ITAL]Hubble[/ITAL] [ITAL]Space[/ITAL] [ITAL]T[/ITAL][ITAL]elescope[/ITAL] Imaging of the Mass-losing Supergiant VY Canis Majoris

Abstract

The highly luminous M supergiant VY CMa is a massive that appears to be in its final death throes, losing mass at high rate en route to exploding as a supernova. Subarcsecond-resolution optical images of VY CMa, obtained with the Faint Object Camera (FOC) aboard the Hubble Space Telescope, vividly demonstrate that mass loss from VY CMa is highly anisotropic. In the FOC images, the optical star VY CMa constitutes the bright, well-resolved core of an elongated reflection nebula. The imaged nebula is ~3'' (~4500 AU) in extent and is clumpy and highly asymmetric. The images indicate that the bright core, which lies near one edge of the nebula, is pure scattered starlight. We conclude that at optical wavelengths VY CMa is obscured from view along our line of sight by its own dusty envelope. The presence of the extended reflection nebula then suggests that this envelope is highly flattened and/or that the is surrounded by a massive circumstellar disk. Such axisymmetric circumstellar density structure should have profound effects on post–red supergiant mass loss from VY CMa and, ultimately, on the shaping of the remnant of the supernova that will terminate its post–main-sequence evolution.