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The Uttar Pradesh State Observatory --- some recollections and some history (1954-1982)
An attempt is made to present a picture of pre-historic and initialformative years of the well known Uttar Pradesh State Observatory,Nainital. The development of academic activities along withinfrastructure are described. The emphasis on the frontline researchwork, self-reliance and international interaction was given during theformative years of the observatory. The largest telescope 104-cm of theobservatory was installed in 1972 and has produced good scientificresults.
| The Perkins catalog of revised MK types for the cooler stars
A catalog is presented listing the spectral types of the G, K, M, and Sstars that have been classified at the Perkins Observatory in therevised MK system. Extensive comparisons have been made to ensureconsistency between the MK spectral types of stars in the Northern andSouthern Hemispheres. Different classification spectrograms have beengradually improved in spite of some inherent limitations. In thecatalog, the full subclasses used are the following: G0, G5, G8, K0, K1,K2, K3, K4, K5, M0, M1, M2, M3, M4, M5, M6, M7, and M8. Theirregularities are the price paid for keeping the general scheme of theoriginal Henry Draper classification.
| The Second Ringer
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| 1985 revised MK spectral standards : stars GO and later
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| Revised MK Spectral Standard Stars Later than G0
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| Revised MK spectral types for G, K, and M stars
A catalog of spectral types of 552 G, K, and M stars is presented, whichis classified on the revised MK system. Stellar representatives of thehalo, disk, and arm populations in all parts of the sky are included.Photoelectric V magnitudes are given, as are intensity estimates of anyfeatures which make the spectrum appear peculiar as compared to thespectrum of a similar normal star. Abundance indices are also providedin the following lines or bands: CN, barium, Fe, calcium, and CH.
| The radius and ellipticity of Uranus from its occultation of SAO 158687
From occultation timings obtained from the Kuiper Airborne Observatoryand from Cape Town for Mar. 10, 1977 occultation of SAO 158687 byUranus, the equatorial radius, Re, of the planet has been determined tobe 26,228 + or - 30 km and its ellipticity epsilon = 1 - Rp/Re = 0.033 +or - 0.007. These values refer to the 1.0 x 10 to the 14th/cu cmnumber-density level, under the assumption that the upper atmosphere iscomposed of H2 and He with a mean molecular weight mu = 2.20. Thedominant source of uncertainty is the position of the center of the ringsystem, which was used to define the center of Uranus in our analysis. Arotation rate of 12.8 + or - 1.7 hours for the planet is implied by ourvalue for the ellipticity, under the assumption that Uranus is inhydrostatic equilibrium below the 1.0 x 10 to the 14th/cu cm numberdensity level.
| The upper atmosphere of Uranus - Mean temperature and temperature variations
The number-density, pressure, and temperature profiles of the Uranianatmosphere in the pressure interval from 0.3 to 30 dynes/sq cm arederived from observations of the occultation of SAO 158687 by Uranus on1977 March 10, observations made from the Kuiper Airborne Observatoryand the Cape Town station of the South African Astronomical Observatory.The mean temperature is found to be about 95 K, but peak-to-peakvariations from 10 K to 20 K or more exist on a scale of 150 km or 3scale heights. The existence of a thermal inversion is established, butthe inversion is much weaker than the analogous inversion on Neptune.The mean temperature can be explained by solar heating in the 3.3 micronmethane band with a methane mixing ratio of 4 x 10 to the -6th combinedwith the cooling effect of ethane with a mixing ratio of not greaterthan 4 x 10 to the -6th. The temperature variations are probably due toa photochemical process that has formed a Chapman layer.
| Evidence of an increase in the microwave brightness temperature of Uranus
Measurements are reported which indicate that the microwave brightnesstemperature of Uranus near 3 cm wavelength has increased by about 35% inthe past decade. It is suggested that changes of this magnitude could becaused by seasonal or latitudinal variations of the microwave opacity ofthe Uranus atmosphere. The data appear to be inconsistent with models ofsynchrotron emission from a trapped radiation belt.
| The occultation of BD -15 deg 3969 by the rings of Uranus
Photoelectric observations of the December 23, 1977, occultation of BD-15 deg 3969 by the rings of Uranus are analyzed. The observations weremade with a 1.5-m IR flux collector and clearly show the occultations ofthe star by the epsilon, delta, gamma, and alpha rings prior to thestar's disappearance behind the planet. Detection of the beta-ringoccultation is uncertain, but several features were observed which maybe due to occultations of the star by objects other than the five majorrings. It is noted that no other occultations with both a duration anddepth comparable to the epsilon-ring event were observed between theorbit of Miranda and the limb of Uranus. The results suggest that theepsilon ring does not consist of two fragments but rather is a completering which may be either circular and inclined slightly with respect tothe four inner rings or coplanar and elliptical.
| The radii of Uranian rings alpha, beta, gamma, delta, epsilon, eta, 4, 5, and 6 from their occultations of SAO 158687
All available timing data for the occultations of SAO 158687 on March10, 1977, by the cited rings of Uranus are analyzed. Least-squares fitsto the data are performed using a model which postulates that ringsalpha, beta, gamma, and delta are circular and coplanar. A solutionobtained under the assumption that the ring plane coincides with theplane of the satellite orbits is adopted which yields radii of 44,844 kmfor ring alpha, 45,799 km for ring beta, 47,746 km for ring gamma, and48,423 km for ring delta. The uncertainties in these values arediscussed along with the apparent shapes and inclinations of these mainrings. The mean radii estimated for the other rings are: 47,323 km forring eta, 42,663 km for ring 4, 42,360 km for ring 5, and 41,980 km forring 6.
| Predicted occultations by the rings of Uranus, 1977-1980
Predictions are made for 12 occultations by the rings of Uranus duringthe 1978, 1979, and 1980 opposition periods. Circumstances of theoccultations are determined for various locations, and the photographicmagnitudes of the occulted stars are found to be within a 12.2 to 15.5range.
| Discovering the rings of Uranus
The article describes the discovery of a system of five thin faint ringsaround Uranus during photoelectric observations of the planet'soccultation of the ninth-magnitude star SAO 158687 from NASA's KuiperAirborne Observatory. Events leading to the unexpected discovery arereviewed, the airborne observations are recounted, and excerpts from atape recording of the conversation aboard the Observatory are providedalong with pre- and post-occultation light curves. Simultaneousobservations from Perth Observatory in Australia are also discussed. Itis noted that five different groups at four observatories have thus farreported occultations of SAO 158687 by the rings, which are allextremely narrow.
| A new satellite of Uranus
During the observation of the occultation of the star SAO 158687 byUranus on March 10, 1977, there occurred an unexpected event whichsuggests the existence of a hitherto unknown satellite of the planet. Onthe basis of a model of the occultation geometry, it is found that theestimated diameter of the body will be around 70 km. The visualmagnitude of the satellite is estimated to be about 19. The light curveobtained during the occultation of SAO 158687 by Uranus is shown in agraph.
| Detection of rings around Uranus
A description is presented of partial occultations of SAO 158687 by aseries of rings around the planet Uranus. A 61-cm telescope at PerthObservatory in Western Australia was used in the investigations.Measurements were made using a conventional single-channel photometerequipped with an RCA C31034B photomultiplier. Uranus was centered in a28-arc sec diameter aperture during the observations. An occultation ofSAO 158687 by Uranus itself did not occur at Perth. However, five briefpartial occultations of SAO 158687 were detected with the chartrecorder. The midtimes, durations, and depths of these events are listedin a table.
| The rings of Uranus
A description is given of the observation of five brief occultations ofthe star SAO 158687 which occurred both before and after its occultationby Uranus on March 10, 1977. The events were observed with athree-channel occultation photometer, attached to a 91-cm telescope. Theobservations indicate that at least five rings encircle the planetUranus. Possible reasons for the narrowness of the Uranus rings arediscussed.
| Uranus occults SAO158687
Experience gained in obtaining atmospheric parameters, oblatenesses, anddiameters of Jupiter and Mars from recent stellar occultations by theseplanets is used to predict what can be learned from the March 1977occultation of the star SAO158687 by Uranus. The spectra of this starand Uranus are compared to indicate the relative instrument intensitiesof the two objects, the four passbands where the relative intensitiesare most nearly equal are listed, and expected photon fluxes from thestar are computed on the assumption that it has UBVRI colors appropriatefor a K5 main-sequence object. It is shown that low photon noise errorscan be achieved by choosing appropriate passbands for observation, andthe rms error expected for the Uranus temperature profiles obtained fromthe occultation light curves is calculated. It is suggested thatobservers of this occultation should record their data digitally foroptimum time resolution.
| Coming occultations by Uranus'rings.
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