EDP Sciences
Free access
Volume 493, Number 1, January I 2009
Page(s) 299 - 308
Section Planets and planetary systems
DOI http://dx.doi.org/10.1051/0004-6361:200810706
Published online 06 November 2008

A&A 493, 299-308 (2009)
DOI: 10.1051/0004-6361:200810706

Resolved debris disc emission around $\eta$ Telescopii: a young solar system or ongoing planet formation?

R. Smith1, L. J. Churcher1, M. C. Wyatt1, M. M. Moerchen2, 3, and C. M. Telesco2

1  Institute of Astronomy (IoA), University of Cambridge, Madingley Road, Cambridge, CB3 0HA, UK
    e-mail: rsed@ast.cam.ac.uk
2  Department of Astronomy, University of Florida, 211 Bryant Space Science Center, PO Box 112055, Gainesville, FL, 32611-2055, USA
3  European Southern Observatory, Alonso de Cordova 3107, Casilla 19001, Vitacura, Santiago 19, Chile

Received 29 July 2008 / Accepted 30 October 2008

Aims. Sixty percent of the A star members of the 12 Myr old $\beta$ Pictoris moving group (BPMG) show significant excess emission in the mid-infrared, several million years after the proto-planetary disc is thought to disperse. Theoretical models suggest this peak may coincide with the formation of Pluto-sized planetesimals in the disc, stirring smaller bodies into collisional destruction. Here we present resolved mid-infrared imaging of the disc of $\eta$ Tel (A0V in the BPMG) and consider its implications for the state of planet formation in this system.
Methods. The source was observed at 11.7 and 18.3 $\mu$m using T-ReCS on Gemini South. The resulting images were compared to simple disc models to constrain the radial distribution of the emitting material.
Results. The emission observed at 18.3 $\mu$m is shown to be significantly extended beyond the PSF along a position angle 8°. This is the first time dust emission has been resolved around $\eta$ Tel. Modelling indicates that the extension arises from an edge-on disc of radius 0.5 arcsec (~24 AU). Combining the spatial constraints from the imaging with those from the spectral energy distribution shows that >50% of the 18 $\mu$m emission comes from an unresolved dust component at ~4 AU.
Conclusions. The radial structure of the $\eta$ Tel debris disc is reminiscent of the Solar System, suggesting that this is a young Solar System analogue. For an age of 12 Myr, both the radius and dust level of the extended cooler component are consistent with self-stirring models for a protoplanetary disc of 0.7 times minimum mass solar nebula. The origin of the hot dust component may arise in an asteroid belt undergoing collisional destruction or in massive collisions in ongoing terrestrial planet formation.

Key words: circumstellar matter -- infrared: stars -- planetary systems -- stars: individual: $\eta$ Telescopii

© ESO 2008