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Massive-Star Supernovae as Major Dust Factories

Gordon, Karl D.; Kennicutt, Robert C.; Panagia, Nino +15 more

We present late-time optical and mid-infrared observations of the Type II supernova 2003gd in the galaxy NGC 628. Mid-infrared excesses consistent with cooling dust in the ejecta are observed 499 to 678 days after outburst and are accompanied by increasing optical extinction and growing asymmetries in the emission-line profiles. Radiative-transfer…

Explaining the Color Distributions of Globular Cluster Systems in Elliptical Galaxies

Yoon, Suk-Jin; Lee, Young-Wook; Yi, Sukyoung Ken

The colors of globular clusters in most large elliptical galaxies are bimodal. This is generally taken as evidence for the presence of two cluster subpopulations that have different geneses. However, here we find that, because of the nonlinear nature of the metallicity-to-color transformation, a coeval group of old clusters with a unimodal metalli…

The Second Ring-Moon System of Uranus: Discovery and Dynamics

Showalter, Mark R.; Lissauer, Jack J.

Deep exposures of Uranus taken with the Hubble Space Telescope reveal two small moons and two faint rings. All of them orbit outside of Uranus's previously known (main) ring system but are interior to the large, classical moons. The outer new moon, U XXVI Mab, orbits at roughly twice the radius of the main rings and shares its orbit with a dust ri…

Probing the Faintest Stars in a Globular Star Cluster

Anderson, Jay; Rich, R. Michael; Stetson, Peter B. +10 more

NGC 6397 is the second closest globular star cluster to the Sun. Using 5 days of time on the Hubble Space Telescope, we have constructed an ultradeep color-magnitude diagram for this cluster. We see a clear truncation in each of its two major stellar sequences. Faint red main-sequence stars run out well above our observational limit and near to th…

New Dust Belts of Uranus: One Ring, Two Ring, Red Ring, Blue Ring

de Pater, Imke; Showalter, Mark R.; Hammel, Heidi B. +1 more

We compared near-infrared observations of the recently discovered outer rings of Uranus with Hubble Space Telescope results. We find that the inner ring, R/2003 U 2, is red, whereas the outer ring, R/2003 U 1, is very blue. Blue is an unusual color for rings; Saturn's enigmatic E ring is the only other known example. By analogy to the E ring, R/20…