T Tauri and its Infrared Companion

T Tau observed at a wavelength of 10 µm (µm = microns, in the infrared), from Koerner, Jensen, Mathieu, and Ghez 1998. Taken at Palomar Observatory with the MIRLIN infrared camera.	T Tau at 0.55 µm (visible light, Hubble Space Telescope image), from Stapelfeldt et al. 1998, at the same scale as the 10 µm image. The spikes to the northeast and southwest are artifacts from the bright star, not real structure.

T Tauri is a young star (about a million years old) with a binary companion. Unlike most binary companions (which accompany more than 60% of all stars), the companion to T Tauri is not visible at optical wavelengths (right hand panel) while it dominates the light of the system at infrared wavelengths (left hand panel).

Because the infrared companion is so bright at infrared wavelengths, it was assumed until recently that it harbored most of the dust (potentially planet-forming material) in the system. However, our recent work has shown that in fact the northern (optically-visible) star has a substantial protoplanetary disk, while the infrared companion has much less disk material:

Image of T Tauri at a wavelength of 3 millimeters, where the circumstellar dust emission can clearly be seen. Image from Akeson, Koerner, and Jensen (1998), from the BIMA millimeter array. For more information, get a copy of the paper, published Sept. 20, 1998 in the Astrophysical Journal.

The fact that T Tau South does not have a substantial protoplanetary disk around further deepens the mystery of why it is invisible at optical wavelengths. It may be behind the outer edge of the T Tau North disk; disk material which is too faint to be seen in the BIMA image above could still block enough visible light to hide T Tau South. Alternatively, there may be an envelope of gas and dust enshrouding the entire T Tau N/S system, with a hole in it toward T Tau N so that it is easily seen in visible light. Evidence for such a cavity can be seen in the Hubble Space Telescope images of Stapelfeldt et al. (1998).

This work was supported by grant AST-9996278 from the National Science Foundation. Any opinions, findings and conclusions, or recommendations expressed in this material are those of the author and do not necessarily reflect the views of the National Science Foundation (NSF).

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