Distorted exoplanets are shaped like a rugby ball

The 3D simulation shows that the exoplanet KOI 1843.03 can be deformed under the impact of strong gravity due to being too close to the host star.

Scientists are studying the exoplanet KOI 1843.03 that orbits a red dwarf star with nearly half the mass of the Sun and about 395 light-years from Earth. Past research shows that KOI 1843.03 has a mass of 44% and a diameter of 60% that of the Earth. KOI 1843.03 orbits closer to its host star than any other known planet. “Completing an orbit in 4,245 hours, a year on this planet is only 1/6 days long on Earth,” said Leslie Rogers, an astrophysicist at the University of Chicago and lead researcher.

Previously, Rogers et al analyzed the effects of the extremely strong gravitational force that KOI 1843.03 certainly experiences due to a close orbit. They speculated it had to be mostly iron to avoid being broken. While the Earth is about 32% iron, Rogers’ team estimates that the amount of iron on KOI 1843.03 is about 66%. According to Rogers, KOI 1843.03 is considered as one of the most iron-rich exoplanets that they ever discovered.

In a new study published in the Astrophysical Journal, Rogers et al. 3D simulated the internal structure of rocky planets with microscopic orbits such as KOI 1843.03. They found that the planet is more likely to be shaped like a rugby ball. “KOI 1843.03 is the most distorted exoplanet we found. Our model shows that KOI 1843.03 is stretched towards its host star with a frame ratio (ratio between width and height) of about 1.8, much higher than the 1.3 ratio of chicken eggs”, said Rogers.

According to Ellen Price, an astrophysicist at the Harvard-Smithsonian Center in Massachusetts, who co-authored the study, the more iron-rich planets may be less distorted. In the future, the researchers plan to model what the deformed rock exoplanets look like when passing in front of their host star.