Universe Today
You’re the grillmaster at the annual family 4th of July BBQ and you’re sweating bullets standing over the grill in the sweltering summer heat. You’re trying to stay cool by pressing a cold beer can on your forehead, but to no avail. You can’t go inside because, once again, you’re the grillmaster and need to watch the food simmering on your freshly cleaned grill. Your brother-in-law is a university astronomy professor and walks over asking how you’re doing. You say, “This heat is killing me. I feel hotter than the barbeque!” Your science teacher brother-in-law slyly says, “Try being an exoplanet.” You roll your eyes.
As it turns out, exoplanets can get barbequed, as demonstrated with HD 80606 b, which is located approximately 217 light-years from Earth, and was discussed in a recent study presented at the 248th meeting of the American Astronomical Society. HD 80606 b has a radius and mass of about one- and four-times Jupiter, respectively, while orbiting extremely close to its host star, also called a “hot” Jupiter. While “hot” Jupiters are very common, what makes HD 80606 b unique is its highly elliptical orbit, meaning its orbit is oval-shaped, which drastically contradicts planets in our solar system, which exhibit almost circular orbits.
As a result, HD 80606 b travels both very far from its star and very close, with the latter resulting in the exoplanet being blasted with extreme temperatures. A single orbit of HD 80606 b takes about 111 days, and it exhibits an eccentricity of 0.93, with eccentricity being measured from 0 to 1, with 0 being a perfect circle. For context, Earth has an eccentricity of 0.0167, with the smallest eccentricity being Venus at 0.0068 and the largest eccentricity being Mercury at 0.2056. HD 80606 b’s highly eccentric orbit takes it as far as 0.85 astronomical units (AU) from its star (Venus’s orbit) to as close as 0.03 AU, or about 10 times to the Sun as Mercury.
Using NASA’s James Webb Space Telescope, the researchers observed HD 80606 b when it passes the closest to its star, known as periastron. Through this, the researchers found that HD 80606 b not only experiences searing temperatures of about 600 degrees Celsius (1,100 degrees Fahrenheit), but the amount of solar energy it receives is about 800 times greater than at other locations in its orbit.
“Observing a planet like HD 80606 b is actually very efficient because its unusual orbit, with the corresponding swings in temperature and chemical composition, allow us to gather data under varying conditions in just hours and apply those findings to other hot Jupiters or more conventional exoplanets,” said Dr. Laura C. Mayorga, who is an exoplanet astronomer at the Johns Hopkins Applied Physics Laboratory and a co-author on the study.
Discovered in 2001, HD 80606 b has a solid history of past studies examining this unique exoplanet and how its highly eccentric orbit influences its temperature and atmosphere. These include a 2026 study published in The Astronomical Journal that suggested the presence of methane and carbon monoxide, which built off a 2023 study published in the Monthly Notices of the Royal Astronomical Society that discussed the ratio of carbon monoxide and methane.
HD 80606 b is part of a growing number of highly eccentric exoplanets that have piqued the interest of the scientific community. This is primarily due to their ability to teach scientists about how exoplanets evolve during a single orbit, whether it’s temperature or atmospheric composition. They have also been the subject of potentially harboring life, including WASP-47 c, which travels both in and out of its star’s habitable zone during its eccentric orbit.
What new insight into HD 80606 b and other highly elliptical exoplanets getting barbequed by their stars would researchers make in the coming years and decades? Only time will tell, and this is why we science!
As always, keep doing science & keep looking up!
