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The loudest astronomical headlines of the year came from both very near (planets orbiting stars in the solar neighborhood) and very far (galaxies and parts of galaxies at redshifts of 1 to 3 and more). We explore these and other happenings in our Solar System (Galileo at Jupiter, Comet Hyakutake), Milky Way (the bursting pulsar, spotted stars), Local Group (masers, MACHOs, and more), and Universe (gravitational lensing, an assortment of extrema).

Real science means wrangling with peers over real ideas. Wouldn't it be thrilling to emulate a real life model of science in action in classrooms? How? By starting with a great, hands-on activity modeling an object in space that introduces both key vocabulary and science concepts with visuals to support retention and learning; encouraging collaboration to enrich student engagement with those concepts as students develop their models; and capping the experience by scaffolding an opportunity for students to engage in scientific argumentation as they discuss the strengths and limitations of their models and brainstorm ways to improve them. Read on to find out how the authors did all of that and more! (Contains 5 online resources.)

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2006.11.015 Byline: Jian-Yang Li (a), Michael F. A'Hearn (a), Lucy A. McFadden (a), Michael J.S. Belton (b) Keywords: Comet Borrelly; Photometry Abstract: Images returned from the Deep Space 1 (DS-1) spacecraft during its encounter with Comet 19P/Borrelly are used to study its disk-integrated and disk-resolved photometry and its thermal properties. A disk-integrated phase function was constructed from a combination of DS-1 images and ground-based observations, giving a geometric albedo of 0.072[+ or -]0.020 and a phase slope of 0.043 magadeg.sup.-1. The shape model of Borrelly [Kirk, R.L., Howington-Kraus, E., Soderblom, L.A., Giese, B., Oberst, J., 2004a. Icarus 167, 54-69] and the ephemerides of DS-1 were used to analyze the disk-resolved photometric data with Hapke's theoretical model. It was found that the surface of Borrelly displays large photometric heterogeneities in its photometric parameters. The single-scattering albedo, w, varies by a factor of 2.5 with an average of 0.057[+ or -]0.009; the asymmetry factor, g, ranges from almost isotropic (-0.1) to strongly backscattering (-0.7) with an average of -0.43[+ or -]0.07; the roughness parameter, I[cedilla], is less than 35[degrees] for most parts of surface but ranges up to 55[degrees] in some areas. Its average is 22[degrees][+ or -]5[degrees]. The observed 1-D temperature profile is modeled well by the standard thermal model (STM) for inactive regions and is found to be consistent with a very low thermal inertia. Water sublimation in the source region of the fan jet is observed to decrease the surface temperature from the STM predictions by 20-40 K. The source areas of two collimated jets could not be determined from either photometric model or thermal model. It is evident that the fan jet activity occurring on Borrelly's surface can be correlated to areas of relatively high albedo, weak backscattering, and high roughness. Author Affiliation: (a) Department of Astronomy, University of Maryland, College Park, MD 20742, USA (b) Belton Space Exploration Initiatives, LLC, 430 S. Randolph Way, Tucson, AZ 85716, USA Article History: Received 14 February 2006; Revised 15 September 2006

The highest resolution (pixel scale 30 km) images of Ceres to date have been acquired by the Advanced Camera for Surveys onboard Hubble Space Telescope, through three wide band filters, centered at 535, 335, and 223 nm, covering more than one rotation of Ceres. The lightcurve at 535 nm agrees with earlier observations at V-band [Tedesco, E.F., Taylor, R.C., Drummond, J., Harwood, D., Nickoloff, I., Scaltriti, F., Schober, H. J., Zappala, V., 1983. Icarus 54, 23-29] in terms of magnitude, amplitude, and shape. The 0.04 magnitude lightcurve amplitude cannot be matched by Ceres' rotationally symmetric shape, and is modeled here by albedo patterns. The geometric albedos at the above three wavelengths are measured to be 0.087 [+ or -] 0.003, 0.056 [+ or -] 0.002, and 0.039 [+ or -] 0.003, respectively. V-band geometric albedo is calculated to be 0.090 [+ or -] 0.003, consistent with earlier observations [Tedesco, E.F., 1989. In: Binzel, R.P., Gehrels, T., Matthews, M.S. (Eds.), Asteroids n. Univ. of Arizona Press, Tucson, pp. 1090-1138]. A strong absorption band (30%) centered at about 280 nm is observed, but cannot be identified with either laboratory UV spectra or the spectra of Europa or Ganymede. The single-scattering albedo has been modeled to be 0.070 [+ or -] 0.002, 0.046 [+ or -] 0.002, and 0.032 [+ or -] 0.003, respectively. The photometric roughness of Ceres' surface is found to be about 44[degrees] [+ or -] 5[degrees] from photometric modeling using Hapke's theory, consistent with earlier radar observations [Mitchell, D.L., Ostro, S.J., Hudson, R.S., Rosema, K.D., Campbell, D.B., Velez, R., Chandler, J. E, Shapiro, I.I., Giorgini, J.D., Yeomans, D.K., 1996. Icarus 124, 113-133]. The first spatially resolved surface albedo maps of Ceres at three wavelengths have been constructed from HST observations, as well as the corresponding color maps. Eleven surface albedo features are identified, ranging in scale from 40-350 kM. Overall the range of these albedo and color variations is small compared to other asteroids and some icy satellites. Keywords: Asteroids; Photometry; Surfaces

NASA is working on a project under which Deep Impact, a 370-kilogram-spacecraft, would collide with a comet, Tempel 1, some 133 million kilometers away from the Earth. The project is expected to shed light on some fundamental scientific questions about comets, including what they are made of and how they formed while reproducing a phenomenon that has affected planetary surfaces throughout the history of the solar system.

A photometric model of (433) Eros at wavelengths from 450 to 1050 nm is constructed using the combination of the images from the multispectral imager (MSI) obtained during the one-year long orbital phase of the NEAR mission, ground-based lightcurves from earlier observations, and our theoretical forward modeling simulations coupled with the NEAR shape model. The single scattering albedo is found to be 0.33 [+ or -] 0.03 at 550 nm, which is smaller than past findings by 30%. The amplitude and width of the opposition effect are 1.4 [+ or -] 0.1 and 0.010 [+ or -] 0.004 from ground based lightcurves. It is confirmed that the asymmetry factor of the single-particle phase function and the surface roughness parameter do not depend on wavelength from 450 to 1050 nm, and their values are estimated to be -0.25 [+ or -] 0.02 and 28[degrees] [+ or -] 3[degrees], respectively, comparable with the earlier measurements from the NEAR NIS data. The geometric albedo and the Bond albedo at 550 nm are calculated to be 0.23 and 0.093, respectively, which make Eros less reflective than previous models, but still slightly more reflective than average S-type asteroids. The lower albedos of Eros are more consistent with our forward modeling simulations, as well as with its spectrum. Eros is a typical S-type asteroid like (951) Gaspra and (243) Ida, and has similar surface regolith properties. Combining the single-scattering albedo with the olivine composition of ordinary chondrites, taking into account space weathering darkening, we constrain the grain size of the regolith particles on Eros to a range of 50 to 100 [micro]m. Keywords: Asteroids, 433 Eros; Photometry; NEAR

We present near-infrared spectrometer (NIS) observations (0.8 to 2.4 [micro]m) of the S-type asteroid 433 Eros obtained by the NEAR Shoemaker spacecraft and report results of our Hapke photometric model analysis of data obtained at phase angles ranging from 1.2 [degrees] to 111.0 [degrees] and at spatial resolutions of 1.25 x 2.5 to 2.75 x 5.5 km/spectrum. Our Hapke model fits successfully to the NEAR spectroscopic data for systematic color variations that accompany changing viewing and illumination geometry. Model parameters imply a geometric albedo at 0.946/[micro]m of 0.27 [+ or -] 0.04, which corresponds to a geometric albedo at 0.550 [micro]m of 0.25 4 [+ or -] 0.05. We find that Eros exhibits phase reddening of up to 10% across the phase angle range of 0-100 [degrees]. We observe a 10% increase in the 1-[micro]m band depth at high phase angles. In contrast, we observe only a 5% increase in continuum slope from 1.486 to 2.363 [micro]m and essentially no difference in the 2-[micro]m band depth at higher phase angles. These contrasting phase effects imply that there are phase-dependent differences in the parametric measurements of 1- and 2- [micro]m band areas, and in their ratio. The Hapke model fits suggest that Eros exhibits a weaker opposition surge than either 951 Gaspra or 243 Ida (the only other S-type asteroids for which we possess disk-resolved photometric observations). On average, we find that Eros at 0.946 [micro]m has a higher geometric albedo and a higher single-scatter albedo than Gaspar or Ida at 0.56 [micro]m; however, Eros's single-particle phase function asymmetry and average surface macroscopic roughness parameters are intermediate between Gaspra and Ida. Only two of the five Hapke model parameters exhibit a notable wavelength dependence: (1) The single-scatter albedo mimics the spectrum of Eros, and (2) there is a decrease in angular width of the opposition surge with increasing wavelength from 0.8 to 1.7 [micro]m. Such opposition surge behavior is not adequately modeled with our shadow-hiding Hapke model, consistent with coherent backscattering phenomena near zero phase. Key Words: asteroid; photometry; spectrophotometry; asteroid surfaces; NEAR; 433 Eros.