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Abstract Using published simulations of the 10 yr Legacy Survey of Space and Time (LSST), we forecast its ability to determine the masses of individual main-belt asteroids (MBAs) through precise astrometry of any pairs of the ≈1.2 million known MBAs undergoing close gravitational encounters during the survey. The uncertaintyσ_Ion the impulse applied to a tracer asteroid by its deflector is derived from the Fisher matrix of the tracer’s astrometric data, including an azimuthal acceleration from the Yarkovsky effect as a free parameter for each tracer. If only LSST observations are available, the mean forecastedσ_Iis 7 × 10⁻⁶m s⁻¹for MBAs at apparent magnitudem_V < 19.5, degrading ≈10× form_V = 23. The forecasted median uncertainty on the mass of a deflector MBA is ≈3 × 10⁻¹⁴M_⊙, with a wide range of variation depending on the (random) configurations of the closest encounters. All of these figures improve ≈ fivefold if strong pre-LSST astrometry is available. Use of LSST data will increase the number of MBAs with masses measured to 20% accuracy or better from the present ≈70 to between 200 and 550, depending on quality of pre-LSST data, if all MBAs have mass-to-reflected-light ratios (M/Ls) at the low end of the currently measured bodies. If high-end M/Ls are more common, 580–1100 bodies will attain a signal-to-noise ratio > 5, including nearly all bodies with absolute magnitudeH < 10 and some as faint asH = 13. We forecast that ≈20 new Jupiter Trojans could also have masses measured at <20% accuracy. Tables of the measurable deflector MBAs and their tracers are provided. 

Abstract We explore the potential of an array of $O\left(100\right)$small fixed telescopes, aligned along a meridian and automated to measure millions of occultations of Gaia stars by minor planets, to constrain gravitational signatures from a “Planet X” mass in the outer solar system. The accuracy of center-of-mass tracking of occulters is limited by photon noise, uncertainties in asteroid shapes, and Gaia’s astrometry of the occulted stars. Using both parametric calculations and survey simulations, we assess the total information obtainable from occultation measurements of main-belt asteroids (MBAs), Jovian Trojans, and trans-Neptunian objects (TNOs). We find that MBAs are the optimal target population due to their higher occultation rates and abundance of objects above Legacy Survey of Space and Time detection thresholds. A 10 yr survey of occultations by MBAs and Trojans using an array of 200 40 cm telescopes at 5 km separation would achieve 5σsensitivity to the gravitational tidal field of a 5M_⊕Planet X at 800 au for >90% of potential sky locations. This configuration corresponds to an initial cost of ≈$15 million. While the survey's sensitivity to tidal forces improves rapidly with increasing number of telescopes, sensitivity to a Planet X becomes limited by degeneracy with the uncertain masses of large moonless TNOs. The 200-telescope survey would additionally detect ≈1800 TNO occultations, providing detailed shape, size, and albedo information. It would also measure the Yarkovsky effect on many individual MBAs, measure masses of many asteroids involved in mutual gravitational deflections, and enable better searches for primordial black holes and departures from general relativity. 

Abstract We report the methods of and initial scientific inferences from the extraction of precision photometric information for the >800 trans-Neptunian objects (TNOs) discovered in the images of the Dark Energy Survey (DES). Scene-modeling photometry is used to obtain shot-noise-limited flux measures for each exposure of each TNO, with background sources subtracted. Comparison of double-source fits to the pixel data with single-source fits are used to identify and characterize two binary TNO systems. A Markov Chain Monte Carlo method samples the joint likelihood of the intrinsic colors of each source as well as the amplitude of its flux variation, given the time series of multiband flux measurements and their uncertainties. A catalog of these colors and light-curve amplitudesAis included with this publication. We show how to assign a likelihood to the distributionq(A) of light-curve amplitudes in any subpopulation. Using this method, we find decisive evidence (i.e., evidence ratio <0.01) that cold classical (CC) TNOs with absolute magnitude 6 <H_r< 8.2 are more variable than the hot classical (HC) population of the sameH_r, reinforcing theories that the former form in situ and the latter arise from a different physical population. Resonant and scattering TNOs in thisH_rrange have variability consistent with either the HCs or CCs. DES TNOs withH_r< 6 are seen to be decisively less variable than higher-H_rmembers of any dynamical group, as expected. More surprising is that detached TNOs are decisively less variable than scattering TNOs, which requires them to have distinct source regions or some subsequent differential processing. 

Abstract We combine photometry of Eris from a 6 month campaign on the Palomar 60 inch telescope in 2015, a 1 month Hubble Space Telescope WFC3 campaign in 2018, and Dark Energy Survey data spanning 2013–2018 to determine a light curve of definitive period 15.771 ± 0.008 days (1σformal uncertainties), with nearly sinusoidal shape and peak-to-peak flux variation of 3%. This is consistent at part-per-thousand precision with theP= 15.785 90 ± 0.00005 day sidereal period of Dysnomia’s orbit around Eris, strengthening the recent detection of synchronous rotation of Eris by Szakáts et al. with independent data. Photometry from Gaia are consistent with the same light curve. We detect a slope of 0.05 ± 0.01 mag per degree of Eris’s brightness with respect to illumination phase averaged acrossg,V, andrbands, intermediate between Pluto’s and Charon’s values. Variations of 0.3 mag are detected in Dysnomia’s brightness, plausibly consistent with a double-peaked light curve at the synchronous period. The synchronous rotation of Eris is consistent with simple tidal models initiated with a giant-impact origin of the binary, but is difficult to reconcile with gravitational capture of Dysnomia by Eris. The high albedo contrast between Eris and Dysnomia remains unexplained in the giant-impact scenario. 

Abstract Using Fisher information matrices, we forecast the uncertaintiesσ_Mon the measurement of a “Planet X” at heliocentric distanced_Xvia its tidal gravitational field’s action on the known planets. Using planetary measurements currently in hand, including ranging from the Juno, Cassini, and Mars-orbiting spacecraft, we forecast a median uncertainty (over all sky positions) of ${\sigma }_M=0.22M_{\oplus }{\left(d_x/400\mathrm{au}\right)}^3.$A 5σdetection of a 5M_⊕Planet X atd_X= 400 au should be possible over the full sky but over only 5% of the sky atd_X= 800 au. The gravity of an undiscovered Earth- or Mars-mass object should be detectable over 90% of the sky to a distance of 260 or 120 au, respectively. Upcoming Mars ranging improves these limits only slightly. We also investigate the power of high-precision astrometry of ≈8000 Jovian Trojans over the 2023–2035 period from the upcoming Legacy Survey of Space and Time (LSST). We find that the dominant systematic errors in optical Trojan astrometry (photocenter motion, nongravitational forces, and differential chromatic refraction) can be solved internally with minimal loss of information. The Trojan data allow cross-checks with Juno/Cassini/Mars ranging, but do not significantly improve the best achievableσ_Mvalues until they are ≳10× more accurate than expected from LSST. The ultimate limiting factor in searches for a Planet X tidal field is confusion with the tidal field created by the fluctuating quadrupole moment of the Kuiper Belt as its members orbit. This background will not, however, become the dominant source of uncertainty until the data get substantially better than they are today.