Astronomers analyze the atmosphere of an exoplanet, evidence of clouds

Updated: Oct 19, 2021

by Thomas Kitchen

Staff Writer

The following story was written by a student on the staff of The Jaguar Times as part of Hilliard Bradley High School’s Journalism Production course.

Nasa develops a hypothetical visualization of WASP-127b. | (credit: NASA).
Nasa develops a hypothetical visualization of WASP-127b. | (credit: NASA).

Exoplanets are planets orbiting stars outside the solar system, and the Exoplanet WASP-127b is a gas giant 0.1647 the mass of Jupiter. It was discovered in 2016 roughly 520 light-years from Earth and orbiting the star WASP-127 every 4.2 days. WASP-127b orbits so close to its star that it’s very hot and inflated. That means the atmosphere is very thin. It is useful to study the contents of the atmosphere based on the light that goes through it from the planet's host star. To achieve this, an international team of astronomers used infrared observations from the NASA/ESA Hubble Space Telescope. Also visible light measurements from the ESPRESSO spectrograph at the European Southern Observatory’s Very Large Telescope in Chile. The astronomers took data on WASP-127b’s atmosphere during two different transits when WASP-127b is in between its host star and earth, making the planet somewhat visible to our telescopes.

Using near-infrared low-resolution data from Hubble the astronomers found the “strongest water band amplitude in an exoplanet”, according to the study by Romain Allart, the lead astronomer, and other astronomers involved. This can only be explained by the presence of clouds. Using the ESPRESSO spectrograph the astronomers analyzed WASP-127b’s thermosphere and detected strong water vapor signals in infrared but none at visible wavelengths; this hints at water vapor at the lower levels of the atmosphere being screened by clouds, but the astronomers didn’t directly detect clouds. Using the data from both of the instruments the astronomers can narrow down the altitude of the clouds to an atmospheric layer with a pressure ranging between 0.3 and 0.5 millibars (1 bar equals 1000 millibars the base unit of the metric system for atmospheric pressure). According to Mrs. Goodwin, a Hilliard Bradley High School science teacher, that's roughly 0.0004% the pressure of Earth's atmosphere at sea level.

When probing the atmosphere of WASP-127b the astronomers also detected sodium “which wouldn’t come as a surprise normally but the element was found at a much lower altitude than expected,” according to Romain Allart. The astronomers didn’t detect the presence of other elements, but they assume they are there. WASP-127b is also unusual in how it orbits. Our solar system is quite orderly. The planets are orbiting close to the Sun's equator and orbit in the same direction as the sun. WASP-127b doesn’t do this. It orbits retrograde to the rotation of its host star and orbits closer to its star's poles. According to Romain Allart, “Such alignment is unexpected for a hot Saturn in an old stellar system and might be caused by an unknown companion." WASP-127b is a noteworthy exoplanet and astronomers want to continue studying this strange world.

When it comes to the search for life outside of earth and the solar system, humanity must analyze the atmospheres of exoplanets. The chemical compositions can tell us a lot about the physical and possibly life-bearing conditions of exoplanets. Though the debate is still up for the possible discovery in the clouds Venus of the chemical phosphine, a noxious gas that on Earth is associated with life. The analysis of the Venusian atmosphere hinting at the possibility of life should excite us to analyze exoplanet atmospheres looking for chemical compounds that can be associated with life. The analysis of WASP-127b's atmosphere is a small dive into the mysteries that exoplanet atmospheres have to offer.