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We present the measurement of the size and surface brightness of the expanding light echoes from supernova (SN) 2014J in the nearby starburst galaxy M82. Hubble Space Telescope (HST) ACS/WFC images were taken ~277 and ~416 days (after the time of B-band maximum light) in the filters F475W, F606W, and F775W, each combined with the three polarizing filters: POL0V, POL60V, and POL120V. The two epochs' imaging reveals the time evolution of at least two major echoes. Three concentric bright regions between position angles (PA, 0^{\circ} from North, counterclockwise). 80^{\circ} ~ 170^{\circ} have projected radius of 0.60" on the sky on ~277 days and expanding to 0.75" on ~416 days, corresponding to scattering materials at a foreground distance of 222\pm37 pc. Another fainter but evident light echo extending over a wide range of PA has radii of 0.75" and 0.96" on ~277 and ~416 days. This corresponds to scattering material at a foreground distance of 367\pm61 pc. Multiple light echoes with S/N > 2.5 reside at smaller radii on ~277 days but become less significant on ~416 days indicating a complex structure of foreground interstellar medium (ISM). The light echo shows bluer color than predicted under a Rayleigh scattering case. We also found the light echo brightened from V_{echo}=21.68\pm0.07 on 2014 September 5, to V_{echo}=21.05\pm0.08 on 2014 November 6, suggesting an enhancement of echoing materials at different distances projected on to the plane of the sky., This paper has been withdrawn due to inappropriate method of analysis

Blue hook stars are a class of subluminous extreme horizontal branch stars that were discovered in UV images of the massive globular clusters omega Cen and NGC 2808. These stars occupy a region of the HR diagram that is unexplained by canonical stellar evolution theory. Using new theoretical evolutionary and atmospheric models, we have shown that the blue hook stars are very likely the progeny of stars that undergo extensive internal mixing during a late helium-core flash on the white dwarf cooling curve. This "flash mixing" produces hotter-than-normal EHB stars with atmospheres significantly enhanced in helium and carbon. The larger bolometric correction, combined with the decrease in hydrogen opacity, makes these stars appear subluminous in the optical and UV. Flash mixing is more likely to occur in stars born with a high helium abundance, due to their lower mass at the main sequence turnoff. For this reason, the phenomenon is more common in those massive globular clusters that show evidence for secondary populations enhanced in helium. However, a high helium abundance does not, by itself, explain the presence of blue hook stars in massive globular clusters. Here, we present new observational evidence for flash mixing, using recent HST observations. These include UV color-magnitude diagrams of six massive globular clusters and far-UV spectroscopy of hot subdwarfs in one of these clusters (NGC 2808)., Comment: To appear in the Proceedings of the Fifth Meeting on Hot Subdwarf Stars and Related Objects (sdOB5), 25 - 29 July 2011, Stellenbosch, South Africa. ASP Conference Series, 10 pages, 5 figures, LaTeX