Meet GJ 740 b— a Super-Earth Orbiting a Red Dwarf Star

James Maynard
Apr 16 · 4 min read

The super-Earth GJ 740 b is no place to call home.

One of our newly-discovered planetary neighbors, GJ 740 b, is a rocky super-Earth, but it’s no place to call home. Image credit: The Cosmic Companion / Created in Universe Sandbox

Red dwarf stars are significantly cooler than our own sun, with surface temperatures between 2,100 and 3,400 degrees Celsius (3,860–6,200 Fahrenheit) — roughly 2,000 C cooler than our parent star. These diminutive, ruddy stars are also smaller than our sun, containing between eight and 45 percent as much mass as the Sun.

Sitting roughly 36 light years from Earth, the GJ 740 system could provide astronomers an intriguing target in the study of planets around alien worlds.

An artist’s impression of GJ 740 b and its parent star. Image credit: Gabriel Pérez Díaz, SMM (IAC)

This newly-discovered exoplanet has a mass about three times greater than Earth, and orbits its star once every 2.4 days.

“This is the planet with the second shortest orbital period around this type of star. The mass and the period suggest a rocky planet, with a radius of around 1.4 Earth radii, which could be confirmed in future observations with the TESS satellite”, explains Borja Toledo Padrón of the Instituto Astrofisica Canarias.

Researchers also found evidence for a second planet in the system — roughly the size of Saturn, orbiting the red dwarf star once every nine years.

Tiny movements of stars caused by the gravitational tug of planets can provide evidence for exoplanets, a technique known as the radial velocity method. Evidence for this second planet, collected through measuring the radial velocity of the star, might be caused by the magnetic field of the star itself, not a planet.

“The main difficulty of this method is related to the intense magnetic activity of this type of stars, which can produce spectroscopic signals very similar to those due to an exoplanet,” explains Jonay I. González Hernández, researcher at IAC.

Further study is needed to confirm or refute this second possible world around GJ 740.

An artist’s concept of the Kepler spacecraft, humanity’s most-successful planet hunter yet. Image credit: NASA/Ames/JPL-Caltech/T. Pyle

“The reality is that we know that this universe, that our galaxy, has billions of stars. We know that stars have planets. So the likelihood that there is life somewhere else to me is just absolutely there.” — Mae Jemison

Currently, we know of around 4,400 planets circling other stars, of which more than 2,600 were discovered by the Kepler spacecraft. This remarkable planet-hunter studied stars, looking for tiny drops in the amount of light seen coming from them, as planets pass “in front” of their star, as seen from Earth.

“The spacecraft was basically a single instrument — a specially designed 3-foot (1-meter) diameter aperture telescope and image sensor array — with a spacecraft built around it. The diameter of the telescope’s mirror was 4 feet, 7 inches (1.4 meters), one of the largest mirrors beyond Earth orbit,” NASA describes.

Professor Eric Agol from the University of Washington discussed the search for exoplanets, including the TRAPPIST-1 system, one of the most-likely places to find life yet discovered. Video credit: The Cosmic Companion

This transit method for detecting alien worlds was utilized in finding more than three-quarters of all known exoplanets.

“In its first mission, from 2009 to 2013, Kepler monitored more than 150,000 stars, watching for tiny dips in starlight as planets crossed in front of their stars. The first mission ended in 2013 when technical problems caused the spacecraft to lose much of its pointing ability. In 2014, it began its second mission, dubbed K2, and continued discovering exoplanets despite its diminished directional capability,” NASA describes.

Although Kepler was decommissioned in 2018, astronomers are still finding new discoveries in its trove of data. Of the 2,600 planets found so far using Kepler, 156 are around cool stars like GJ 740. This data suggests that red dwarf stars like this one host an average of at least 2.5 planets that orbit their stars in less than 200 days.

Just a few short decades ago, we were uncertain if planets were common or rare around other stars. This new discovery is the latest evidence that our galaxy is teeming with other worlds — and, perhaps, life.

Analysis of the discovery was published in the journal Astronomy & Astrophysics.

James Maynard is the founder and publisher of The Cosmic Companion. He is a New England native turned desert rat in Tucson, where he lives with his lovely wife, Nicole, and Max the Cat.

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