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The eight-planet Kepler-90 system exhibits the greatest multiplicity of planets found to date. All eight planets are transiting and were discovered in photometry from the NASA Kepler primary mission. The two outermost planets, g (Pg = 211 days) and h (Ph = 332 days), exhibit significant transit-timing variations (TTVs), but were only observed six and three times, respectively, by Kepler. These TTVs allow for the determination of planetary masses through dynamical modeling of the pair’s gravitational interactions, but the paucity of transits allows a broad range of solutions for the masses and orbital ephemerides. To determine accurate masses and orbital parameters for planets g and h, we combined 34 radial velocities (RVs) of Kepler-90, collected over a decade, with the Kepler transit data. We jointly modeled the transit times of the outer two planets and the RV time series, then used our two-planet model to predict their future times of transit. These predictions led us to recover a transit of Kepler-90 g with ground-based observatories in 2024 May. We then combined the 2024 transit and several previously unpublished transit times of planets g and h with the Kepler photometry and RV data to update the masses and linear ephemerides of the planets, finding masses for g and h of 15.0 ± 1.3 M⊕ and 203 ± 16 M⊕, respectively, from a Markov Chain Monte Carlo analysis. These results enable further insights into the architecturally rich Kepler-90 system and pave the way for atmospheric characterization with space-based facilities.

We report the discovery of the transiting planet GJ 238 b, with a radius of 0.566 ± 0.014 R ⊕ (1.064 ± 0.026 times the radius of Mars) and an orbital period of 1.74 days. The transit signal was detected by the TESS mission and designated TOI-486.01. The star’s position close to the southern ecliptic pole allows for almost continuous observations by TESS when it is observing the southern sky. The host star is an M2.5 dwarf with V = 11.57 ± 0.02 mag, K = 7.030 ± 0.023 mag, a distance of 15.2156 ± 0.0030 pc, a mass of 0.4193−0.0098+0.0095 M ☉, a radius of 0.4314−0.0071+0.0075 R ☉, and an effective temperature of 3485 ± 140 K. We validate the planet candidate by ruling out or rendering highly unlikely each of the false positive scenarios, based on archival data and ground-based follow-up observations. Validation was facilitated by the host star’s small size and high proper motion of 892.633 ± 0.025 mas yr–1.

AU Mic is a young (22 Myr), nearby exoplanetary system that exhibits excess transit timing variations (TTVs) that cannot be accounted for by the two known transiting planets nor stellar activity. We present the statistical “validation” of the tentative planet AU Mic d (even though there are examples of “confirmed” planets with ambiguous orbital periods). We add 18 new transits and nine midpoint times in an updated TTV analysis to prior work. We perform the joint modeling of transit light curves using EXOFASTv2 and extract the transit midpoint times. Next, we construct an O−C diagram and use Exo-Striker to model the TTVs. We generate TTV log-likelihood periodograms to explore possible solutions for d’s period, then follow those up with detailed TTV and radial velocity Markov Chain Monte Carlo modeling and stability tests. We find several candidate periods for AU Mic d, all of which are near resonances with AU Mic b and c of varying order. Based on our model comparisons, the most-favored orbital period of AU Mic d is 12.73596 ± 0.00793 days (T C,d = 2458340.55781 ± 0.11641 BJD), which puts the three planets near 4:6:9 mean-motion resonance. The mass for d is 1.053 ± 0.511 M ⊕, making this planet Earth-like in mass. If confirmed, AU Mic d would be the first known Earth-mass planet orbiting a young star and would provide a valuable opportunity in probing a young terrestrial planet’s atmosphere. Additional TTV observations of the AU Mic system are needed to further constrain the planetary masses, search for possible transits of AU Mic d, and detect possible additional planets beyond AU Mic c.

We present an analysis of Na-He collisional profiles at high density and very low temperature in a unified line shape semi-classical theory which contains the impact as well the quasistatic limits. Clearly understanding the variation of shape of the two fine-structure components of the 3s−3p line with increasing helium density allows us to understand experimental spectra of a Na atom attached to He nanodroplets. We compare our collisional approach to path integral Monte Carlo calculations using the same ab initio Na-He molecular potentials.

Neptune-sized planets exhibit a wide range of compositions and densities, depending on factors related to their formation and evolution history, such as the distance from their host stars and atmospheric escape processes. They can vary from relatively low-density planets with thick hydrogen–helium atmospheres 1 , 2 to higher-density planets with a substantial amount of water or a rocky interior with a thinner atmosphere, such as HD 95338 b (ref.  3 ), TOI-849 b (ref.  4 ) and TOI-2196 b (ref.  5 ). The discovery of exoplanets in the hot-Neptune desert 6 , a region close to the host stars with a deficit of Neptune-sized planets, provides insights into the formation and evolution of planetary systems, including the existence of this region itself. Here we show observations of the transiting planet TOI-1853 b, which has a radius of 3.46 ± 0.08 Earth radii and orbits a dwarf star every 1.24 days. This planet has a mass of 73.2 ± 2.7 Earth masses, almost twice that of any other Neptune-sized planet known so far, and a density of 9.7 ± 0.8 grams per cubic centimetre. These values place TOI-1853 b in the middle of the Neptunian desert and imply that heavy elements dominate its mass. The properties of TOI-1853 b present a puzzle for conventional theories of planetary formation and evolution, and could be the result of several proto-planet collisions or the final state of an initially high-eccentricity planet that migrated closer to its parent star. Observations of the super-massive Neptune-sized transiting planet TOI-1853 b show a mass almost twice that of any other Neptune-sized planet known so far and a bulk density implying that heavy elements dominate its mass.

The giant planet KELT-9b has a dayside temperature of about 4,600 K, which is sufficiently high to dissociate molecules and to evaporate its atmosphere, owing to its hot stellar host. Hot Jupiter-like exoplanet Hot Jupiters are exoplanets that are physically similar to Jupiter, but are strongly irradiated by their host stars. Until now, the most extreme example was WASP-33b, but its atmosphere is still cool enough to contain molecules. Scott Gaudi et al . report the discovery of KELT-9b, which has a dayside temperature of about 4,600 kelvin. This is sufficiently high to dissociate molecules, so the primary sources of opacity in the dayside atmosphere of KELT-9b are probably atomic metals. The atmosphere might be evaporated before the host star reaches the end of its life. The amount of ultraviolet irradiation and ablation experienced by a planet depends strongly on the temperature of its host star. Of the thousands of extrasolar planets now known, only six have been found that transit hot, A-type stars (with temperatures of 7,300–10,000 kelvin), and no planets are known to transit the even hotter B-type stars. For example, WASP-33 is an A-type star with a temperature of about 7,430 kelvin, which hosts the hottest known transiting planet, WASP-33b (ref. 1 ); the planet is itself as hot as a red dwarf star of type M (ref. 2 ). WASP-33b displays a large heat differential between its dayside and nightside 2 , and is highly inflated–traits that have been linked to high insolation 3 , 4 . However, even at the temperature of its dayside, its atmosphere probably resembles the molecule-dominated atmospheres of other planets and, given the level of ultraviolet irradiation it experiences, its atmosphere is unlikely to be substantially ablated over the lifetime of its star. Here we report observations of the bright star HD 195689 (also known as KELT-9), which reveal a close-in (orbital period of about 1.48 days) transiting giant planet, KELT-9b. At approximately 10,170 kelvin, the host star is at the dividing line between stars of type A and B, and we measure the dayside temperature of KELT-9b to be about 4,600 kelvin. This is as hot as stars of stellar type K4 (ref. 5 ). The molecules in K stars are entirely dissociated, and so the primary sources of opacity in the dayside atmosphere of KELT-9b are probably atomic metals. Furthermore, KELT-9b receives 700 times more extreme-ultraviolet radiation (that is, with wavelengths shorter than 91.2 nanometres) than WASP-33b, leading to a predicted range of mass-loss rates that could leave the planet largely stripped of its envelope during the main-sequence lifetime of the host star 6 .

Temperate Earth-sized exoplanets around late-M dwarfs offer a rare opportunity to explore under which conditions planets can develop hospitable climate conditions. The small stellar radius amplifies the atmospheric transit signature, making even compact secondary atmospheres dominated by N 2 or CO 2 amenable to characterization with existing instrumentation 1 . Yet, despite large planet search efforts 2 , detection of low-temperature Earth-sized planets around late-M dwarfs has remained rare and the TRAPPIST-1 system, a resonance chain of rocky planets with seemingly identical compositions, has not yet shown any evidence of volatiles in the system 3 . Here we report the discovery of a temperate Earth-sized planet orbiting the cool M6 dwarf LP 791-18. The newly discovered planet, LP 791-18d, has a radius of 1.03 ± 0.04  R ⊕ and an equilibrium temperature of 300–400 K, with the permanent night side plausibly allowing for water condensation. LP 791-18d is part of a coplanar system 4 and provides a so-far unique opportunity to investigate a temperate exo-Earth in a system with a sub-Neptune that retained its gas or volatile envelope. On the basis of observations of transit timing variations, we find a mass of 7.1 ± 0.7  M ⊕ for the sub-Neptune LP 791-18c and a mass of 0.9 − 0.4 + 0.5 M ⊕ for the exo-Earth LP 791-18d. The gravitational interaction with the sub-Neptune prevents the complete circularization of LP 791-18d’s orbit, resulting in continued tidal heating of LP 791-18d’s interior and probably strong volcanic activity at the surface 5 , 6 . The authors report on a temperate Earth-sized planet orbiting the cool M6 dwarf LP 791-18 with a radius of 1.03 ± 0.04  R ⊕ and an equilibrium temperature of 300–400 K, with the permanent night side plausibly allowing for water condensation.

The James Webb Space Telescope will be able to probe the atmospheres and surface properties of hot, terrestrial planets via emission spectroscopy. We identify 18 potentially terrestrial planet candidates detected by the Transiting Exoplanet Survey Satellite (TESS) that would make ideal targets for these observations. These planet candidates cover a broad range of planet radii (R p ∼ 0.6–2.0R ⊕) and orbit stars of various magnitudes (K s = 5.78–10.78, V = 8.4–15.69) and effective temperatures (T eff ∼ 3000–6000 K). We use ground-based observations collected through the TESS Follow-up Observing Program (TFOP) and two vetting tools—DAVE and TRICERATOPS—to assess the reliabilities of these candidates as planets. We validate 13 planets: TOI-206 b, TOI-500 b, TOI-544 b, TOI-833 b, TOI-1075 b, TOI-1411 b, TOI-1442 b, TOI-1693 b, TOI-1860 b, TOI-2260 b, TOI-2411 b, TOI-2427 b, and TOI-2445 b. Seven of these planets (TOI-206 b, TOI-500 b, TOI-1075 b, TOI-1442 b, TOI-2260 b, TOI-2411 b, and TOI-2445 b) are ultra-short-period planets. TOI-1860 is the youngest (133 ± 26 Myr) solar twin with a known planet to date. TOI-2260 is a young (321 ± 96 Myr) G dwarf that is among the most metal-rich ([Fe/H] = 0.22 ± 0.06 dex) stars to host an ultra-short-period planet. With an estimated equilibrium temperature of ∼2600 K, TOI-2260 b is also the fourth hottest known planet with R p < 2 R ⊕.

NASA’s Transiting Exoplanet Survey Satellite (TESS) mission has been uncovering a growing number of exoplanets orbiting nearby, bright stars. Most exoplanets that have been discovered by TESS orbit narrow-line, slow-rotating stars, facilitating the confirmation and mass determination of these worlds. We present the discovery of a hot Jupiter orbiting a rapidly rotating ( vsin(i)=35.1±1.0 km s−1) early F3V-dwarf, HD 115447 (TOI-778). The transit signal taken from Sectors 10 and 37 of TESS's initial detection of the exoplanet is combined with follow-up ground-based photometry and velocity measurements taken from Minerva-Australis, TRES, CORALIE, and CHIRON to confirm and characterize TOI-778 b. A joint analysis of the light curves and the radial velocity measurements yields a mass, a radius, and an orbital period for TOI-778 b of 2.76−0.23+0.24 M J, 1.370 ± 0.043 R J, and ∼4.63 days, respectively. The planet orbits a bright (V = 9.1 mag) F3-dwarf with M = 1.40 ± 0.05 M ⊙, R = 1.70 ± 0.05 R ⊙, and logg=4.05±0.17 . We observed a spectroscopic transit of TOI-778 b, which allowed us to derive a sky-projected spin–orbit angle of 18° ± 11°, consistent with an aligned planetary system. This discovery demonstrates the capability of smaller-aperture telescopes such as Minerva-Australis to detect the radial velocity signals produced by planets orbiting broad-line, rapidly rotating stars.