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Evidence suggests that, when compact objects such as black holes and neutron stars form, they may receive a ‘natal kick’, during which the stellar remnant gains momentum. Observational evidence for neutron star kicks is substantial 1 , 2 , yet is limited for black hole natal kicks, and some proposed black hole formation scenarios result in very small kicks 3 – 5 . Here we report that the canonical black hole low-mass X-ray binary (LMXB) V404 Cygni is part of a wide hierarchical triple with a tertiary companion at least 3,500 astronomical units ( au ) away from the inner binary. Given the orbital configuration, the black hole probably received a sub-5 km s −1 kick to have avoided unbinding the tertiary. This discovery lends support to the idea that at least some black holes form with nearly no natal kick. Furthermore, the tertiary in this system lends credence to evolutionary models of LMXBs involving a hierarchical triple structure 6 . Remarkably, the tertiary is evolved, indicating that the system formed 3–5 billion years ago and that the black hole has removed at least half a solar mass of matter from its evolved secondary companion. During the event in which the black hole formed, it is required that at least half of the mass of the black hole progenitor collapsed into the black hole; it may even have undergone a complete implosion, enabling the tertiary to remain loosely bound. Analysis of the black hole low-mass X-ray binary V404 Cygni shows that it is part of a wide hierarchical triple whose configuration provides evidence that some black holes form with nearly no natal kick.  

A planet’s orbital alignment places important constraints on how a planet formed and consequently evolved. The dominant formation pathway of ultra-short-period planets (P < 1 day) is particularly mysterious as such planets most likely formed further out, and it is not well understood what drove their migration inwards to their current positions. Measuring the orbital alignment is difficult for smaller super-Earth/sub-Neptune planets, which give rise to smaller amplitude signals. Here we present radial velocities across two transits of 55 Cancri (Cnc) e, an ultra-short-period super-Earth, observed with the Extreme Precision Spectrograph. Using the classical Rossiter–McLaughlin method, we measure 55 Cnc e’s sky-projected stellar spin–orbit alignment (that is, the projected angle between the planet’s orbital axis and its host star’s spin axis) to be λ=10+17∘−20∘ with an unprojected angle of ψ=23+14∘−12∘. The best-fit Rossiter–McLaughlin model to the Extreme Precision Spectrograph data has a radial velocity semi-amplitude of just 0.41+0.09−0.10 m s−1. The spin–orbit alignment of 55 Cnc e favours dynamically gentle migration theories for ultra-short-period planets, namely tidal dissipation through low-eccentricity planet–planet interactions and/or planetary obliquity tides.Measurements of the Rossiter–McLaughlin effect for the ultra-short-period super-Earth 55 Cancri e reveal a signal with a semi-amplitude of 0.41+0.09-0.10 m s−1, in close alignment with its star and potentially misaligned with the other planets in the system. Such a configuration favours a non-violent migration pathway for 55 Cnc e.

Giant exoplanets orbiting close to their host stars are unlikely to have formed in their present configurations 1 . These ‘hot Jupiter’ planets are instead thought to have migrated inward from beyond the ice line and several viable migration channels have been proposed, including eccentricity excitation through angular-momentum exchange with a third body followed by tidally driven orbital circularization 2 , 3 . The discovery of the extremely eccentric ( e  = 0.93) giant exoplanet HD 80606 b (ref.  4 ) provided observational evidence that hot Jupiters may have formed through this high-eccentricity tidal-migration pathway 5 . However, no similar hot-Jupiter progenitors have been found and simulations predict that one factor affecting the efficacy of this mechanism is exoplanet mass, as low-mass planets are more likely to be tidally disrupted during periastron passage 6 – 8 . Here we present spectroscopic and photometric observations of TIC 241249530 b, a high-mass, transiting warm Jupiter with an extreme orbital eccentricity of e  = 0.94. The orbit of TIC 241249530 b is consistent with a history of eccentricity oscillations and a future tidal circularization trajectory. Our analysis of the mass and eccentricity distributions of the transiting-warm-Jupiter population further reveals a correlation between high mass and high eccentricity. The spectroscopic and photometric observations of a high-mass, transiting warm Jupiter, TIC 241249530 b, with an orbital eccentricity of 0.94, provide evidence that hot Jupiters may have formed by means of a high-eccentricity tidal-migration pathway.

Although nearly 6,000 exoplanets are currently known, in most cases our knowledge is limited to a handful of the planet's orbital characteristics and bulk properties such as radius and mass. The James Webb Space Telescope (JWST) can expand our knowledge not only by probing exoplanet atmospheres, but also by measuring additional orbital and physical properties of exoplanets, thanks to its superior light-gathering power and measurement precision. Here, we describe the potential of JWST to unveil dynamical phenomena that were previously beyond our reach, such as tidal distortion and inflation, rotational flattening, planetary rings, and moons.

A planet's axial tilt (\"obliquity\") substantially affects its atmosphere and habitability. It is thus essential to comprehend the various mechanisms that can excite planetary obliquities, particularly at the primordial stage. Here, we explore planetary obliquity excitation induced by the early evolution of the host star. A young, distended star spins rapidly, resulting in a large gravitational quadrupole moment that induces nodal recession of the planet's orbit. As the star contracts and spins down, the nodal recession frequency decreases and can cross the planet's spin axis precession frequency. An adiabatic encounter results in the planet's capture into a secular spin-orbit resonance and excites the obliquity to large values. We find planets within \\(a \\lesssim 1 \\ \\mathrm{AU}\\) are most affected, but adiabatic capture depends on the initial stellar radius and spin rate. The overall picture is complicated by other sources of perturbation, including the disk, multiple planets, and tidal dissipation. Tides make it such that stellar oblateness-induced obliquity excitation is transient since tidal perturbations cause the resonance to break once high obliquities are reached. However, this early transient excitation is important because it can prime planets for long-term capture in a secular spin-orbit resonance induced by planet-planet interactions. Thus, although stellar oblateness-induced resonances are short-lived, they facilitate the prevalence of long-lived non-zero obliquities in exoplanets.

At high eccentricities, tidal forcing excites vibrational modes within orbiting bodies known as dynamical tides. In this paper, we implement the coupled evolution of these modes with the body's orbit in the \\texttt{REBOUNDx} framework, an extension to the popular \\(N\\)-body integrator \\texttt{REBOUND}. We provide a variety of test cases relevant to exoplanet dynamics and demonstrate overall agreement with prior studies of dynamical tides in the secular regime. Our implementation is readily applied to various high-eccentricity scenarios and allows for fast and accurate \\(N\\)-body investigations of astrophysical systems for which dynamical tides are relevant.

Planetary systems with mean-motion resonances (MMRs) hold special value in terms of their dynamical complexity and their capacity to constrain planet formation and migration histories. The key towards making these connections, however, is to have a reliable characterization of the resonant dynamics, especially the so-called \"libration amplitude\", which qualitatively measures how deep the system is into the resonance. In this work, we identify an important complication with the interpretation of libration amplitude estimates from observational data of resonant systems. Specifically, we show that measurement noise causes inferences of the libration amplitude to be systematically biased to larger values, with noisier data yielding a larger bias. We demonstrated this through multiple approaches, including using dynamical fits of synthetic radial velocity data to explore how the the libration amplitude distribution inferred from the posterior parameter distribution varies with the degree of measurement noise. We find that even modest levels of noise still result in a slight bias. The origin of the bias stems from the topology of the resonant phase space and the fact that the available phase space volume increases non-uniformly with increasing libration amplitude. We highlight strategies for mitigating the bias through the usage of particular priors. Our results imply that many known resonant systems are likely deeper in resonance than previously appreciated.

The planets within compact multi-planet systems tend to have similar sizes, masses, and orbital period ratios, like \"peas in a pod\". This pattern was detected when considering planets with radii between 1 and 4 \\(R_\\oplus\\). However, these same planets show a bimodal radius distribution, with few planets between 1.5 and 2 \\(R_{\\oplus}\\). The smaller \"super-Earths\" are consistent with being stripped rocky cores, while the larger \"sub-Neptunes\" likely have gaseous H/He envelopes. Given these distinct structures, it is worthwhile to test for intra-system uniformity separately within each category of planets. Here, we find that the tendency for intra-system uniformity is twice as strong when considering planets within the same size category than it is when combining all planets together. The sub-Neptunes tend to be \\(1.7^{+0.6}_{-0.3}\\) times larger than the super-Earths in the same system, corresponding to an envelope mass fraction of about 2.6% for a \\(5\\,M_{\\oplus}\\) planet. For the sub-Neptunes, the low-metallicity stars are found to have planets with more equal sizes, with modest statistical significance (\\(p\\sim 0.005\\)). There is also a modest \\((\\sim\\)2-\\(\\sigma)\\) tendency for wider-orbiting planets to be larger, even within the same size category.

Compact systems of multiple close-in super-Earths/sub-Neptunes (\"compact multis\") are a ubiquitous outcome of planet formation. It was recently discovered that the outer edges of compact multis are located at smaller orbital periods than expected from geometric and detection biases alone, suggesting some truncation or transition in the outer architectures. Here we test whether this \"edge-of-the-multis\" might be explained in any part by distant giant planets in the outer regions (\\(\\gtrsim 1\\) AU) of the systems. We investigate the dynamical stability of observed compact multis in the presence of hypothetical giant (\\(\\gtrsim 0.5 \\ M_{\\mathrm{Jup}}\\)) perturbing planets. We identify what parameters would be required for hypothetical perturbing planets if they were responsible for dynamically sculpting the outer edges of compact multis. \"Edge-sculpting\" perturbers are generally in the range \\(P\\sim100-500\\) days for the average compact multi, with most between \\(P\\sim200-300\\) days. Given the relatively close separation, we explore the detectability of the hypothetical edge-sculpting perturbing planets, finding that they would be readily detectable in transit and radial velocity data. We compare to observational constraints and find it unlikely that dynamical sculpting from distant giant planets contributes significantly to the edge-of-the-multis. However, this conclusion could be strengthened in future work by a more thorough analysis of the detection yields of the perturbing planets.