An exoplanet the size of Neptune, denser than steel, has been discovered by a team of international astronomers. They believe its composition may result from a massive planetary collision.
The astronomers were astonished when they extended their gaze 545 light-years away and discovered a remarkably unique exoplanet.
This exoplanet is TOI-1853b, which has a radius 3.46 times that of Earth. It orbits its host star, a K-dwarf star approximately 80% the size of the Sun, every 1.24 Earth days. Despite its relatively small radius, its mass is truly astonishing: 73.2 times that of Earth. In comparison, Neptune’s mass is only 17.15 times that of Earth.
With such size and mass, the team of scientists calculated that TOI-1853b has a density of 9.7 grams/cm3. Meanwhile, Neptune has an average density of 1.64 grams per cubic centimeter, while our Earth has a density of only 5.15 grams per cubic centimeter. Iron has a density of 7.87 grams per cubic centimeter, which is similar to that of steel.
This exoplanet is the size of Neptune – yet perplexingly, it has a mass 73.2 times that of Earth. For comparison, Neptune has a mass 17.15 times that of Earth, making it “denser than steel,” with its mass “nearly double that of any known Neptune-sized planet to date.” (Image: Scitechdaily).
The density of TOI-1853b indicates that its composition must include many denser materials with little atmosphere.
To classify exoplanets or planets orbiting stars beyond our Sun, astronomers rely on descriptions of the Solar System. Upon noticing an intriguing object, roughly the size of Neptune and near a K-dwarf star, they sought further details using various ground-based and space telescopes. After confirming what they observed was indeed a planet and not a star, they were left with a puzzle to solve: what could have caused such a unique planet to form?
The best explanation for its unusual characteristics is a catastrophic collision. This new research was published in the journal Nature.
In the study published on August 31 in the journal Nature, scientists led by Luca Naponiello from the University of Rome Tor Vergata suggest that this is the result of a collision between planets. These massive impacts would strip away some of the lighter atmosphere and water, leaving behind a multitude of rocks. (Image: Inverse).
To date, more than 5,500 exoplanets have been discovered, and from this, astronomers have learned that exoplanets come in many sizes and compositions.
According to study co-author Phil Carter, a planetary scientist at the University of Bristol, exoplanets often “have no analogs” in our Solar System.
The research team ran simulations of collision scenarios to find answers to why this exoplanet (named TOI-1853b) is so peculiar. The researchers concluded that initially, TOI-1853b may have been a giant water-rich gas planet.
Associate Professor and co-author Dr. Zoë Leinhardt concluded: “We have never investigated such extreme impacts before because they are not what we expected. There is still much work to be done to improve the material models underlying our simulations and to expand the range of extreme impacts modeled.”
Carter explained in a university statement that to lose its atmosphere and lighter ice while becoming the extremely dense world it is today, another massive object, like a planet, would have to collide with TOI-1853b at a speed of 75 km/s.
This planet provides new evidence of the prevalence of massive impacts during the formation of planets across the galaxy. This discovery helps connect theories of planetary formation based on the Solar System with the formation of exoplanets. The discovery of this extreme planet offers new insights into the formation and evolution of planetary systems. (Image: ZME).
“This planet gives us quite a surprise,” Jingyao Dou, a co-author of the study and a research fellow at the University of Bristol, shared in a statement.
The team plans to conduct further observations to search for traces of an atmosphere around TOI-1853b and analyze its composition to determine whether the predicted collision scenario actually occurred.
This new work also exemplifies what modern telescopes can achieve. This research was made possible by 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 Galileo National Telescope in the Canary Islands.
