A Dust Ring around ε Eridani: Analog to the Young Solar System

Abstract

Dust emission around the nearby star ǫ Eridani has been imaged using a new submillimetre camera (SCUBA at the JCMT). At 850 µm wavelength a ring of dust is seen, peaking at 60 AU from the star and with much lower emission inside 30 AU. The mass of the ring is at least ∼ 0.01 M ⊕ in dust, while an upper limit of 0.4 M ⊕ in molecular gas is imposed by CO observations. The total mass is comparable to the estimated amount of material, 0.04-0.3 M ⊕ , in comets orbiting the Solar System.The most probable origin of the the ring structure is that it is a young analogue to the Kuiper Belt in our Solar System, and that the central region has been partially cleared by the formation of grains into planetesimals. Dust clearing around ǫ Eri is seen within the radius of Neptune's orbit, and the peak emission at 35-75 AU lies within the estimated Kuiper Belt zone of 30-100 AU radius. ǫ Eri is a main-sequence star of type K2V (0.8 M ⊙ ) with an estimated age of 0.5-1.0 Gyr, so this interpretation is consistent with the early history of the Solar System where heavy bombardment occurred up to ≈ 0.6 Gyr. An unexpected discovery is substructure within the ring, and these asymmetries could be due to perturbations by planets.

Orbital migration and the frequency of giant planet formation

“…The latter conclusion is robust so long as the distribution of observed system inclinations as seen from Earth is roughly random; that is, as long as the measured M p sin i yields actual masses on average less than a factor of two larger. To date, five systems with known inclinations (HD 209458, 55 Cnc, HD 210277, ρ CrB, and Eri) all have i > ∼ 30 degrees and thus have mass factors less than 2 (Charbonneau et al 2000;Henry et al 2000;Trilling & Brown 1998;Trilling et al 2000;Greaves et al 1998). Additionally, by tidal arguments, υ And, HD 75289, HD 187123, 51 Peg, and HD 217107 are all constrained to have i > ∼ 30 degrees as well, although there are no direct observations as yet to confirm this (Trilling 2000); the Hipparcos data implies an inclination ∼25 degrees for υ And (Mazeh et al 1999).…”

Search for cold debris disks around M-dwarfs

“…Dust masses of debris disks around A-to K-type main sequence stars. Note that HD 34700 and HD 39944 previously classified as debris disks have been rejected; HD 34700 is a T Tauri (Sterzik et al 2005) and has gas emission and HD 39944 was confused with a background galaxy (Moór et al 2006 Greaves et al (2004); b Greaves et al (1998); c Liu et al (2004); d Najita & Williams (2005); e Zuckerman et al (1993); f Sheret et al (2004); h Wyatt et al (2003); i Williams et al (2004); j Holmes et al (2003); k Sylvester et al (1996); l Wilner et al (2003); m Wyatt et al (2005). Liu 2004;Krist et al 2005) that found the size ∼200 AU smaller than the one for GJ 842.2 while these two stars have the same spectral type but one is twenty times younger.…”

Visions of Nature's Planet Foundry: Images of Circumstellar Disks

“…Each panel is labeled with the object name, wavelength, and the size of the image field of view. From left to right in each row, the image sources are references top: (13), (3), (33); center: (23), (15), (14); and bottom: (35), (4), (4).…”

“…They have also been imaged in debris disks; however, it is not known if the central dust clearing in these cases has been accomplished by dynamical or radiative processes. Several debris disks have noteworthy radial structure: HR 4796, f Eri, and Fomalhaut have been resolved as relatively narrow rings (39,14,8), while HD 141569 has a prominent radial gap (39). Radial density gradients have proven difficult to infer in optically thick young disks.…”