We show, by comparing observations with theoretical models, that the observed Kuiper Belt size distribution is well matched by coagulation models, which start with an initial planetesimal population ...with radii of about 1 km, and subsequent collisional evolution. We find that the observed size distribution above R ~ 30 km is primordial, i.e., it has not been modified by collisional evolution over the age of the solar system, and that the size distribution below R ~ 30 km has been modified by collisions and that its slope is well matched by collisional evolution models that use published strength laws. We find that results from recent KBO occultation surveys and the observed KBO size distribution can be best matched by an initial planetesimal population that contained about equal mass per logarithmic mass bin in bodies ranging from 0.4 km to 4 km in radius.
1I/'Oumuamua was discovered by the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS 1) on 2017 October 19. Unlike all previously discovered minor planets, this object was determined ...to have eccentricity e > 1.0, suggesting an interstellar origin. Since this discovery and within the limited window of opportunity, several photometric and spectroscopic studies of the object have been made. Using the measured light curve amplitudes and rotation periods we find that, under the assumption of a triaxial ellipsoid, a density range 1500 < < 2800 kg m−3 matches the observations and no significant cohesive strength is required. We also determine that an aspect ratio of 6 1:1 is most likely after accounting for phase-angle effects and considering the potential effect of surface properties. This elongation is still remarkable, but less than some other estimates.
Abstract The Solar system Notification Alert Processing System ( snaps ) is a Zwicky Transient Facility (ZTF) and Rubin Observatory alert broker that will send alerts to the community regarding ...interesting events in the solar system. snaps is actively monitoring solar system objects and one of its functions is to compare objects (primarily main belt asteroids) to one another to find those that are outliers relative to the population. In this paper, we use the SNAPShot1 data set, which contains 31,693 objects from ZTF, and derive outlier scores for each of these objects. snaps employs an unsupervised approach; consequently, to derive outlier rankings for each object, we propose four different outlier metrics such that we can explore variants of the outlier scores and add confidence to the outlier rankings. We also provide outlier scores for each object in each permutation of 15 feature spaces, between two and 15 features, which yields 32,752 total feature spaces. We show that we can derive population outlier rankings each month at Rubin Observatory scale using four Nvidia A100 GPUs, and present several avenues of scientific investigation that can be explored using population outlier detection.
Abstract
We present here the design, architecture, and first data release for the Solar System Notification Alert Processing System (SNAPS). SNAPS is a solar system broker that ingests alert data ...from all-sky surveys. At present, we ingest data from the Zwicky Transient Facility (ZTF) public survey, and we will ingest data from the forthcoming Legacy Survey of Space and Time (LSST) when it comes online. SNAPS is an official LSST downstream broker. In this paper we present the SNAPS design goals and requirements. We describe the details of our automatic pipeline processing in which the physical properties of asteroids are derived. We present SNAPShot1, our first data release, which contains 5,458,459 observations of 31,693 asteroids observed by ZTF from 2018 July to 2020 May. By comparing a number of derived properties for this ensemble to previously published results for overlapping objects we show that our automatic processing is highly reliable. We present a short list of science results, among many that will be enabled by our SNAPS catalog: (1) we demonstrate that there are no known asteroids with very short periods and high amplitudes, which clearly indicates that in general asteroids in the size range 0.3–20 km are strengthless; (2) we find no difference in the period distributions of Jupiter Trojan asteroids, implying that the L4 and L5 clouds have different shape distributions; and (3) we highlight several individual asteroids of interest. Finally, we describe future work for SNAPS and our ability to operate at LSST scale.
Abstract
The Galileo spacecraft had distant encounters with Earth in 1990 and 1992. Limited Solid State Imager (SSI) data acquired during these encounters has been previously presented, but the ...majority of the data from these Earth flybys have not been presented in the literature. Observations of Earth taken from afar are both rare and directly relevant to the development of any future exo-Earth direct imaging mission. Here we present a pipeline that vets, calibrates, and measures the disk-integrated brightness of the Earth, in multiple filters, from the complete SSI data sets from both the 1990 and 1992 Galileo flybys. The result is over 1500 usable photometric measurements for Earth as an analog for an exoplanet. The 1990 data set includes full rotational lightcurves in six bandpasses spanning the optical range. The 1992 data set is more limited, with lightcurves only spanning 14 hr. Time-averaged photometry for both encounters is presented while variability and color are discussed relative to findings from NASA’s EPOXI mission (which also provided photometric lighturves for Earth). The new Galileo/SSI data are used to further validate the Virtual Planetary Laboratory 3D spectral Earth model, which often serves as a stand-in for true disk-integrated observations of our planet. The revived Galileo/SSI data for Earth is a testament to the ability of NASA’s Planetary Data System to maintain data over decades-long timescales. The disk-integrated products derived from these data add to a very short list of calibrated and published whole-disk observations of the Pale Blue Dot.
Data from the New Horizons mission to Pluto show no craters on Sputnik Planum down to the detection limit (2 km for low resolution data, 625 m for high resolution data). The number of small Kuiper ...Belt Objects that should be impacting Pluto is known to some degree from various astronomical surveys. We combine these geological and telescopic observations to make an order of magnitude estimate that the surface age of Sputnik Planum must be less than 10 million years. This maximum surface age is surprisingly young and implies that this area of Pluto must be undergoing active resurfacing, presumably through some cryo-geophysical process. We discuss three possible resurfacing mechanisms and the implications of each one for Pluto's physical properties.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract
We present photometric data for minor planets observed by the Transiting Exoplanet Survey Satellite during its Cycle 1 operations. In total, we extracted usable detections for 37,965 ...objects. We present an examination of the reliability of the rotation period and light-curve amplitudes derived from each object based upon the number of detections and the normalized Lomb–Scargle power of our period fitting and compare and contrast our results with previous similar works. We show that for objects with 200 or more photometric detections and a derived normalized, generalized Lomb–Scargle power greater than 0.2, we have an 85% confidence in that period; this encompasses 3492 rotation periods we consider to be highly reliable. We independently examine a series of periods first reported by Pál et al.; periods derived in both works found to have similar results should be considered reliable. Additionally, we demonstrate the need to properly account for the true proportion of slow rotators (
P
> 100 hr) when inferring shape distributions from sparse photometry.
The recently discovered minor body 1I/2017 U1 ('Oumuamua) is the first known object in our solar system that is not bound by the Sun's gravity. Its hyperbolic orbit (eccentricity greater than unity) ...strongly suggests that it originated outside our solar system; its red color is consistent with substantial space weathering experienced over a long interstellar journey. We carry out a simple calculation of the probability of detecting such an object. We find that the observed detection rate of 1I-like objects can be satisfied if the average mass of ejected material from nearby stars during the process of planetary formation is ∼20 Earth masses, similar to the expected value for our solar system. The current detection rate of such interstellar interlopers is estimated to be 0.2 yr−1, and the expected number of detections over the past few years is almost exactly one. When the Large Synoptic Survey Telescope begins its wide, fast, deep all-sky survey, the detection rate will increase to 1 yr−1. Those expected detections will provide further constraints on nearby planetary system formation through a better estimate of the number and properties of interstellar objects.
1I/'Oumuamua is the first confirmed interstellar body in our solar system. Here we report on observations of 'Oumuamua made with the Spitzer Space Telescope on 2017 November 21-22 (UT). We integrated ...for 30.2 hr at 4.5 m (IRAC channel 2). We did not detect the object and place an upper limit on the flux of 0.3 Jy (3 ). This implies an effective spherical diameter less than 98, 140, 440 m and albedo greater than 0.2, 0.1, 0.01 under the assumption of low, middle, or high thermal beaming parameter , respectively. With an aspect ratio for 'Oumuamua of 6:1, these results correspond to dimensions of 240:40, 341:57, 1080:180 m, respectively. We place upper limits on the amount of dust, CO, and CO2 coming from this object that are lower than previous results; we are unable to constrain the production of other gas species. Both our size and outgassing limits are important because 'Oumuamua's trajectory shows non-gravitational accelerations that are sensitive to size and mass and presumably caused by gas emission. We suggest that 'Oumuamua may have experienced low-level post-perihelion volatile emission that produced a fresh, bright, icy mantle. This model is consistent with the expected value and implied high-albedo value for this solution, but, given our strict limits on CO and CO2, requires another gas species-probably H2O-to explain the observed non-gravitational acceleration. Our results extend the mystery of 'Oumuamua's origin and evolution.
Abstract
Using data from the Sloan Digital Sky Survey Moving Object Catalog, we study color as a function of size for C-complex families in the main asteroid belt to improve our understanding of ...space weathering of carbonaceous materials. We find two distinct spectral slope trends: Hygiea type and Themis type. The Hygiea-type families exhibit a reduction in spectral slope with increasing object size until a minimum slope value is reached and the trend reverses with increasing slope with increasing object size. The Themis family shows an increase in spectral slope with increasing object size until a maximum slope is reached and the spectral slope begins to decrease slightly or plateaus for the largest objects. Most families studied show the Hygiea-type trend. The processes responsible for these distinct changes in spectral slope affect several different taxonomic classes within the C-complex and appear to act quickly to alter the spectral slopes of the family members.
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