WASP-12b: The Doomed Planet That Glows Like a Blackbody

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17 Jul 2023

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🌟 Welcome to the Fiery Worlds Series:

👋Hello, dear readers,
Welcome to the captivating Fiery Worlds Series, where we embark on an exhilarating journey to explore the enigmatic exoplanet WASP-12b and other fascinating celestial bodies! In this thrilling series, we'll dive into the depths of space to unravel the mysteries surrounding these distant worlds and expand our understanding of the cosmos. Hold on tight as we take you on a voyage through blazing atmospheres, vanishing gases, and peculiar orbits!

🔍 Article 1: WASP-12b: The Doomed Planet That Glows Like a Blackbody

🙏Welcome to the first article of a series about WASP-12b, a fascinating exoplanet that is on a death spiral toward its host star. In this article, you will learn about the discovery, properties, and fate of this doomed planet, and why it is one of the most extreme and interesting worlds ever found. You will also see some images that I have created to illustrate the planet and its star, using an artificial intelligence model. I hope you enjoy reading this article as much as I enjoyed writing it. Let’s begin!

Photo - WASP-12b | Wikimedia Commons

🪨WASP-12b is one of the most extreme exoplanets ever discovered. It orbits very close to its host star, WASP-12, a yellow dwarf similar to our Sun but slightly larger and hotter. The planet is so close that it completes one orbit in just over a day, and it experiences intense tidal forces that stretch and distort its shape. The star also heats up the planet to such high temperatures that it glows like a blackbody, emitting infrared radiation that can be detected from Earth.

⚡How WASP-12b was discovered

🪨WASP-12b was discovered in 2008 by the Wide Angle Search for Planets (WASP) project, which uses a network of telescopes to monitor thousands of stars for signs of planetary transits. A transit occurs when a planet passes in front of its star, blocking some of its light and causing a small dip in its brightness. By measuring the depth and duration of the dip, astronomers can infer the size and orbital period of the planet.

🪨WASP-12b was one of the first planets detected by WASP, and it immediately stood out for its unusual properties. It has a mass of about 1.4 times that of Jupiter, but a radius of about 1.8 times, making it one of the most inflated planets known. This means that it has a very low density, about 0.2 grams per cubic centimeter, or less than that of cork. It also has an orbital distance of only 3.4 million kilometers from its star, or about 0.02 astronomical units (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 WASP-12b is being destroyed

✨Being so close to its star has dire consequences for WASP-12b. The planet is tidally locked, meaning that it always shows the same face as its star, just like the Moon does to Earth. This creates a huge temperature difference between the day and night sides of the planet, which can reach up to 3000 K (about 2700 °C or 4900 °F). The day side is so hot that it vaporizes metals such as iron and magnesium, creating a thick atmosphere that extends far beyond the planet’s surface.

🌟The star’s gravity also pulls on the planet’s atmosphere, creating a stream of gas that flows from the planet to the star. This process is called Roche lobe overflow, and it means that WASP-12b is losing mass at a rate of about 10^-7 solar masses per year (or about 200 million kilograms per second). This is equivalent to losing about three Earth masses every billion years.

🪨The mass loss also affects the planet’s orbit, making it shrink over time. A recent study by Antonetti and Goodman estimated that WASP-12b’s orbital period has decreased by about 29 milliseconds per year since its discovery. This means that the planet is spiraling toward its star, heading toward certain destruction.

How WASP-12b looks like 🥚

🪨WASP-12b is one of the few exoplanets that have been directly observed in multiple wavelengths of light. Because of its high temperature and large size, it produces a significant amount of infrared radiation that can be detected by space telescopes such as Spitzer and Hubble. These observations have revealed some surprising features of WASP-12b’s appearance.

❇️One of these features is that WASP-12b has a very low albedo, or reflectivity, of only about 0.06. This means that it absorbs almost all of the light that hits it, making it appear very dark in visible light. In fact, it is one of the darkest planets ever found, with a color similar to that of fresh asphalt.

✨Another feature is that WASP-12b has a very simple emission spectrum or the distribution of light that it emits at different wavelengths. The spectrum is well approximated by a blackbody curve, which describes the radiation emitted by an ideal object that absorbs all incoming light and re-emits it according to its temperature. A blackbody spectrum does not show any distinctive features or variations that would indicate the presence of different molecules or elements in the atmosphere.

📌This suggests that WASP-12b has an almost isothermal atmosphere, meaning that it has a uniform temperature throughout its depth. This could be explained by efficient heat transport from the day to the night side of the planet, or by a lack of chemical reactions that would create temperature gradients. It also implies that WASP-12b’s atmosphere is mostly composed of hydrogen and helium, with very low abundances of other elements.

How WASP-12b will end 💥

🪨WASP-12b’s fate is uncertain, but it is likely that it will not survive for much longer. As it gets closer to its star, it will experience stronger tidal forces that will deform and disrupt its structure. Eventually, it will reach a point where it can no longer hold itself together, and it will be torn apart by the star’s gravity. This point is called the Roche limit, and it depends on the planet’s density and composition.

Antonetti and Goodman calculated the Roche limit for WASP-12b assuming that it has a polytropic structure, meaning that its pressure and density follow a simple power-law relation. They found that the Roche limit is about 1.2 million kilometers from the star or about 0.008 AU. This is only slightly smaller than the planet’s current orbital distance, which means that WASP-12b is very close to its Roche limit.

The authors also estimated how long it will take for WASP-12b to reach its Roche limit, based on its mass loss rate and orbital decay rate. They found that this could happen in as little as 10 years, or as long as 10 million years, depending on the uncertainties in the measurements and assumptions. However, they noted that their model does not account for possible feedback effects between the mass loss and the orbital decay, which could accelerate or delay the process.

Conclusion

🪨WASP-12b is a remarkable example of how extreme environments can shape the properties and evolution of exoplanets. It is one of the hottest, largest, darkest, and most doomed planets ever discovered, and it offers a unique opportunity to study the physics and chemistry of tidally distorted and evaporating worlds. However, time is running out for WASP-12b, as it is on a death spiral toward its star. We may witness its final moments in the near future, or we may miss them altogether.

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😒Question for Reader: What do you think about WASP-12b? Do you find it fascinating or terrifying? Do you think there are other planets like it in the galaxy? 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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