Direct Measurement of the Size of the Large Kuiper Belt Object (50000) Quaoar

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© 2004. The American Astronomical Society. All rights reserved. Printed in U.S.A.
, , Citation Michael E. Brown and Chadwick A. Trujillo 2004 AJ 127 2413 DOI 10.1086/382513

1538-3881/127/4/2413

Abstract

We imaged the recently discovered bright Kuiper belt object (50000) Quaoar with the Hubble Space Telescope High Resolution Camera to directly determine its size. The point-spread function (PSF) of each of 16 images was carefully measured from a field star 13'' from Quaoar, and the expected PSF at the location of Quaoar was convolved with Quaoar's motion vector and a model resolved disk. A least-squares analysis was performed to find the best-fit disk size. The apparent diameter of Quaoar was resolved as 40.4 ± 1.8 milliarcseconds. Accounting for the uncertainty due to an unknown limb-darkening function, the size of Quaoar is 1260 ± 190 km with red and blue albedos of 0.092 and 0.101, respectively. These albedos are significantly higher than the canonically assumed value of 4%. Quaoar is the largest currently known minor planet.

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10.1086/382513