HD169142's dusty environment

Few circumstellar disks have been directly observed. We have used sensitive differential polarimetric techniques to overcome atmospheric speckle noise in order to image the circumstellar material around HD 169142. The detected envelope or disk is considerably smaller than expectations based on the measured strength of the far-IR excess from this system.

Progress toward understanding the evolution of disk-like stellar systems will be greatly aided by improved techniques and new imaging measurements of candidate objects. Photometry from the UV-to-far IR of several likely unevolved stars show spectral evidence of circumstellar material (cf. Malfait et al. 1998). The problem of how these will evolve toward planetary systems is of great interest, but we are far from understanding the general conditions which lead to planet formation from premainsequence objects. With more than 50 planetary systems detected (Marcy and Butler, 2000) it is the observational clues to the premainsequence systems which are particularly scarce -- only a few resolved observations of circumstellar disk systems exist.

The data below shows the faint circumstellar envelop around HD169142. The relatively small angular extent of this disk-like cloud has been measured without high-order adaptive optics. Its detection here demonstrates the utility of dual-beam imaging IR polarimetry for overcoming atmospheric speckle noise and for achieving high photometric dynamic range in the angular vicinity of bright sources.

 

This figure shows the dusty environment around the star designated HD169142. The star lies at the center and the cloud of dust extends several hundred astronomical units (the average Earth-Sun distance) from the star. Resolved dust clouds have been detected in only a handful of stars beyond the Sun