Astronomers in Japan and Arizona, using data from the James Webb Space Telescope, have revealed a unique type of exoplanet unlike any in the solar system.
The exoplanet — defined as a planet orbiting a star other than the sun — is named Enaiposha and is just 48 light-years away, putting it in the solar system’s immediate neighborhood.
That also makes it close enough for astronomers to see whether it has an atmosphere and what kind. That’s exactly what astronomers at the National Astronomical Observatory of Japan and the University of Arizona/Steward Observatory did—and they found something unexpected.
‘Super Venus’
The latest data on Enaiposha, also called GJ 1214 b and Gliese 1214 b, suggests it has a carbon-dioxide-rich atmosphere, challenging previous notions about the composition of exoplanets of its size.
Though exoplanets tend to be classed as a “super-Earth” or a “mini Neptune,” Enaiposha’s carbon dioxide-dominated atmosphere makes it more likely to be a “super Venus.”
“The detected CO2 signal from the first study is tiny, and so it required careful statistical analysis to ensure that it is real,” said Kazumasa Ohno at the National Astronomical Observatory of Japan, who co-led the study.
Water World?
Enaiposha has been studied closely since its discovery in 2009, but until JWST came along, astronomers couldn’t see through its thick blanket of clouds. That allows it to reflect a lot of its parent star’s light, making it cooler than anticipated.
By using its Mid-Infrared Instrument, JWST has been able to reveal major new insights into its atmosphere. In May 2023, scientists at the University of Oxford tracked Enaiposha, then described as a “sub-Neptune,” through an entire orbit of its star, with its changing heat seen as it passed through phases, similar to how we see the moon, Venus and Mercury from Earth.
In addition to finding a big temperature difference between the planet’s day and night sides, scientists discovered that Enaiposha’s atmosphere is enriched with heavier molecules, such as methane and water.
Thirteenth Constellation
Enaiposha is in the constellation Ophiuchus (pronounced “Or-few-cuss), a vast summer constellation and one of 13 that the sun travels through each year. The other 12 are familiar to everyone as signs of the zodiac, so why isn’t Ophiuchus one of them?
The ancient Babylonians divided the ecliptic—the apparent path of the sun through the sky—into twelve 30° sectors and assigned each one equally to one of the twelve constellations or “signs” that intersected it. Since 13 is an unlucky number, one was dropped. Ophiuchus got booted out despite the sun spending a long time within it from Nov. 29–Dec. 17 (commonly thought of as Sagittarius despite the sun being in that constellation from Dec. 17–Jan. 20.
Wishing you clear skies and wide eyes.
