Astronomers Discover Hidden Earth-Like Worlds Orbiting Nearby Dwarf Stars

Studies of 15 M-type stars have revealed new insights into the potential presence of exoplanets.

A new study led by astronomers at Heidelberg University reveals that Earth-like planets may be much more common than we thought, especially around small, low-mass stars.

Using data from the CARMENES project, an international team discovered four new exoplanets and precisely measured their characteristics. They found that planets similar in size and composition to Earth seem to frequently orbit stars that have less than one-sixth the mass of our Sun.

This is exciting news for the ongoing search for life beyond our solar system. These lightweight stars, known as M-dwarfs, are not only the most common type of star in our galaxy, but they also offer promising conditions for detecting potentially habitable worlds nearby.

The key tool behind these discoveries is the CARMENES spectrograph, located at the Calar Alto Observatory in southern Spain. Designed and built at Heidelberg University’s Königstuhl Observatory, this advanced instrument scans M-dwarfs for subtle wobbles caused by the gravitational tug of orbiting planets. These tiny shifts in motion help astronomers detect planets that might otherwise remain hidden.

Analyzing the Data: Four New Worlds Identified

For the current study, the researchers chose 15 stars from a catalog of 2,200 M-dwarfs of the CARMENES program and analyzed their radial velocity data. The speed of a star can be precisely measured by recording a high-resolution spectrum and analyzing the spectral lines.

The researchers discovered four new planets based on the data; the largest one has a mass 14 times greater than our Earth and orbits its host star in approximately 3.3 years. The other planets have between 1.03 and 1.52 Earth masses and orbital periods from 1.43 to 5.45 days.

Statistical analyses show that stars with less than 0.16 solar masses have, on average, about two planets with less than three Earth masses. “It is quite remarkable how often small planets occur around very low-mass stars,” stresses study lead Dr. Adrian Kaminski from the Königstuhl Observatory, which is part of the Centre for Astronomy of Heidelberg University. Larger planets, on the other hand, are rarer. “This suggests that low-mass stars tend to form smaller planets in close orbits,” states the Heidelberg astronomer.

Inching Closer to Finding Habitable Worlds

Among the approximately 5,000 planets previously discovered in other solar systems, none is a true “twin” of the Earth in terms of mass, radius, surface temperature, and type of parent star. However, the newly discovered planets meet at least the first three criteria, explains Prof. Dr. Andreas Quirrenbach, director of the Königstuhl Observatory.

“Small, rocky planets in the so-called habitable zone – the area around a star where water could exist in liquid form – are potential candidates for habitable worlds. Since M-dwarfs are very common and radiate their energy constantly into space over billions of years, they could provide stable environments for the development of life,” states the astronomer and expert in the search for exoplanets. This finding provides clues as to where the search for habitable planets could be most promising.

Reference: “The CARMENES search for exoplanets around M dwarfs – Occurrence rates of Earth-like planets around very low-mass stars” by A. Kaminski, S. Sabotta, J. Kemmer, P. Chaturvedi, R. Burn, J. C. Morales, J. A. Caballero, I. Ribas, A. Reiners, A. Quirrenbach, P. J. Amado, V. J. S. Béjar, S. Dreizler, E. W. Guenther, A. P. Hatzes, Th. Henning, M. Kürster, D. Montes, E. Nagel, E. Pallé, V. Pinter, S. Reffert, M. Schlecker, Y. Shan, T. Trifonov, M. R. Zapatero Osorio and M. Zechmeister, 8 April 2025, Astronomy & Astrophysics.
DOI: 10.1051/0004-6361/202453381

Along with astronomers from Heidelberg University, researchers from Bulgaria, Germany, India, Norway, Spain, and the USA contributed to the study. Among others, the Spanish Ministry of Science, the European Union, the Bulgarian National Science Fund, and the German Research Foundation funded the research work.

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