April 2015

Saturday, Jan 31–Sunday, May 17
5:00 pm
Astronomical: Photographs of Our Solar System and Beyond

The evolution of photography has been inextricably bound up with the field of astronomy. Since photography's earliest days, it has been used as a tool to advance astronomical observation and thought, yielding some of the most curious and compelling images in the medium's history. Featuring works by a diversity of makers ranging from pioneering scientists to artists and amateurs, this exhibition surveys mankind's ongoing efforts to chart and understand an expanding universe.

Center for Creative Photography Gallery
1030 N. Olive Rd.

Free to the public
Center for Creative Photography Gallery: Room
Monday, Apr 6
4:00 pm — 5:00 pm
TAP Colloquium: Smadar Naoz
Dr. Smadar Naoz
Assistant Professor
University of California, Los Angeles

New insights from triples and implications at different scales

Many gravitational triple systems are in a hierarchical configuration – two objects orbit each other in a relatively tight inner binary while the third object is on a much wider orbit. The secular approximation for the evolution of hierarchical triple configurations has proven to be very useful in many astrophysical contexts, from planetary to triple-star systems. In this approximation the orbits may change shape and orientation, on time-scales longer than the orbital time-scales, but the semi major axes are constant. In early studies of hierarchical secular three-body systems (Kozai 1962;Lidov 1962), the wider orbit was set to be circular and one of the tight binary members is assumed to be a test (massless) particle. In this situation, the component of the tight orbit’s angular momentum along the total angular momentum is conserved, and the lowest order of the approximation (i.e., the quadrupole approximation) is valid. I will discussed recent developments that showed that considering systems beyond the test particle approximation, or circular orbits, requires the next level of approximation for a correct representation of the physics, called the octupole-level, which leads to qualitative different behavior of the system. In this case, the angular momenta component of the tight and wide orbits along the total angular momentum is not conserved. Most interestingly, at the this level of approximation, for an eccentric wide orbit, the tight orbit can reach extremely high
eccentricities and undergo chaotic flips in its orientation. This behavior has important implications to the evolution of triple systems, and I will explore few examples.

TAP Colloquia
Kuiper Space Sciences: Room 312
Tuesday, Apr 7
2:00 pm — 5:00 pm
Final Ph.D. Defense: Catherine M. Elder
Final Defense
Ph.D. in Planetary Sciences

Catherine M. Elder
Department of Planetary Sciences

The Effects of Melt on Impact Craters on Icy Satellites and on the Dynamics of Io's Interior
Kuiper Space Sciences: Room 309
Tuesday, Apr 14
3:45 pm — 5:00 pm
LPL Colloquium: Dr. Catherine Johnson
Dr. Catherine Johnson
University of British Columbia

Mercury's Magnetic Field: Stories from the Planet, Present and Past

Mercury is the only inner solar system body other than Earth to possess an active core dynamo-driven magnetic field, and the only planet with a highly dynamic, small magnetosphere. Measurements made by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft have provided a wealth of data on Mercury's magnetic field environment. Mercury's weak magnetic field was discovered 40 years ago by the Mariner 10 spacecraft; but its large-scale geometry, strength and origin could not be definitively established. MESSENGER data have shown that the field is dynamo-generated and can be described as an offset axisymmetric dipole field: the magnetic equator lies ~0.2 RM (RM = 2440 km) north of the geographic equator and the dipole moment is 0.03% that of Earth's. Re-analysis of the Mariner 10 observations has established that there has been no measurable secular variation in the internal field over 40 years. The spherical harmonic degree power spectra for the field and its secular variation provide critical constraints for viable dynamo models. Induced core fields result from time-varying magnetopause fields and their magnitude confirms the core radius estimated from MESSENGER gravity and Earth-based radar data. Field-aligned currents have been identified, that likely close in the planetary interior at depths below the base of the crust. Recent magnetic field measurements at altitudes below 50 km have the potential to resolve fields of crustal origin, which have not been seen at higher altitudes.
Kuiper Space Sciences: Room 312
Monday, Apr 20
4:00 pm — 5:00 pm
TAP Colloquium: Norbert Wex
TAP Colloquia
Kuiper Space Sciences: Room 312
Tuesday, Apr 21
3:45 pm — 5:00 pm
LPL Colloquium: Dr. Alexander Hayes
Dr. Alexander Hayes
Assistant Professor
Cornell University
Kuiper Space Sciences: Room 312
Monday, Apr 27
4:00 pm — 5:00 pm
TAP Colloquium: Cora Dvorkin
TAP Colloquia
Kuiper Space Sciences: Room 312
Tuesday, Apr 28
3:45 pm — 5:00 pm
LPL Graduate Student Colloquia: Hamish Hay and Shane Stone
Hamish Hay
Graduate Student in the Department of Planetary Sciences

Shane Stone
Graduate Student in the Department of Planetary Sciences
Kuiper Space Sciences: Room 312