Imagine a planet as large as Jupiter but with the density of cotton candy. These celestial oddities, known as “super-puffs” or “cotton candy planets,” are a rare class of exoplanets that defy our understanding of planetary formation and composition. Nothing quite like them exists in our solar system.
What are Cotton Candy Planets?
Cotton candy planets are extrasolar planets with remarkably low densities, akin to that of cotton candy. For example, WASP-193 b is around 1.5 times the width of Jupiter but has just over a tenth of the gas giant’s mass. This makes it the second-lightest planet in the exoplanet catalog. Another example is Kepler-51 d, a Neptune-like world which is lighter than WASP-193 b.
To put this in perspective:
- Earth has a density of 5.5 grams per cubic centimeter.
- Jupiter has a density of around 1.3 grams per cubic centimeter.
- WASP-193 b has a density of just 0.059 grams per cubic centimeter, comparable to cotton candy’s density of roughly 0.05 grams per cubic centimeter.
Recent Discoveries and Observations
Recent data from NASA’s Hubble Space Telescope has offered clues into the chemistry of super-puffy planets located in the Kepler 51 system. This exoplanet system, which has three super-puffs orbiting a young Sun-like star, was first discovered by NASA’s Kepler space telescope in 2012. It wasn’t until 2014 that the low densities of these planets were determined.
Hubble observations allowed astronomers to refine mass and size estimates, confirming their puffy nature. Though only several times the mass of Earth, their hydrogen/helium atmospheres are so bloated that they are nearly the size of Jupiter. They might look as big and bulky as Jupiter, but are roughly a hundred times lighter in terms of mass.
The Mystery of their Composition
The composition of these planets remains largely mysterious. It is thought that WASP-193 b, like other gas giants, is composed mostly of hydrogen and helium. These gases may form a massively overinflated atmosphere, tens of thousands of miles wider than Jupiter’s atmosphere.
Challenges to Existing Theories
The existence of cotton candy planets challenges existing models of planetary formation. It is difficult to explain how these planets can inflate to such an extent. WASP-193b is an outlier that does not fit into current formation theories.
Future Research
Future observations, especially with the James Webb Space Telescope (JWST), could provide insights into the atmospheric composition of cotton candy planets. The JWST’s sensitivity to longer infrared wavelengths might allow it to peer through cloud layers and determine what these planets are made of. By studying the atmospheres of these planets, scientists hope to constrain their evolutionary paths. WASP-193 b could be an ideal exoplanet target for the James Webb Space Telescope. The bigger a planet’s atmosphere, the more light can go through.
A Window into Planet Evolution
The Kepler-51 system, with its three super-puffs, is relatively young, only 500 million years old compared to our 4.6-billion-year-old Sun. Models suggest these planets formed outside the star’s “snow line” and migrated inward. Over billions of years, their low-density atmospheres should evaporate into space.
These oddball worlds provide a unique opportunity to test theories of early planet evolution. Although much remains unknown, continued investigation promises to reveal valuable insights into the diversity and formation of planets beyond our solar system.
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