A Planet Larger Than Jupiter with the Density of Cotton Candy

Incredible Discovery: A Planet Larger Than Jupiter with the Density of Cotton Candy

The discovery of exoplanet WASP-193b has challenged existing theories of planetary formation. This gas giant, approximately 50% larger than Jupiter yet possessing a density 25 times lower, exhibits characteristics akin to the lightness of cotton candy. Located about 1,200 light-years from Earth, WASP-193b's unique properties provide insights into the diversity of planetary systems and the complexities of planet formation. This article explores its discovery, physical and orbital characteristics, theoretical challenges, and future research directions.

The search for exoplanets—planets orbiting stars beyond our Solar System—has revolutionized our understanding of the universe. Thousands of these worlds have been discovered, revealing a stunning variety of planetary sizes, compositions, and atmospheric conditions.

Among these, some planets stand out due to their extreme properties. WASP-193b, a gas giant with an exceptionally low density, is one of the most unusual exoplanets ever observed. With a size 1.5 times that of Jupiter but a density similar to cotton candy, it challenges traditional planetary formation theories.

This article delves into the characteristics of WASP-193b, the methods used in its discovery, and its implications for planetary science and astrobiology.

Discovery and Observation

WASP-193b was identified by the Wide Angle Search for Planets (WASP) project, an international collaboration dedicated to detecting exoplanets using the transit method. This method involves observing periodic dimming in a star’s brightness caused by a planet passing in front of it.

The planet orbits a Sun-like star in the constellation Serpens, located approximately 1,200 light-years from Earth. Its discovery required detailed analysis using telescopes in Chile and other locations to confirm its existence and gather data on its size, mass, and orbital parameters.

The Transit Method and Radial Velocity Measurements

Astronomers primarily use two methods to study exoplanets:

Transit Method: WASP-193b was discovered when scientists noticed its host star dimming periodically, indicating the presence of a planet passing in front of it. The amount of light blocked allowed astronomers to estimate its size.

Radial Velocity Measurements: After the transit detection, follow-up observations measured the gravitational influence of WASP-193b on its star, determining its mass. Surprisingly, the planet’s mass was far lower than expected for its size.

Physical Characteristics

Size and Density

WASP-193b’s most striking feature is its extremely low density. With a radius about 1.5 times that of Jupiter but only 0.14 times its mass, its density is approximately 0.059 g/cm³—comparable to cotton candy, which has a density of about 0.05 g/cm³.

For comparison:

Earth’s density: 5.51 g/cm³

Jupiter’s density: 1.33 g/cm³

Saturn’s density: 0.69 g/cm³ (the least dense planet in our Solar System)

WASP-193b’s density: 0.059 g/cm³ (one of the lowest known)

This makes WASP-193b one of the "puffiest" planets ever discovered.

Atmospheric Composition and Structure

Given its low density, WASP-193b is classified as a "super-puff" or "cotton candy" planet. Such planets are thought to have:

Extremely extended atmospheres, composed mainly of hydrogen and helium.

A large fraction of their volume occupied by a puffy, low-mass atmosphere rather than a dense planetary core.

Potential cloud layers made of water vapor, methane, and other light molecules.

Astronomers speculate that stellar radiation might be causing atmospheric inflation, preventing the planet from contracting into a denser form.

Orbital Characteristics

WASP-193b orbits its star at a relatively close distance, completing one full orbit in just a few days. This short orbital period suggests that:

The planet is tidally locked, meaning one side always faces the star while the other remains in perpetual darkness.

Its atmosphere is superheated by stellar radiation, leading to potential atmospheric escape.

The planet’s close proximity to its star makes it an excellent candidate for further studies of atmospheric loss mechanisms.

Challenges to Planetary Formation Theories

WASP-193b’s unusually low density challenges existing models of planetary formation. Typically, gas giants form beyond the snow line—the region of a star system where temperatures are cold enough for water ice to condense. In these regions, a planetary core can accumulate mass rapidly and attract a thick atmosphere.

However, WASP-193b's properties suggest alternative scenarios:

Extreme atmospheric inflation: The planet’s atmosphere could have expanded due to intense stellar irradiation.

Lack of a heavy core: Unlike Jupiter, which has a rocky core, WASP-193b might have formed without a dense center, making it more vulnerable to expansion.

Loss of heavier elements: The planet might have formed with a normal density but lost heavy elements due to interactions with its star.

These hypotheses require further investigation, and WASP-193b could lead to new models of planet formation.

Comparisons with Other Super-Puff Planets

WASP-193b is not the only known super-puff planet. Other examples include:

Kepler-51d: One of three super-puff planets in the Kepler-51 system, with a density similar to Styrofoam.

HAT-P-67b: A hot gas giant with an extremely low density.

K2-33b: A young super-puff planet still forming its atmosphere.

Comparing WASP-193b to these planets can help astronomers understand why such worlds exist.

Implications for Exoplanetary Science

WASP-193b is significant because it:

Expands the range of known planet types.

Challenges planetary formation models.

Offers a unique target for atmospheric studies.

May provide insights into exoplanetary habitability.

Although WASP-193b itself is unlikely to support life, studying its atmosphere can improve techniques used to analyze more Earth-like planets.

Future Observations and Research

James Webb Space Telescope (JWST)

The James Webb Space Telescope (JWST) is expected to:

Analyze WASP-193b’s atmospheric composition using spectroscopy.

Search for molecules like water vapor, methane, and hydrogen.

Study atmospheric escape mechanisms.

Ground-Based Observations

Additional data from ground-based telescopes will help refine estimates of its mass, radius, and temperature, improving our understanding of how such planets evolve.

Long-Term Studies

If WASP-193b is losing atmosphere over time, long-term studies could reveal whether it will eventually shrink into a denser planet.

WASP-193b is one of the most fascinating exoplanets discovered to date. With a size greater than Jupiter but a density 25 times lower, it challenges our understanding of planetary physics and formation.

Its cotton candy-like density suggests that planetary diversity is even greater than previously thought. Future observations with advanced telescopes will provide deeper insights into its composition and evolution, helping us refine planetary formation models.

The study of planets like WASP-193b is crucial for understanding the vast diversity of worlds beyond our Solar System and the forces shaping them.

References

(vanguardia.com)

(cnnchile.com)

(huffingtonpost.es)

(muyinteresante.com)