|Exoplanet K2-18 b orbits a red dwarf star and has an extended atmosphere containing at least some water vapor, as seen in this artist's concept. The system also contains another exoplanet sitting closer to the star, but it lies inside of the star's habitable zone|
Topics: Astronomy, Astrophysics, Black Holes, Exoplanets, Hubble
Astronomers have finally uncovered water vapor in the atmosphere of a super-Earth exoplanet orbiting within the habitable zone of its star. The find means that liquid water could also exist on the rocky world's surface, potentially even forming a global ocean.
The discovery, made with NASA's Hubble Space Telescope, serves as the first detection of water vapor in the atmosphere of such a planet. And because the planet, dubbed K2-18 b, likely sports a temperature similar to Earth, the newfound water vapor makes the world one of the most promising candidates for follow-up studies with next-generation space telescopes.
"This is the only planet right now that we know outside the solar system that has the correct temperature to support water, it has an atmosphere, and it has water in it, making this planet the best candidate for habitability that we know right now," lead author Angelos Tsiaras, an astronomer at University College London, said in a press conference.
|Researchers created this enhanced view of Enceladus’ south polar region by combining Cassini images taken through infrared, green, and ultraviolet filters. The tiger stripe fractures, the source of the plumes venting gas and dust into space, are prominently visible at center.|
NASA/JPL-Caltech/SSI/Lunar and Planetary Institute/Paul Schenk (LPI, Houston)
“In the old time Pallas [Athena] heaved on high Sicily, and on huge Enceladus dashed down the isle, which burns with the burning yet of that immortal giant, as he breathes fire underground.”
— Quintus Smyrnaeus, The Fall of Troy
Saturn’s sixth-largest moon, Enceladus has a diameter of only 310 miles (500 kilometers), and a mass less than 1/50,000 that of Earth. When it comes to places to look for life, however, Enceladus is at the top of the list, and it’s right in our cosmic backyard.
A bit ignored at first
English astronomer William Herschel discovered Enceladus in 1789, but it remained an enigma until the Cassini mission began orbiting Saturn in 2004. Prior to Cassini, Enceladus was a bit ignored. We didn’t know liquid water could exist that far out in the solar system, so why would anyone be that interested in another boring, dead ball of ice?
That all changed one year later, when Cassini’s magnetometer (think: fancy compass) detected something strange in Saturn’s magnetic field near Enceladus. This suggested the moon was active. Subsequent passes by Enceladus revealed four massive fissures — dubbed “tiger stripes” — in a hot spot centered on the south pole. And emanating from those cracks was a massive plume of water vapor and ice grains. Enceladus lost its label of being a dead relic of a bygone era and leaped to center stage as a dynamic world with a subsurface ocean.