WASP-12b: The Planet That Defies Expectations

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18 Jul 2023

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👋Hello, dear readers,
Welcome to the second part of the series on WASP-12b, the planet that defies expectations.

📢In this part, we will explore some of the mysteries and surprises that this fascinating exoplanet has to offer. But before we do that, we strongly recommend that you read the first part of the series, titled "WASP-12b: The Doomed Planet That Glows Like a Blackbody".
In that part, we introduced you to WASP-12b, a gas giant planet that orbits very close to its host star, WASP-12. We explained How WASP-12b looks like, How WASP-12b was discovered, How WASP-12b is being destroyed, & How WASP-12b will end. We also described how this planet has a very high temperature and emits infrared light like a blackbody. If you haven’t read the first part yet, you can find it [1st Article-link here].

📢Now that you are familiar with the basic facts about WASP-12b, let’s dive into some of the more intriguing aspects of this planet. In this part, we will discuss:

How it is losing mass at a rapid rate
How WASP-12b has a very unusual atmosphere
How did WASP-12b got so inflated?
How WASP-12b got so close to its star

😒We hope you enjoy reading this part as much as we enjoyed writing it. And don’t forget to stay tuned for the third part of the series, where we will speculate about the future of WASP-12b and its star. Thank you for your interest in this amazing planet.

🔍 Article 2

`"WASP-12b: The Planet That Defies Expectations".`

🪐WASP-12b is not only one of the most extreme exoplanets ever discovered but also one of the most puzzling. It has several features that challenge our understanding of how planets form and evolve, and how they interact with their host stars. In this article, we will explore some of these features and the mysteries they pose.

How it is losing mass at a rapid rate

🪐WASP-12b is losing mass at a rapid rate because it is very close to its host star, WASP-12. The star’s gravity is pulling the planet’s atmosphere and creating a tail of gas that escapes from the planet. Some of the gas may also fall onto the star, creating an accretion disk. According to some studies, WASP-12b may lose up to 3% of its mass every billion years. This means that the planet will eventually be destroyed by its star unless its orbit changes or stabilizes. WASP-12b is one of the few exoplanets that show clear evidence of mass loss in infrared observations. This makes it a very interesting and unique object to study.

How WASP-12b has a very unusual Atmosphere

🪐WASP-12b has a very unusual atmosphere, unlike any other planet we know of. Most hot Jupiters, which are gas giant planets that orbit very close to their stars, have atmospheres rich in water vapor and methane. These molecules are common in the universe and can form from hydrogen and oxygen or carbon, respectively. However, WASP-12b has no water vapor or methane in its atmosphere, despite having plenty of hydrogen, oxygen, and carbon. Instead, it has carbon monoxide and atomic hydrogen as the dominant molecules.

✳️Carbon monoxide is a toxic gas that is usually found in trace amounts in planetary atmospheres. It can form from the reaction of carbon and oxygen at high temperatures. Atomic hydrogen is hydrogen that has been split into individual atoms by intense radiation or heat. It is very reactive and can combine with other atoms to form molecules. However, on WASP-12b, the atomic hydrogen is so abundant that it prevents other molecules from forming.

🤔The reason for WASP-12b’s unusual atmosphere is not fully understood, but it may have something to do with its extreme environment. WASP-12b is so close to its star that it receives about 4,000 times more radiation than Earth does from the Sun. This radiation may break down water and methane molecules into their constituent atoms, and also ionize some of the atoms, creating a plasma. The plasma may interact with the star’s magnetic field and create electric currents that heat up the planet’s atmosphere even more. The high temperature may favor the formation of carbon monoxide over methane since carbon monoxide is more stable at higher temperatures. The high temperature may also prevent the atomic hydrogen from recombining into molecular hydrogen since the recombination process releases energy that would heat up the atmosphere even more.

🪐WASP-12b’s atmosphere is one of the most exotic and extreme atmospheres ever observed. It challenges our understanding of how planets form and evolve, and how chemistry works under different conditions. It also offers a glimpse into what other kinds of planets may exist in the universe, beyond our expectations.

How did WASP-12b got so inflated ❓

🌿One of the most striking features of WASP-12b is its large size relative to its mass. It has a radius of about 1.8 times that of Jupiter, but a mass of only 1.4 times. This gives it a very low density of about 0.2 grams per cubic centimeter or less than that of cork. How did WASP-12b get so inflated?

🍀One possible explanation is that WASP-12b’s inflation is caused by its intense heating from its host star. The star’s radiation deposits a lot of energy into the planet’s atmosphere, which expands and pushes against the planet’s gravity. This could inflate the planet’s radius by up to 20%.

Photo: Comparison of best-fit size of the exoplanet WASP-12 b with the Solar System planet Jupiter |By- Wikimedia Commons

🍁However, this explanation alone cannot account for the full extent of WASP-12b’s inflation. According to theoretical models, a planet with WASP-12b’s mass and temperature should have a radius of about 1.5 times that of Jupiter, not 1.8. There must be some other factor that contributes to the planet’s inflation.

🍂One possibility is that WASP-12b has a very large core or a layer of heavy elements under its atmosphere. This could reduce the planet’s compressibility, or its ability to shrink under pressure and make it more resistant to contraction. However, this would also imply that WASP-12b has a very high metallicity or the fraction of elements heavier than hydrogen and helium in its composition. This would be unusual for a gas-giant planet, especially one that formed close to its star.

🍃Another possibility is that WASP-12b has some additional source of internal heat, besides the star’s radiation. This could be due to tidal dissipation, or the conversion of orbital energy into heat by the planet’s deformation. However, this would require that WASP-12b has a non-zero eccentricity, or deviation from a circular orbit, which has not been detected so far.

🥬A third possibility is that WASP-12b has some mechanism that prevents heat from escaping from its interior, such as a thick cloud layer or a strong magnetic field. This could trap heat inside the planet and prevent it from cooling and contracting. However, this would also affect the planet’s emission spectrum, which does not show any signs of such features.

How WASP-12b got so close to its star ❓

❇️Another intriguing feature of WASP-12b is its very small orbital distance from its host star. It orbits at only 3.4 million kilometers from the star, or about 0.02 AU, where 1 AU is the distance between Earth and the Sun. This is much closer than Mercury, which orbits at about 0.4 AU from the Sun. How did WASP-12b get so close to its star?

✨One possible explanation is that WASP-12b formed farther away from its star, and then migrated inward over time due to gravitational interactions with other planets or the protoplanetary disk. This process is called planetary migration, and it is thought to be common among hot Jupiters, or gas giant planets that orbit very close to their stars.

✳️However, this explanation faces some challenges when applied to WASP-12b. First, it requires that there were other planets or disk material in the system that could have perturbed WASP-12b’s orbit and caused it to migrate. However, no such companions have been detected so far around WASP-12. Second, it requires that WASP-12b migrated fast enough to avoid being destroyed by its star before reaching its current position. However, this depends on the details of the migration mechanism and the properties of the star and the planet.

✴️Another possible explanation is that WASP-12b formed in situ, or in its current location near its star. This process is called in situ formation, and it is thought to be rare among hot Jupiters, but not impossible.

📌However, this explanation also faces some challenges when applied to WASP-12b.

💫First, it requires that there was enough material close to the star to form a gas giant planet in the first place. However, this is unlikely because the high temperatures near the star would have vaporized most of the solids that are needed for planet formation.

✡️Second, it requires that WASP-12b survived the intense radiation and stellar winds from its star without losing too much mass or atmosphere. However, this is difficult because the planet is currently losing mass at a high rate due to Roche lobe overflow.

Conclusion

🪐WASP-12b is a planet that defies expectations and challenges our understanding of planetary physics. It has several features that are hard to explain by current theories, such as its large size, low density, dark color, simple spectrum, and small orbital distance. It is a planet that invites further exploration and investigation before it is gone forever.

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😒Question for Reader: What do you think about WASP-12b? Do you find it intriguing or perplexing? Do you think there are other explanations for its features that we have not considered? Let me know your thoughts in the comments below.

`I hope you enjoyed reading my article. I hope you learned something new and interesting from them. I hope you also had fun and felt curious and excited about this topic!`

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📚 Sources:

Tidally distorted barytropes and their Roche limits, with application to WASP-12b | Link
Re-Evaluating WASP-12b: Strong Emission at 2.315 micron, Deeper Occultations, and an Isothermal Atmosphere | Link
Planet WASP-12b is on a death spiral, say scientists | Link
Planet WASP-12b is on a death spiral, say scientists | sciencedaily
Planet WASP-12b is on a death spiral, say scientists | Princeton University.

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