 Eridani b has a temperature of about 427 degrees Celsius, hot enough to melt lead, but still rather cold compared with other gas giants, which reach temperatures above 537 degrees Celsius.
Previous Jupiter-like exoplanets have shown only faint traces of methane, far different from the heavy methane atmospheres of the gas giants in our solar system.
Jupiter-like exoplanets that have been discovered so far are much hotter than models have predicted, hinting that they could have formed much faster as material collapses quickly to make a very hot planet.
The core-buildup process can also form rocky planets like the Earth, while the process of fast-collapsing materials might make only giant gas planets, the researchers said.
The planet 51 Eridani b is young enough to reveal clues about how it was created.
The study, published in the journal Science, included researchers Rahul Patel from Stony Brook University, New York and Abhijith Rajan from Space Telescope Science Institute, Baltimore.