Kuiper belts around nearby stars

Abstract

Context. The existence of dusty debris disks around a large fraction of solar type main-sequence stars, inferred from excess far-IR and submillimetre emission compared to that expected from stellar photospheres, suggests that leftover planetesimal belts analogous to the asteroid-and comet reservoirs of the solar system are common. Aims. Sensitive submillimetre observations are essential to detect and characterise cold extended dust originating from collisions of small bodies in disks, belts, or rings at Kuiper-belt distances (30-50 AU or beyond). Measurements of the flux densities at these wavelengths will extend existing IR photometry and permit more detailed modelling of the Rayleigh-Jeans tail of the disks spectral energy distribution (SED), effectively constraining dust properties and disk extensions. By observing stars spanning from a few up to several hundred Myr, the evolution of debris disks during crucial phases of planet formation can be studied. Methods. We observed 22 exo-Kuiper-belt candidates at 870 μm, as part of a large programme with the LABOCA bolometer at the APEX telescope. Dust masses (or upper limits) were calculated from integrated 870 μm fluxes, and fits to the SED of detected sources revealed the fractional dust luminosities f dust , dust temperatures T dust , and power-law exponents β of the opacity law. Results. A total of 10 detections with at least 3σ significance were made, out of which five (HD 95086, HD 131835, HD 161868, HD 170773, and HD 207129) have previously never been detected at submillimetre wavelengths. Three additional sources are marginally detected with >2.5σ significance. The best-fit β parameters all lie between 0.1 and 0.8, in agreement with previous results indicating the presence of significantly larger grains than those in the ISM. From our relatively small sample we estimate f dust ∝ t −α , with α ∼ 0.8−2.0, and identify an evolution of the characteristic radial dust distance R dust that is consistent with the t 1/3 increase predicted from models of self-stirred collisions in debris disks.

Resolved Co Gas Interior to the Dust Rings of the Hd 141569 Disk

“…Using the MIRIAD task uvfit we fit a Gaussian to the short baseline 870 μm visibilities and measure a total flux of 8.2×10 −3 Jy ( Table 1). Previous single-dish measurements of the continuum measure fluxes of 10.9 ± 1.3 mJy at 850 μm (Sandell et al 2011) and 12.6 ± 4.6 mJy at 870 μm (Nilsson et al 2010). Our 870 μm continnum flux of 8.2 ± 2.4 mJy is consistent with, although slightly smaller than, these measurements likely due to missing short-baseline flux.…”

“…In debris disks the dust temperature at a given radius is often found to be higher than that for blackbody grains, or conversely the observed radial location of the dust grains is larger than predicted for blackbody grains (Booth et al 2013). Previous models of dust emission from the HD 141569 system (Li & Lunine 2003;Nilsson et al 2010) find typical dust temperatures of 50-200 K in the outer disk, higher than our estimated blackbody temperature of 51 K, consistent with the presence of small dust grains.…”

Scope for a small circumsolar annular gravitational contribution to the Pioneer anomaly without affecting planetary orbits

“…In this respect the statement, quoted in Sect. 5, concerning the far sector of a Kuiper belt model where infrared measurements place "no real IR limit on sector mass" (Teplitz et al 1999) appears significant, and in relation to exo-Kuiper belt dust mass estimation, submillimeter thermal radiation gives "just a lower limit" (Nilsson et al 2010).…”

“…High values for mass in the Kuiper belt region of the present day, compared to the fractions of 0.1 M ⊕ found by studying precessional data for Mercury, Venus, Earth and Mars (Iorio 2007c), could only be gravitationally sustainable if the Kuiper belt formed a part of a greater annulus making near zero radial gravitation in the inner planetary region. But this is less of a constraint if the mass is located much further away in a belt extending to hundreds of AU, like the exo-Kuiper belts beginning to be observed around other Sun-like stars (Nilsson et al 2010;Marshall et al 2011;Donaldson et al 2012).…”

“…Quite separately, during the last decade, the evidence for the abundance of exoplanets and circumstellar disks containing gaps and rings gradually became very prominent, helping to place our Solar System into its evolutionary context (Meyer et al 2007;Moro-Martin et al 2008;Weinberger 2008;Moro-Martin 2013). Extensive exoKuiper belts around Sun-like stars are also being seen (Nilsson et al 2010;Marshall et al 2011;Donaldson et al 2012) and modeled in preparation for further observations (Ertel et al 2012). This perhaps suggests the importance today of looking more deeply into the physical possibilities lying beneath one particular stone, which we believe was first lifted in relation to the Pioneer anomaly, by de Diego et al (2006).…”