Gaia DR3 data (both Gaia EDR3 and the full Gaia DR3) are based on data collected between 25 July 2014 (10:30 UTC) and 28 May 2017 (08:44 UTC), spanning a period of 34 months. As a comparison, Gaia DR2 was based on 22 months of data and Gaia DR1 was based on observations collected during the first 14 months of Gaia's routine operational phase. Survey completeness: The Gaia EDR3 catalogue is essentially complete between G=12 and G=17. The source list for the release is incomplete at the bright end and has an ill-defined faint magnitude limit, which depends on celestial position. The combination of the Gaia scan law coverage and the filtering on data quality which will be done prior to the publication of Gaia EDR3, does lead to some regions of the sky displaying source density fluctuations that reflect the scan law pattern. In addition, small gaps exist in the source distribution, for instance close to bright stars. Astrometry: The parallax improvement is typically 20% with respect to Gaia DR2. The proper motions are typically a factor two better than in Gaia DR2. An overall reduction of systematics has been achieved. E.g., the parallax zero point deduced from the extragalactic sources is about -20{mu}as. A tentative correction formula for the parallax zero point will be provided. Closer to the release date of Gaia Early Data Release 3, an update will be given on the astrometry. Photometry: The G-band photometric uncertainties are ~0.25mmag for G<13, 1mmag at G=17, and 5mmag at G=20mag. The GBP-band photometric uncertainties are ~1mmag for G<13, 10mmag at G=17, and 100mmag at G=20mag. The GRP-band photometric uncertainties are ~1mmag for G<13, 5mmag at G=17, and 50mmag at G=20mag. Closer to the release date of Gaia Early Data Release 3, an update will be given on the photometry. Gaia EDR3 does not contain new radial velocities. The radial velocities of Gaia Data Release 2 have been added to Gaia EDR3 in order to ease the combination of spectrosopic and astrometric data. Radial velocities: Gaia EDR3 hence contains Gaia DR2 median radial velocities for about 7.21 million stars with a mean G magnitude between ~4 and ~13 and an effective temperature (Teff) in the range ~3550 to 6900K. The overall precision of the radial velocities at the bright end is of the order of ~200-300m/s while at the faint end, the overall precision is ~1.2km/s for a Teff of 4750K and ~3.5km/s for a Teff of 6500K. Before publication in Gaia EDR3, an additional filtering has been performed onto the Gaia DR2 radial velocities to remove some 4000 sources that had wrong radial velocities. Please be aware that the Gaia DR2 values are assigned to the Gaia EDR3 sources through an internal cross-match operation. In total, ~10000 Gaia DR2 radial velocities could not be associated to a Gaia EDR3 source. Astrophysical parameters: Gaia EDR3 does not contain new astrophysical parameters. Astrophysical parameters have been published in Gaia DR2 and a new set is expected to be released with the full Gaia DR3 release. Variable stars: Gaia EDR3 does not contain newly classified variable stars. For the overview of the currently available variable stars from Gaia DR2, have a look here. Classifications for a larger set of variable stars are expected with the full Gaia DR3 release. Solar system objects: A large set of solar system objects with orbits will become available with the full Gaia DR3 release. Information on the currently available asteroids in Gaia DR2 can be found here. Documentation: Data release documentation is provided along with each data release in the form of a downloadable PDF and a webpage. The various chapters of the documentation have been indexed at ADS allowing them to be cited. Please visit the Gaia Archive (https://gea.esac.esa.int/archive) to access this documentation, and make sure to check out all relevant information given through the documentation overview page (https://www.cosmos.esa.int/web/gaia-users/archive).
Astrometric observations performed by the Gaia Follow-Up Network for Solar System Objects (Gaia-FUN-SSO) play a key role in ensuring that moving objects first detected by ESA's Gaia mission remain recoverable after their discovery. An observation campaign on the potentially hazardous asteroid (99942) Apophis was conducted during the asteroid's latest period of visibility, from 12/21/2012 to 5/2/2013, to test the coordination and evaluate the overall performance of the Gaia-FUN-SSO . The 2732 high quality astrometric observations acquired during the Gaia-FUN-SSO campaign were reduced with the Platform for Reduction of Astronomical Images Automatically (PRAIA), using the USNO CCD Astrograph Catalogue 4 (UCAC4, Cat. I/322) as a reference. The astrometric reduction process and the precision of the newly obtained measurements are discussed. We compare the residuals of astrometric observations that we obtained using this reduction process to data sets that were individually reduced by observers and accepted by the Minor Planet Center.
We report on our detailed characterization of Earth's second known temporary natural satellite, or minimoon, asteroid 2020CD3. An artificial origin can be ruled out based on its area-to-mass ratio and broadband photometry, which suggest that it is a silicate asteroid belonging to the S or V complex in asteroid taxonomy. The discovery of 2020CD3 allows for the first time a comparison between known minimoons and theoretical models of their expected physical and dynamical properties. The estimated diameter of 1.2_-0.2_^+0.4^m and geocentric capture approximately a decade after the first known minimoon, 2006RH120, are in agreement with theoretical predictions. The capture duration of 2020CD3 of at least 2.7yr is unexpectedly long compared to the simulation average, but it is in agreement with simulated minimoons that have close lunar encounters, providing additional support for the orbital models. 2020CD3's atypical rotation period, significantly longer than theoretical predictions, suggests that our understanding of meter-scale asteroids needs revision. More discoveries and a detailed characterization of the population can be expected with the forthcoming Vera C. Rubin Observatory Legacy Survey of Space and Time.
We present 1428 individual astrometric measurements of 256 trans-Neptunian objects made with Hubble Space Telescope (HST). The observations were collected over three years with two instruments, the Wide Field Planetary Camera 2 and the Advanced Camera for Surveys High Resolution Camera, as part of four HST programs. We briefly describe the data and our analysis procedures. The submission of these measurements to the Minor Planet Center increased the individual arc length of objects by 1.83 days to 8.11 years. Of the 256 total objects, 62 (24.2%) had arc length increases of >=3 years. The arc length for 60 objects (23.4%) was increased by a factor of 2 or greater.
Inner Oort cloud objects (IOCs) are trans-Plutonian for their entire orbits. They are beyond the strong gravitational influences of the known planets, yet close enough to the Sun that outside forces are minimal. Here we report the discovery of the third known IOC after Sedna and 2012 VP113, called 2015 TG387. This object has a perihelion of 65+/-1 au and semimajor axis of 1170+/-70 au. The longitude of perihelion angle, {omega}, for 2015 TG387 is between that of Sedna and 2012 VP113 and thus similar to the main group of clustered extreme trans-Neptunian objects (ETNOs), which may be shepherded into similar orbital angles by an unknown massive distant planet called Planet X, or Planet Nine. The orbit of 2015 TG387 is stable over the age of the solar system from the known planets and Galactic tide. When including outside stellar encounters over 4 Gyr, 2015 TG387's orbit is usually stable, but its dynamical evolution depends on the stellar encounter scenarios used. Surprisingly, when including a massive Planet X beyond a few hundred au on an eccentric orbit that is antialigned in longitude of perihelion with most of the known ETNOs, we find that 2015 TG387 is typically stable for Planet X orbits that render the other ETNOs stable as well. Notably, 2015 TG387's argument of perihelion is constrained, and its longitude of perihelion librates about 180{deg} from Planet X's longitude of perihelion, keeping 2015 TG387 antialigned with Planet X over the age of the solar system.
With an estimated diameter in the 320 to 350km range, (704) Interamnia is the fifth largest main belt asteroid and one of the few bodies that fills the gap in size between the four largest bodies with D>400km (Ceres, Vesta, Pallas and Hygiea) and the numerous smaller bodies with diameter 200 km. However, despite its large size, little is known about the shape and spin state of Interamnia and, therefore, about its bulk composition and past collisional evolution. We aimed to test at what size and mass the shape of a small body departs from a nearly ellipsoidal equilibrium shape (as observed in the case of the four largest asteroids) to an irregular shape as routinely observed in the case of smaller (D<=200km) bodies. We observed Interamnia as part of our ESO VLT/SPHERE large program (ID: 199.C-0074) at thirteen different epochs. In addition, several new optical lightcurves were recorded. These data, along with stellar occultation data from the literature, were fed to the All-Data Asteroid Modeling (ADAM) algorithm to reconstruct the 3D-shape model of Interamnia and to determine its spin state. Interamnia's volume-equivalent diameter of 332+/-6km implies a bulk density of {rho}=1.98+/-0.68g/cm^3^, which suggests that Interamnia - like Ceres and Hygiea - contains a high fraction of water ice, consistent with the paucity of apparent craters. Our observations reveal a shape that can be well approximated by an ellipsoid, and that is compatible with a fluid hydrostatic equilibrium at the 2{sigma}level. The rather regular shape of Interamnia implies that the size and mass limit, under which the shapes of minor bodies with a high amount of water ice in the subsurface become irregular, has to be searched among smaller (D<=300km) less massive (m<=3x10^19^kg) bodies.
The main purpose of the Infrared Astronomical Satellite (IRAS) was to survey the sky in four infrared wavelength bands centered at 12, 25, 60 and 100 um. Data for 25 comets, 1811 known asteroids and ~TBD asteroids without orbits were obtained and accepted into this IRAS asteroid and comet catalog, which is the largest, least biased and most uniform survey of asteroids and comets. For the IRAS Asteroid Survey, 7,015 sightings from 1,811 individual asteroids that were of sufficient quality have been accepted into the asteroid catalog. Diameters, albedos and various technical parameters have been derived for these minor planet. The IRAS comet catalog contains the detection history for each comet reliably detected in the ADAS search. Positions were searched for all periodic comets that passed near the sun or earth during the period from 1982 to 1985 plus all comets that were observed during that period.
The IRAS Minor Planet Survey (1992) supplements the asteroid data given in the IRAS Asteroid and Comet Survey (1986; catalog <VII/91>); comets are not included in IMPS. All asteroids with reasonably well-known orbits as of December 1990 are covered. In particular, IMPS updates the processing of asteroids numbered 1 through 3318 and extends this processing to asteroid number 4679 plus 2,632 asteroids with preliminary (two or more opposition) orbits. IMPS processed only IRAS survey observations; Low Resolution Spectrometer, Serendipitous, and Additional Observations data were not processed.
A total of six deep exposures (using the astronomical observation template CAM01 with a 6" pixel field of view) through the ISOCAM LW10 filter (IRAS band 1, i.e., 12{mu}m) were obtained on a ~15' square field centered on the ecliptic plane. Point sources were extracted using the technique described in 1999 by Deert et al. Twoknown asteroids appear in these frames, and 20 sources moving with velocities appropriate for main-belt asteroids are present. Most of the asteroids detected have flux densities less than 1 mJy, that is, between 150 and 350 times fainter than any of the asteroids observed by IRAS. These data provide the first direct measurement of the 12{mu}m sky-plane density for asteroids on the ecliptic equator. The median zodiacal foreground, as measured by ISOCAM during this survey, is found to be 22.1+/-1.5mJy/pixel, i.e. 26.2+/-1.7MJy/sr. The results presented here imply that the actual number of kilometer-sized asteroids may be higher than several recent estimates based upon observations at visual wavelengths and are in reasonable agreement with the statistical asteroid model. Using results from the observations presented here, together with three other recent population estimates, we conclude that the cumulative number of main-belt asteroids with diameters greater than 1km is (1.2+/-0.5)x10^6^.
Various properties of Jovian Trojan asteroids such as composition, rotation periods, and photometric amplitudes, or the rate of binarity in the population, can provide information and constraints on the evolution of the group and of the solar system itself. Here we present new photometric properties of 45 Jovian Trojans from the K2 mission of the Kepler space telescope, and present phase-folded light curves for 44 targets, including (11351) Leucus, one of the targets of the Lucy mission. We extend our sample to 101 asteroids with previous K2 Trojan measurements, then compare their combined amplitude and frequency distributions to other ground-based and space data. We show that there is a dichotomy in the periods of Trojans with a separation at ~100hr. We find that 25% of the sample are slow rotators (P>=30hr), an excess that can be attributed to binary objects. We also show that 32 systems can be classified as potential detached binary systems. Finally, we calculate density and rotation constraints for the asteroids. Both the spin barrier and fits to strengthless ellipsoid models indicate low densities and thus compositions similar to populations of comets and trans-Neptunian objects throughout the sample. This supports the scenario of outer solar system origin for Jovian Trojans.
