A planet located 950 light-years from Earth is explosively losing its atmosphere and forming a tail about 18 times the size of Jupiter in the process. This makes the gas tail one of the largest planetary structures seen outside the solar system.
The exoplanet, or exoplanet, known as HAT-P-32 b, is about 68% the mass of Jupiter, but is twice the width of the largest planet in the solar system. HAT-P-32 is only 3.2 million miles from its parent star, or about 3% of the Earth-Sun distance, and completes an orbit every 2.2 days. This proximity means that the gas giant is being roasted by radiation from its parent star, classifying HAT-P-32 b as a “hot Jupiter”.
Astronomers have observed HAT-P-32 b’s trailing gas tail created from helium spewing from its atmosphere using telescopes from the ground, including the University of Texas’ Hobby-Eberly telescope at MacDonald Observatory in Austin. “We observed this planet and its host star through long-term sequential spectroscopy, and observations made of the star and planet over two nights,” said Zhujian Zhang, lead author of the paper and a postdoctoral fellow at the University of California Santa Cruz’s Department of Astronomy and Astrophysics. in the current situation. “And what we found is that there is a huge tail of helium gas attached to the planet. And the tail is large — about 53 times the radius of the planet — made up of gas escaping from the planet.”
By learning more about how hot Jupiter lost its atmosphere, a team of researchers hopes to build a better picture of planetary evolution. This could help resolve the puzzling absence of a certain type of planet in the exoplanet catalog.
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Using hot Jupiter to explore ‘hot Neptune desert’
Since the first planets outside our solar system were first discovered in the 1990s, exoplanet hunters have discovered more than 5,000 worlds orbiting distant stars, and they come in a range of shapes, masses, and properties. However, there remains a bewildering gap in our exoplanet catalog.
Astronomers have discovered a wide range of large Jupiter-sized planets orbiting close to their stars and fewer, but still large numbers of small Earth-size worlds close to their stellar parents.
But what seems to be missing are the intermediate-sized planets orbiting close to their parent stars. Astronomers refer to such planets as “hot Neptunes” after the icy giant in the solar system of similar size, so the absence of such worlds is called the “hot Neptune desert”.
One possible explanation for this absence is that planets close to their stars are stripped of their atmospheres and thus lose mass.
“If we can take pictures of planets in the process of losing their atmosphere, we can study how quickly a planet loses its mass and what are the mechanisms that cause its atmosphere to escape from the planet,” Zhang said. “Nice to have some examples to see, like Operation HAT-P-32 b in action.”
The team studied HAT-P-32 b, which was discovered in 2011, by observing the light from its parent star, which is about the same size as the Sun and is only slightly hotter than our own. When hot Jupiter passes in front of the star, starlight is filtered through the planet’s atmosphere.
Because chemical elements absorb light at specific frequencies, astronomers can compare starlight filtered through the atmosphere with starlight that has not, helping them determine the chemical composition of a planet’s atmosphere. The search for these absorption gaps is called “transmission spectroscopy”.
Conducting transmission spectroscopy of HAT-P-32 b revealed deep absorption lines of helium in starlight as the planet transits the star.
“The uptake of helium is stronger than we would expect from the atmosphere of stars. This excess uptake of helium must be caused by the planet’s atmosphere,” Zhang said. “When the planet passes, its atmosphere is so massive that it blocks part of the atmosphere that sucks in the helium line, and that causes this overabsorption. And that’s how we found out that HAT-P-32 b is an interesting planet.”
But to understand it better, they created a 3D simulation of a hot Jupiter using the Texas Advanced Computing Center (TACC) Stampede2 supercomputer. Computer modeling of the planet revealed it to be even more interesting than these observations suggested.
Computer simulations developed by Harvard-Smithsonian Center for Astrophysics theoretical and computational researcher Morgan MacLeod and colleagues model the interaction between the planet’s gas flow and the stellar wind from its parent star.
This showed that the planetary outflow was late and ahead of HAT-P-32 b in its orbital trajectory.
The team was also able to calculate the rate of loss of the planet’s mass, and found that it would take 40 billion years for HAT-P-32 b to lose its entire atmosphere. However, the planet is unlikely to survive this period; F-type stars, such as the planet’s host star HAT-P-32 A, are only 2 to 4 billion years old, after which they deplete the hydrogen in their cores used in nuclear fusion.
This causes the star’s core to collapse and the outer layers to swell as nuclear fusion is still going on. This increases the star’s radius up to a hundred times, creating a red giant. When HAT-P-32 A undergoes this process, the exoplanet is so close that it and its remaining atmosphere will likely be swallowed up.
In the future, the team plans to study other planets similar to HAT-P-32 b to monitor their evolution. In addition, the researchers behind the supercomputer model will now develop other complex simulations of exoplanet dynamics.
This could provide simulations that can model other effects such as the mixing of gases in planetary atmospheres and even how winds move through the atmospheres of planets hundreds or even thousands of light-years from Earth, too far away to detect these effects with current telescopes. .
“Now is the time to have supercomputers with the computational power to make it happen,” Zhang concluded. “We need computers to make true predictions based on recent advances in theory and data interpretation. Supercomputers bridge model and data.”
The team’s research is published in the journal Science Advances.