Explore the vast range of titles available.

Astronomers have discovered thousands of planets outside the Solar System 1 , most of which orbit stars that will eventually evolve into red giants and then into white dwarfs. During the red giant phase, any close-orbiting planets will be engulfed by the star 2 , but more distant planets can survive this phase and remain in orbit around the white dwarf 3 , 4 . Some white dwarfs show evidence for rocky material floating in their atmospheres 5 , in warm debris disks 6 – 9 or orbiting very closely 10 – 12 , which has been interpreted as the debris of rocky planets that were scattered inwards and tidally disrupted 13 . Recently, the discovery of a gaseous debris disk with a composition similar to that of ice giant planets 14 demonstrated that massive planets might also find their way into tight orbits around white dwarfs, but it is unclear whether these planets can survive the journey. So far, no intact planets have been detected in close orbits around white dwarfs. Here we report the observation of a giant planet candidate transiting the white dwarf WD 1856+534 (TIC 267574918) every 1.4 days. We observed and modelled the periodic dimming of the white dwarf caused by the planet candidate passing in front of the star in its orbit. The planet candidate is roughly the same size as Jupiter and is no more than 14 times as massive (with 95 per cent confidence). Other cases of white dwarfs with close brown dwarf or stellar companions are explained as the consequence of common-envelope evolution, wherein the original orbit is enveloped during the red giant phase and shrinks owing to friction. In this case, however, the long orbital period (compared with other white dwarfs with close brown dwarf or stellar companions) and low mass of the planet candidate make common-envelope evolution less likely. Instead, our findings for the WD 1856+534 system indicate that giant planets can be scattered into tight orbits without being tidally disrupted, motivating the search for smaller transiting planets around white dwarfs. A giant planet candidate roughly the size of Jupiter but more than 14 times as massive is observed by TESS and other instruments to be transiting the white dwarf star WD 1856+534.

Astronomers have found more than a dozen planets transiting stars that are 10–40 million years old 1 , but younger transiting planets have remained elusive. The lack of such discoveries may be because planets have not fully formed at this age or because our view is blocked by the protoplanetary disk. However, we now know that many outer disks are warped or broken 2 ; provided the inner disk is depleted, transiting planets may thus be visible. Here we report observations of the transiting planet IRAS 04125+2902 b orbiting a 3-million-year-old, 0.7-solar-mass, pre-main-sequence star in the Taurus Molecular Cloud. The host star harbours a nearly face-on (30 degrees inclination) transitional disk 3 and a wide binary companion. The planet has a period of 8.83 days, a radius of 10.7 Earth radii (0.96 Jupiter radii) and a 95%-confidence upper limit on its mass of 90 Earth masses (0.3 Jupiter masses) from radial-velocity measurements, making it a possible precursor of the super-Earths and sub-Neptunes frequently found around main-sequence stars. The rotational broadening of the star and the orbit of the wide (4 arcseconds, 635 astronomical units) companion are both consistent with edge-on orientations. Thus, all components of the system are consistent with alignment except the outer disk; the origin of this misalignment is unclear. Observations of a 3-million-year-old pre-main-sequence star with a misaligned disk reveal a giant orbiting planet; the system is ideal for studying the early formation and migration of planets.

New radio telescope arrays offer unique opportunities for large-scale commensal SETI surveys. Ethernet-based architectures are allowing multiple users to access telescope data simultaneously by means of multicast Ethernet subscriptions. Breakthrough Listen will take advantage of this by conducting a commensal SETI survey on the MeerKAT radio telescope in South Africa. By subscribing to raw voltage data streams, Breakthrough Listen will be able to beamform commensally anywhere within the field of view during primary science observations. The survey will be conducted with unprecedented speed by forming and processing 64 coherent beams simultaneously, allowing the observation of several million objects within a few years. Both coherent and incoherent observing modes are planned. We present the list of desired sources for observation and explain how these sources were selected from the Gaia DR2 catalog. Given observations planned by MeerKAT’s primary telescope users, we discuss their effects on the commensal survey and propose a commensal observing strategy in response. Finally, we outline our proposed approach toward observing one million nearby stars and analyze expected observing progress in the coming years.

To date the majority of planets known to exist outside of our solar system (exoplanets) have been discovered indirectly, yet the direct detection of exoplanets is the future of exoplanet characterization. Searching for signs of life (biosignatures) on worlds beyond our solar system through the next generation of ground-based extremely large telescopes is one of the top priorities for the next decade of astronomy. Yet this is extremely challenging from a technological perspective in that planets are very close to their host stars and very faint, making it difficult to disentangle the faint planet signal from the star. The Extreme Wavefront Control Lab at Steward Observatory is developing technology and methodology for this challenging science through the MagAO-X instrument, an extreme high-contrast imaging instrument on the 6.5 m Magellan Clay Telescope and a pathfinder for the high contrast imager GMagAO-X which will be part of the upcoming 24.5 m Giant Magellan Telescope planned for the 2030s. In my PhD work at the University of Arizona I have employed the capabilities of MagAO-X, and it’s predecessor MagAO, for stellar and substellar astrophysical research. In this work I will describe how we achieve high-contrast imaging with MagAO-X, a survey I analyzed using binary stars for data reduction, a survey I designed using the power of MagAO-X for exoplanet science through white dwarf stars in binaries, and simulation work I am conducting preparing for exoplanet detections through reflected light with MagAO-X and GMagAO-X.

New radio telescope arrays offer unique opportunities for large-scale commensal SETI surveys. Ethernet-based architectures are allowing multiple users to access telescope data simultaneously by means of multicast Ethernet subscriptions. Breakthrough Listen will take advantage of this by conducting a commensal SETI survey on the MeerKAT radio telescope in South Africa. By subscribing to raw voltage data streams, Breakthrough Listen will be able to beamform commensally anywhere within the field of view during primary science observations. The survey will be conducted with unprecedented speed by forming and processing 64 coherent beams simultaneously, allowing the observation of several million objects within a few years. Both coherent and incoherent observing modes are planned. We present the list of desired sources for observation and explain how these sources were selected from the Gaia DR2 catalog. Given observations planned by MeerKAT’s primary telescope users, we discuss their effects on the commensal survey and propose a commensal observing strategy in response. Finally, we outline our proposed approach toward observing one million nearby stars and analyze expected observing progress in the coming years.

The long-period giant planet HR 5183 b has one of the most extreme orbits among exoplanets known to date, and represents a test for models of their dynamical evolution. In this work we use Hipparcos-Gaia astrometry to measure the orbital inclination of this planet for the first time and find \\(i=89.9^{+13.3\\circ}_{-13.5}\\), fully consistent with edge-on. The long orbital period and high eccentricity of HR 5183 b are supported by our results, with \\(P=102^{+84}_{-34}\\) years and \\(e=0.87 \\pm 0.04\\). We confirm that HR 5183 forms a physically bound binary with HIP 67291 at a projected separation of 15400 AU, and derive new constraints on the orbit of this pair. We combine these results to measure the mutual inclination between the planetary and binary orbits; we observe significant evidence for misalignment, which remains even after accounting for bias of the prior towards high mutual inclinations. However, our results are too imprecise to evaluate a recent prediction that the mutual inclination should reflect the formation history of HR 5183 b. Further observations, especially the release of the full Gaia astrometric data, will allow for improved constraints on the planet-binary mutual inclination. \\(52 \\pm 16\\%\\) of known planets with eccentricities \\(e\\geq 0.8\\) are found in multiple star systems, a rate that we find to be greater than for the overall planet population to moderate significance (\\(p=0.0075\\)). This supports the hypothesis that dynamical interactions with wide stellar companions plays an important role in the formation of highly eccentric exoplanets.

The extensive timespan of modern radial velocity surveys has made the discovery of long-period substellar companions more common in recent years, however measuring the true masses of these objects remains challenging. Astrometry from the Gaia mission is expected to provide mass measurements for many of these long-period companions, but this data is not yet available. However, combining proper motion data from Gaia DR2 and the earlier Hipparcos mission makes it possible to measure true masses of substellar companions in favourable cases. In this work, we combine radial velocities with Hipparcos-Gaia astrometry to measure the true masses of two recently discovered long-period substellar companion candidates, HD 92987 B and HD 221420 b. In both cases, we find that the true masses are significantly higher than implied by radial velocities alone. A \\(2087 \\pm 19\\) m s\\(^{-1}\\) astrometric signal reveals that HD 92987 B is not close to its \\(17\\) \\(M_J\\) minimum mass but is instead a \\(0.2562 \\pm 0.0045\\) \\(M_\\odot\\) star viewed at a near-polar orbital inclination, whereas the \\(22.9 \\pm 2.2\\) \\(M_J\\) HD 221420 b can be plausibly interpreted as a high-mass \"super-planet\" or a low-mass brown dwarf. With semi-major axes of \\(\\sim\\)10 AU both companions are interesting targets for direct imaging, and HD 221420 b in particular would be a benchmark metal-rich substellar object if it proves possible to directly detect. Our results demonstrate the power of Hipparcos-Gaia astrometry for studying long-period planet and brown dwarf candidates discovered from radial velocity surveys.

Aims: This work proposes a new SETI search methodology under the assumption that a sufficiently advanced civilization could skip the middle man of converting starlight to energy to food preparation, and could directly harness their star's energy for food prep. Methods: We define the concept of the Flavor Zone (FZ): the optimal distance from a star for cooking food. To develop this definition we propose the toy model of a Digiorno-Like Object (DLO) and define the FZ as the regime for optimal cooking according to package directions. We examine the effect of orbit on DLO cooking times and paradigms. Finally, we study the feasibility of detection of DLOs in their FZs with current technology. Results: We determined that DLOs aren't detectable with current technology nor should anyone ever try.

We present the unplanned detection of a white dwarf companion to the star HD 218261 in mid-infrared (10-16 \\(\\mu\\)m) observations with JWST/MIRI. This star was observed as a calibrator for coronagraphic observations of the exoplanet host HR 8799. HD 218261 B has only previously been detected by Gaia, and only in visible light. We confidently detect the companion in the mid-infrared, where it is less luminous than the primary by a factor of ~10\\(^4\\). The visible and mid-infrared photometry are consistent with a white dwarf of \\(T_\\text{eff}\\approx10000\\) K, \\(M\\approx0.8 M_\\odot\\), though observation of its optical spectrum is required to precisely constrain its physical parameters. These results demonstrate that precise mid-infrared photometry of white dwarf companions to bright stars can be obtained with MIRI, opening up new possibilities for studying white dwarfs in close binaries.

The next generation of ground- and space-based observatories will enable direct imaging and characterization of cold, mature planets through thermal emission and, for the first time, reflected light detection. Known RV and astrometrically detected planets provide a known population for detection and characterization observations. However, many of the most promising targets lack orbital parameters of sufficient precision to confidently predict their location on relative to the star for a direct imaging campaign. We have developed \\texttt{projecc}, an open source Python package designed to generate sky-plane planet location posteriors from literature orbit solutions. This tool aims to facilitate community preparation for direct imaging observations of known planets. In this work we describe \\texttt{projecc} and use it to examine two case study systems relevant to reflected light imaging with ELTs: GJ~876~b, which we find has a well-constrained prediction, and Proxima Centauri b, whose location remains highly uncertain.%, as well as one potential target for \\textsl{Roman} CGI, HD~219134~h, which we estimate has a 40\\% probability of being in a detectable sky location at any given time. We provide a web app for exploring reflected light planet targets and their orbit solutions, including predictions from literature for 17 additional planets, located at https://reflected-light-planets.streamlit.app/. We also discuss future upgrades to \\texttt{projecc}.