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Observations show that one or both of the protoplanetary disks in the young binary system HK Tauri are significantly inclined to the binary orbital plane, demonstrating that the necessary conditions exist for the misalignment-driven mechanisms thought to produce the unusual orbits of some extrasolar planets. Genesis of eccentric exoplanet orbits Solar System planets all have nearly coplanar, circular orbits. So it has been surprising to find that many extrasolar planets follow very elliptical orbits, or orbits that tilt at an angle from the host star's equator. With a view to establishing a mechanism that could explain how such orbits arise, Eric Jensen and Rachel Akeson studied the young binary system HK Tauri. They obtained images of planet-forming disks misaligned by 60° or more, such that one or both of the disks are significantly inclined to the binary orbital plane. The results demonstrate that the necessary conditions exist for planetary orbits to be modified by misalignment-driven mechanisms, and that these conditions are present at the time of planet formation, possibly a result of the binary formation process. Many extrasolar planets follow orbits that differ from the nearly coplanar and circular orbits found in our Solar System; their orbits may be eccentric 1 or inclined with respect to the host star’s equator 2 , 3 , and the population of giant planets orbiting close to their host stars suggests appreciable orbital migration 4 . There is at present no consensus on what produces such orbits. Theoretical explanations often invoke interactions with a binary companion star in an orbit that is inclined relative to the planet’s orbital plane 4 , 5 . Such mechanisms require significant mutual inclinations between the planetary and binary star orbital planes. The protoplanetary disks in a few young binaries are misaligned 6 , 7 , 8 , 9 , 10 , 11 , 12 , but often the measurements of these misalignments are sensitive only to a small portion of the inner disk, and the three-dimensional misalignment of the bulk of the planet-forming disk mass has hitherto not been determined. Here we report that the protoplanetary disks in the young binary system HK Tauri are misaligned by 60 to 68 degrees, such that one or both of the disks are significantly inclined to the binary orbital plane. Our results demonstrate that the necessary conditions exist for misalignment-driven mechanisms to modify planetary orbits, and that these conditions are present at the time of planet formation, apparently because of the binary formation process.

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 .

It is commonly accepted that exoplanets with orbital periods shorter than one day, also known as ultra-short-period (USP) planets, formed further out within their natal protoplanetary disks before migrating to their current-day orbits via dynamical interactions. One of the most accepted theories suggests a violent scenario involving high-eccentricity migration followed by tidal circularization. Here we present the discovery of a four-planet system orbiting the bright (V = 10.5) K6 dwarf star TOI-500. The innermost planet is a transiting, Earth-sized USP planet with an orbital period of ~13 hours, a mass of 1.42 ± 0.18  M ⊕ , a radius of 1.16 6 − 0.058 + 0.061 R ⊕ and a mean density of 4.8 9 − 0.88 + 1.03 g cm − 3 . Via Doppler spectroscopy, we discovered that the system hosts 3 outer planets on nearly circular orbits with periods of 6.6, 26.2 and 61.3 days and minimum masses of 5.03 ± 0.41  M ⊕ , 33.12 ± 0.88  M ⊕ and 15.0 5 − 1.11 + 1.12 M ⊕ , respectively. The presence of both a USP planet and a low-mass object on a 6.6-day orbit indicates that the architecture of this system can be explained via a scenario in which the planets started on low-eccentricity orbits then moved inwards through a quasi-static secular migration. Our numerical simulations show that this migration channel can bring TOI-500 b to its current location in 2 Gyr, starting from an initial orbit of 0.02 au. TOI-500 is the first four-planet system known to host a USP Earth analogue whose current architecture can be explained via a non-violent migration scenario. TOI-500 hosts at least four planets, the innermost of which is an Earth-sized ultra-short-period body with a density similar to Earth. The architecture of the TOI-500 system can be explained by a slow, secular, low-eccentricity migration scenario.

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.

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.

We report the analysis of circumbinary discs formed in a radiation hydrodynamical simulation of star cluster formation. We consider both pure binary stars and pairs within triple and quadruple systems. The protostellar systems are all young (ages < \\(10^5\\) yrs). We find that the systems that host a circumbinary disc have a median separation of \\(\\approx 11\\) au, and the median characteristic radius of the discs is \\(\\approx 64\\) au. We find that \\(89\\) per cent of pure binaries with semi-major axes \\(a<1\\) au have a circumbinary disc, and the occurrence rate of circumbinary discs is bimodal with log-separation in pure binaries with a second peak at \\(a \\approx 50\\) au. Systems with \\(a>100\\) au almost never have a circumbinary disc. The median size of a circumbinary disc is between \\(\\approx 5-6\\ a\\) depending on the order of the system, with higher order systems having larger discs relative to binary separation. We find the underlying distribution of mutual inclinations between circumbinary discs and binary orbit of both observed and simulated discs to not differ statistically.

The effect of stellar multiplicity on planetary architecture and orbital dynamics provides an important context for exoplanet demographics. We present a volume-limited catalog up to 300 pc of 66 stars hosting planets and planet candidates from Kepler, K2 and TESS with significant Hipparcos-Gaia proper motion anomalies, which indicate the presence of companions. We assess the reliability of each transiting planet candidate using ground-based follow-up observations, and find that the TESS Objects of Interest (TOIs) with significant proper motion anomalies show nearly four times more false positives due to Eclipsing Binaries compared to TOIs with marginal proper motion anomalies. In addition, we find tentative evidence that orbital periods of planets orbiting TOIs with significant proper motion anomalies are shorter than those orbiting TOIs without significant proper motion anomalies, consistent with the scenario that stellar companions can truncate planet-forming disks. Furthermore, TOIs with significant proper motion anomalies exhibit lower Gaia differential velocities in comparison to field stars with significant proper motion anomalies, suggesting that planets are more likely to form in binary systems with low-mass substellar companions or stellar companions at wider separation. Finally, we characterize the three-dimensional architecture of LTT 1445 ABC using radial velocities, absolute astrometry from Gaia and Hipparcos, and relative astrometry from imaging. Our analysis reveals that LTT 1445 is a nearly flat system, with a mutual inclination of 2.88 deg between the orbit of BC around A and that of C around B. The coplanarity may explain why multiple planets around LTT 1445 A survive in the dynamically hostile environment of this system.

The radius valley carries implications for how the atmospheres of small planets form and evolve, but this feature is visible only with highly precise characterizations of many small planets. We present the characterization of nine planets and one planet candidate with both NASA TESS and ESA CHEOPS observations, which adds to the overall population of planets bordering the radius valley. While four of our planets - TOI 118 b, TOI 455 b, TOI 560 b, and TOI 562 b - have already been published, we vet and validate transit signals as planetary using follow-up observations for five new TESS planets, including TOI 198 b, TOI 244 b, TOI 262 b, TOI 444 b, and TOI 470 b. While a three times increase in primary mirror size should mean that one CHEOPS transit yields an equivalent model uncertainty in transit depth as about nine TESS transits in the case that the star is equally as bright in both bands, we find that our CHEOPS transits typically yield uncertainties equivalent to between two and 12 TESS transits, averaging 5.9 equivalent transits. Therefore, we find that while our fits to CHEOPS transits provide overall lower uncertainties on transit depth and better precision relative to fits to TESS transits, our uncertainties for these fits do not always match expected predictions given photon-limited noise. We find no correlations between number of equivalent transits and any physical parameters, indicating that this behavior is not strictly systematic, but rather might be due to other factors such as in-transit gaps during CHEOPS visits or nonhomogeneous detrending of CHEOPS light curves.

TOI-1899 b is a rare exoplanet, a temperate Warm Jupiter orbiting an M-dwarf, first discovered by Cañas et al. (2020) from a TESS single-transit event. Using new radial velocities (RVs) from the precision RV spectrographs HPF and NEID, along with additional TESS photometry and ground-based transit follow-up, we are able to derive a much more precise orbital period of \\(P = 29.090312_{-0.000035}^{+0.000036}\\) d, along with a radius of \\(R_p = 0.99 \\pm 0.03~R_J\\). We have also improved the constraints on planet mass, \\(M_p = 0.67 \\pm 0.04~M_J\\), and eccentricity, which is consistent with a circular orbit at 2\\(\\sigma\\) (\\(e = 0.044_{-0.027}^{+0.029}\\)). TOI-1899 b occupies a unique region of parameter space as the coolest known (\\(T_{eq} \\approx\\) 380 K) Jovian-sized transiting planet around an M-dwarf; we show that it has great potential to provide clues regarding the formation and migration mechanisms of these rare gas giants through transmission spectroscopy with JWST as well as studies of tidal evolution.