Understanding Spatial and Spectral Morphologies of Ultracompact H II Regions
Understanding the effects of geometry and rotation on pulsar intensity profiles
Understanding the Geometry of Astrophysical Magnetic Fields
Understanding the H2/HI Ratio in Galaxies
Understanding the physics of the X-factor
Understanding the spiral structure of the Milky Way using the local kinematic groups
Unexpected Formation Modes of the First Hard Binary in Core Collapse
Unidentified Features in the Ultraviolet Spectrum of X Per
Unification of Luminous Type 1 Quasars through CIV Emission
Unification of Radio Galaxies and Their Accretion/Jet Properties
Uniform detection of the pre-main sequence population in the 5 embedded clusters related to the H\,II region NGC\,2174 (Sh2-252)
Unifying boxy bulge and planar long bar in the Milky Way
Universal Nonlinear Small-Scale Dynamo
Universal Scaling Function of Velocity Rotation in Spiral galaxies
Universality of young cluster sequences
Unravelling the origins of S0 galaxies using maximum likelihood analysis of planetary nebulae kinematics
Unresolved X-ray emission in M31 and constraints on progenitors of Classical Novae
Unstable $m=1$ modes of counter-rotating Keplerian discs
Unveiling Extragalactic Star Formation Using Radio Recombination Lines: An EVLA Pilot Study with NGC 253
Unveiling hidden properties of young star clusters: differential reddening, star-formation spread and binary fraction