This immense 'Styrofoam' planet could help solve a huge mystery

Contributed by
May 19, 2017

You probably remember making one of those solar system models out of wire, paint and Styrofoam balls for your school’s annual science fair—it was either that or a volcano that erupted with baking soda and food coloring. Now a planet peculiarly like Styrofoam could shed light on the mysterious existence of inflated giant planets.

Planets probably don’t inflate like balloons (or junior high science experiments), but researchers investigating the obscure orb known as KELT-11b are unsure of how it blew up to its behemoth size. The KELT (Kilodegree Extremely Little Telescope) survey first zeroed in on this extreme gas giant when it was in transit of its host star KELT-11. It may be only a fifth as massive as Jupiter, but at nearly one and a half times larger, it has a ridiculously thick atmosphere and the approximate density of your go-to building material back in the sixth grade.

The planet is one of the most inflated planets known,” said astronomer and Lehigh assistant professor of physics Joshua Pepper, in a study recently published in The Astronomical Journal, and “it promises to become one of the benchmark systems for the study of inflated exoplanets.”

KELT-11b and Jupiter size comparison. Jupiter is the denser planet.

KELT-11b orbits a dying star which is burning its nuclear fuel as it transitions to a red giant. It will end up devoured by fire in the next hundred million years or so. This star’s phase of living fast and dying hard may shine light on how gas supergiants like KELT-11b get to be so enormous. The intense brightness of KELT-11 that illuminates its orbiting planet is an advantage for researchers wanting to measure atmospheric properties on a precise level. Astronomers are using this opportunity not just to observe, but also to develop advanced telescope instruments that will better detect which gases are swirling in the atmospheres of alien planets.  

That heat causes expansion is probably another thing you learned in science class that may demystify planetary inflation. Researchers are theorizing that because KELT-11 expands and starts to invade KELT 11b’s orbit as it exhausts its fuel, the “puffy planet” may be so immense because of a ruthless bombardment of radiation from its star’s death throes. Underdense planets close enough to a star in this situation are thought to expand from exposure to such intense heat. Kelt-11b’s unusually low density makes it especially prone to extreme expansion.

“This additional radiation may cause close-in planets like KELT-11b to inflate like a balloon,” said KELT principal investigator Scott Gaudi, who is also a co-author of the study. “Additional study of KELT-11b and systems like it are needed to explore this possibility.”  

(via Lehigh University News)


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