Astronomers have discovered a new exoplanet orbiting the young star TOI-5734, located about 106 light-years from Earth. This planet is smaller than Neptune but larger than Earth: its radius is 2.1 times that of Earth, its mass is 9.1 Earth masses, and its density is slightly lower than Earth's. The planet is classified as a hot sub-Neptune exoplanet due to its size and proximity to its star—it completes a full orbit in just 6.18 days at a distance of 0.06 astronomical units. The surface temperature reaches approximately 688 K.

The star TOI-5734 belongs to the K spectral class and is a relatively young dwarf star with a mass of 0.72 solar masses and a radius of 0.64 solar radii. The planet TOI-5734 b is located at the upper edge of the so-called "radius valley"—a gap between 1.5 and 2.0 Earth radii where very few planets have been found. This suggests the planet may be undergoing a transformation phase. Studies indicate that TOI-5734 b could be losing its atmosphere due to photoevaporation and may lose its primary envelope in about 300 million years, eventually becoming a rocky super-Earth.

Two main instruments were used to detect this exoplanet. The first was the TESS (Transiting Exoplanet Survey Satellite), which determined the planet's size by observing the decrease in the star's brightness as the planet passed across its disk. This event was first recorded in 2022. To confirm the discovery, the HARPS-N instrument was used, allowing scientists to measure the planet's mass, radius, and overall density. The data obtained provided important insights into the evolutionary processes of planetary systems.