Study Findings: TESS Planet Occurrence Rates Reveal the Disappearance of the Radius Valley around Mid-to-late M Dwarfs

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Image (Credit): Artist’s rendering of NASA’s Transiting Exoplanet Survey Satellite (TESS). (NASA)

The Astronomical Journal abstract of study findings:

We present the deepest systematic search for planets around mid-to-late M dwarfs to date. We have surveyed 8134 mid-to-late M dwarfs observed by the Transiting Exoplanet Survey Satellite with a custom-built pipeline and recover 77 vetted transiting planet candidates. We characterize the sensitivity of our survey via injection–recovery and measure the occurrence rate of planets as a function of orbital period, instellation, and planet radius. We measure a cumulative occurrence rate of 1.10 ± 0.16 planets per star with radii >1 R⊕ orbiting within 30 days. This value is consistent with the cumulative occurrence rate around early M dwarfs, making M dwarfs collectively the most prolific hosts of small close-in planets. Unlike the bimodal radius valley exhibited by close-in planet populations around FGK and early M dwarfs, we recover a unimodal planet radius distribution peaking at 1.25 ± 0.05 R⊕. We additionally find 0.954 ± 0.147 super-Earths and 0.148 ± 0.045 sub-Neptunes per star, with super-Earths outnumbering sub-Neptunes 5.5:1, firmly demonstrating that the radius valley disappears around the lowest-mass stars. The dearth of sub-Neptunes around mid-to-late M dwarfs is consistent with predictions from water-rich pebble accretion models that predict a fading radius valley with decreasing stellar mass. Our results support the emerging idea that the sub-Neptune population around M dwarfs is composed of water-rich worlds. We find no hot Jupiters in our survey and set an upper limit of 0.012 hot Jupiters per mid-to-late M dwarf within 10 days.

Citation: Erik Diego Gillis et al. TESS planet occurrence rates reveal the disappearance of the radius valley around mid-to-late M dwarfs. AJ 171 317 (2026).

DOI: https://doi.org/10.3847/1538-3881/ae5810

Study-related stories:

Phys.org – “The Most Common Planets in the Galaxy Don’t Appear Around the Most Common Stars, TESS Observations Suggest”

Newsbreak – “TESS Uncovers Cosmic Surprise: Galaxy’s Most Common Planets Skip Its Most Common Star”

Universe Today – “Closing The Exoplanet Radius Gap”

Space Quote: NASA Has Lessons for Automating American Industry

Posted on by onespaceman2000
Credit: Image by David Yonatan González Aburto from Pixabay.

“At NASA, decades of designing humanoid robots for environments that don’t forgive narrow thinking revealed that the machines that failed were the ones built for a single scenario. The ones that succeeded could multitask and be reprogrammed– for deployment in different settings. The arm built for the Space Shuttle, for example, was designed to position an astronaut who would catch and later release a satellite. It turned out the robot was better at making the catch itself — but positioning astronauts proved useful for other tasks, like repairing the Hubble Space Telescope.”

-Statement by Dr. Robert Ambrose, Chairman of Robotics and Artificial Intelligence at alliant and former Chief of the Software, Robotics and Simulation Division at NASA. He was discussing robotics in a Fortune magazine story titled “Former NASA Robotics Chief: America is Building the Wrong Kind of Robots — and China Knows It.” It is nice to see that NASA can teach the private sector a few things about preparing for the future. The agency has a wealth of information that can be shared with the private sector and allied countries. We just need to recognize the treasure trove of information we have accumulated at NASA over the years and do our best to preserve it and build upon it.

Twelfth Starship Launch Successful

Posted on by onespaceman2000
Credit: SpaceX

Fortunately, the first SpaceX Starship launch of the year (and the twelfth for the rocket) went well yesterday with only a few bumps along the way. While it was not perfect, given that it was the first test of a new version of the rocket, it was a good night for the rocket-maker and NASA.

Here is SpaceX’s description of some of the bumps last night:

Following stage separation, the Super Heavy booster performed a directional flip maneuver and attempted its boostback burn. It was unable to light all planned engines and performed a partial boostback burn that ended early. Super Heavy attempted to reignite its engines for the landing burn before experiencing a hard splashdown in the Gulf of America. During its ascent burn to space, Starship lost one of the Raptor 3 vacuum engines but demonstrated its engine-out capability and achieved its planned trajectory.

This latest test is encouraging, but would be more encouraging is a solid schedule of more tests this year to ensure the Starship will be ready for the Artemis III low Earth orbit tests next year. SpaceX is still significantly behind schedule on it launches. For instance, this twelfth launch was delayed many times.

Both SpaceX and Blue Origin are racing to be part of the Artemis III test in late 2027 to see if NASA is really ready for a crewed landing on the Moon in 2028. This latest launch brings SpaceX that much closer.

Sci-Fi Quote: Another Star Wars Movie to Save the Day

Posted on by onespaceman2000
Credit: Lucasfilm Ltd.

“Mainly, I’m tired of the world around us, and I’m tired of everything sucking so much. “The Mandalorian” series, which stylistically harkens back to the great spaghetti westerns of the mid-1960s, has brought great joy and escapism, and I will celebrate this new movie and savor its joy and escapism, no matter what any critic or cinema scold says.”

-Statement by USA TODAY columnist Rex Huppke in his column regarding the release of The Mandalorian and Grogu in theaters today. The Hollywood Reporter noted that movie is likely to make some money, but unlikely to give the Star Wars franchise the boost it needs to escape it own inability to create sufficient long-term interest in a galaxy far, far away.

Pic of the Week: Crescent Mars

Posted on by onespaceman2000
Image (Credit): Mars as captured on May 15, 2026 by NASA’s Psyche mission as it approached the planet for a gravity assist. (NASA/JPL-Caltech/ASU)

This week’s image comes from the Psyche spacecraft that is utilizing Martian gravity for its flight plan on its way to the asteroid Psyche in the asteroid belt. This image of a crescent Mars is one of many drive-by photos for both science and our enjoyment.

Here is more on this Martian part of the mission from NASA:

Because Psyche approached Mars from a high phase angle, the planet appeared as a thin crescent in the days running up to the close approach, lit by sunlight reflecting off its surface. In observations from the spacecraft’s multispectral imager, the crescent appeared brighter and extended farther around the planet’s disk than anticipated because of the strong scattering of sunlight through the planet’s dusty atmosphere. As Psyche passed from Mars’ nighttime skies to daytime, it took a rapid series of pictures of the surface around the time of closest approach.

“We’ve captured thousands of images of the approach to Mars and of the planet’s surface and atmosphere at close approach. This dataset provides unique and important opportunities for us to calibrate and characterize the performance of the cameras, as well as test the early versions of our image processing tools being developed for use at the asteroid Psyche,” said Jim Bell, the Psyche imager instrument lead at Arizona State University (ASU) in Tempe. “As the spacecraft continues its journey after the flyby, we’ll continue calibration imaging of Mars for the rest of the month as it recedes into the distance.”