A planet with a minimum mass of 0.84 Jupiter masses (MJ) has been indirectly detected in a close orbit (radius 0.11 astronomical units, period 14.65 days) around the star 55 Cancri, which is of ...spectral type G8 and about 3 billion years old. The detection of excess infrared emission from this system also suggests the presence of circumstellar dust. Our Solar System has a disk of dust (and larger bodies) that is roughly coplanar with the planets-the so-called Kuiper Belt. Here we report infrared coronagraphic observations of 55 Cancri in which the light from the primary star is blocked, allowing us to image a circumstellar dust disk. We find that the dust lies in a disk that extends to at least 40 AU, comparable to the expected extent for our Kuiper Belt, whereas the inferred mass of the disk is approximately ten times that estimated for our Kuiper Belt. The disk around 55 Cancri is relatively dark at a wavelength of 2.3 µm, which is consistent with absorption of light by methane ice on the dust particles. Assuming that the disk is coplanar with the planet, we determine the planet's mass to be 1.9−0.4+1.1 Jupiter masses. All the available evidence is suggestive of a mature planetary system around 55 Cancri.
We use Spitzer Space Telescope 24 {mu}m data to search for debris disks among 122 AFGKM stars from the {approx}670 Myr clusters Hyades, Coma Ber, and Praesepe, utilizing a number of advances in data ...reduction and determining the intrinsic colors of main-sequence stars. For our sample, the 1{sigma} dispersion about the main-sequence V-K{sub S} , K{sub S} -24 locus is approximately 3.1%. We identify seven debris disks at 10% or more ({>=}3{sigma} confidence level) above the expected K{sub S} -24 for purely photospheric emission. The incidence of excesses of 10% or greater in our sample at this age is 5.7{sup +3.1} {sub -1.7}%. Combining with results from the literature, the rate is 7.8{sup +4.2}{sub -2.1}% for early-type (B9-F4) stars and 2.7{sup +3.3}{sub -1.7}% for solar-like (F5-K9) stars. Our primary sample has strict criteria for inclusion to allow comparison with other work; when we relax these criteria, three additional debris disks are detected. They are all around stars of solar-like type and hence reinforce our conclusion that disks around such stars are still relatively common at 670 Myr and are similar to the rate around early-type stars. The apparently small difference in decay rates between early-type and solar-like stars is inconsistent with the first-order theoretical predictions that the later type stellar disks would decay an order of magnitude more quickly than the earlier type ones.
Abstract
The surfaces of airless bodies such as asteroids are exposed to many phenomena that can alter their physical properties. Bennu, the target of the OSIRIS-REx mission, has demonstrated how ...complex the surface of a small body can be. In 2019 November, the potentially hazardous asteroid 2015 JD
1
experienced a close approach of 0.033 1 au from the Earth. We present results of the physical characterization of 2015 JD
1
based on ground-based radar, spectroscopy, and photometric observations acquired during 2019 November. Radar polarimetry measurements from the Arecibo Observatory indicate a morphologically complex surface. The delay-Doppler images reveal a contact binary asteroid with an estimated visible extent of ∼150 m. Our observations suggest that 2015 JD
1
is an E-type asteroid with a surface composition similar to aubrites, a class of differentiated enstatite meteorites. The dynamical properties of 2015 JD
1
suggest that it came from the
ν
6
resonance with Jupiter, and spectral comparison with major E-type bodies suggests that it may have been derived from a parental body similar to the progenitor of the E-type (64) Angelina. Significantly, we find rotational spectral variation across the surface of 2015 JD
1
from the red to blue spectral slope. Our compositional analysis suggests that the spectral slope variation could be due to the lack of iron and sulfides in one area of the surface of 2015 JD
1
and/or differences in grain sizes.
We report on observations of activity in near-Earth object (3552) Don Quixote using the Spitzer Space Telescope and ground-based telescopes around its 2018 perihelion passage. Spitzer observations ...obtained six months before perihelion show extended emission around the target's nucleus that is most likely caused by molecular band emission from either CO2 or CO, but we find no significant emission from dust. Ground-based optical observations taken close to perihelion reveal for the first time activity in the optical wavelengths, which we attribute to solar light reflected from dust particles. IRAM millimeter radio observations taken around the same time are unable to rule out CO as the driver of the molecular band emission observed with Spitzer. The comparison of the gas activity presented here with observations performed during Don Quixote's previous apparition suggests that activity in Don Quixote is recurrent. We conclude that (3552) Don Quixote is most likely a weakly active comet.
Abstract
The Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) will discover ∼6 million solar system planetesimals, providing in total over a billion photometric and astrometric ...measurements in 6 broad-band filters. Rubin Observatory's automated data reduction pipelines will employ difference imaging; templates representing the static sky will be subtracted from the nightly LSST observations in order to identify transient sources, including solar system moving objects. These templates are expected to be generated by coadding high quality images of the same pointing from the previous year's survey observations. The first year of LSST operations will require a different method for generating templates, if solar system discoveries are to be reported daily like Year 2 and beyond. We make recommendations for template production in the LSST's first year and present the opportunities for solar system small body transient and time domain science enhanced by this change.
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