Three young exoplanets that are in the Kepler 51 system, discovered by the space telescope Hubble of NASA in 2012, have a mass density so low that, although their dimensions are comparable with Jupiter, are 100 times lighter than the largest planet in our solar system.
New Hubble data has provided the first clues about the chemistry of two of these “super swollen” planets. Orbiting a young star like the Sun at about 2,600 light years away from our solar system, and their atmospheres of hydrogen / helium are so swollen that are almost the size of Jupiter, according to a statement from the agency.
In fact, they have a density of less than 0.1 grams per cubic centimeter. Hence, the texture of these planets has been compared with that of "cotton candy".
With the help of the Hubble telescope , the team of astronomers sought the presence of some elements, especially water, in the atmospheres of the planets, called Kepler-51 by 51 d. Hubble observed the planets when they passed in front of their star, in order to observe the infrared color of their 'sunsets'.
Astronomers deducted the amount of light absorbed by the atmosphere under infrared light. This type of observation allows scientists to look for indicators of the chemical constituents of the planets, such as water.
As a result, the team of researchers discovered that the spectra of both planets have no revealing chemical signature. Scientists attribute this result to high clouds of particles in their atmospheres.
However, unlike Earth's water clouds, clouds on these planets may be composed of salt crystals or photochemical mists, such as those found on Saturn's largest moon, Titan.
The team concluded that the low densities of these planets are partly a consequence of the youth of the system (about 500 million years, compared to the 4.6 billion years of the Sun). The models suggest that these planets formed outside the star's "freezing line," the region of possible orbits in which frozen materials can survive, and subsequently moved inwards.
Now that the planets are closer to the star, their low density atmospheres could evaporate in the following thousands of years. "This system offers a unique laboratory to test theories of the early evolution of the planets," said Zach Berta-Thomson of the University of Colorado at Boulder.
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