Explore the vast range of titles available.

Exomoons represent a crucial missing puzzle piece in our efforts to understand extrasolar planetary systems. To address this deficiency, we here describe an exomoon survey of 70 cool, giant transiting exoplanet candidates found by Kepler. We identify only one exhibiting a moon-like signal that passes a battery of vetting tests: Kepler-1708 b. We show that Kepler-1708 b is a statistically validated Jupiter-sized planet orbiting a Sun-like quiescent star at 1.6 au. The signal of the exomoon candidate, Kepler-1708 b-i, is a 4.8 σ effect and is persistent across different instrumental detrending methods, with a 1% false-positive probability via injection–recovery. Kepler-1708 b-i is ~2.6 Earth radii and is located in an approximately coplanar orbit at ~12 planetary radii from its ~1.6 au Jupiter-sized host. Future observations will be necessary to validate or reject the candidate. A 4.8 σ exomoon candidate is found around gas giant Kepler-1708 b, which orbits at 1.6 au around its star. It is the only candidate from a dedicated survey that analysed 70 cool giant exoplanets discovered by Kepler. Kepler-1708 b-i has a radius of 2.6 Earth radii and orbits its planet at 12 planetary radii.

The quest for Earth-like planets is a major focus of current exoplanet research. Although planets that are Earth-sized and smaller have been detected, these planets reside in orbits that are too close to their host star to allow liquid water on their surfaces. We present the detection of Kepler-186f, a 1.11 ± 0.14 Earth-radius planet that is the outermost of five planets, all roughly Earth-sized, that transit a 0.47 ± 0.05 solar-radius star. The intensity and spectrum of the star's radiation place Kepler-186f in the stellar habitable zone, implying that if Kepler-186f has an Earth-like atmosphere and water at its surface, then some of this water is likely to be in liquid form.

The giant planets of the Solar System host systems of multiple moons, where the Earth has only one large natural satellite, Luna. There are many man-made satellites in residence around the Earth and a handful of small asteroids that can persist as temporary natural satellites. With this observation, one can wonder how many large natural satellites (i.e., moons) could orbit the Earth over long timescales. We perform a series of N-body simulations that consider three different satellite masses (Ceres-, Pluto, and Luna-like), where each mass type is nested around an Earth-mass planet orbiting a Sun-like star. The innermost moon begins orbiting near the host planet's Roche radius, while additional moons are added using the mutual Hill radius between adjacent satellites. Our simulations reveal, as an upper limit, that an Earth-mass planet could host up to 7 Ceres-mass, 4 Pluto-mass, or 3 Luna-mass moons with an uncertainty of 1 moon respectively. However, the true limitation for moons is likely to be fewer than these upper limits as gravitational interactions with other planets can periodically alter the extent of the host planet's Hill radius or outward tidal migration (due to interactions with the host planet itself) can force collisions or scattering events.

α Centauri A is the closest solar-type star to the Sun and offers an excellent opportunity to detect the thermal emission of a mature planet heated by its host star. The MIRI coronagraph on the James Webb Space Telescope can search the 1–3 au (1″–2″) region around α Cen A which is predicted to be stable within the α Cen AB system. We demonstrate that with reasonable performance of the telescope and instrument, a 20 hr program combining on-target and reference star observations at 15.5 μm could detect thermal emission from planets as small as ∼5 R ⊕. Multiple visits every 3–6 months would increase the geometrical completeness, provide astrometric confirmation of detected sources, and push the radius limit down to ∼3 R ⊕. An exozodiacal cloud only a few times brighter than our own should also be detectable, although a sufficiently bright cloud might obscure any planet present in the system. While current precision radial velocity (PRV) observations set a limit of 50–100 M ⊕ at 1–3 au for planets orbiting α Cen A, there is a broad range of exoplanet radii up to 10 R ⊕ consistent with these mass limits. A carefully planned observing sequence along with state-of-the-art post-processing analysis could reject the light from α Cen A at the level of ∼10−5 at 1″–2″ and minimize the influence of α Cen B located 7″–8″ away in the 2022–2023 timeframe. These space-based observations would complement on-going imaging experiments at shorter wavelengths as well as PRV and astrometric experiments to detect planets dynamically. Planetary demographics suggest that the likelihood of directly imaging a planet whose mass and orbit are consistent with present PRV limits is small, ∼5%, and possibly lower if the presence of a binary companion further reduces occurrence rates. However, at a distance of just 1.34 pc, α Cen A is our closest sibling star and certainly merits close scrutiny.

Observations with the Kepler Space Telescope revealed a special planetary class: a planet that orbits a pair of stars instead of just one, or a circumbinary planet (CBP). The first bona fide CBP (Kepler-16b) was confirmed via photometry in 2011 by the Kepler Mission using only the first two years of observations. In subsequent studies and discoveries of CBPs, it became apparent that these worlds are detectable through transit photometry only temporarily due to the fast precession of planetary orbit relative to our line-of-sight (i.e., limited transitability). We re-evaluate the photodynamical modeling of Kepler-16b using the full four years of observations from the Kepler mission, which includes four additional transits by the CBP. Our photodynamical model mostly agrees with the previous results, except it requires a slightly more massive CBP. Using our best-fitting models, we will estimate when Kepler-16b will again transit its host stars relative to our line-of-sight and whether these transits would be detectable using data from the Transiting Exoplanet Survey Satellite. The potential transitability of the other Kepler CBPs will also be discussed.

α Centauri A is the closest solar-type star to the Sun and offers an excellent opportunity to detect the thermal emission of a mature planet heated by its host star. The MIRI coronagraph on the James Webb Space Telescope can search the 1–3 au (1″–2″) region around α Cen A which is predicted to be stable within the α Cen AB system. We demonstrate that with reasonable performance of the telescope and instrument, a 20 hr program combining on-target and reference star observations at 15.5 μm could detect thermal emission from planets as small as ∼5 R ⊕. Multiple visits every 3–6 months would increase the geometrical completeness, provide astrometric confirmation of detected sources, and push the radius limit down to ∼3 R ⊕. An exozodiacal cloud only a few times brighter than our own should also be detectable, although a sufficiently bright cloud might obscure any planet present in the system. While current precision radial velocity (PRV) observations set a limit of 50–100 M ⊕ at 1–3 au for planets orbiting α Cen A, there is a broad range of exoplanet radii up to 10 R ⊕ consistent with these mass limits. A carefully planned observing sequence along with state-of-the-art post-processing analysis could reject the light from α Cen A at the level of ∼10−5 at 1″–2″ and minimize the influence of α Cen B located 7″–8″ away in the 2022–2023 timeframe. These space-based observations would complement on-going imaging experiments at shorter wavelengths as well as PRV and astrometric experiments to detect planets dynamically. Planetary demographics suggest that the likelihood of directly imaging a planet whose mass and orbit are consistent with present PRV limits is small, ∼5%, and possibly lower if the presence of a binary companion further reduces occurrence rates. However, at a distance of just 1.34 pc, α Cen A is our closest sibling star and certainly merits close scrutiny.

Centauri A is the closest solar-type star to the Sun and offers an excellent opportunity to detect the thermal emission of a mature planet heated by its host star. The MIRI coronagraph on the James Webb Space Telescope can search the 1-3 au (1″-2″) region around Cen A which is predicted to be stable within the Cen AB system. We demonstrate that with reasonable performance of the telescope and instrument, a 20 hr program combining on-target and reference star observations at 15.5 m could detect thermal emission from planets as small as ∼5 R⊕. Multiple visits every 3-6 months would increase the geometrical completeness, provide astrometric confirmation of detected sources, and push the radius limit down to ∼3 R⊕. An exozodiacal cloud only a few times brighter than our own should also be detectable, although a sufficiently bright cloud might obscure any planet present in the system. While current precision radial velocity (PRV) observations set a limit of 50-100 M⊕ at 1-3 au for planets orbiting Cen A, there is a broad range of exoplanet radii up to 10 R⊕ consistent with these mass limits. A carefully planned observing sequence along with state-of-the-art post-processing analysis could reject the light from Cen A at the level of ∼10−5 at 1″-2″ and minimize the influence of Cen B located 7″-8″ away in the 2022-2023 timeframe. These space-based observations would complement on-going imaging experiments at shorter wavelengths as well as PRV and astrometric experiments to detect planets dynamically. Planetary demographics suggest that the likelihood of directly imaging a planet whose mass and orbit are consistent with present PRV limits is small, ∼5%, and possibly lower if the presence of a binary companion further reduces occurrence rates. However, at a distance of just 1.34 pc, Cen A is our closest sibling star and certainly merits close scrutiny.

Over 2500 eclipsing binaries were identified and characterized from the ultraprecise photometric data provided by the Kepler space telescope. Kepler is now beginning its second mission, K2, which is proving to again provide ultraprecise photometry for a large sample of eclipsing binary stars. In the 1951 light curves covering 12 days in the K2 engineering dataset, we have identified and determined the ephemerides for 31 candidate eclipsing binaries that demonstrate the capabilities for eclipsing binary science in the upcoming campaigns in K2. Of those, 20 are new discoveries. We describe both manual and automated approaches to harvesting the complete set of eclipsing binaries in the K2 data, provide identifications and details for the full set of candidate eclipsing binaries present in the engineering dataset, and discuss the prospects for application of eclipsing binary searches in the K2 mission.

All 4 giant planets in the Solar System host systems of multiple moons, whereas the terrestrial planets only host up to 2 moons. The Earth can capture small asteroids as temporary satellites, which begs the question as to how many moons could stably orbit the Earth, or an Earth-mass exoplanet. We perform a series of N-body simulations of closely-spaced equal mass moons in nested orbits around an Earth-mass planet orbiting a Sun-like star. The innermost moon begins near the host planets Roche radius, and the system is packed until the outermost moon begins near the stability limit for single moons. The initial spacing of the moons follows an iterative scheme commonly used for studies of compact planetary systems around single stars. For 3-moons system, we generate MEGNO maps to calculate periodic and chaotic regions and to identify the destabilizing MMRs. Our calculations show that the maximum number of moons depends on the assumed masses of the satellites (Ceres-, Pluto-, and Luna-mass) that could maintain stable orbits in a tightly-packed environment. Through our N-body simulations, we find stable configurations for up to 7 \\(\\pm\\) 1 Ceres-mass, 4 \\(\\pm\\) 1 Pluto-mass, and 3 \\(\\pm\\) 1 Luna-mass moons. However, outward tidal migration will likely play a substantial role in the number of moons on stable orbits over the 10 Gyr stellar lifetime of a Sun-like star.

Modern studies of the early solar system routinely invoke the possibility of an orbital instability among the giant planets triggered by gravitational interactions between the planets and a massive exterior disk of planetesimals. Previous works have suggested that this instability can be substantially delayed (\\(\\sim\\)100s Myr) after the formation of the giant planets. Bodies in the disk are typically treated in a semi-active manner, wherein their gravitational force on the planets is included, but interactions between the planetesimals are ignored. We perform \\(N\\)-body numerical simulations using GENGA, which makes use of GPUs to allow for the inclusion of all gravitational interactions between bodies. Although our simulated Kuiper belt particles are more massive than the probable masses of real primordial Kuiper belt objects, our simulations indicate that the self-stirring of the primordial Kuiper belt is very important to the dynamics of the giant planet instability. We find that interactions between planetesimals dynamically heat the disk and typically prevent the outer solar system instability from being delayed by more than a few tens of million years after giant planet formation. Longer delays occur in a small fraction of systems that have at least 3.5 AU gaps between the planets and planetesimal disk. Our final planetary configurations match the solar system at a rate consistent with other previous works in most regards. Pre-instability heating of the disk typically yields final Jovian eccentricities comparable to the modern solar system value, which has been a difficult constraint to match in past works.