We present 1210 Johnson/Cousins B, V , R, and I photometric observations of 22 recent Type Ia supernovae (SNe Ia) : SNe 1993ac, 1993ae, 1994M, 1994S, 1994T, 1994Q, 1994ae, 1995D, 1995E, 1995al, 1995ac, 1995ak, 1995bd, 1996C, 1996X, 1996Z, 1996ab, 1996ai, 1996bk, 1996bl, 1996bo, and 1996bv. Most of the photometry was obtained at the Fred Lawrence Whipple Observatory of the HarvardSmithsonian Center for Astrophysics in a cooperative observing plan aimed at improving the database for SNe Ia. The redshifts of the sample range from cz \ 1200 to 37,000 km s~1 with a mean of cz \ 7000 km s~1.

We describe new planetesimal accretion calculations in the Kuiper Belt that include fragmentation and velocity evolution. All models produce two power law cumulative size distributions, N C ∝ r −2.5 for radii ∼ < 0.3-3 km and N C ∝ r −3 for radii ∼ > 1-3 km. The power law indices are nearly independent of the initial mass in the annulus, M 0 ; the initial eccentricity of the planetesimal swarm, e 0 ; and the initial size distribution of the planetesimal swarm. The transition between the two power laws moves to larger radii as e 0 increases. The maximum size of objects depends on their intrinsic tensile strength, S 0 ; Pluto formation requires S 0 ∼ > 300 erg g −1 . The timescale to produce Pluto-sized objects, τ P , is roughly proportional to M −1 0 and e 0 , and is less sensitive to other input parameters. Our models yield τ P ≈ 30-40 Myr for planetesimals with e 0 = 10 −3 in a Minimum Mass Solar Nebula. The production of several 'Plutos' and ∼ 10 5 50 km radius Kuiper Belt objects leaves most of the initial mass in 0.1-10 km radius objects that can be collisionally depleted over the age of the solar system. These results resolve the puzzle of large Kuiper Belt objects in a small mass Kuiper Belt.

We present observations of the interstellar interloper 1I/2017 U1 ('Oumuamua) taken during its 2017 October flyby of Earth. The optical colors B -V=0.70±0.06, V -R=0.45±0.05, overlap those of the D-type Jovian Trojan asteroids and are incompatible with the ultrared objects that are abundant in the Kuiper Belt. With a mean absolute magnitude H V =22.95 and assuming a geometric albedo p V =0.1, we find an average radius of 55 m. No coma is apparent; we deduce a limit to the dust mass production rate of only ∼2×10 −4 kg s, ruling out the existence of exposed ice covering more than a few m 2 of the surface. Volatiles in this body, if they exist, must lie beneath an involatile surface mantle 0.5 m thick, perhaps a product of prolonged cosmic-ray processing in the interstellar medium. The light curve range is unusually large at ∼2.0±0.2 mag. Interpreted as a rotational light curve the body has axis ratio ³ -+ 6.3 1.1 1.3 :1 and semi-axes ∼230 m×35 m. A 6:1 axis ratio is extreme relative to most small solar system asteroids and suggests that albedo variations may additionally contribute to the variability. The light curve is consistent with a two-peaked period ∼8.26 hr, but the period is non-unique as a result of aliasing in the data. Except for its unusually elongated shape, 1I/2017 U1 is a physically unremarkable, sub-kilometer, slightly red, rotating object from another planetary system. The steady-state population of similar, ∼100 m scale interstellar objects inside the orbit of Neptune is ∼10 4 , each with a residence time of ∼10 years.

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