An international team of astronomers has discovered the first superhot Neptune orbiting its nearest star LTT 9779. Scientists have detailed their observations and conclusions in the journal Nature Astronomy.
The recently discovered superhot Neptune orbits so close to its star that it lasts only 19 hours a year. Stellar radiation heats the planet to over 1,700 ° C. At these temperatures, heavy elements such as iron can ionize in the atmosphere and molecules dissociate, creating a unique laboratory for studying the chemistry of planets outside the solar system.
Although the discovered world weighs twice as much as Neptune, it is also slightly larger and has the same density. Therefore, LTT 9779b should have a huge core with a mass of about 28 Earth masses and an atmosphere that makes up about 9% of the total mass of the planet.
The system itself is about half the age of the Sun, 2 billion years old, and given the intense radiation exposure, a planet like Neptune cannot be expected to maintain its atmosphere for so long as to solve the intriguing riddle of how such an incredible system came to be.
LTT 9779 is a sun-like star located 260 light-years away. In an astronomical sense, it is literally “on the doorstep”. The planet is very rich in metals, its atmosphere contains twice as much iron as the Sun. This could be a key indicator that superhot Neptune was originally a much larger gas giant since these bodies predominantly form near the stars with the highest iron content.
The first indications of the existence of a planet were made with the Transit Exoplanet Research Satellite (TESS) as part of its mission to detect small transiting planets. In early November 2018, the transit signal was quickly confirmed as coming from a planetary body using observations made with the High Accuracy Radial-Speed Planet Searcher (HARPS) instrument mounted on the 3.6m telescope at ESO la Silla observatory in the north. Chile. HARPS uses the Doppler wobble method to measure planetary masses and orbital characteristics such as orbital periods. When objects are detected to be moving, Doppler measurements can be organized to effectively confirm planetary nature. In the case of LTT 9779b, the team was able to confirm the planet’s existence after just one week of observations.
The discovery of LTT 9779b at such an early stage in the TESS mission was a complete surprise; a game that paid off. LTT 9779b is a truly rare beast that exists in a sparsely populated area of planetary space parameters. The planet exists in the so-called Neptune desert, a region devoid of planets.
Professor James Jenkins of the Department of Astronomy, University of Chile
The planet does have a significant atmosphere, and it orbits a relatively bright star. This means that future studies of the planet’s atmosphere may reveal some mysteries related to how such planets form, how they evolve, and what they are. The planet is very hot, which motivates the search for elements heavier than hydrogen and helium, as well as ionized atomic nuclei. This “incredible planet”, according to scientists, is so rare that the chances of finding one like this are slim. This makes studying it all the more important.