Twice as big as Earth, the exoplanet 55 Cancri e likely has an atmosphere thicker than Earth's but with ingredients that could be similar to those of Earth's atmosphere, says a new study.
The atmosphere of this mysterious planet could contain nitrogen, water and even oxygen -- molecules found in our atmosphere, too -- but with much higher temperatures throughout, the researchers said.
The density of the planet is also similar to Earth, suggesting that it, too, is rocky. The intense heat from the host star would be far too great to support life, however, and could not maintain liquid water, according to the study published in The Astronomical Journal.
"Scientists have been debating whether this planet has an atmosphere like Earth and Venus, or just a rocky core and no atmosphere, like Mercury. The case for an atmosphere is now stronger than ever," said study co-author Renyu Hu, astronomer at NASA's Jet Propulsion Laboratory in Pasadena, California.
The findings are based on data from NASA's Spitzer Space Telescope.
The planet, which is believed to have lava flows on its surface and large amount of diamonds in its interior by some scientists, is so close to its star, the same side of the planet always faces the star, such that the planet has permanent day and night sides.
Using an improved model of how energy would flow throughout the planet and radiate back into space, the researchers found that the night side of the planet is not as cool as previously thought.
The "cold" side is still quite toasty by Earthly standards, with an average of 1,300 to 1,400 degrees Celsius, and the hot side averages 2,300 degrees Celsius.
The difference between the hot and cold sides would need to be more extreme if there were no atmosphere, the study said.
Spitzer observed 55 Cancri e between June 15 and July 15, 2013, using a camera specially designed for viewing infrared light, which is invisible to human eyes.
Infrared light is an indicator of heat energy. By comparing changes in brightness Spitzer observed to the energy flow models, the researchers realised an atmosphere with volatile materials could best explain the temperatures.