SETI Institute Weekly Colloquium - Upcoming Speakers
Be among the first to learn about an exciting new exoplanet discovery—a Jupiter-like planet called “51 Eri b” that orbits a star a 100 light years away in the constellation of Eridanus.
Using a powerful new imaging device, astronomers have espied a Jupiter-like exoplanet 100 light-years distant in the constellation of Eridanus. Unlike most planets found around other stars, 51 Eri b has been seen directly. The instrument employed to make the discovery has also made a spectroscopic analysis of the light reflected from the planet, and has detected gases similar to those in Jupiter’s atmosphere.
Because GPI not only images exoplanets but also spreads their light for chemical analysis, astronomers can search for such common gases as water and methane in their atmospheres. Researchers had expected to see methane in directly-imaged exoplanets based on the temperature and chemistry of these worlds, but had failed to detect these molecules in large quantities using earlier instruments. However, the observations of 51 Eri b made with GPI have clearly revealed a methane-dominated atmosphere similar to that of Jupiter.
An extraordinarily complex instrument the size of a small car, GPI is attached to one of the world’s biggest telescopes – the 8-meter Gemini South instrument in Chile. It began its survey of stars last year.
The host star, 51 Eri, is very young, a mere 20 million years old, and is slightly hotter than the Sun. The exoplanet 51 Eri b, whose mass is estimated to be roughly twice that of Jupiter, appears to orbit its host star at a distance 13 times greater than the Earth-Sun distance. If placed in our own solar system, 51 Eri b’s orbit would lie between those of Saturn and Neptune.
Despite decades of experience with human missions in low Earth orbit (LEO), we have only scant, outdated information applicable to human missions to planetary surfaces, where contamination concerns and planetary protection requirements raise unusual challenges. It has been over 40 years since the Apollo program dealt with the challenges of humans living, exploring and returning from the surfaces of celestial bodies. Join us for a forward looking discussion on how changes in science, technology and policies are impacting future human exploration plans. Developing the necessary infrastructure, habitats, spacesuits, rovers, operations and plans for human missions beyond LEO is a very long term process, and the identification of strategic knowledge gaps in science and technology is an important part of the incremental path forward.
Measurements of the demographics of exoplanets over a range of planet and
host star properties provide fundamental empirical constraints on theories of planet formation and evolution. Because of its unique sensitivity to low-mass, long-period, and free-floating planets, microlensing is an essential complement to our arsenal of planet detection methods.
Dr. Gaudi will review the microlensing method, and discuss results to date from ground-based microlensing surveys. Finally, Dr. Gaudi will motivate a space-based microlensing survey with WFIRST-AFTA, which when combined with the results from Kepler, will yield a nearly complete picture of the demographics of planetary systems throughout the Galaxy.
Because of the continuous, high-precision photometry available from the Kepler spacecraft, the Kepler team discovered a type of eccentric binary star named heartbeat stars. In these systems, the two stars come close enough to each other to cause large, periodic changes in the tidal deformation and mutual irradiation of the stars. Additionally, these tidal forces are known to cause the stars in some of these systems to continually ‘ring’ at shorter periods. Currently, we have discovered more than 150 of these in the Kepler data and have been taking extensive follow-up spectroscopy to model andunderstand these systems.
Dr. Mullally will present an overview of these systems and discuss how these systems are allowing us to explore the physics of stellar tidal dissipation.
Palaeomagnetic observations offer important insights into the origin of Earth's interior, but a detailed reconstruction of the underlying dynamics is not feasible. A practical alternative is to construct a stochastic model for the time evolution of the dipole field.
Slow changes in the field are described by a deterministic (drift) term, whereas short-time fluctuations are represented by a random (noise) term. Estimates for the drift and noise terms can be recovered from a time series of variations in the axial dipole moment over the past 2 million years. The results are used to predict a number of statistical properties of the palaeomagnetic field, including the average rates of magnetic reversals and excursions.
Dr. Buffet will explain how a physical interpretation of the stochastic models suggests that reversals and excursions are part of a continuum of time variations in Earth's magnetic field, arising from convective fluctuations in the core. Relatively modest changes the amplitude of convective fluctuations can produce large changes in reversal rates, including the well-known occurrence of superchrons lasting longer than 10 million years.
Astrobiology, the study of emergence of life and the its distribution in the Universe, addresses the most fundamental questions in science: "How does life begin ?" and "Are we alone ?" Over the last 20 years, we have discovered that planets are bountiful in the galaxy and that one in every five solar-type stars has a planet in the habitable zone. We have learned that extremophiles have spread to essential every niche – even the seemingly most inhospitable ones – on our planet. And we have learned that life started essentially as soon as conditions permitted, within some 200 million of the late heavy bombardment, or perhaps even earlier. This has resulted in a paradigm shift from "Life on Earth is unique" to the premise "life is widespread". As a result, searching for biosignatures in space has taken on a life by itself. In this talk, Dr. Tielens will summarize this shift in our thinking and the global processes that may have influenced the first steps towards life.
The focus in this talk will be on astrochemistry – the starting point of astrobiology – the chemical evolution that takes place in space where simple molecules are transformed into complex molecules and complex molecules are broken down to simple ones. This chemical dance of the elements produces a wide variety of organic compounds. I will review the processes that drive this chemical evolution in space, particularly in regions of star and planet formation. The focus will be on understanding the raw materials that are delivered to newly formed planets and their relationship to the building blocks from which prebiotic material was formed and biological systems evolve.
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.
In the first part of the talk Dr. Gomes will review some of the Machian motivations for shape dynamics and sketch its construction. In the second half, Dr. Gomes will talk about recent developments on black holes in this formulation, and discuss some positive aspects of its ongoing quantization program.