How to Take Pictures of Baby Planets
Kate Follette, Amherst College
Of the thousands of known extrasolar planets, why are the dozen or so directly imaged exoplanets among the most important despite their apparently anomalous properties within the general exoplanet population (>10 astronomical units, >2x the mass of Jupiter)? What are the prospects for (and recent successes in) detecting younger, lower-mass and/or closer-in planets via direct imaging? I will discuss the current state of the art in the field of high-contrast imaging of extrasolar planets and the disks of gas and dust from which planets form (“circumstellar disks”). I will place particular emphasis on a subset of objects that host both disks and (likely) planets – the so-called “transitional disks”. These young circumstellar disks are almost certainly actively undergoing planet formation, and yet the presence of disk material complicates our ability to isolate light from planets and/or protoplanets embedded within them. I will end by discussing recent results from the Giant Accreting Protoplanet Survey (GAPplanetS) of 15 southern-hemisphere transition disks. The GAPlanetS survey aims to find protoplanets embedded in transitional disks through a distinctive signature at hydrogen wavelengths, and has so far discovered: 2-3 planets, 1 accreting M-dwarf stellar companion, and 1 disk feature masquerading as a planet.
Rethinking the Fundamentals of Classical Nova Explosions
Laura Chomiuk, MSU
Over the past few years, a revolution has been taking place in our understanding of classical novae, largely driven by the discovery of GeV gamma-rays emanating from these garden-variety explosions. These gamma-rays hint that shocks are energetically important—perhaps even dominant—in novae. I will present our burgeoning understanding of shocks in novae, from both multi-wavelength observational and theoretical perspectives, and illustrate how novae can be used as testbeds to understand other shock-powered explosions.
Cold Gas and the Evolution of Early-type Galaxies
Lisa Young, New Mexico Tech
A major theme of galaxy evolution is understanding how today’s Hubble sequence was
established — what makes some galaxies red spheroidals and others blue disks, and what
drives their relative numbers and their spatial distributions. One way of addressing these
questions is that galaxies themselves hold clues to their formation in their internal
structures. Recent observations of early-type galaxies in particular (ellipticals and
lenticulars) have shown that their seemingly placid, nearly featureless optical images can
be deceptive. Kinematic data show that the early-type galaxies have a wide variety of
internal kinematic structures that are the relics of dramatic merging and accretion
events. A surprising number of the early-type galaxies also contain cold atomic and
molecular gas, which is significant because their transitions to the red sequence must
involve removing most of their cold gas (the raw material for star formation). We can now
also read clues to the evolution of early-type galaxies in the kinematics and the
metallicity of their gas, and possibly also in the rare isotope abundance patterns in the
cold gas. Numerical simulations are beginning to work on reproducing these cold gas
properties, so that we can place the early-type galaxies into their broader context.