'Extraterrestrial' exoplanet discovered as dense as cotton candy

Astronomers found nearly 15 exoplanets in the Kepler 51 star system with a density of less than 0.1 grams of matter per cubic centimeter.

The exoplanets were discovered based on data from NASA's Hubble Space Telescope. They are about the size of Jupiter but are only one-hundredth the mass, lead researcher Jessica Libby-Roberts from the University of Colorado Boulder, USA, said in a statement.

Graphics simulating the Kepler 51 star system. (Image: NASA / ESA)

The team tried to look deeper into the planets' atmospheres but encountered a problem: their atmospheres were not transparent but covered with a layer of opaque. They also tried to search for water but could not observe signs of any molecule.

Using computer simulations and other tools, astronomers hypothesized that Kepler 51's exoplanet is composed primarily of hydrogen and helium. The light properties of these two gases create a super-bulky structure like a cotton candy. However, the surface of the exoplanets seems to be covered by a dense layer of clouds made up of methane gas.

"This is an example of how incredible extrasolar planets are. They offer the opportunity to study things that are very different from ours," says Zachory Berta-Thompson, co-author. of the study said.

The Kepler 51 star system is about 2,400 light-years from Earth and is relatively young, only about 500 million years. The study of exoplanets may provide clues about the origin of the solar system as well as life on Earth.

The team's findings were published in the Astronomical Journal.