Photoelectric magnitudes and color of Uranus.

Abstract

view Abstract Citations References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Photoelectric magnitudes and color of Uranus. Giclas, H. L. Abstract The brightness of Uranus was observed photoelectrically in three colors on 46 nights during the oppositions of 1950, 1951, and 1952 with a conventional I P2 I photomultiplier photometer attached to the Cassegrain focus of the Lowell 42- inch reflector. The approximate effective wave lengths for each color is 3750 A for the violet; 4550 A blue, and 5250 A for the yellow. Two color indices, yellow-blue and yellow-violet, and a yellow magnitude were derived from the mean of each night of observation. The probable error of a single night's observation of the magnitude is ~O.0045 mag.; for the yellow-blue index the probable error is about half this amount; for the yellow-violet index the probable error is four times that of yellow-blue index. Measurements were made in wave lengths stated above, but conversion to the system of Johnson and Morgan has been derived.1 All magnitudes were reduced to the mean opposition distance for 1950. The individual determinations of the magnitude for each single night's run were investigated for possible short-period variations which might be correlated with the planet's rotation period, but nothing which might be ascribed to this cause was found. The nightly mean magnitude was plotted against the phase angle, but no clear cut relationship was indicated. The mean opposition brightness and color on the Johnson- Morgan system are listed in the following table. SUMMARY OF OPPOSITION MAGNITUDES Year U-V B-V V 1950 0.829 0.546 5.441 1951 0.807 0.547 5.433 1952 0.788 0.535 5.452 It is found from these observations that the real Variation in brightness of Uranus, if any, over the whole period observed is restricted to less than 0.01 mag. The much larger variations reported by other observers during this period are not confirmed. We also find less than o.o8 mag. difference in mean brightness of Uranus now as compared to the value obtained photoelectrically by Stebbins in 1927.2 These measures of Uranus' brightness have been compared to the values of the solar constant measured concurrently, but no correlation between the small fluctuations in each is found. The same is also true of comparison with magnetic observations of sunspots. I.A~. J. 117, 313, 1953. 2.Lick Obs. Bull. `3, 180, 2927. Lowell Observatory, Flagstaff, Ariz. Publication: The Astronomical Journal Pub Date: December 1953 DOI: 10.1086/106859 Bibcode: 1953AJ.....58..215G full text sources ADS |