Previous | Session 34 | Next
L. T. Smith, B. E. Schaefer (LSU), M. W. Buie (Lowell)
The Pluto-Charon system has complex photometric variations on all time scales; due to rotational modulations of dark markings across the surface, the changing orientation of the system as viewed from Earth, occultations and eclipses between Pluto and Charon, as well as the melting and freezing of frosts on the surface. The earliest reliable light curve for Pluto is from 1954, yet earlier photometry might show a relatively bright Pluto before frosts melted to form Pluto's thin atmosphere around its perihelion. We are reporting on a new accurate light curve of Pluto for 1933. We used 43 excellent quality images of Pluto on 32 plates taken on 15 nights from March 1933 to March 1934. Most of these plates were taken with the Mount Wilson 60" and 100" telescopes, but 7 of the plates (now at the Harvard College Observatory) were taken with the 12" and 16" Metcalf doublets at Oak Ridge. The plates were measured with an iris diaphragm photometer, which has a one-sigma photometric error on these plates ranging from 0.06-0.11 mag as measured by the repeatability of constant comparison stars. We used 17 nearby comparison stars per plate. The modern B and V magnitudes for the comparison stars was measured with the 1.0-m SMARTS telescope at Cerro Tololo. The color terms to convert from the plate's photographic system to the Johnson B system were corrected for even though they are small in size. We will compare our derived light curve with a very detailed model of Pluto's brightness changes.
Previous | Session 34 | Next
Bulletin of the American Astronomical Society, 37 #2
© 2005. The American Astronomical Soceity.