Astronomers have discovered a bizarre phenomenon in the distant cosmos: a giant planet that is losing its atmosphere and leaving a huge trail of gas behind it. The planet, called HAT-P-32b, is about the size of Jupiter but much less dense. It orbits very close to its star, which heats up its atmosphere and causes it to escape into space. The escaping gas forms a long tail that spans over 53 times the planet’s radius, making it the largest known planetary structure in the universe.
HAT-P-32b: A Hot Jupiter with a Twist
HAT-P-32b is an exoplanet, which means it is a planet outside our solar system. It was first detected in 2011 by the Hungarian-made Automated Telescope Network (HATNet) project. The planet belongs to a class of exoplanets known as “hot Jupiters”, which are gas giants that orbit very close to their stars and have very high temperatures. However, HAT-P-32b is not a typical hot Jupiter. It has some unusual features that make it stand out from the rest.
- It is very inflated: Despite having only about 68% of Jupiter’s mass, HAT-P-32b has almost twice its radius. This means it has a very low density, similar to that of cork or styrofoam. Scientists think that the intense heat from its star makes the planet expand like a balloon.
- It has an extreme orbit: HAT-P-32b orbits its star at a distance of only 3.2 million miles, which is about 30 times closer than Earth is to the sun. This means it completes one orbit in only 53 hours, or about two Earth days. The planet is also tidally locked to its star, which means it always shows the same face to it, like the moon does to Earth.
- It has a massive tail: HAT-P-32b is losing its atmosphere at a rapid rate due to the strong radiation and stellar wind from its star. The escaping gas forms a long tail that trails behind the planet as it orbits. The tail is composed mainly of helium atoms that are ionized by ultraviolet light from the star. The tail is so large that it covers an area of about 1.5 billion square miles, or about three times the surface area of the sun.
How Scientists Discovered the Planet’s Tail
The tail of HAT-P-32b was not visible in optical light, so astronomers had to use other methods to detect it. They used a technique called transit spectroscopy, which involves measuring how the light from the star changes when the planet passes in front of it. By analyzing the spectrum of the starlight, they can infer what elements are present in the planet’s atmosphere and how much they absorb or emit light.
The researchers used data from two telescopes: the Hobby-Eberly Telescope (HET) in Texas and the Nordic Optical Telescope (NOT) in Spain. They observed several transits of HAT-P-32b and found that the planet’s atmosphere blocked more light than expected at certain wavelengths. This indicated that there was something extra in the planet’s vicinity that was absorbing light.
To confirm their findings, they used a 3D simulation from the Stampede2 supercomputer at the Texas Advanced Computing Center (TACC). They modeled how the gas would behave around the planet and how it would affect the starlight. They found that their simulation matched well with their observations, confirming that HAT-P-32b has a giant tail of gas.
Why This Discovery Matters
The discovery of HAT-P-32b’s tail is important for several reasons. First, it shows that exoplanets can have very diverse and dynamic atmospheres that can change over time. Second, it reveals a new way of studying exoplanet atmospheres using transit spectroscopy and computer simulations. Third, it provides clues to an unsolved puzzle in exoplanet science: why there are fewer Neptune-sized planets than expected in short-period orbits around stars.
Scientists think that some of these planets may have lost their atmospheres due to stellar heating and erosion, becoming smaller and denser over time. HAT-P-32b may be an example of such a planet in the process of shrinking. By studying its tail, scientists can learn more about how planets evolve and how they interact with their stars.
