Investigations by a team of astrophysicists have led to the sighting of some of the largest gas tails ever seen escaping a exoplanet, thanks to the dedicated study at the McDonald Observatory of The University of Texas.
The celestial body known as HAT-P-32b, a behemoth nearly double the size of Jupiter, has been discovered to be shedding its atmosphere. This creates majestic trails of helium stretching behind and in front of it as it soars through space. Impressively, these tails are over 50 times the radius of the exoplanet itself, as reported in Science Advances journal.
Gigantic Tails of Helium from HAT-P-32b
Exoplanets shedding material isn’t novel, as debris trails can result from impactful collisions, or the neighboring star’s heat can cause the exoplanet’s atmosphere to be propelled into space. But the extent of HAT-P-32b’s gaseous tails is unparalleled.
“The proportion of these extended tails to the size of both the exoplanet and its star is astounding,” commented Zhoujian Zhang, NASA Sagan fellow at the University of California, Santa Cruz, and leader of the study under The University of Texas at Austin HET Exospheres Project. This project focuses on understanding atmospheres of exoplanets.
Understanding HAT-P-32b’s Extraordinary Tails
Investigating the atmosphere of an exoplanet is achieved by observing the planet’s “transit,” which is the motion across its parent star. For instance, it constitutes a transit when Venus aligns between Earth and Sun.
A star, during a transit, throws light through the planet’s atmosphere (if existent), allowing astronomers to analyze the composition through a process known as spectroscopy. Different elements are detected through the color bands by splitting the light into a spectrum.
Despite HAT-P-32b’s tails having been detected previously, the exact size was unknown due to observations only happening during transits.
“We would have missed it without the long-timeframe observations from the Hobby-Eberly Telescope,” said Caroline Morley, assistant professor at The University of Texas at Austin. “It allowed us to view the exoplanet for its entire orbit.”
Observations spanning several nights revealed the true extent of HAT-P-32b’s tails as the team watched the exoplanet cross its star and tracked it days before and after.
The Cause and Effect of HAT-P-32b’s Trails
The gas trails are likely the result of the parent star’s heat boiling the planet’s atmosphere off. HAT-P-32b is considered a “hot Jupiter,” an enormous, steamy, gaseous exoplanet in close proximity to its star. This proximity heats up the gas in HAT-P-32b’s atmosphere causing it to swell, so much that it escapes the planet’s gravity and is sucked into orbit around its star.
“Our discoveries on HAT-P-32b offer insights into the interaction between other planets and their stars,” Morley stated. “By taking precise measurements of hot Jupiters like this, we can apply our findings to a broader range of planets.”
The Hobby-Eberly Telescope (HET) and Its Role in Studying Atmospheres
The HET, with its high-resolution device, the Habitable-Zone Planet Finder spectrograph, is well equipped to study the atmospheres of exoplanets. It is particularly adept at observing near-infrared wavelengths, including those linked with helium, enabling astronomers to detect escaping gases from exoplanets like HAT-P-32b.
One unique feature of the HET is that it surveys the same section of the sky each night with its large, 55-degree tilted mirror. This provides high-precision, long-term observations of the same sky area every night.
“Due to nightly monitoring for several days, we can uncover immense structures like this,” Zhang added. “There might be another exoplanet with expansive escaping atmospheres waiting for discovery.”
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