Two New Earth-like Planets Discovered

Artist rendering of ’Teegarden’s Star’ and its two companions.

Artist rendering of ’Teegarden’s Star’ and its two companions. | Mathias Zechmeister, University of Göttingen

International research team with Heidelberg participation finds companions of "Teegarden’s Star"

With the aid of the highly complex CARMENES measuring instrument, a team of researchers from Germany and Spain has discovered two new earth-like planets. They orbit one of our closest neighbouring stars, "Teegarden’s Star", which is located a mere 12.5 light years from Earth. One of its companions is more similar to Earth than any other known planet. The principal investigator of the CARMENES project is Andreas Quirrenbach, Director of the Königstuhl State Observatory, which is part of the Centre for Astronomy of Heidelberg University.

CARMENES is a novel astronomical measuring instrument designed to detect earth-like planets, particularly planets near light, i.e. low-mass, stars. It is being deployed on the 3.5-metre telescope of the Calar Alto Observatory near Almería in southern Spain. The highly complex instrument consisting of two spectrographs was developed and built by an international consortium of eleven German and Spanish institutions; researchers from the Königstuhl State Observatory were significantly involved in its construction and operation. They constructed one of the two spectrographs and are now in charge of continuously monitoring and improving the quality of the data.

"Teegarden’s Star" is one of the smallest stars currently known. It is approximately ten times lighter than the sun and has a temperature of approximately 3,000°C. Although the star is so close to Earth, it wasn’t discovered until 2003. The CARMENES team has been observing "Teegarden’s Star" for about three years and tracked its regular changes in velocity. The analysis of the data by astrophysicists of the University of Göttingen clearly points to the existence of two planets. According to the researchers, the two resemble the inner planets of our solar system and are only slightly heavier than Earth. They are located in the so-called habitable zone, where water can be present in liquid form. "Teegarden’s Star" is the smallest star where researchers have thus far been able to measure the mass of a planet directly.

Prof. Quirrenbach explains that planetary systems around similar stars are indeed known, but so far, they have always been detected using the transit method. In the transit method, the planets have to pass visibly in front the star and darken it for a moment, which happens only in a very small fraction of all planetary systems. The existence of the two planets near "Teegarden’s Star" was deduced from the data  obtained with CARMENES,  from which the orbits of planets around so-called cool stars can be inferred with unprecedented sensitivity.

In the CARMENES project, German and Spanish astronomers have been searching for planets around stars in the solar neighbourhood since 2016. Cooperation partners are the universities of Göttingen, Hamburg und Heidelberg, the Max Planck Institute for Astronomy in Heidelberg, the Thüringen State Observatory Tautenburg, institutes of the Spanish National Research Council, the Institute of Astrophysics of Canarias, the Complutense University of Madrid, and the Calar Alto Observatory. With the discovery of the new planets, the number of new planets has now climbed to eleven. The participation of Heidelberg University in CARMENES was supported by funding from the State of Baden-Württemberg, the German Research Foundation and the Klaus Tschira Foundation.

Mathias Zechmeister et al.: The CARMENES search for exoplanets around M dwarfs - Two temperate Earth-mass planet candidates around Teegarden’s Star. Astronomy & Astrophysics (2019),

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