Pair of Earth-Like Planets Discovered Around Teegarden’s Star — Howdy, Neighbors!

The Cosmic Companion
Jun 19 · 4 min read

Two planets only slightly more massive than our own world have been discovered orbiting Teegarden’s Star, a red dwarf just 12.5 light years from Earth. A three-year-long study of the star revealed the presence of these worlds, which could potentially hold some of the conditions necessary for life.

Teegarden’s Star is a relative neighbor to our solar system, but it was not discovered until 2003. Due to the star’s cool temperature of just 2,700 degrees Celsius (4,900 degrees Fahrenheit) and possessing less than 10 percent of the mass of our Sun, this small, dim star remained undetected until recently.

Sunsets on Teegarden b and c could be stunning, as the close proximity of their parent star would make for an amazing sight. Image credit: PHL @ UPR Arecibo

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

Teegarden’s Star is the smallest star for which researchers have successfully measured the mass of an orbiting exoplanet. This star, more than eight billion years old, is the 24th closest stellar body to the Earth, and it is the fourth-closest system containing habitable planets.

It Isn’t an Easy Life, to be Sure…

“The innermost planet Teegarden b has a 60% chance of having a temperate surface environment, that is temperatures between 0° to 50°C. Surface temperature should be closer to 28°C [82°F] assuming a similar terrestrial atmosphere but could be higher or lower depending on its composition,” Abel Mendez reports for the Planetary Habitablity Laboratory (PHL) at the University of Puerto Rico at Arecibo (UPR Arecibo).

Teegarden b is just slightly more massive than the Earth, and it revolves around its parent star once every 5.9 days. Researchers at PHL give this world a Earth Similarity Index ranking (ESI) of 95 percent.

One of the great challenges to the development of life on these planets is the possibility of strong flares emitted from their sun. These events could play havoc with these worlds, potentially stripping them of any atmosphere or oceans which may have formed on the surfaces of these planets.

Life is far less likely to be found on Teegarden c, a world which orbits its parent star once every 11.4 Earth days. Although slightly larger than its planetary sibling, Teegarden c is much colder. Surface temperatures on this world are estimated to hover around -47 degrees Celsius (56 degrees below zero Fahrenheit). These frigid conditions, similar to those found on Mars, gives this planet a mere three percent chance of possessing a temperate climate, and an ESI of 68 percent. A thick atmosphere, especially one rich in greenhouse gases, could raise temperatures on the surface of that world.

Most planets circling other stars are found using the transit system, as astronomers note dips in brightness as planets pass between their star and our home world. However, the worlds found orbiting Teegarden’s Star were discovered using the radial-velocity (R-V) method. In these studies, astronomers look for movements of stars consistent with the presence of extrasolar planets. More than 200 observations of the star went into this finding, revealing the presence of this pair of previously-unknown worlds. So far, this method has been utilized to uncover the existence of 800 exoplanets in other solar systems.

“This is a great success for the Carmenes project, which was specifically designed to search for planets around the lightest stars,” stated Ansgar Reiners of the University of Göttingen.

Looking in on the Neighbors

Due to the alignment of our solar system with Teegarden’s Star, any extraterrestrial astronomers on one of these worlds would be able to detect the Earth utilizing the transit system, researchers stated.

Astronomers on planets orbiting Teegarden’s Star would be able to easily detect the Earth using the transit method of detecting distant worlds. Image credit: Universität Göttingen

Approximately 4,000 exoplanets have been cataloged around other suns, while thousands more await confirmation. The majority of these were found by astronomers studying data from the now-defunct Kepler spacecraft.

Today, the Transiting Exoplanet Survey Satellite (TESS) is conducting the first-ever all-sky survey for exoplanets, while following our home world from a high-Earth orbit (HEO). During the course of its first three months in space, the observatory found three exoplanets which were later confirmed by astronomers on Earth. In April, NASA announced the craft revealed the presence of a world roughly the size of our home world.

A look at how the TESS observatory will image the entire sky in search for alien worlds. Image credit: MIT/George Ricker

With the discovery of the dual planets orbiting Teegarden’s star, astronomers now know of 52 worlds around other stars where temperatures are neither too warm, nor too cold, for water to collect, potentially forming oceans. Of these, 19 have masses similar to our home world, and are thought to have rocky surfaces, suggesting the possibility of Earth-like conditions.

A look at the 19 exoplanets most like the Earth, in a graphic from the Planetary Habitability Laboratory at the University of Puerto Rico at Arecibo. Image credit: PHL @ UPR Arecibo

“From the exoplanet data, astronomers can now say with confidence that one out of every five stars hosts a world where life as we know it could form.

So, when you’re standing out there under the night sky, choose five random stars.

Chances are, one of them has a world in its Goldilocks zone where liquid water could be flowing across its surface and life might already exist.”

― Adam Frank, Light of the Stars: Alien Worlds and the Fate of the Earth

Astronomers currently believe that most stars are surrounded by families of planets, suggesting Teegarden’s Star may also host other worlds, so far undiscovered by astronomers.

Finding planets like Earth surrounding a star this close to us suggests how many worlds still remain unseen by the human race. As we learn more about the neighborhood around our Solar System, it seems increasingly likely we may soon find life on other worlds.

The Cosmic Companion

Exploring the wonders of the Cosmos, one mystery at a time

The Cosmic Companion

Written by

James Maynard is the author of two books, and thousands of articles about space and science. E-mail:

The Cosmic Companion

Exploring the wonders of the Cosmos, one mystery at a time

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