Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userDiscovery and Physical Characterization of a Large Scattered Disk Object at 92 AU
88
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We report the observation and physical characterization of the possible dwarf planet UZ (DeeDee), a dynamically detached trans-Neptunian object discovered at 92 AU. This object is currently the second-most distant known trans-Neptunian object with reported orbital elements, surpassed in distance only by the dwarf planet Eris. The object was discovered with an $r$-band magnitude of 23.0 in data collected by the Dark Energy Survey between 2014 and 2016. Its 1140-year orbit has $(a,e,i) = (109~mathrm{AU}, 0.65, 26.8^{circ})$. It will reach its perihelion distance of 38 AU in the year 2142. Integrations of its orbit show it to be dynamically stable on Gyr timescales, with only weak interactions with Neptune. We have performed followup observations with ALMA, using 3 hours of on-source integration time to measure the objects thermal emission in the Rayleigh-Jeans tail. The signal is detected at 7$sigma$ significance, from which we determine a $V$-band albedo of $13.1^{+3.3}_{-2.4}mathrm{(stat)}^{+2.0}_{-1.4}mathrm{(sys)}$ percent and a diameter of $635^{+57}_{-61}mathrm{(stat)}^{+32}_{-39}mathrm{(sys)}$~km, assuming a spherical body with uniform surface properties.
rate research
Read More
We present a new Subaru/HiCIAO high-contrast H-band polarized intensity (PI) image of a nearby transitional disk associated with TW Hydrae. The scattered light from the disk was detected from 0.2 to 1.5 (11 - 81 AU) and the PI image shows a clear axisymmetric depression in polarized intensity at ~ 0.4 (~ 20 AU) from the central star, similar to the ~ 80 AU gap previously reported from HST images. Azimuthal polarized intensity profile also shows the disk beyond 0.2 is almost axisymmetric. We discuss two possible scenarios explaining the origin of the polarized intensity depression: 1) a gap structure may exist at ~ 20 AU from the central star because of shallow slope seen in the polarized intensity profile, and 2) grain growth may be occurring in the inner region of the disk. Multi-band observations at NIR and millimeter/sub-millimeter wavelengths play a complementary role in investigating dust opacity and may help reveal the origin of the gap more precisely.
The goal of this work is to determine the physical characteristics of resonant, detached and scattered disk objects in the transneptunian region, observed mainly in the framework of the TNOs are Cool! Herschel Open Time Key Program. Based on thermal emission measurements with the Herschel/PACS and Spitzer/MIPS instruments we determine size, albedo, and surface thermal properties for 23 objects using radiometric modelling techniques. This is the first analysis in which the physical properties of objects in the outer resonances are determined for a notable sample. In addition to the results for individual objects, we have compared these characteristics with the bulk properties of other populations of the transneptunian region. The newly analyzed objects show a large variety of beaming factors, indicating a diversity of thermal properties, and in general, they follow the albedo-colour clustering identified earlier for Kuiper belt objects and Centaurs, further strengthening the evidence for a compositional discontinuity in the young Solar System.
We present long-baseline Atacama Large Millimeter/submillimeter Array (ALMA) observations of the 870 micron continuum emission from the nearest gas-rich protoplanetary disk, around TW Hya, that trace millimeter-sized particles down to spatial scales as small as 1 AU (20 mas). These data reveal a series of concentric ring-shaped substructures in the form of bright zones and narrow dark annuli (1-6 AU) with modest contrasts (5-30%). We associate these features with concentrations of solids that have had their inward radial drift slowed or stopped, presumably at local gas pressure maxima. No significant non-axisymmetric structures are detected. Some of the observed features occur near temperatures that may be associated with the condensation fronts of major volatile species, but the relatively small brightness contrasts may also be a consequence of magnetized disk evolution (the so-called zonal flows). Other features, particularly a narrow dark annulus located only 1 AU from the star, could indicate interactions between the disk and young planets. These data signal that ordered substructures on ~AU scales can be common, fundamental factors in disk evolution, and that high resolution microwave imaging can help characterize them during the epoch of planet formation.
Asteroids of size larger than 0.15 km generally do not have periods smaller than 2.2 hours, a limit known as cohesionless spin barrier. This barrier can be explained by the cohesionless rubble-pile structure model. There are few exceptions to this <<rule>>, called LSFRs (Large Super-Fast Rotators), as (455213) 2001 OE84, (335433) 2005 UW163 and 2011 XA3. The near-Earth asteroid (436724) 2011 UW158 was followed by an international team of optical and radar observers in 2015 during the flyby with Earth. It was discovered that this NEA is a new candidate LSFR. With the collected lightcurves from optical observations we are able to obtain the amplitude-phase relationship, sideral rotation period ($PS = 0.610752 pm 0.000001$ h), a unique spin axis solution with ecliptic coordinates $ lambda = 290^{circ} pm 3^{circ}$, $beta = 39^{circ} pm 2^{circ}$ and the asteroid 3D model. This model is in qualitative agreement with the results from radar observations.
Study of cosmic dust and planetary aerosols indicate that some of them contain a large number of aggregates of the size that significantly exceeds the wavelengths of the visible light. In some cases such large aggregates may dominate in formation of the light scattering characteristics of the dust. In this paper we present the results of computer modelling of light scattering by aggregates that contain more than 1000 monomers of submicron size and study how their light scattering characteristics, specifically polarization, change with phase angle and wavelength. Such a modeling became possible due to development of a new version of MSTM (Multi Sphere T-Matrix) code for parallel computing. The results of the modeling are applied to the results of comet polarimetric observations to check if large aggregates dominate in formation of light scattering by comet dust. We compare aggregates of different structure and porosity. We show that large aggregates of more than 98% porosity (e.g. ballistic cluster-cluster aggregates) have angular dependence of polarization almost identical to the Rayleigh one. Large compact aggregates (less than 80% porosity) demonstrate the curves typical for solid particles. This rules out too porous and too compact aggregates as typical comet dust particles. We show that large aggregates not only can explain phase angle dependence of comet polarization in the near infrared but also may be responsible for the wavelength dependence of polarization, which can be related to their porosity.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
