New research suggests that some exoplanets may be significantly smaller than was previously assumed. The culprit in these overestimations is the atmospheric haze and clouds surrounding the exoplanets, causing them to seem larger than they actually are.
The study, published in the Monthly Notices of the Royal Astronomical Society
, was led by Dr. Helmut Lammer and his team of astronomers at the Space
Research Institute (IWF) of the Austrian Academy of Sciences. Lammer's team used the European Space Agency (ESA) CoRoT space telescope to more closely examine the upper atmosphere of two planets, seemingly similar in size. The inner planet, however, was significantly less massive and so it appeared to have a much lower density than the outer planet.
The planets orbit their host star in 5 and 12 days, and with such short orbits, Lammer and his team estimated that the atmosphere of the lower mass planet should have burned off within 100 million years due to excessive heating. Because the star is in fact billions of years old, they concluded that, rather than having a significantly lower density, the inner planet was actually around half the size they previously thought.
Lammer claims it is likely that an extended atmosphere is to blame for throwing off the astronomers' observations:
"The radius is based on what we see when the planet makes its transit," he said in a press release
. "This is probably distorted by clouds and haze high in the atmosphere, in a region where atmospheric pressure is otherwise very low."
The new evidence also ensures that scientists will take this into account when first measuring exoplanets, as well as when they review previous measurements. Co-author Luca Fosseti suggests that scientists may want to reassess the data from previous studies, such as the findings of NASA's Kepler Mission.
"Since Kepler has also discovered several similar low-density and low-mass planets, it is very likely that the size measured for many of them also differ from the true value, so there could be a bias in the results," said Fosseti.
The research could provide more insight into the future studies of exoplanets, such as the impending ESA
CHaracterising ExOPlanets Satellite (CHEOPS) mission, due to launch near the end of next year. And since smaller planets are generally more Earth-like, this could mean that a significant number of planets we've written off as uninhabitable gas giants are worth a second look.