Free Astronomy Magazine November-December 2023

47 NOVEMBER-DECEMBER 2023 ASTRO PUBLISHING the research team is to find its pos- sible origin, because none of the current theoretical models of planet formation predict that there could be a planet with these characteris- tics. Two possible scenarios for its formation have been proposed: in one of them it could have been pro- duced by collisions between massive protoplanets, that is between plan- ets which were in formation in that planetary system. These collisions might have elimi- nated the major part of the atmos- phere of TOI-1853b, leaving its solid nucleus exposed, which would ex- plain its high density within a mod- erate size. Another possibility is that TOI- 1853b might originally have been a gas giant similar to Jupiter, or even more massive, and could have taken a highly elliptical orbit due to inter- actions with other planets. This would have made it pass very close to its star, causing it to lose the outer layers of its atmosphere, and stabilizing its orbit at its current dis- tance from the star. “At the time being, we cannot dis- tinguish which of these formation scenarios is more plausible, al- though we should not rule out that later theoretical studies based on this discovery might lead to new models for the formation of very massive Neptunes” , explains Enric Pallé, a researcher at the IAC who participated in the study. TOI-1853b was first identified in 2020 as a planetary candidate with data from NASA’s TESS (Transiting Exoplanet Survey Satellite) which used the method of transits, which means observing the periodic dips in the light from a star caused by a planet in orbit round it when it crosses between us and the star. The confirmation that TOI-1853b is a planet, and the measurement of its mass and density were possible thanks to spectroscopic observa- tions of the star’s radial velocity ob- tained by the team using the HARPS-N (High Accuracy Radial Ve- locity Planet Searcher for the North- ern hemisphere) on the Telescopio Nazionale Galileo (TNG), at the Roque de los Muchachos Observa- tory, (La Palma, Canary Islands). N eptune imaged by Voyager 2 on August 31, 1989. Sum of orange, green, and blue filtered images. [NASA, Kevin Gill] !