INTERSTELLAR DUST PROBES

Targets:

Several dozen stars scattered along the Milky Way

Several stars in the Large Magellanic Cloud

We now appreciate that stars are born, grow old and die. Stars are born in regions of space where the interstellar medium, mostly gas and dust, has a higher density. The dust, in particular, has a fundamental role during star formation, in trapping and then radiating away the heat generated when a forming star contracts. During a star's late stages of evolution, it loses part of its mass back to the interstellar medium, either as a wind of gas or flow of solid particles.

With the targets selected for this program, we aim to study the interstellar dust in both our Galaxy and the next nearest galaxy to us. These targets will act as sources of light upon which the dust imprints its signature, specifically in the polarization that such light then acquires. The WUPPE observations are the most extensive set of UV polarimetry in existence.

The existing interstellar polarization data is limited to the optical and, for some stars, to the near-infrared spectral regions (except for a few observations made with the Space Telescope before installation of COSTAR to correct the focus problem). WUPPE data will be invaluable in providing information about the behavior of the polarization with wavelength in the ultraviolet. Also, it is known from the interstellar extinction studies that the dust shows an absorption feature at 2175Å, in the wavelengths which are encompassed by WUPPE. UV observations have great potential in providing further clues to the nature of the interstellar dust and the cause of the 2175Å absorption over what is provided by observations in visible light and IR.
And understanding of the behavior of interstellar polarization provided by WUPPE observations should also help us remove the effects of interstellar polarization from observations of objects which are intrinsically polarized.