Past Seminars

Development of instrumentation for Cosmic Microwave Background (CMB) measurements with the SPT-3G and CMB Stage-4 experiments

Ritoban Basu Thakur

University of Chicago
Jul 29, 2016

Astrophysics Seminar
MSI Conference Room

The 3rd Generation South Pole Telescope (SPT 3G) will measure the CMB in three frequency bands with over 15000 polarization sensitive superconducting bolometers. With SPT-3G we will probe essential Physics of the early universe, perhaps the most important ones being: B-modes from inflationary gravitational waves, total mass of neutrinos and the neutrino mass hierarchy. Partnerships with experiments like BICEP/KECK, DES etc. will enhance our understanding of topics beyond the recombination epoch as well. In this talk I will discuss the design of SPT-3G, provide an overview of ongoing work and highlight the science cases. I will further discuss some offshoots of the SPT-3G efforts, which are aimed at the even more ambitious Stage-4 CMB experiments currently under planning and recommended by the P5 & NRC Antarctic report panels. These new projects include: (a) Development of Kinetic Inductance Devices (KIDs) for CMB measurement which will be essential when Stage 4 telescopes must operate ~500,000 detectors. Reading out this vast number of detectors is not trivial and KIDs have the potential for vastly simplifying the instrumentation. (b) Additionally precise measurement of the CMB frequency spectrum can enlighten us about the energetics of the early universe prior to recombination. One of the most interesting cases for this is characterizing dark matter decay at early times. The Fourier Transform Spectrometer (FTS) being developed for SPT-3G will pave the path for future high precision FTSs experiments like PIXIE.

More about Ritoban Basu Thakur →

The Gravitational-Wave Universe seen by Pulsar Timing Arrays

Chiara Mingarelli

California Institute of Technology
May 31, 2016

Special Astrophysics Seminar
Bell Room (103), Rutherford Building

Galaxy mergers are a standard aspect of galaxy formation and evolution, and most (likely all) large galaxies contain supermassive black holes.  As part of the merging process, the supermassive black holes should in-spiral together and eventually merge, generating a background of gravitational radiation in the nanohertz and microhertz regime.  Processes in the early Universe such as relic gravitational waves and cosmic strings may also generate gravitational radiation in the same frequency band.  An array of precisely timed pulsars spread across the sky can form a galactic-scale gravitational wave detector in the nanohertz band.  I describe the efforts to develop the pulsar timing array concept, and the recent limits that have emerged from North American and international efforts to constrain astrophysical phenomena at the heart of supermassive black hole mergers.

More about Chiara Mingarelli →

Where and how were the heaviest nuclei produced?

Maxime Brodeur

Notre Dame University
May 24, 2016

Special Astrophysics Seminar
Bell Room (103), Rutherford Building

Nearly half of all elements beyond iron were produced via processes involving extremely exotic nuclei in an unclear astrophysical site. Indeed, the synthesis of these heavy nuclei is known to be the fruit of a succession of a rapid capture of neutrons and beta-decays describing a path along an uncharted region of the nuclear chart. Therefore, abundance calculations of nuclei produced by this process rely on nuclear models, which in turn rely on experimental data of exotic nuclei closer to the 'valley of stability'. Among various experimental inputs, atomic masses appear as being the quantity to which the abundance pattern is the most sensitive. A world-wide effort is ongoing to map out this 'terra-incognita' of unknown atomic masses through high precision mass measurements. Current state-of-the-art mass spectrometry techniques for exotic nuclei will be introduced and some current and future developments will be discussed.

More about Maxime Brodeur →

The measurement of stellar masses in <z> = 0.5 galaxies using the micro-lensing of quasars

Paul Schechter

May 13, 2016

Special Astrophysics Seminar
MSI Conference Room

We measure the stellar mass surface densities of early type galaxies by observing the micro-lensing of macro-lensed quasars caused by individual stars, including stellar remnants, brown dwarfs and red dwarfs too faint to produce photometric or spectroscopic signatures. Instead of observing multiple micro-lensing events in a single system, we combine single epoch X-ray snapshots of ten quadruple systems, and compare the measured relative magnifications for the images with those computed from macro-models.  We use these to normalize a stellar mass fundamental plane constructed using a Salpeter IMF with a low mass cutoff of 0.1 solar masses and treat the zeropoint of the surface mass density as a free parameter.  Our method measures the GRAININESS of the gravitational potential produced by individual stars, in contrast to methods that decompose a smooth total gravitational potential into two smooth components, one stellar and one dark.  We find the median likelihood value for the normalization factor F by which the Salpeter stellar masses must be multiplied is 1.53, with a one sigma confidence range, dominated by small number statistics, of 0.95 < F < 2.5.

More about Paul Schechter →

Understanding the Long-term Optical/Near-Infrared Color Variability in Fermi Blazars

Jedidah Isler

Vanderbilt University
Apr 12, 2016

Astrophysics Seminar
Bell Room (103), Rutherford Building

We have undertaken a 7-year, multiwavelength program to observe a sample of blazars in various Fermi gamma-ray states, using the Small and Medium Aperture Research Telescope System (SMARTS) 1.3m + ANDICAM instrument in Cerro Tololo, Chile. We present near-daily optical and infrared (OIR) color variability diagrams of these sources and compare the OIR flux and color to the Fermi gamma-ray flux on similar cadence. We then analyze the color variability properties on short and long timescales, as compared to the length of an average gamma-ray flare, to better constrain the physical mechanisms responsible for the variability properties that we observe. From this long-term observational data, we develop a schematic representation of the possible color variability behaviors in blazars and how it is related to the thermal disk and non-thermal jet contributions in both Flat Spectrum Radio Quasars and BL Lac objects.

More about Jedidah Isler →
Download Poster (1.59MB)

Synthetic Biology and Experimental Evolution for Space Exploration

Betul Kacar

Harvard University
Apr 5, 2016

MSI Seminar
MSI Conference Room

-

More about Betul Kacar →
Download Poster (399.85KB)

All the X-ray binaries in the Universe:  X-ray Emission from Normal and Starburst Galaxies Near and Far

Ann Hornschemeier

Goddard Space Flight Center
Mar 29, 2016

Astrophysics Seminar
Bell Room (103), Rutherford Building

Excitement has mounted recently over the role of X-ray emission from galaxies in early heating of the Intergalactic Medium (IGM), demonstrating that understanding of X-ray emission from normal and starburst galaxies may have significant impact on structure formation in the Universe. Here we present our research on constraining the X-ray SED of galaxies across cosmic time via several complementary approaches. In the very local universe (d <~ 30 Mpc including the Local Group) we are using NuSTAR to understand the accretion states and total output of black hole and neutron star binaries using the important lever arm of 0.5-30 keV emission.  At intermediate distances (10-100 Mpc), we are comparing the X-ray output of galaxies with star formation histories and population synthesis model predictions using both Chandra and XMM data. In the slightly more distant universe (z~0.1-0.2) we can find rare analogs to primordial starbursts via wide-field optical/UV surveys that may be studied with Chandra. We will finish with a discussion of starburst galaxies emitting X-rays at z>4, which thanks to the extremely deep Chandra Deep Field-South 7 Ms survey, are better constrained than ever before. I will discuss survey strategy and how the various pieces of the puzzle fit together regarding the X-ray output of galaxies and their X-ray binary populations over cosmic time. Time permitting, I will finish with some discussion of next-generation facilities.

Download Poster (1.65MB)

AGN feedback in Clusters of Galaxies

Julie Hlavacek-Larrondo

University of Montreal
Mar 15, 2016

Astrophysics Seminar
Bell Room (103), Rutherford Building

The last few decades have shown us that radio jets originating from supermassive black holes can interact strongly with their surrounding medium. During this talk, I will review the current status of this field, known as AGN feedback, while focusing on the most massive black holes in the Universe, those that lie at the centers of galaxy clusters. I will review the physics behind these interactions and then focus on the evolution of radio feedback over cosmic time while presenting new results from clusters discovered via the South Pole Telescope.

More about Julie Hlavacek-Larrondo →
Download Poster (1.56MB)

The Role of Space Law in Space Activities

Ram Jakhu

McGill University Centre for Research of Air and Space Law
Mar 8, 2016

MSI Seminar
MSI Conference Room

Space activities are carried out pursuant to scientific discoveries, with the use of space technology, for meeting various Earthly human needs, mainly pursuant to relevant national public policies, and essentially within applicable legal and regulatory framework(s). Therefore, for the conduct of space activities smoothly, it is imperative to fully comprehend international space law as well as national space laws and regulations. The value of space policies and the space law-making process, which refers to how space law has been and is being made, should not the underestimated. This lecture will address some basic principles of international space law as well as Canadian rules and law-making process. The presentation is designed especially for non-lawyers.

More about Ram Jakhu →
Download Poster (433.71KB)

Searching for Gravitational Waves with Advanced LIGO

Ben Farr

University of Chicago
Feb 23, 2016

Astrophysics Seminar
Bell Room (103), Rutherford Building

Advanced LIGO recently completed its first observing run, which collected gravitational wave data with unprecedented sensitivity between September 2015 and January 2016. One of Advanced LIGO's primary goals is to detect and characterize gravitational waves from transient sources such as the coalescence of binary compact objects containing neutron stars and/or stellar mass black holes. I will describe the search and characterization methods being employed in the advanced-detector era.

More about Ben Farr →
Download Poster (1.64MB)

Planetary Dynamos: The Curious Case of Saturn

Sabine Stanley

University for Toronto
Feb 16, 2016

MSI Seminar
MSI Conference Room

Magnetic field measurements by the Cassini mission have confirmed the earlier Pioneer 11 and Voyager missions' results that Saturn's observed magnetic field is extremely axisymmetric. For example, Saturn's dipole tilt is less than 0.06 degrees. The near-perfect axisymmetry of Saturn's dipole is troubling because of Cowling's Theorem which states that an axisymmetric magnetic field cannot be maintained by a dynamo. However, Cowling's Theorem applies to the magnetic field generated inside the dynamo source region and we can avert any contradiction with the theorem if we can find reason for a non-axisymmetric field generated inside the dynamo region to have an axisymmetric potential field observed at satellite altitude. Stevenson (1980) proposed that the Helium Insolubility Layer (HIL), which forms at the top of the metallic hydrogen layer in Saturn, could provide such a mechanism. This layer is stably stratified and electrically conducting. Differential rotation in this layer, which surrounds the dynamo source region, could act to attenuate the non-axisymmetric features and hence produce an axisymmetric observed magnetic field. Here we use numerical dynamo simulations to demonstrate that the HIL can produce a more axisymmetric field. We also demonstrate an important theoretical consequence of this axisymmetrization process: the secular variation of the axisymmetric field components must be extremely slow. Observational evidence suggests this may be the case for Saturn. In addition, we present numerical dynamo simulations that reproduce the observed axisymmetry of Saturn's field and confirm the extremely slow secular variation rates in highly axisymmetric models. A consequence of this result is that we can use time variation of the axisymmetric field to learn about the non-axisymmetric field components which are not observed in present data from Cassini.

More about Sabine Stanley →
Download Poster (471.61KB)

Yesterday, today and tomorrow: CMB cosmology with ACT, Planck and ACTPol

Renee Hlozek

University of Toronto
Feb 9, 2016

Astrophysics Seminar
Bell Room (103), Rutherford Building

CMB cosmology is currently undergoing a data-rich epoch, with measurements on small scales from experiments like the Atacama Cosmology Telescope (ACT) and its polarisation instrument, ACTPol, adding to measurements on larger scales by Planck, WMAP and most recently BICEP. I will contextualise the measurements and present constraints on models of interest to small-scale experiments; while paying attention to the  foregrounds that complicate our measurements of the primordial microwave sky. I will illustrate how we need to push on both the theory and data side - briefly highlighting a re-analysis of 2013 Planck data, where we found that the 217GHz x 217GHz  detector set spectrum used in the Planck analysis is responsible for some of the tension between the Planck parameters and other astronomical measurements. I'll discuss how the picture has changed with updated Planck data. Finally I'll highlight the recent ACTPol results, and outline how experiments like AdvACT and others will open up the window on the epoch of reionisation; our least explored epoch to date.

More about Renee Hlozek →
Download Poster (1.63MB)

A tale of two fast radio bursts

Vikram Ravi

California Institute of Technology
Feb 2, 2016

MSI Seminar
MSI Conference Room

A population of millisecond-timescale gigahertz-frequency “fast radio bursts” (FRBs), with signatures of propagation through plasma column densities of cosmological proportions, has recently been identified. Evidence is mounting that FRBs are indeed extragalactic, in which case they may represent new, exotic astrophysical phenomena, and hold great promise for fundamental cosmology. I will present results on two bursts recently detected at the Parkes telescope, which together suggest that FRBs originate in rare, distant cataclysms. FRB 131104 has a candidate radio afterglow with properties characteristic of a relativistic explosion. FRB 150807, with a remarkable band-averaged flux density of 120 Jy and evidence for rapid diffractive scintillation, appears to originate at greater than a gigaparsec from the Milky Way in a sparse environment. A population synthesis analysis provides additional evidence that at least a subset of the FRB population propagates over cosmologically significant distances. With apologies to Charles Dickens, this is the age of wisdom yet of foolishness, the epoch of belief yet of incredulity; it nonetheless appears that a new field of astrophysics may be beginning.

More about Vikram Ravi →
Download Poster (587.75KB)

Kepler, K2, and TESS — Space-based asteroseismology

Steve Kawaler

Iowa State University
Jan 26, 2016

Astrophysics Seminar
Bell Room (103), Rutherford Building

By awakening us to the amazing abundance of other planetary systems, the Kepler mission has been a landmark in advancing our understanding of the Universe. The basis for these discoveries is accurate photometry, with high duty cycle, of over 100,000 stars. The data corresponding to planetary transit events, though, is far less than 0.1% of the total amount of data obtained. The remaining >99.9% of the data is an exquisite record of the time-domain behavior of an enormous variety of stars. These photometric time series enable us to probe the interiors of stars by revealing their normal modes of oscillation — a technique known as asteroseismology. In this talk I'll discuss the remarkable strides that asteroseismology has been able to make using the remarkable archive of Kepler photometry, the ongoing efforts of the follow-on K2 mission, and plans for future missions such as TESS.

More about Steve Kawaler →
Download Poster (1.59MB)

Outbursts Around Dead Stars: How Dwarf Novae Are Testing Our Fundamental Fluid Dynamics Theory of Accretion Disks

Omer Blaes

UC Santa Barbara
Jan 19, 2016

MSI Seminar
MSI Conference Room

Dwarf novae are transient optical outbursts observed from close binary systems containing a white dwarf that is accreting material from a companion star. This accreting material takes the form of a differentially rotating disk around the white dwarf, a structure that is of wide-ranging importance in astrophysics, from protoplanetary disks around young stars to quasars and gamma-ray bursts. Understanding how angular momentum is transported and gravitational binding energy is dissipated is of fundamental importance to all these systems. Dwarf novae are somewhat special, however, in that their observed outbursts are caused by a thermodynamic instability in the disk with short recurrence times, allowing for exquisitely detailed and extensive observations of their variability. This variability has challenged our fundamental theories of angular momentum transport in accretion disks, and I will discuss recent progress in reconciling this theory with observations. This, in turn, has generated deeper appreciation of the complex nonlinear dynamics of these flows, with interesting physics puzzles that remain to be solved.

More about Omer Blaes →
Download Poster (448.80KB)

Growing black holes: from the first seeds to active galactic nuclei

Mar Mezcua

University of Montreal
Jan 12, 2016

Astrophysics Seminar
Bell Room (103), Rutherford Building

How supermassive black holes form and grow is still one of the long-standing questions in astronomy. Supermassive black holes of up to 10^9 solar masses already existed when the Universe was less than ~1 Gyr old. To reach this mass in such a short time, they should have started as seed intermediate-mass black holes (IMBHs) of 100-10^6 solar masses and grow very fast via accretion and mergers. Such IMBHs are the missing link between stellar and supermassive black holes and they should be present in the nucleus of low-mass galaxies and in the halos of large galaxies, e.g. in the form of ultraluminous X-ray sources (ULXs). In this talk I will present observational evidence that a population of IMBHs in dwarf galaxies similar to those seed black holes populating the early Universe exists. With the use of large, deep, multiwavelength surveys like COSMOS, these sources are detected up to z~4. I will also show that, in the local Universe, IMBHs can be additionally detected as extreme ULXs with powerful radio emission in galaxies having undergone a minor merger event. The later supermassive black hole growth can be explained by the accretion of gas coming from galactic scales. At kpc scales, this gas can be transported to the nuclear regions through galaxy mergers, which can trigger active galactic nuclei (AGN) activity and can be detected in the form of binary AGN. At scales of a few 100 pc, dust lanes can be the channels of inflow of material from the outer parts of the galaxy to the nuclear region, as evidenced by the finding that the spiral structure of the nuclear cold molecular gas traced by ALMA observations correlates with that of the dust. The nuclear dust lanes are in addition able to obscure the nucleus of low-luminosity AGN and to explain the collimation of the ionised gas, which questions the role of the dusty torus proposed by the Unified Model of AGN.

More about Mar Mezcua →
Download Poster (1.63MB)

Why Material From Enceladus' Ocean Keeps Getting Ejected Into Space

Edwin Kite

University of Chicago
Dec 1, 2015

MSI Seminar
MSI Conference Room

Spacecraft observations suggest that the plumes of Saturn’s moon Enceladus draw water from a subsurface ocean, but the sustainability of conduits linking ocean and surface is not understood. Observations show sustained (though tidally modulated) fissure eruptions throughout each orbit, and since the 2005 discovery of the plumes. Peak plume flux lags peak tidal extension by ∼1 radian, suggestive of resonance. Here we show that a model of the tiger stripes as tidally- flexed slots that puncture the ice shell can simultaneously explain the persistence of the eruptions through the tidal cycle, the phase lag, and the total power output of the tiger stripe terrain, while suggesting that the eruptions are maintained over geological timescales. The delay associated with flushing and refilling of O(1) m-wide slots with ocean water causes erupted flux to lag tidal forcing and helps to buttress slots against closure, while tidally pumped in-slot flow leads to heating and mechanical disruption that staves off slot freeze-out. Much narrower and much wider slots cannot be sustained. In the presence of long-lived slots, the 10^6-yr average power output of the tiger stripes is buffered by a feedback between ice melt-back and subsidence to ∼5 GW, which is equal to the observed power output, suggesting long-term stability. Turbulent dissipation makes testable predictions for the final flybys of Enceladus by the Cassini spacecraft. Our model shows how open connections to an ocean can be reconciled with, and sustain, long-lived eruptions. Turbulent dissipation in long-lived slots helps maintain the ocean against freezing, maintains access by future Enceladus missions to ocean materials, and is plausibly the major energy source for tiger stripe activity.

More about Edwin Kite →
Download Poster (428.24KB)

Mapping dark matter on the largest and smallest scales

Gil Holder

McGill University
Nov 24, 2015

Astrophysics Seminar
Bell Room (103), Rutherford Building

Dark matter is everywhere, but its nature remains unclear. Through gravitational lensing, we can now make maps of dark matter on a wide range of scales. I will talk about the two ends of the scale: gravitational lensing of the cosmic microwave background providing maps on Gpc scales, approaching the scale of the cosmological horizon, and strong lensing of dusty star-forming galaxies providing maps of dark matter substructure on scales of 100 pc or less. In addition to providing new insights into the relation between dark matter and luminous matter, the small-scale maps can be used to test the nature of dark matter itself while the large-scale maps can be used to give new perspectives on neutrino masses.

More about Gil Holder →
Download Poster (1.65MB)

Exploring the Outer Solar System: now in vivid colour

Michele Bannister

NRC Herzberg
Nov 17, 2015

MSI Seminar
MSI Conference Room

The outer reaches of our Solar System are home to hundreds of thousands of small icy worlds - the leftover remnants of planetesimal formation. Their present orbits are a sculpted signature of the migrations of the giant planets, particularly Neptune, during the early history of the Solar System. Yet the faintness and highly eccentric orbits of most of these worlds mean only a tiny fraction have yet been discovered. With the Outer Solar System Origins Survey, the highest-ranked Large Program on CFHT 2013-16, we are providing nearly half a thousand new outer Solar System discoveries, with exquisitely well-determined orbital parameters. Our complementary Large Program on Gemini North, “Colours of the Outer Solar System Origins Survey”, is observing a magnitude-complete sample of the brightest of our discoveries in the optical and infrared at unprecedented precision. These colours provide information on the ices, silicates and organic compounds on the surfaces of these small worlds. Together, the colours and dynamical information will allow us to map the structure of the outer Solar System, answering questions about how Neptune migrated, and the radially changing composition of the original planetesimal disk.

More about Michele Bannister →
Download Poster (415.10KB)

The habitable zone as seen through the atmosphere

Colin Goldblatt

University of Victoria
Nov 10, 2015

Astrophysics Seminar
University of Victoria

The dominant paradigm in assigning "habitability" to terrestrial planets is to define a circumstellar habitable zone: the locus of orbital radii in which the planet is neither too hot nor too cold for life as we know it. I'll review the atmospheric physics that has led to hard boundaries being set for the habitable zone and show recent work which shows multiple stable states and challenges these boundaries. The width of the habitable zone is turns out to be determined by the atmospheric inventories of di-nitrogen and carbon dioxide. Yet Earth teaches us that these abundances are very heavily influenced (perhaps even controlled) by biology. This is paradoxical: the habitable zone seeks to define the region a planet should be capable of harbouring life; yet whether the planet is inhabited determines these boundaries. This matters, because future life detection missions may use habitable zone boundaries in mission design. I propose that we must amend the paradigm of habitability to acknowledge that habitability depends on inhabitance; for life as we know it is a planetary scale—and planet dominating—phenomenon.

Download Poster (1.68MB)

One Photon, two photon red(shifted) photon, blue photon: Superconducting devices for Astrophysics

Roger O'Brient

NASA Jet Propulsion Laboratory
Nov 3, 2015

MSI Seminar
MSI Conference Room

I will discuss how novel superconducting detector technology has enabled our team to make unprecedented constraints on inflationary tensor modes using the BICEP and Keck Array telescopes.  We are preparing for the next phase of this program—BICEP4—and I will describe technology development in support of this, specifically using Kinetic Inductance Parametric UP-conversion (KPUP) for TES readout.  KPUPs are closely related to KIDs, and I will describe our prototype KID-based spectrometers for cosmic tomography.  Lastly, I’ll describe our designs of millimeter wave parametric amplifiers that should operate at the quantum limit.  We aspire to use these for space-based spectroscopy and spatial interferometry.

Download Poster (1.42MB)

The Palomar (non)Transient Factory: Teaching an old dog new tricks

Thomas Prince

California Institute of Technology
Oct 27, 2015

Astrophysics Seminar
Bell Room (103), Rutherford Building

The Palomar Transient Factory (PTF) has been in operation since 2009, yielding new results on extragalactic transients including supernovae, gamma-ray bursts, and tidal disruption events.  However, over its 6 years of operation, PTF has also gathered photometry data on over 500 million objects in the Northern Sky, with some fields being observed several thousand times. I will describe some of the interesting science that has come from study of non-transient, but variable, objects using PTF.  This is just  a glimpse of the expected yield from the Zwicky Transient Facility (ZTF), to be operational in 2017, with a throughput 20 times that of PTF. Among the "new tricks" we have taught PTF is the capability of operating in dense stellar fields.  We have already carried out the best optical variability study of the Galactic Plane and will follow that in 2018 with a much more extensive publicly accessible Galactic Plane variability survey using ZTF.

More about Thomas Prince →
Download Poster (1.62MB)

Chasing proto-planetary disks and high-z galaxies with the LMT

James Lowenthal

Smith College
Oct 13, 2015

Astrophysics Seminar
Bell Room (103), Rutherford Building

The 50-meter Large Millimeter Telescope (LMT) — a joint project of UMass Amherst and INAOE, Mexico — is nearing completion on 5000m Sierra La Negra, and is now operating with a 32-m surface in “Early Science” mode.  Some of the most luminous galaxies in the Universe are dusty starbursts at redshifts z>4 that are invisible in the optical but easily detected at 1-3 mm with LMT.  I will review the status of this new facility and some of its recent results, including redshifts measured using CO emission lines, resolution of previously blended Herschel sources, gravitationally lensed submillimeter galaxies out to z~5, and dust maps of proto-planetary disks in nearby Galactic star-forming regions.

More about James Lowenthal →
Download Poster (1.61MB)

Long-term Integrations of the Solar System

Hanno Rein

University of Toronto
Oct 13, 2015

Astrophysics Seminar
Bell Room (103), Rutherford Building

I'll discuss the differences between symplectic and non-symplectic integrators in the context of long term orbit simulations of the Solar System. In particular, I'll present our recent implementation of the non-symplectic Gauss-Radau scheme, IAS15, as well as the symplectic integrator WHFast. These algorithms are the most accurate and fastest algorithms running on standard computer architectures. Both of them achieve sub-linear energy error growth (Brouwer's law) over a billion dynamical times (more than 10^10 timesteps). I'll talk about the tricks we used to write code that is both fast but also ensures that all important floating-point operations are unbiased. Our integrators are freely available and come with an easy to use python wrapper. I will give an live demo on how to use them at the end of my talk

More about Hanno Rein →
Download Poster (1.59MB)

Seeing Through the Clouds: The Thermal Emission and Reflected Light of Super-Earths with Flat Transmission Spectra

Caroline Morley

UC Santa Cruz
Oct 6, 2015

MSI Seminar
MSI Conference Room

Vast resources have been dedicated to characterizing the handful of planets with radii between Earth’s and Neptune’s that are accessible to current telescopes. Observations of their transmission spectra have been inconclusive and do not constrain the atmospheric composition. Of the approximately four small planets studied to date, all have radii in the near-IR consistent with being constant in wavelength, likely showing that these small planets are consistently enshrouded in thick hazes and clouds. I will explore the types of clouds and hazes that can completely obscure transmission spectra. I will then show the effect that these thick clouds have on the thermal emission and reflected light spectra of small exoplanets. I present a path forward for understanding this class of small planets: by understanding the thermal emission and reflectivity of small planets, we can potentially break the degeneracies and better constrain the atmospheric compositions.

More about Caroline Morley →
Download Poster (436.58KB)

Understanding Haze Formation in Planetary Atmospheres: Lessons from the Lab

Sarah Hörst

John Hopkins University
Sep 22, 2015

MSI Seminar
MSI Conference Room

From exoplanets, with their surprising lack of spectral features, to Titan and its characteristic haze layer, numerous planetary atmospheres may possess photochemically produced particles or haze. With few exceptions, we lack strong observational constraints (in situ or remote sensing) on the size, shape, density, and composition of these particles. Photochemical models, which can generally explain the observed abundances of smaller, gas phase species, are not well suited for investigations of much larger, solid phase species. Laboratory investigations of haze formation in planetary atmospheres therefore play a key role in improving our understanding of the formation and composition of haze particles. I will discuss a series of experiments aimed at improving our understanding of haze in the atmospheres of Titan, the early Earth, exoplanets, and any other atmospheres composed of a combination of N2, CH4, CO, CO2, and/or O2. In particular, I will discuss investigations of the density of Titan aerosol analogues (“tholins”), the effect of energy source on incorporation of nitrogen into tholin, the effect of CO on haze formation, and the possible presence of haze during the rise of oxygen on the early Earth.

More about Sarah Hörst →
Download Poster (440.75KB)

MSI Faculty Jamboree

MSI Faculty

McGill University
Sep 15, 2015

MSI Seminar
Bell Room (103), Rutherford Building

MSI Faculty Jamboree

Check our Past Seminars from: