Abstract
Noctilucent Clouds (NLCs) are tenuous ice clouds that form near the extremely cold (<150K) mesopause region (80-85 km) during the summer months at high-latitudes. NLC are seen during twilight hours when the sun is 6-16┬↓ below the horizon so the clouds are still illuminated while the observer is in darkness. Observations by the Solar Backscatter Ultraviolet (SBUV) instruments on the NOAA satellites have shown that the occurrence and brightness of NLCs have been increasing prompting serious speculation concerning their possible role in climate change. The Aeronomy of Ice in the Mesosphere (AIM) satellite, launched April 2007, has given us new quantitative measurements of the clouds from above extending over the polar cap region. Here we present the first detailed comparison of satellite and ground-based optical measurements of these tenuous clouds using SBUV and AIM observations with two-station optical image measurements collected during campaigns in Canada and Alaska during summer 2007.

Partial Covering of the Broad Emission Line Region by an Fe I-rich Intervening Weak Mg II Absorber

Abstract
Four Mg II clouds (with Mg II 2796 equivalent width of 0.14&Aring;) have been detected along the line of sight of quasar HE0001-2340 at z=0.4523. Three of these clouds display properties that are normal for Mg II absorbers; however, the fourth cloud is extremely unusual. It contains Fe I, which is not known to exist in other extragalactic absorbers, as well as Mn II, Ca I, and Ca II. Its Mg II absorption line profile is also indicative of partial covering of the quasar's broad emission line region, with a covering factor of 0.6, implying an extremely small cloud size. We explore Cloudy photoionization models for two possibilities: a cloud with a covering factor of 0.6, and one of 1.0 (full coverage). We conclude that the only way to produce the Fe I observed in the system is by using the model with partial coverage, and show that such models produce a small cloud size, as consistent with this theory. No other published absorption line system is known to partially cover the quasar, except for those covering a gravitational lens. We theorize that such small absorbers (0.01 pc< r <1 pc), with very low temperatures, high quantities of molecular hydrogen, and masses similar to that of the sun must be commonplace, and that they are observed so rarely merely because of the selection effect due to their size. Thousands of similar systems, containing similar bare molecular clouds, may be located in the outskirts of galaxies. This system was studied using resolution R=45,000 data UVES/VLT data from the ESO archive, and research was supported by the National Science Foundation under Grant AST-07138 and by the REU Supplement Program.

A Study of Differential Rotation on II Pegasi Using Starspot Imaging

Abstract
II Pegasi is an RS CVn binary star system consisting of a main-sequence star and a K2IV subgiant, which are tidally locked with a 6.724333-day period. The subgiant is known to exhibit large dark starspots on its surface. Starspots are thought to represent regions of strong magnetic field, which suppress convection causing the region to be cooler and thus darker than the surrounding stellar surface. The brightness of the star varies as the star's rotation carries the spots into and out of view of Earth. In this study B- and V- filter light curves obtained from 1987-2007 via the Vanderbilt/Tennessee State 0.4-m automated Photometric Telescope were inverted to produce images of the starspots to look for evidence of latitude-dependent differential rotation. The surface maps presented here exhibit evolution of the starspots over time and provide convincing evidence that the star's equatorial regions rotate faster than higher latitudes.