Astrophysics & Planetary Sciences Colloquium

Remote sensing of the universe, including Earth and its atmosphere, largely relies on extracting information from photons/electromagnetic waves. To optimize information extraction, instruments and data analysis have to be looked at as a system. The colloquium will highlight examples of this systems approach to optical instrumentation that I have been involved in over the past few decades.

Hypothesized in the 1960s with the first evidence in the 1990s, the origin, quantity, and distribution of water on the Moon – and other airless bodies – is one of the most exciting questions in planetary sciences. Where did it come from? How much is there? What processes at what rates control the modern day distribution? And where *exactly* is the water? Fine-scale spatial knowledge of distribution is needed so that we can send landed missions to measure and sample for textures, elements, the presence of other volatiles, and isotopes to answer the questions above.

I will discuss NASA's Lucy mission, which is the first reconnaissance of the Jupiter Trojan asteroids. Asteroids are the leftovers from the age of planet formation. But, unlike the planets themselves, they have remained relatively unchanged since they formed. As a result, they hold vital clues to how our Solar System formed and evolved, and thus can be considered the fossils of planet formation. Lucy will visit eight of these important objects between 2027 and 2033.

A surprising discovery has been compact systems of Earth to super- Earth-sized planets. While compact systems are common, their origin is debated. A prevalent assumption is that compact systems formed after the infall of gas and solids to the circumstellar disk ended. However, observational evidence suggests accretion may commence earlier. We propose that compact systems are surviving remnants of planet accretion during the end stages of infall.

Abstract: The discovery of thousands of planets orbiting stars beyond the solar system has fundamentally shifted our view of Earth’s place in the Universe, has captivated the public imagination, and has transformed research priorities in astrophysics. We are now actively searching for atmospheres on temperate, terrestrial planets, and are developing the technical tools to find and characterize “Earth-2.0”.

Abstract: This talk will explore how quantum radiation - known as Hawking radiation – emerges when a black hole forms in the gravitational collapse of a star. While it has long been known that black holes emit energy, its precise origin has been debated. Over the decades, some researchers proposed that this energy is released directly from the collapsing star, producing a sudden burst that may potentially disrupt the collapse.

Abstract: The scales of asteroid strength, from centimeters to tens of meters or more, can in principle be connected via the well-known Weibull theory (Weibull 1951) that explains in probabilistic terms why small samples of a rock are stronger than the whole. There are fewer weak flaws to be exploited in a smaller sample. This leads to a statistical understanding of size-dependent strength that has been implemented in fragmentation and damage models for planetary materials (Melosh et al., 1992; Benz and Asphaug 1994, 1995). The Weibull analysis enabled Cotto-Figueroa et al.

The corona is a layer of hot plasma that surrounds the Sun, traces out its complex magnetic field, and ultimately expands into interplanetary space as the supersonic solar wind. This complex and unpredictable system varies over many orders of magnitude in space and time, so it's not surprising that we still do not have a complete theoretical understanding of its origins. In this talk, I will present some new observations and theoretical concepts that are helping us get closer to finally identifying and characterizing the physical processes responsible for the corona and solar wind.

The Hubble Space Telescope story has been a fascinating study in public policy, engineering, ethics, and science. The Hubble is perhaps the most productive scientific instrument ever created by humans. In May 2009, a team of astronauts flew to the Hubble Space Telescope on space shuttle Atlantis. On their 13-day mission and over the course of 5 spacewalks they completed an extreme makeover of the orbiting observatory.