Hubble Gets a Whiff of Super-Earth Atmosphere For The First Time

The toasty planet’s atmosphere is similar to a gas giant’s

super-Earth Janssen
This artist’s impression shows the super-Earth 55 Cancri e in front of its parent star. ESA/Hubble, M. Kornmesser

For the first time, scientists have analyzed the atmosphere of an exoplanet known as a “super-Earth.” Using data gleaned from the Hubble Telescope, researchers from University College London have found that the hot planet has an atmosphere made mostly of hydrogen and helium, similar to what one might find in a gas giant.

Astronomers have studied super-Earths for years, but this is the first time anyone has been able to detect hints of an atmosphere on one about 40 light-years away. According to a study published in the Astrophysical Journal, the planet in question, known as “55 Cancri e” or “Janssen,” appears to have held onto a large amount of hydrogen and helium gas leftover from the nebula its solar system was born from—an unusual find, considering that the planet is blisteringly close to its sun, Elizabeth Howell reports for Discovery News.

Planet Janssen was one of the earliest super-Earths ever found, but it’s still one of the strangest. First discovered in 2004, Janssen has the closest orbit to its sun of any super-Earth detected so far, which led scientists to believe that the combination of its exposure to solar radiation and surface temperature of over 3632 degrees Fahrenheit would have burned off any traces of an atmosphere, Howell writes. Instead, Janssen has become a test case demonstrating that analyzing spectral data from the Hubble can help astronomers identify the “fingerprint” of a super-Earth’s atmosphere.

"This is a very exciting result because it's the first time that we have been able to find the spectral fingerprints that show the gases present in the atmosphere of a super-Earth," study co-author Angelos Tsiaras said in a statement. "Our analysis of 55 Cancri e's atmosphere suggests that the planet has managed to cling on to a significant amount of hydrogen and helium from the nebula from which it formed."

In order to suss out whether an exoplanet has an atmosphere, astronomers scan for changes in the light given off by a star as the planet passes between it and the Earth. If the planet has no atmosphere, the light waves will pass by unchanged. If there is a trace of gas surrounding it, though, it will alter the starlight’s frequency, which can help astronomers tell not only that an atmosphere exists, but what it is made of, Jonathan Webb reports for the BBC.

The researchers still aren’t sure how Janssen has held onto its atmosphere, considering how light hydrogen and helium are. However, they did detect traces of hydrogen cyanide—a poisonous gas that supports a theory that the super-Earth is so rich in carbon that it may have a diamond core, Eric Berger writes for Ars Technica.

"If the presence of hydrogen cyanide and other molecules is confirmed in a few years time by the next generation of infrared telescopes, it would support the theory that this planet is indeed carbon rich and a very exotic place," study co-author and astronomer Jonathan Tennyson said in a statement.

For now, the researchers will continue to study Janssen as they continue scanning other super-Earths for their own atmospheres.