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[ITAL]Hubble[/ITAL] [ITAL]Space[/ITAL] [ITAL]T[/ITAL][ITAL]elescope[/ITAL] Wide Field Planetary Camera 2 Observations of η Carinae

1998; Institute of Physics; Volume: 116; Issue: 5 Linguagem: Inglês

10.1086/300581

1538-3881

Jon A. Morse, Kris Davidson, John Bally, Dennis Ebbets, Bruce Balick, Adam Frank,

Astro and Planetary Science

Hubble Space Telescope (HST) continuum and emission-line images of η Carinae obtained with the Planetary Camera (PC) of the Wide Field Planetary Camera 2 show a startling wealth of detailed structure in the expanding Homunculus Nebula and outer debris field. Using a combination of dithering and image deconvolutions, we have achieved a resolution of about 50 mas over the ∼30'' field of view covered by the PC. The complex network of bright cells and reddish, dusty lanes that lace the surfaces of the bipolar lobes of the Homunculus resemble similar structures observed in recent HST images of planetary nebulae. The contrast between these dust lanes and the adjacent bright cells, together with the dimensions of these features, is used to estimate the opacity and density of the obscuring material. Though radiation pressure is expected to accelerate the dust lanes by less than 10–20 km s-1 with respect to the 650 km s-1 expansion of the Homunculus, it may be the source of the instability responsible for their formation, and we discuss the formation of the bright cells and dusty filaments in this context. We present new data on the debris field beyond the Homunculus. This region contains a set of high-velocity "whiskers" (or "streamers") that show bipolar kinematics that associate them with the radially expanding lobes of the Homunculus and extend away from the central star like shrapnel from an explosion with trailing strings. The whiskers are several arcseconds long but often less than 01 wide, with some having length-to-width ratios exceeding 100. They are also remarkably uniform in brightness. We observe excess UV light several arcseconds northwest of the central star in the vicinity of a recent burst of radio emission. This "blue glow" appears to emanate from the equatorial region between the bipolar lobes. Though we cannot confirm temporal variability of this excess light, it may be connected with a burst of ultraviolet radiation that escaped the central region and ionized gas in this direction, perhaps generating radio-wavelength hydrogen recombination line emission. The near-ultraviolet glow in our images may be produced by fluorescent Fe II emission lines in the bandpass of the F336W filter, as seen in our recent HST Goddard High Resolution Spectrograph observations of this region.