On the heels of the first photographs of planets orbiting other stars comes another first for so-called extrasolar planets: an atmosphere containing carbon dioxide (CO2). Nature News and Science News report that a forthcoming journal article will detail the discovery of CO2 around HD 189733 b, a planet roughly equivalent to Jupiter in mass that orbits a star some 63 light-years away.

HD 189733 b, discovered in 2005, has already yielded other exoplanet milestones: it was the first found to host an atmosphere containing methane and was also among the first found to harbor water vapor. All of these discoveries have been made without seeing the planet in the conventional sense: to ascertain a planet's traits, the light spectrum of the parent star is compared with the star's emission as the planet passes in front of it. In the latest finding, the data came from the Hubble Space Telescope.

Although it has now been shown to have many of the signs of life as we know it, HD 189733 b is extremely hot, due to its proximity to its parent star. (Mercury, the planet closest to the sun in our solar system, orbits more than 12 times as far from the sun as HD 189733 b does from its star.) A recent analysis estimated the exoplanet's atmospheric temperature to be roughly 1,950 degrees Fahrenheit (1,065 degrees Celsius).

CREDIT: NASA/JPL-Caltech/Harvard-Smithsonian CfA