They believe its composition may be the result of a giant planetary collision.
Astronomers were astonished when they extended their gaze 545 light-years away and found an extraordinary exoplanet, named TOI-1853b.
TOI-1853b, which is roughly the size of Neptune, has a radius 3.46 times that of Earth’s; Neptune’s radius is 3.88 times that of Earth’s. However, the similarities end there.
This exoplanet orbits its parent star, an orange dwarf about 80% the size of the Sun, every 1.24 Earth days. Although its radius isn’t large, its mass is truly astounding: 73.2 times that of Earth. In contrast, Neptune has a mass 17.15 times that of Earth.
With its size and mass, scientists calculated that TOI-1853b has a density of 9.7 grams per cubic centimeter. In comparison, Neptune has an average density of 1.64 grams per cubic centimeter, and Earth’s density is 5.15 grams per cubic centimeter. Iron has a density of 7.87 grams per cubic centimeter, similar to the density of steel.
It is an exoplanet the size of Neptune, but remarkably, it has a mass 73.2 times that of Earth. To put it in perspective, Neptune has a mass 17.15 times that of Earth, making this exoplanet “denser than steel,” and its mass is “almost double that of any previously known Neptune-sized planet.” Image: Scitechdaily
The density of TOI-1853b suggests that its composition must contain denser materials and lacks a substantial atmosphere.
To classify exoplanets or planets orbiting stars other than the Sun, astronomers rely on descriptions of our Solar System. After spotting an intriguing object nearly the size of Neptune in close proximity to a dwarf star, they sought more detailed information using various ground-based and space-based telescopes. Once they confirmed that what they saw was indeed a planet and not a star, they were left with a puzzle: what caused such a unique planet to form?
The most plausible explanation for its peculiar features is a catastrophic collision. This recent research was published in the journal Nature.
Until now, more than 5,500 exoplanets have been discovered, revealing a wide range of sizes and compositions among them.
According to co-author Dr. Phil Carter, a planetary scientist at the University of Bristol, exoplanets often “don’t have analogs” in our Solar System.
The research team ran collision simulations to find an answer to why this exoplanet, TOI-1853b, is so unusual. They concluded that initially, TOI-1853b may have been a giant water-rich exoplanet.
Assistant professor and co-author Dr. Zoë Leinhardt concluded, “We haven’t previously looked for such extreme effects because we didn’t expect them. There is much work to be done to improve the material models that underpin our simulations and to extend the range of extreme impacts that are modeled.”
Carter explained that to strip away its atmosphere and make it as dense as it is now, a massive object like another planet would have had to collide with TOI-1853b at a speed of 75 kilometers per second.
This planet provides new evidence of the prevalence of significant events during the formation of planets across the galaxy. This discovery helps bridge the theories of planet formation based on our Solar System with the formation of exoplanets. The identification of this extreme planet offers fresh insights into the formation and evolution of planetary systems. Image: ZME
“This planet is a big surprise for us,” said Jingyao Dou, a co-author and a research student at the University of Bristol.
The team plans to conduct further observations to search for traces of an atmosphere around TOI-1853b and analyze its composition to determine if the predicted collision scenario indeed occurred.
This recent study also showcases what modern astronomy can achieve, thanks to data from NASA’s Transiting Exoplanet Survey Satellite (TESS) in space, as well as the Keck II telescope in Hawaii, the Gemini North telescope in Hawaii, the Southern Astrophysical Research Telescope in Chile, and the Nazionale Galileo telescope in the Canary Islands.