Red Dwarf Stars Might Be Able to Hold Onto Their Atmospheres After All

This 2018 artist’s concept shows what the TRAPPIST-1 planetary system may look like, based on available data about the planets’ diameters, masses and distances from the host star (far left). New research shows that while TRAPPIST-1b, second from the left, has no atmosphere, TRAPPIST-1e, third from the right, could have a long-term stable atmosphere.NASA/JPL-Caltech

Exoplanets are a fascinating aspect of the study of the Universe. TRAPPIST-1 is perhaps one of the most intriguing exoplanet systems discovered to date with no less than 7 Earth-sized worlds. They orbit a red dwarf star which can unfortunately be a little feisty, hurling catastrophic flares out into space. These flares could easily strip atmospheres away from the alien worlds rendering them uninhabitable. A new piece of research suggests this may not be true and that the rocky planets may be able to maintain a stable atmosphere after all. 

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Exoplanets Could be Hiding Their Atmospheres

Illustration of the tidally locked world TRAPPIST-1f. Credit: NASA/JPL-Caltech

Most of the exoplanets we’ve discovered orbit red dwarf stars. This isn’t because red dwarfs are somehow special, simply that they are common. About 75% of the stars in the Milky Way are red dwarfs, so you would expect red dwarf planets to be the most abundant. This also means that most habitable worlds are going to orbit these small, cool stars, and that has some significant consequences for our search for life.

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SETI Scientists Scan TRAPPIST-1 for Technosignatures

Three of the TRAPPIST-1 planets – TRAPPIST-1e, f and g – dwell in their star’s so-called “habitable zone. CreditL NASA/JPL

If you are going to look for intelligent life beyond Earth, there are few better candidates than the TRAPPIST-1 star system. It isn’t a perfect choice. Red dwarf stars like TRAPPIST-1 are notorious for emitting flares and hard X-rays in their youth, but the system is just 40 light-years away and has seven Earth-sized worlds. Three of them are in the potentially habitable zone of the star. They are clustered closely enough to experience tidal forces and thus be geologically active. If intelligent life arises easily in the cosmos, then there’s a good chance it exists in the TRAPPIST-1 system.

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TRAPPIST-1 Outer Planets Likely Have Water

Three of the TRAPPIST-1 planets – TRAPPIST-1e, f and g – dwell in their star’s so-called “habitable zone. CreditL NASA/JPL

The TRAPPIST-1 solar system generated a swell of interest when it was observed several years ago. In 2016, astronomers using the Transiting Planets and Planetesimals Small Telescope (TRAPPIST) at La Silla Observatory in Chile detected two rocky planets orbiting the red dwarf star, which took the name TRAPPIST-1. Then, in 2017, a deeper analysis found another five rocky planets.

It was a remarkable discovery, especially because up to four of them could be the right distance from the star to have liquid water.

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Will We Know if TRAPPIST-1e has Life?

Artist's impression of the Archean Eon. Credit: Tim Bertelink/Wikimedia

The search for extrasolar planets is currently undergoing a seismic shift. With the deployment of the Kepler Space Telescope and the Transiting Exoplanet Survey Satellite (TESS), scientists discovered thousands of exoplanets, most of which were detected and confirmed using indirect methods. But in more recent years, and with the launch of the James Webb Space Telescope (JWST), the field has been transitioning toward one of characterization. In this process, scientists rely on emission spectra from exoplanet atmospheres to search for the chemical signatures we associate with life (biosignatures).

However, there’s some controversy regarding the kinds of signatures scientists should look for. Essentially, astrobiology uses life on Earth as a template when searching for indications of extraterrestrial life, much like how exoplanet hunters use Earth as a standard for measuring “habitability.” But as many scientists have pointed out, life on Earth and its natural environment have evolved considerably over time. In a recent paper, an international team demonstrated how astrobiologists could look for life on TRAPPIST-1e based on what existed on Earth billions of years ago.

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Could Earth Life Survive on a Red Dwarf Planet?

This artist's illustration shows planets orbiting a red dwarf star. Many red dwarfs have planets in their habitable zones, but red dwarf flaring might mean those zones aren't habitable at all. New research explores the idea. Image Credit: NASA

Even though exoplanet science has advanced significantly in the last decade or two, we’re still in an unfortunate situation. Scientists can only make educated guesses about which exoplanets may be habitable. Even the closest exoplanet is four light-years away, and though four is a small integer, the distance is enormous.

That doesn’t stop scientists from trying to piece things together, though.

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Six Planets Found Orbiting an Extremely Young Star

Artist rendering of the TOI-1136 system and its young star flaring. Credit: Rae Holcomb/Paul Robertson/UCI

The field of exoplanet study continues to grow by leaps and bounds. As of the penning of this article, 5,572 extrasolar planets have been confirmed in 4,150 systems (with another 10,065 candidates awaiting confirmation. Well, buckle up because six more exoplanets have been confirmed around TOI-1136, a Sun-like star located roughly 276 light-years from Earth. This star is less than 700 million years old, making it relatively young compared to our own (4.6 billion years). This system will allow astronomers to observe how systems like our own have evolved with time.

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TRAPPIST-1c Isn’t the Exo-Venus We Were Hoping For. But Don’t Blame the Star

A recent study accepted to The Astrophysical Journal uses computer models to investigate why the exoplanet, TRAPPIST-1c, could not possess a thick carbon dioxide (CO2) atmosphere despite it receiving the same amount of solar radiation from its parent star as the planet Venus receives from our Sun, with the latter having a very thick carbon dioxide atmosphere. This study comes after a June 2023 study published in Nature used data from NASA’s James Webb Space Telescope (JWST) to ascertain that TRAPPIST-1c does not possess a carbon dioxide atmosphere. Both studies come as the TRAPPIST-1 system, which is located approximately 41 light-years from Earth and orbits its star in just 2.4 days, has received a lot of attention from the scientific community in the last few years due to the number of confirmed exoplanets within the system and their potential for astrobiology purposes.

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TRAPPIST-1 Has Flares. What Does This Mean for its Planets?

Most exoplanets orbit red dwarf stars because they're the most plentiful stars. This is an artist's illustration of what the TRAPPIST-1 system might look like from a vantage point near planet TRAPPIST-1f (at right). Credits: NASA/JPL-Caltech
Most exoplanets orbit red dwarf stars because they're the most plentiful stars. This is an artist's illustration of what the TRAPPIST-1 system might look like from a vantage point near planet TRAPPIST-1f (at right). Credits: NASA/JPL-Caltech

The TRAPPIST-1 system continues to fascinate astronomers, astrobiologists, and exoplanet hunters alike. In 2017, NASA announced that this red dwarf star (located 39 light-years away) was orbited by no less than seven rocky planets – three of which were within the star’s habitable zone (HZ). Since then, scientists have attempted to learn more about this system of planets to determine whether they could support life. Of particular concern is the way TRAPPIST-1 – like all M-type (red dwarf) stars – is prone to flare-ups, which could have a detrimental effect on planetary atmospheres.

Using the James Webb Space Telescope (JWST), an international team of astrophysicists led by the University of Colorado Boulder (CU Boulder) took a closer look at this volatile star. As they describe in their paper (which recently appeared online), the Webb data was used to perform a detailed spectroscopic investigation of four solar flares bursting around TRAPPIST-1. Their findings could help scientists characterize planetary environments around red dwarf stars and measure how flare activity can affect planetary habitability.

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Can JWST Tell the Difference Between an Exo-Earth and an Exo-Venus?

Earth and Venus. Why are they so different and what do the differences tell us about rocky exoplanet habitability? Image Credit: NASA

As of this month, astronomers have discovered 5,506 exoplanets orbiting other stars. That number is growing daily, and astronomers are hoping, among other things, to find Earth-like worlds. But will we know one when we see it? How might we be able to tell an Earth-like garden from a Venus-like pressure cooker from upwards of 40 light years away? Is JWST up to the challenge?

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