Observational Astronomy

A Holographic Quantum Theory of Spacetime

The theory called Holographic Space-time is an attempt to generalize String Theory so that one can discuss local regions of space-time. It's key feature is a mapping between quantum concepts and the geometry of space-time. Causality conditions are imposed, as in quantum field theory, by insisting that things which cannot have mutual quantum interference are things that are causally separated. Geometrical sizes are encoded via the Holographic Principle: the number of quantum states in a region is determined by the area of a certain surface surrounding that region.

Brown Dwarf Variability and implications for Exoplanets

Brown dwarfs are sub-stellar objects that occupy the region of parameter space between gas giant planets, like Jupiter, and the smallest bona fide stars.  Since brown dwarfs never achieve sustained core hydrogen fusion, they are destined to cool over cosmic timescales from thousands to hundreds of degrees Kelvin.  Observations and models of these strange worlds reveal hydrogen-dominated atmospheres with a variety of trace molecular species, as well as metal, dust, and salt condensates.

Shape dynamics: a relational view of the Universe

Shape Dynamics is a new theory of gravity which removes the notion of local relativistic time from the guiding principles of gravity in the universe. It is a very promising approach which has been shown to be equivalent to Einstein's Theory of General Relativity, without being embedded in time. It is inspired by adherence to Mach's Principle, which is violated by Einstein's theory.
 
Shape Dynamics provides new tools in the quest for a theory that describes quantum gravity.
 

Siding Spring at Mars, 209P/Linear at Earth and other close encounters with comets SETI Talks

Nine days after the event, SETI Institute meteor astronomer Dr. Peter Jenniskens gives an update on what we know so far from the close encounter of comet Siding Spring with Mars on October 19, and the study of meteor showers on Earth, including the shower that was seen during the close passage of comet 209P/Linear by Earth in May.

The Gemini Planet Imager initial performance and data analysis

Gemini Planet Imager schematicThe Gemini Planet Imager (GPI) is a dedicated facility for directly imaging and spectroscopically characterizing extrasolar planets. It combines a very high-order adaptive optics system, a diffraction-suppressing coronagraph, and an integral field spectrograph with low spectral resolution but high spatial resolution. GPI has been tuned for maximum sensitivity to faint planets near bright stars.

Our Galactic Center

milky way galaxy illustrationAbstract: Evidence has been accumulating for several decades that many galaxies harbor central mass concentrations that may be in the form of black holes with masses between a few million to a few billion times the mass of the Sun.

Khayyam: A Tunable Spatial Heterodyne Spectrometer for Broadband Observation of Diffuse Emission Line Targets

Shane telescope at Lick ObservatoryAbstract: Sona Hosseini will report on progress toward development of a tunable spatial heterodyne spectrometer (TSHS) at the fixed focus of the Coudé Auxiliary Telescope (CAT) in the Shane Telescope at Lick Observatory (Khayyam).

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