Astronomers using the TESS space telescope have discovered an unusual planetary system consisting of orange and white dwarfs, as well as a gas giant. Studies of such systems are important for understanding the influence of stars on the characteristics of planets in multiple systems. The preprint of the work is published on the arXiv.org website.
Despite the fact that about half of all stars in the Milky Way are systems of two or more bodies, by now the vast majority of known exoplanets have been found in single stars. The presence of companions in a star strongly affects the architecture and properties of the planetary system, in particular, it can limit the space where stable orbits of planets are possible, shorten the lifetime of protoplanetary disks, or suppress the formation of planetesimals. Another important and little-studied problem is understanding the relationship between the evolution of stars and their planets. Most of the known exoplanets were found in main sequence stars, which at the end of their life can turn into a red giant with the formation of a white dwarf, which can subsequently destroy and absorb nearby exoplanets or planetesimals.
A group of astronomers led by David V. Martin of Ohio State University announced the discovery of an unusual system TOI-1259, located 385 light years from the Sun and consisting of a dwarf star of spectral type K, an exoplanet and a white dwarf. The system was initially observed by the TESS space telescope between July 2019 and July 2020, and then studied by several ground-based telescopes.
The orange dwarf TOI-1259A has a mass of 0.68 times the mass of the Sun, a radius of 0.73 times the radius of the Sun and an effective temperature of 4775 Kelvin. Its companion is the white dwarf TOI-1259B, which has an estimated mass of 0.56 solar masses, a radius of 0.013 solar radii, and an effective temperature of 6300 kelvin. The distance between the stars is 1,648 astronomical units, and the age of the system is estimated at 4.08 billion years. The exoplanet TOI-1259Ab, which is part of the system, makes one revolution around the K-dwarf in 3.48 Earth days and has a mass of 0.44 Jupiter’s masses and a radius of 1.02 Jupiter’s radius.
It is assumed that the progenitor of the white dwarf was a star with an approximate mass of 1.59 solar masses, which was much closer to its companion (900 astronomical units) than it is now. As for the exoplanet, if it initially formed as a gas giant, then the Kozai-Lidov resonance, which caused the migration of the body, could lead to its current orbital configuration. In addition, astronomers have concluded that TOI-1259Ab is a good target for exploring the exoplanet’s atmosphere with the future James Webb Space Telescope.
Earlier, we talked about how the excess of hydrogen on a white dwarf was explained by the absorption of planetesimals by rich water and for the first time found a planetary-scale object in a white dwarf.