site.btaInternational Team, Led by Bulgarian PhD Student, Discovers Planet

An international team, led by Bulgarian Atanas Stefanov, a PhD student at the Institute of Astrophysics of the Canary Islands (IAC), has discovered a planet named GJ 3998 d. The discovery was made on March 11 and was published in the scientific journal Astronomy & Astrophysics. The planet has been added to the NASA database, Stefanov, who is the senior author of the study, said in an interview with BTA’s Elena Pavlova.

He said that the project is part of the HADES programme, an international effort to explore planetary systems around red dwarfs through the Telescopio Nazionale Galileo telescope at Roque de los Muchachos Observatory on the island of La Palma.

Stefanov graduated in Astrophysics from University College London and has been a PhD student for a year. He shared that he had always wanted to become an astronomer and after graduating from the Acad. Kiril Popov High School of Mathematics in Plovdiv, he decided to pursue astrophysics. Born in Smolyan (Southern Bulgaria), the young scientist still visits his hometown to spend time with his family.

Stefanov began working on the IAC project in May 2024. The team's main goal was to study planets around red dwarfs that are close to the Solar System.

There are three planets in this system. The first two were discovered in 2016, when researchers suggested the possibility of a third planet. They initially dismissed the signal as being caused by the star’s activity. Analysis of the data took about half a year. “And now, nine years later, the data strongly support the existence of a third planet orbiting the red dwarf GJ 3998, which is one of the closest stars to the Sun, located 59 light years away,” Stefanov said.

Astrophysicists believe the newly discovered planet is a super-Earth, with a mass at least six times that of Earth. “They also believe that it is like a sister planet to Earth. It is probably rocky, heavier than Earth, and lighter than Neptune. It orbits the red dwarf in 41.8 days,” he noted.

“What is especially interesting about this planet is that the star it orbits is smaller and cooler than the Sun, and the planet is closer to it than Earth is to the Sun. However, the plant receives only 20% more energy from the star than Earth does from the Sun. This suggests that the planet’s temperature is likely to be slightly higher than Earth's,” the scientist added.

“Planets, especially small-mass ones, rarely exist alone - they prefer to have company. Often, when we revisit a system with new measurements and new methods, we discover planets that were previously overlooked,” Stefanov said.

According to him, the newly discovered planet is a good candidate for atmospheric analysis. Stefanov and his team believe it might have conditions suitable for life, but proving this will take decades of technological improvement. He added that the ANDES spectrograph of the European Southern Observatory's ELT telescope and the 50-metre Exo Life Finder telescope, which is designed to search for biomarkers in exoplanet atmospheres, are being developed.

“Despite nearly 6,000 planets having been discovered, we have yet to find an Earth-like planet orbiting a star similar to the Sun. This is the next major goal of astronomy,” the scientist said. He recalled that astronomers recently confirmed the existence of a quartet of small rocky planets orbiting Barnard's Star, one of the closest stars to the Solar System.