50 Million Stars Per Night
50 MU as resolution VLBI images of AGN's at lambda 3 mm
50 TeV HEGRA Sources and Infrared Radiation
500 K and Below - Finding Ultracool Dwarfs with the UKIRT/WFCAM and VISTA surveys
500-3200 A observations of the interacting binary stars V356 SGR and Beta LYR
51 Eri and GJ 3305: A 10-15 Myr old binary star system at 30 parsecs
51 Ophiuchus: A Possible Beta Pictoris Analog Measured with the Keck Interferometer Nuller
51 Pegasi - a planet-bearing Maunder minimum candidate
51.8 micron forbidden O III line emission observed in four galatic H II regions
511 keV line and diffuse gamma rays from moduli
511 keV line from millisecond pulsars in the Galactic center
511 keV line from Q balls in the Galactic Center
511 KeV photons from superconducting cosmic strings
53 Cam and the question of a preferred phase relation between the light and magnetic variations of the magnetic stars.
53 Persei: a slowly pulsating B star
53 PISCIUM - Peculiar amplitude modulation or transient variability?
53 Piscium, a confirmed Beta CMa variable star
531 new spectroscopic redshifts from the CDFS and a test on the cosmological relevance of the GOODS-South field
54 Cam - A new variable star
55 Cancri: A Coplanar Planetary System that is Likely Misaligned with its Star