Volume 520, September-October 2010
|Number of page(s)||18|
|Section||Planets and planetary systems|
|Published online||24 September 2010|
The Edgeworth-Kuiper debris disk
Astrophysikalisches Institut, Friedrich-Schiller-Universität Jena,
Schillergäßchen 2–3, 07745 Jena, Germany e-mail: email@example.com
Accepted: 8 June 2010
The Edgeworth-Kuiper belt (EKB) and its presumed dusty debris is a natural reference for extrsolar debris disks. We re-analyze the current database of known transneptunian objects (TNOs) and employ a new algorithm to eliminate the inclination and the distance selection effects in the known TNO populations to derive expected parameters of the “true” EKB. Its estimated mass is MEKB = 0.12 , which is by a factor of ~15 larger than the mass of the EKB objects detected so far. About a half of the total EKB mass is in classical and resonant objects and another half is in scattered ones. Treating the debiased populations of EKB objects as dust parent bodies, we then “generate” their dust disk with our collisional code. Apart from accurate handling of destructive and cratering collisions and direct radiation pressure, we include the Poynting-Robertson (P-R) drag. The latter is known to be unimportant for debris disks around other stars detected so far, but cannot be ignored for the EKB dust disk because of its much lower optical depth. We find the radial profile of the normal optical depth to peak at the inner edge of the classical belt, ≈40 AU. Outside the classical EKB, it approximately follows τ r-2 which is roughly intermediate between the slope predicted analytically for collision-dominated (r-1.5) and transport-dominated (r-2.5) disks. The size distribution of dust is less affected by the P-R effect. The cross section-dominating grain size still lies just above the blowout size (~ 1 2μm), as it would if the P-R effect was ignored. However, if the EKB were by one order of magnitude less massive, its dust disk would have distinctly different properties. The optical depth profile would fall off as τ r-3, and the cross section-dominating grain size would shift from ~ 1 2μm to ~ 100μm. These properties are seen if dust is assumed to be generated only by known TNOs without applying the debiasing algorithm. An upper limit of the in-plane optical depth of the EKB dust set by our model is τ = 2 × 10-5 outside 30 AU. If the solar system were observed from outside, the thermal emission flux from the EKB dust would be about two orders of magnitude lower than for solar-type stars with the brightest known infrared excesses observed from the same distance. Herschel and other new-generation facilities should reveal extrasolar debris disks nearly as tenuous as the EKB disk. We estimate that the Herschel/PACS instrument should be able to detect disks at a ~ 1 2MEKB level.
Key words: Kuiper belt: general / methods: statistical / methods: numerical / planetary systems / circumstellar matter / infrared: planetary systems
© ESO, 2010
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