An international research team discovers two new Earth-like planets near Teegarden's star

Teegarden’s Star and its two planets, our Solar System in the background. Credit: University of Göttingen, Institute for Astrophysics.

An international team led by the University of Göttingen (Germany) with participation by researchers from the Instituto de Astrofísica de Canarias (IAC) have discovered, using the CARMENES high-resolution spectrograph at the Calar Alto Observatory (Almería) two new planets like the Earth around one of the closest stars within our galactic neighbourhood. 

"Teegarden's star" is only about 12.5 light years away from Earth and is one of the smallest known stars. It is only about 2,700 °C warm and about ten times lighter than the Sun. Although it is so close to us, the star wasn't discovered until 2003. The scientists observed the star for about three years. The results were published in the journal Astronomy and Astrophysics. 

Ilustración de la zona habitable para diferentes estrellas. Crédito: Chester Harman, Planets: PHL @ UPR Arecibo, NASA/JPL.

Their data clearly show the existence of two planets. "The two planets resemble the inner planets of our solar system," explains lead author Mathias Zechmeister of the Institute for Astrophysics at the University of Göttingen. "They are only slightly heavier than Earth and are located in the so-called habitable zone, where water can be present in liquid form." 

"We have been observing this star for three years to look for periodic variations in its velocity, explains Mathias Zechmeister, a researcher at the University of Göttingen, the first author of the paper. The observations showed that two planets are orbiting it, both of them similar to the planets in the inner part of the Solar System. They are just a little bigger than the Earth and are situated in the "inhabitable zone" where water can exist as a liquid. "It is possible that the two planets are part of a larger system," says Stefan Dreizler, another University of Göttingen researcher and a co-author of the paper.

Los dos planetas están ubicados dentro de la zona habitable alrededor de la Estrella de Teegarden. Crédito: Universidad de Göttingen, Instituto de Astrofísica.

The astronomers suspect that the two planets could be part of a larger system. "Many stars are apparently surrounded by systems with several planets," explains co-author Professor Stefan Dreizler of the University of Göttingen. Teegarden's star is the smallest star where researchers have so far been able to measure the weight of a planet directly. "This is a great success for the Carmenes project, which was specifically designed to search for planets around the lightest stars," says Professor Ansgar Reiners of the University of Göttingen, one of the scientific directors of the project. 

Although planetary systems around similar stars are known, they have always been detected using the "transit method" - the planets have to pass visibly in front of the star and darken it for a moment, which only happens in a very small fraction of all planetary systems. Such transits have not yet been found for the new planets. But the system is located at a special place in the sky: from Teegarden's star you can see the planets of the solar system passing in front of the Sun. 

"An inhabitant of the new planets would therefore have the opportunity to view the Earth using the transit method," says Reiners. The new planets are the tenth and eleventh discovered by the team. 

Transits of solar system objects as seen from Teegarden’s Star. Credit: University of Göttingen, Institute for Astrophysics.

An artist's concept of the local stellar neighborhood showing Teegarden's Star which is the Sun's third-closest stellar neighbor, slightly farther than the Alpha Centauri at 7.8 light years from Earth in the direction of the constellation Aries. Credit: NASA/Walt Feimer.

This is a size comparison of "SO25300.5+165258" (red sphere on left) and the Sun. The radius of Teegarden's Star is just 1/7 that of the Sun. "SO25300.5+165258" has only about seven percent of the mass of the Sun, and it is 300,000 times fainter. The star's feeble glow is the reason why it has not been seen until now, despite being relatively close. Credit: NASA/Walt Feimer.

Animation of the local stellar neighborhood. Credit: NASA

Source: University of Göttingen, IAC, NASA,