Ilaria Carleo; Amadeo Castro-González; Enric Pallé; Felipe Murgas; Grzegorz Nowak; Gaia Lacedelli; Thomas Masseron; Emily W. Wong; Patrick Eggenberger; Vincent Bourrier; Dawid Jankowski; Krzysztof Goździewski; Douglas R. Alves; James S. Jenkins; Sergio Messina; Keivan G. Stassun; Jose I. Vines; Matteo Brogi; David R. Ciardi; Catherine A. Clark; William Cochran; Karen A. Collins; Hans J. Deeg; Elise Furlan; Davide Gandolfi; Samuel Geraldía González; Artie P. Hatzes; Coel Hellier; Steve B. Howell; Judith Korth; Jorge Lillo-Box; John H. Livingston; Jaume Orell-Miquel; Carina M. Persson; Seth Redfield; Boris Safonov; David Baker; Rafael Delfin Barrena Delgado; Allyson Bieryla; Andrew Boyle; Pau Bosch-Cabot; Núria Casasayas Barris; Stavros Chairetas; Jerome P. De Leon; Izuru Fukuda; Akihiko Fukui; Pere Guerra; Kai Ikuta; Kiyoe Kawauchi; Emil Knudstrup; Florence Libotte; Michael B. Lund; Rafael Luque; Eduardo Lorenzo Martín Guerrero De Escalante; Bob Massey; Edward J. Michaels; Giuseppe Morello; Norio Narita; Hannu Parvianien; Richard P. Schwarz; Avi Shporer; Monika Stangret; Noriharu Watanabe; Cristilyn N. Watkins (2026).��.��Astronomy & Astrophysics, 707, A4.��

As scientists discover more types of exoplanets (planets outside our solar system), they are rethinking what conditions might allow a planet to be habitable. Traditionally, the “habitable zone” is defined as the range of distances from a star where liquid water could exist on a planet’s surface. In this study, the authors propose a broader concept called the��“temperate zone,”��defined by the amount of stellar energy a planet receives (instellation), specifically between 0.1 and 5 times the amount Earth gets from the Sun. This wider range includes more planets that might potentially support life under different conditions.

The researchers also introduce the TEMPOS survey, which focuses on measuring the sizes of planets orbiting very cool, small stars known as M dwarfs. As part of this effort, they discovered and confirmed two planets: TOI-6716 b and TOI-7384 b. TOI-6716 b is about the same size as Earth, while TOI-7384 b is larger (closer to a “mini-Neptune”). Both orbit relatively cool M dwarf stars and complete an orbit in just a few days. The team used multiple methods—including ground-based observations, high-resolution imaging, and statistical validation—to confirm these planets and precisely measure their sizes.

Both planets receive relatively high levels of stellar energy, placing them near the hotter inner edge of the proposed temperate zone. This means they may be too warm for Earth-like conditions, but they are still valuable for studying planetary environments. Notably, TOI-6716 b could be a promising target for the James Webb Space Telescope, especially for��transmission spectroscopy��(a technique that analyzes starlight passing through a planet’s atmosphere to detect its composition), if it has retained an atmosphere. Overall, this work expands the range of planets considered potentially interesting for habitability studies and contributes new targets for future observation.

Figure 1.

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This study focuses on understanding how gas giant planets—large planets like Jupiter—form around low-mass, relatively cool stars (called M dwarfs), where such planets are thought to be rare. To improve our knowledge, the researchers launched the GATOS program, which aims to confirm and study candidate planets discovered by NASA’s TESS space telescope. They combined detailed observations from two instruments (HARPS and NIRPS) that measure��radial velocity—tiny shifts in a star’s motion caused by the gravitational pull of an orbiting planet—to confirm the planets and determine their properties. They also used brightness measurements (photometry) from TESS and ground-based telescopes to track when planets pass in front of their stars (transits). A new data-processing technique was introduced to reduce interference from Earth’s atmosphere in the measurements.

Using this approach, the team confirmed two gas giant planets orbiting small stars. One is a “hot Jupiter” (a gas giant very close to its star) orbiting TOI-3288 A every 1.43 days, and the other is a slightly cooler “warm Jupiter” orbiting TOI-4666 every 2.91 days. They measured each planet’s mass and size, finding them comparable to Jupiter but with different temperatures due to their distances from their stars. Looking more broadly at similar systems, the researchers observed that smaller, cooler stars tend to host less massive gas giants, unless the stars are rich in heavier elements (referred to as “metallicity”), which seems to support the formation of larger planets. They also found that gas giants around low-mass stars are more common in binary star systems (where two stars orbit each other), suggesting that gravitational interactions between stars may help trigger planet formation or alter planetary orbits. Overall, these findings help explain how giant planets can form in environments where they were previously thought to be unlikely.

HR diagram of all��Gaia��DR3 nearby stars with a parallax of��π��≥ 5 mas, using the broad-band��G��magnitude versus the colour��G_BP��(blue) minus��G_RP��(red). The colours indicate log(g). Stars without a log(g) measurement are shown in grey. The six targets presented in this paper as part of the NIRPS-GTO giants sub-programme are overplotted (outlined black circles), along with five stars identified as giant stars using this method. TOI-3288 and TOI-4666 (outlined black squares), hosting gas giants, are visible on the main sequence. This figure can be generated using��Gaia-HR, available at��.

Astronomers have observed that planets similar in size to Neptune are rarely found orbiting Sun-like stars with very short orbital periods of about four days or less. This region is known as the Neptune desert. Because such planets are uncommon, each new discovery provides important clues about how these planets form and evolve.

We report the discovery of TOI-333b, a planet located in the Neptune desert. It has a mass of about 20 times that of Earth (20.1 ± 2.4 Earth masses), a radius about 4.3 times Earth’s, and a bulk density of 1.42 g/cm³. The planet orbits an F7V-type star every 3.78 days. Its host star is slightly more massive and hotter than the Sun, with a mass of 1.2 solar masses and an effective temperature of about 6240 K. The system is likely younger than 1 billion years, based on the strength of the lithium absorption line near 6708 angstroms, which is commonly used as an age indicator in stars.

Models suggest that TOI-333b likely has a relatively small hydrogen and helium (H/He) gas envelope, making up only about 8 to 19 percent of its total mass. Other models, such as those for irradiated ocean worlds, suggest it could instead contain a significant amount of water, with about 20 percent of its mass in H2O and a rocky core making up roughly one third of the planet. Overall, the planet is likely dominated either by a mostly rocky interior with very little gas or by a rocky world with a large water component.

Compared with other known planets in the Neptune desert, TOI-333b is more massive than about 77 percent of them and larger than about 82 percent. Its host star is also among the hottest known for planets in this region. Because of these properties, the TOI-333 system provides a valuable opportunity to study how Neptune-sized planets evolve in close orbits around hot stars.

Fig 1: Left��: TESS-detrended light curve phase-folded to the best-fitting period listed in����and zoomed to show the transit event. The blue and white circles correspond to modelled photometric data and binned data with the associated photon noise error. The blue line and shaded region show the median transit model and its 1σ confidence interval.��Centre��: same as the left panel for the LCOGT-SAAO telescope.��Right��: same as the left panel for the NGTS mission.��Bottom��: Residuals of the best-fit model.

We report the confirmation and characterization of four hot Jupiter-type exoplanets initially detected by TESS: TOI-1295 b, TOI-2580 b, TOI-6016 b, and TOI-6130 b. Using observations with the high-resolution echelle spectrograph MaHPS on the 2.1 m telescope at Wendelstein Observatory, together with NEID at Kitt Peak National Observatory and TRES at the Fred Lawrence Whipple Observatory, we confirmed the planetary nature of these four planet candidates. We also performed precise mass measurements. All four planets are found to be hot Jupiters with orbital periods between 2.4 and 4.0 days. The sizes of these planets range from 1.29 to 1.64 Jupiter radii, while their masses range from 0.6 to 1.5 Jupiter masses. Additionally, we investigated whether there are signs of other planets in the systems but have found none. Lastly, we compared the radii of our four objects to the results of an empirical study of radius inflation and see that all four demonstrate a good fit with the current models. These four planets belong to the first array of planets confirmed with MaHPS data, supporting the ability of the spectrograph to detect planets around fainter stars as faint as��V��= 12.

Fig. 1

Speckle sensitivity curve and auto correlation function (ACF) of TOI-1295 obtained with the SAI Speckle polarimeter.

The star K2-19 is known to host two Neptune-sized planets that orbit very close to each other in a precise gravitational pattern called a 3:2 resonance, meaning their orbital periods are tightly linked. Because of this interaction, the planets do not pass in front of their star at perfectly regular intervals, producing strong variations in transit timing that carry information about their masses and orbits. Earlier studies, based on about 3 years of data, estimated relatively large planetary masses and unexpectedly high orbital eccentricities, or deviations from circular orbits. These high eccentricities were difficult to explain with standard models of planet formation, which motivated a new analysis using a much longer observational record.

In this study, we analyzed 10 years of transit observations using a detailed photodynamical model that accounts for the planets’ mutual gravitational effects. The longer data set confirms the earlier mass estimates for both planets, but significantly revises their orbital shapes. Instead of highly elongated orbits, the planets are now found to have much lower eccentricities, which are more in line with what is expected from conventional planet formation theories, although the orbits are still not perfectly circular. We show that the previously reported high eccentricities were driven by a single problematic transit observation taken during twilight, where observational effects caused the start of the transit to be misidentified, leading to a timing error of about 12 minutes.

Using data that span multiple long-term interaction cycles between the planets, we also applied a simpler analytical approach based on Fourier analysis of the transit-timing variations. This method reproduced the planet mass estimates to within about 2% of the full photodynamical results and did so without being sensitive to the exact eccentricities. In addition, we report evidence for a possible third planet located farther out in the system. Finally, updated modeling of the internal structure of the inner planet, K2-19 b, suggests a metal content consistent with formation through core accretion, the standard process thought to build most planets.

Fig. 1

Detection of the candidate planet e.��Left: gray data points represent the K2 data without the transits of planets b, c, and d. The orange data points show the mean GP model. The black light curve indicates the four transits we found.��Center: periodogram of the nuance algorithm.��Right: phased light curve without the noise model (gray points), binned (dark gray), and transit model (black line).

]]> /valiant/2025/12/19/toi-7166-b-a-habitable-zone-mini-neptune-planet-around-a-nearby-low-mass-star/ Fri, 19 Dec 2025 16:49:55 +0000 /valiant/?p=5567 Barkaoui, K., Pozuelos, F. J., Rackham, B. V., Burgasser, A. J., Triaud, A. H. M. J., Serra-Ricart, M., Timmermans, M., Yalçinkaya, S., Soubkiou, A., Stassun, K. G., Collins, K. A., Amado, P. J., Baştürk, Ö., Burdanov, A. Yu., Davis, Y. T., de Wit, J., Demory, B.-O., Deveny, S. J., Dransfield, G., Ducrot, E., Gillon, M., Chew, Y. G. M., Hooton, M. J., Hörne, K. D., Howell, S. B., Muñoz, C. J., Jehin, E., Jenkins, J. M., Littlefield, C., Martín, E. L., Niraula, P., Pedersen, P. P., Queloz, D., Scott, M. G., Sefako, R. R., Shporer, A., Stockdale, C. J., Softich, E. R., Sota, A., Tofflemire, B. M., Şimşir, Ö., Varas, R., Lang, F. Z., & Zúniga-Fernández, S. S. (2025).��.��Monthly Notices of the Royal Astronomical Society,��544(2), 2637–2652.��

We report the discovery and confirmation of a new exoplanet, called TOI-7166 b, that orbits a nearby, small, cool star. The planet was confirmed by combining observations from NASA’s Transiting Exoplanet Survey Satellite (TESS) with very precise brightness measurements from ground-based telescopes taken in multiple colors. These data were supported by additional information from spectroscopy, high-contrast imaging, archival images, and statistical tests to rule out false signals. The host star is an M4-type red dwarf located about 35 parsecs from the Sun and has a relatively small mass and radius compared with the Sun.

TOI-7166 b completes one orbit every 12.9 days. This places it near the inner edge of the star’s Habitable Zone, the region where temperatures could allow liquid water to exist under the right conditions. Based on how much energy it receives from its star (its insolation flux), the planet’s estimated equilibrium temperature is about K, assuming it reflects no light (a zero Bond albedo). Because the host star is relatively bright, TOI-7166 b is well suited for follow-up studies using the radial velocity method, which can measure the planet’s mass and overall density.

In addition, the combination of the star’s strong infrared brightness and the planet’s size relative to the star makes TOI-7166 b an excellent candidate for transmission spectroscopy with the James Webb Space Telescope. These observations could reveal details about the planet’s atmosphere, including its composition, making TOI-7166 b a particularly valuable target for future studies of potentially habitable worlds around low-mass stars.

Figure 1.

TESS��target pixel file image of TOI-7166 observed in Sectors 82 made by��tpfplotter��(A. Aller et��al.��2020). Red dots show the location of��Gaia��DR3 sources and the yellow shaded regions show the photometric apertures used for photometric measurements extraction.

]]> /valiant/2025/11/23/two-warm-earth-sized-exoplanets-and-an-earth-sized-candidate-in-the-m5v-m6v-binary-system-toi-2267/ Sun, 23 Nov 2025 16:58:22 +0000 /valiant/?p=5456 Zúniga-Fernández, Sebastian., Pozuelos, Francisco J., Devora-Pajares, Martín., Cuello, Nicolas., Greklek-McKeon, Michael., Stassun, Keivan Guadalupe., van Grootel, Valérie., Rojas-Ayala, Bárbara., Korth, Judith., Günther, Maximilian N., Burgasser, Adam J., Hsu, Chihchun., Rackham, Benjamin V., Barkaoui, Khalid., Timmermans, Mathilde., Cadieux, Charles., Alonso, Roi., Strakhov, Ivan A., Howell, Steve B., Littlefield, Colin., Furlan, Elise., Amado, Pedro J., Jenkins, Jon M., Twicken, Joseph D., Sucerquia, Mario., Davis, Yasmin T., Schanche, Nicole E., Collins, Karen A., Burdanov, Artem Yu., Davoudi, Fatemeh., Demory, Brice Olivier., Delrez, Laetitia., Dransfield, Georgina., Ducrot, Elsa., García, Lionel J., Gillon, Michaël., Gómez Maqueo Chew, Y. Gómez Maqueo., Janó-Muñoz, Clàudia., Jehin, Emmanuël., Murray, Catriona Anne., Niraula, Prajwal., Pedersen, Peter Pihlmann., Queloz, Didier., Rebolo-Lopez, Rafael., Scott, Madison G., Sebastian, Daniel., Hooton, Matthew J., Thompson, Samantha J., Triaud, Amaury H.M.J., de Wit, Julien., Ghachoui, Mourad., Benkhaldoun, Z., Doyon, René Crossed Dsign©., Lafrenière, David., Casanova, Víctor M., Sota, Alfredo., Plauchu-Frayn, Ilse., Khandelwal, Akanksha., Zong Lang, Francis., Schroffenegger, Urs., Wampfler, Susanne F., Lendl, Monika A., Schwarz, Richard P., Murgas, Felipe., Palle´, Enric B., & Parviainen, Hannu. (2025).��.��Astronomy and Astrophysics,��702, A85.��

We report the discovery of two “warm” exoplanets orbiting a very tight pair of small, cool stars called TOI-2267. This binary system consists of an M5 star (TOI-2267A) and an M6 star (TOI-2267B) that appear extremely close together in the sky—only 0.384 arcseconds apart—which corresponds to a physical separation of about 8 astronomical units. The system is located just 22 parsecs from our Solar System. To confirm that the signals we detected were truly planets, we combined data from NASA’s Transiting Exoplanet Survey Satellite (TESS) with ground-based observations, high-resolution imaging, archival measurements, and statistical validation techniques.

Based on the available data, we cannot yet tell for certain which of the two stars the planets actually orbit. If the planets orbit TOI-2267A, they are close to Earth-sized, with radii of 1.00±0.11 and 1.14±0.13 Earth radii for TOI-2267 b (which orbits every 2.28 days) and TOI-2267 c (which orbits every 3.49 days). If they instead orbit TOI-2267B, their radii would be slightly larger due to the star’s dimmer brightness, at 1.22±0.29 and 1.36±0.33 Earth radii.

TESS data also show a third, strong periodic signal at 2.03 days, labeled TOI-2267.02. Statistical analysis suggests this signal is also likely caused by a planet, but follow-up observations from the ground did not detect it, so it remains a “planetary candidate.” Its radius would be roughly Earth-sized—0.95±0.12 or 1.13±0.30 Earth radii—depending on whether it orbits star A or B.

If the candidate is confirmed, orbital dynamics show that all three planets cannot orbit the same star without becoming unstable. The most likely arrangements are that planets b and c orbit one star while .02 orbits the other, or that .02 and c orbit the same star while b orbits the other. A configuration where .02 and b orbit the same star appears unstable. The fact that planets b and c lie close to a 3:2 mean-motion resonance (meaning their orbital periods are in a nearly perfect 3:2 ratio) also suggests they orbit the same star, with .02 around the other.

If this scenario is correct, TOI-2267 would be the most compact binary system known to host planets around��both��stars. This makes it a rare and valuable system for understanding how planets form and evolve in environments where two stars orbit extremely close together.

Fig. 1

Spectral energy distribution of TOI-2267. Red symbols represent the observed photometric measurements, where the horizontal bars represent the effective width of the passband. Blue symbols are the model fluxes from the best-fit NextGen stellar atmosphere model for the two stellar components (hot component in blue, cool component in red, combined light in black).

The TOI-1438 system, discovered by NASA’s Transiting Exoplanet Survey Satellite (TESS), contains multiple planets orbiting a Sun-like star. To confirm these planets and measure their properties, astronomers collected detailed follow-up observations over five years using high-resolution spectrographs, including HARPS-N and HIRES. The host star, classified as a K0V-type star, was found to have two confirmed planets—both slightly smaller than Neptune—known as TOI-1438 b and TOI-1438 c.

Planet b has a radius about 3 times that of Earth and a mass about 9 times larger, while planet c is slightly smaller and more massive, with a radius about 2.8 times and a mass about 10.6 times that of Earth. These planets orbit their star every 5.1 and 9.4 days, respectively, receiving 145 and 65 times the amount of sunlight that Earth receives from the Sun. Their calculated densities—1.8 and 2.9 grams per cubic centimeter—suggest that both planets have interiors rich in volatile materials such as water or other light molecules, rather than being purely rocky.

Modeling of their internal structures indicates that planet b likely has a hydrogen-helium (H/He) atmosphere making up to about 2.5% of its mass, while planet c has a much thinner envelope, with less than 0.2% of its mass in H/He. Regardless of the exact makeup of their cores—whether a mix of rock and metal or rock and ice—both planets appear to require a volatile-rich outer layer.

In addition to these two confirmed planets, the team detected another signal in the star’s radial velocity data that may indicate the presence of a third, much larger, non-transiting planet. This possible outer planet would orbit once every 7.6 years, have a minimum mass roughly twice that of Jupiter, and follow a slightly oval-shaped (eccentric) orbit. However, some of the same signals could also be caused by variations in the star’s own activity, so further long-term observations are needed to confirm whether this third planet truly exists.

If verified, TOI-1438 would be an unusual three-planet system featuring two small, close-in sub-Neptunes and one distant, massive planet—a configuration rarely observed among known planetary systems.

Fig. 1

Final results of the Gemini North speckle imaging of TOI-1438. The blue and red curves show the 5 σ contrast curves in 562 nm and 832 nm filters, respectively, as a function of the angular separation out to 1.2″. The inset shows the reconstructed 832 nm image with a 1″ scale bar. TOI-1438 was found to have no close companions from the diffraction limit out to 1.2″ and within the magnitude contrast levels achieved.

Sub-Neptune exoplanets—planets smaller than Neptune but larger than Earth—are the most common type of planet discovered so far. Because there are no planets like them in our own Solar System, scientists are still trying to understand what they are made of and how they form. Earlier studies have shown that many of these planets do not have simple, clear atmospheres made mostly of hydrogen and helium, but their exact atmospheric makeup remains uncertain.

In this study, researchers examined HD 86226 c, a sub-Neptune that is about 2.2 times the size of Earth and 7.25 times its mass. It orbits a Sun-like star every four days and has a very high temperature of about 1311 K (around 1900°F). Because it is so hot, this planet should not have methane-based hazes that often make other sub-Neptune atmospheres cloudy. That makes it a good candidate for studying a clear atmosphere.

Using the Hubble Space Telescope, the team observed the planet as it passed in front of its star, analyzing the starlight that filtered through its atmosphere. Surprisingly, the data showed a featureless spectrum, meaning there were no strong signals of specific gases—just a flat line consistent with a constant transit depth of about 418 ± 14 parts per million. This lack of features rules out a clear hydrogen-helium atmosphere and suggests that the planet’s atmosphere is either very rich in heavier elements (with metallicity more than about 200 times that of the Sun) or filled with clouds made of materials such as silicates (rock), iron, or manganese sulfide.

These results show that HD 86226 c behaves differently from other sub-Neptunes studied so far, which often show hazy or aerosol-filled atmospheres. Future observations with the James Webb Space Telescope could reveal whether this planet truly has a metal-rich atmosphere or hosts unusual types of clouds, helping scientists better understand the diversity of sub-Neptune worlds across the galaxy.

Sub-Neptune targets of the SPACE program. HD 86226c is shown with a green square marker, and the other SPACE targets are shown in purple. Top: temperature-radius plane. Gray circles show the known population of planets with radii between 1.8 R_⊕��and 4 R_⊕��based on the entries of the NASA Exoplanet Archive��in May 2024. Black crosses mark JWST Cycle 1–4 targets, except for the SPACE targets TOI-431 d and HD 86226 c, which will be observed in Cycle 4. Bottom: mass-radius plane. Color curves show models from����for various planetary compositions and temperatures.