The flux of small asteroids near the Earth

Fifteen new EA's (Earth approachers) have been discovered since September, among them the smallest asteroids on record: 1990 UN, 1991 BA, and 1991 JR, which are in the 10 to 100 m size range (Scotti et al. 1991b). For the first time, we can make estimates of the fluxes near the Earth of these small objects, thought to be the immediate parents of meteorites, from direct observation. In this paper, I show that for EA's larger than a few 100 m, the magnitude-frequency dependence we observe is consistent with the cumulative magnitude-frequency relation, m(H), established for the main belt asteroids. Assuming this relation extends to smaller sizes, however, the probability for discovering both 1990 UN and 1991 JR was 15 percent, and for discovering 1991 BA only 1 percent. Objects smaller than approx. 100 m are therefore increasingly overabundant compared to an extrapolation from larger objects, with the excess increasing with decreasing size. Near 10 m, the most probable flux near the Earth is two orders of magnitude higher. This is in agreement with the flux extrapolated from observations of bright meteors and fireballs. It is thus likely that processes other than collisional breakup of asteroidal material begin to supply the population of small objects near the Earth at sizes near 100 m. Tantalizing clues from spectral measurements and orbital associations suggest that these objects may be the debris from extinct, short-period comets

Discovery of a planetary-sized object in the scattered Kuiper belt

We present the discovery and initial physical and dynamical characterization of the object 2003 UB313. The object is sufficiently bright that for all reasonable values of the albedo it is certain to be larger than Pluto. Pre-discovery observations back to 1989 are used to obtain an orbit with extremely small errors. The object is currently at aphelion in what appears to be a typical orbit for a scattered Kuiper belt object except that it is inclined by about 44 degrees from the ecliptic. The presence of such a large object at this extreme inclination suggests that high inclination Kuiper belt objects formed preferentially closer to the sun. Observations from Gemini Observatory show that the infrared spectrum is, like that of Pluto, dominated by the presence of frozen methane, though visible photometry shows that the object is almost neutral in color compared to Pluto's extremely red color. 2003 UB313 is likely to undergo substantial seasonal change over the large range of heliocentric distances that it travels; Pluto at its current distance is likely to prove a useful analog for better understanding the range of seasonal changes on this body.Comment: 9 pages, 1 figur

Dependence of Maximum Trappable Field on Superconducting Nb3Sn Cylinder Wall Thickness

Uniform dipole magnetic fields from 1.9 to 22.4 kOe were permanently trapped, with high fidelity to the original field, transversely to the axes of hollow Nb3Sn superconducting cylinders. These cylinders were constructed by helically wrapping multiple layers of superconducting ribbon around a mandrel. This is the highest field yet trapped, the first time trapping has been reported in such helically wound taped cylinders, and the first time the maximum trappable field has been experimentally determined as a function of cylinder wall thickness.Comment: 8 pages, 4 figures, 1 table. PACS numbers: 74.60.Ge, 74.70.Ps, 41.10.Fs, 85.25.+

Automated detection of asteroids in real-time with the Spacewatch telescope

The Spacewatch telescope on Kitt Peak is being used to survey for near-earth asteroids using a Tektronix TK2048 CCD in scanning mode. We hope to identify suitable low delta v candidates amongst the near-earth asteroid population as possible exploration targets, to identify those objects which pose a danger to life on earth, and to study the physical properties of the objects in near-earth space. Between Sep. 1990 and Jun. 1991, 14 new earth-approaching asteroids including 1 Aten, 9 Apollo, and 4 Amor type asteroids were detected by automated software and discriminated by their angular rates from the rest of the detected asteroids in near-real time by the observer. The average of about 1.5 earth-approaching asteroids per month is comparable to the total number found by all other observatories combined. One other Apollo type asteroid was detected by the observer as a long trailed image. The positions of this last object were measured and the object was tracked by the observer in real time. This object was determined to be a 5-10 meter diameter object which passed within 170,000 kilometers of earth. Of the 14 automatically detected earth-approaching asteroids, 10 have been found at distances in excess of 0.5 AU from earth. An average of more than 2000 asteroids are detected each month. Positions, angular rates, and brightnesses are determined for each of these asteroids in real-time

Evaluating the Progress of Atmospheric Research in Understanding the Mechanics Behind Tropical Cyclone-Induced Tornadogenesis

As tropical cyclones make landfall along coastlines all over the world, havoc is wreaked on families, businesses, economies, etc. A generally overlooked topic is one of the inherent dangers in tropical cyclone landfalls. These can produce tornadoes in the spiral rain bands coming ashore by encountering increasingly higher frictional convergence. The second component will be assessing which other parameters could be analyzed on a synoptic timescale to evaluate how we can potentially improve longer term predictions of tropical cyclone (TC)-induced tornadogenesis. The analysis showed that the combination of high low-level moisture, vertical temperature gradients, and enhanced vertical wind shear is the key factor that links landfalling tropical cyclones to associated tornadogenesis prior to, during, and/or after the time of landfall. An integral part of the process preceding TC-induced tornadogenesis is the enhanced vertical temperature gradient that develops as the storm maintains warm-core characteristics aloft but develops cold-core characteristics closer to the surface. The examination of forecaster perspectives showed that over the past few years there is strong evidence of forecaster improvement based upon greater cognizance of forecast variables linked to TC-induced tornadoes

The Youthful Appearance of the 2003 EL61 Collisional Family

We present new solar phase curve observations of the 2003 EL61 collisional family showing that all the members have light-scattering properties similar to the bright icy satellites and dwarf planets. Compared to other Kuiper Belt objects, the five family members we observe (2003 EL61, 2002 TX300, 2003 OP32, 2005 RR43, and 1995 SM55) have conspicuously neutral color (V-I = 0.6-0.8 mag) and flat phase curves at small phase angles (phase coefficients of 0.0 - 0.1 mag deg-1). Comparing the phase curves we observe for other icy Kuiper Belt objects to the phase curves of icy satellites, we find that the flat phase curves of the 2003 EL61 family are an indication they have high albedo surfaces coated with fresh ice in the last ~100 Myr. We examine possible resurfacing processes and find none that are plausible. To avoid the influence of cosmic radiation that darkens and reddens most icy surfaces on times scales > ~100 Myr, the family members must be unusually depleted in carbon, or else the collision that created the family occurred so recently that the parent body and fragments have not had time to darken. We also find a rotation period of 4.845 (+/- 0.003) h with amplitude 0.26 (+/- 0.04) mags for 2003 OP32.Comment: 12 pages, 3 tables, 4 figure

The Surface of 2003 EL_(61) in the Near-Infrared

We report the detection of crystalline water ice on the surface of 2003 EL_(61). Reflectance spectra were collected from the Gemini North telescope in the 1.0 to 2.4 μm wavelength range and from the Keck telescope across the 1.4-2.4 μm wavelength range. The signature of crystalline water ice is obvious in all data collected. Like the surfaces of many outer solar system bodies, the surface of 2003 EL_(61) is rich in crystalline water ice, which is energetically less favored than amorphous water ice at low temperatures, suggesting that resurfacing processes may be taking place. The near-infrared color of the object is much bluer than a pure water ice model. Adding a near-infrared blue component such as hydrogen cyanide or phyllosilicate clays improves the fit considerably, with hydrogen cyanide providing the greatest improvement. The addition of hydrated tholins and bitumens also improves the fit, but is inconsistent with the neutral V - J reflectance of 2003 EL_(61). A small decrease in reflectance beyond 2.3 μm may be attributable to cyanide salts. Overall, the reflected light from 2003 EL_(61) is best fit by a model of 2/3-4/5 pure crystalline water ice and 1/3-1/5 near-infrared blue component such as hydrogen cyanide or kaolinite. The surface of 2003 EL_(61) is unlikely to be covered by significant amounts of dark material such as carbon black, as our pure ice models reproduce published albedo estimates derived from the spin state of 2003 EL_(61)

Jefferson\u27s Patient Encounter Log System (PELS)

No abstract available

Near Infrared Surface Properties of the Two Intrinsically Brightest Minor Planets (90377) Sedna and (90482) Orcus

We present low resolution K band spectra taken at the Gemini 8 meter telescope of (90377) Sedna and (90482) Orcus (provisional designations 2003 VB12 and 2004 DW, respectively), currently the two minor planets with the greatest absolute magnitudes (i.e. the two most reflective minor planets). We place crude limits on the surface composition of these two bodies using a Hapke model for a wide variety of assumed albedos. The unusual minor planet (90377) Sedna was discovered on November 14, 2003 UT at roughly 90 AU with 1.6 times the heliocentric distance and perihelion distance of any other bound minor planet. It is the first solar system object discovered between the Kuiper Belt and the Oort Cloud, and may represent a transition population between the two. The reflectance spectrum of (90377) Sedna appears largely featureless at the current signal-to-noise ratio, suggesting a surface likely to be highly processed by cosmic rays. For large grain models (100 micron to 1 cm) we find that (90377) Sedna must have less than 70% surface fraction of water ice and less than 60% surface fraction of methane ice to 3 sigma confidence. Minor planet (90482) Orcus shows strong water ice absorption corresponding to less than 50% surface fraction for grain models 25 micron and larger. Orcus cannot have more than 30% of its surface covered by large (100 mm to 1 cm) methane grains to 3 sigma confidence.Comment: Accepted for publication in the Astrophysical Journa