A group of scientists have recently harnessed the power of NASA’s Hubble Space Telescope to establish the weather conditions of an alien planet. The scientists, led by researchers in the Department of Astronomy and Astrophysics at the University of Chicago, discovered thick layers of high-altitude clouds that blanket much of the planet.
Atmospheric Study of GJ1214b Super-Earth
The planet in question is known as GJ1214b (a.k.a. Gliese 1214b) – a super-Earth type planet. Super-Earths are extrasolar planets that have masses intermediate between that of Earth and smaller gas giants, such as Neptune, which is around 17 Earth masses. Generally, super-Earths are almost exclusively classified by their mass, with the term offering no insight into a particular planet’s temperature, composition or environment, relative to Earth.
Recent exploration of planets around other stars (exoplanets) has demonstrated that super-Earths, including GJ1214b, are some of the most frequent types of planets within the Milky Way galaxy. However, since no super-Earth planets exist within our Solar System, much is to be gleaned about their physical characteristics.
With this in mind, studies are beginning to turn towards investigation of the atmospheric conditions of these planets. For example, researchers from MIT and the Harvard-Smithsonian Center for Astrophysics published a paper exploring the ability of some super-Earths to retain massive hydrogen-rich atmospheres. The authors stated it was possible to differentiate between hydrogen-rich and hydrogen-poor atmospheres, based upon transmission spectra alone.
Taking exoplanet GI581 as an example, the researchers determined that a hydrogen-rich atmosphere reveals a large transmission signal. In addition, super-Earths that possess massive hydrogen atmospheres reportedly reveal strong spectral features due to water. Meanwhile, those exoplanets that had lost the majority of their hydrogen, and had no liquid ocean, were marked by carbon dioxide and an absence of water.
Hubble Space Telescope Finds Evidence of Cloudy Weather
In the latest study, the research team – led by the University of Chicago’s Laura Kreidberg and Jacob Bean – believe they have detected evidence of clouds, in the atmosphere of exoplanet GJ1214b, using data obtained from the Hubble Space Telescope. The research represented the largest Hubble program dedicated to understanding a single exoplanet, yielding 96 hours of telescope time spread out over an 11 month period.
Kreidberg, who is first author of the latest paper, talked about the larger implications of her team’s research:
“We really pushed the limits of what is possible with Hubble to make this measurement… This advance lays the foundation for characterizing other Earths with similar techniques.”
Located just 40 light-years from Earth, GJ1214b orbits its host star GJ1214; the parent star is situated in the constellation Ophiuchus. Due to GJ1214b’s proximity to our Solar System, along with the relatively small size of its host star, the exoplanet is one of the most easy to observe, transiting super-Earths. It passes in front of its parent star, every 38 hours, providing scientists with ample opportunity to investigate its atmosphere, as light filters through it.
Kreidberg and Bean, along with their colleagues, employed Hubble to measure the transmission spectrum of GJ1214b in near-infrared wavelengths. From this data, the researchers believe they now have definitive evidence to indicate the presence of high clouds, covering much of the planet. Such clouds, however, conceal a great deal of information about the nature of GJ1214b’s lower atmosphere and surface.
Previous studies, spearheaded by Bean in 2010, suggested the planet had an atmosphere that was, perhaps, dominated by water vapor. On the other hand, based upon the first spectra, collected using a ground-based telescope, the exoplanet was also conjectured to have been home to a hydrogen-rich atmosphere with high-altitude clouds.
In their latest study, the scientists found no “chemical fingerprints” in the planet’s atmosphere, eliminating the possibility that the super-Earth has cloud-free atmospheres that are comprised of carbon dioxide, carbon monoxide, methane, nitrogen or water vapor.
In explaining these findings, the group offer a new explanation; GJ1214b possesses high-altitude clouds in its atmosphere with unknown compositions. However, models of super-Earth atmospheres have predicted the clouds could be made from potassium chloride or zinc sulfide, which could exist at the extreme temperatures of 450 degrees Fahrenheit found on the planet. Kreidberg briefly discussed this possibility during a recent press release:
“You would expect very different kinds of clouds to form than you would expect, say, on Earth.”
Referring to the launch of NASA’s next high-profile space telescope – the 6.5m James Webb Space Telescope (JWST) – Kreidberg suggests it will become even easier to study these exoplanets. Describing the new telescope as “transformative,” she explains that JWST will be capable of peering through the clouds of exoplanets, like GJ1214b.
The research findings were published in the Jan. 2 issue of the journal Nature, entitled Clouds in the atmosphere of the super-Earth exoplanet GJ1214b.
By James Fenner