Jeremy Bailey's Research Projects — Atmospheres of Planets, Exoplanets and Stars

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Jeremy Bailey

My research group studies the atmospheres of stars, exoplanets, and Solar-system planets using a combination of advanced instrument development, observing programs on large telescopes, and state-of-the-art modelling tools.

Our Instruments:   We have developed the HIPPI (HIgh Precision Polarimetric Instrument) family of instruments. These instruments measure the polarization of stars at parts-per-million levels of precision. These include HIPPI, commissioned in 2014, and used on the Anglo-Australian 3.9m telescope (AAT). HIPPI is currently the world's most sensitive astronomical polarimeter and is regularly used on the AAT for programs on the polarization of exoplanets and stars. Mini-HIPPI commissioned in 2016 is an ultra-compact version of the instrument that can be used on small telescopes such as our on-campus 35cm telescope. We are currently developing HIPPI-2, an improved instrument which we plan to install on the Gemini North 8m telescope in Hawaii, as well as other smaller telescopes.

Our instruments are built entirely in-house in our own Planetary Atmospheres laboratory at UNSW. We use a range of innovative technologies, including widespread use of 3D printing enabling a rapid-prototyping approach, an Internet-of-Things (IoT) architecture for instrument control and low-power low-voltage electonic systems. The methods we use enable us to develop state-of-the-art instruments at remarkably low costs compared with conventional methods.

Our Observing Programs:   We have a number of observing programs using our own polarimetric instruments. A key project is the attempt to detect polarized light reflected from the atmospheres of extrasolar planets. Currently we are looking at hot-Jupiter type planets where we look for the small polarization present in the compbined light of the star and the planet. It can tell us about the presence and nature of clouds in the panets atmosphere as well as determining the inclination and hence mass of the planet. In the future such techniques should enable us to detect the presence of liquid water on the surface or in the atmosphere of Earth-like exoplanets.

We also have a number of programs aimed at understanding the polarization of stars. The precision of our instruments allow us to detect levels of polarization that were previously unobservable. Understanding the polarization of stars at the parts-per-million level is important for our observations of exoplanets, but also tells us about stellar atmospheres, debris-disks around stars, and the interstellar medium.

We also have observing programs on planets and exoplanets using other instruemtns. We have been studying the infrared eclipses of exoplanets using the IRIS2 instrument on the AAT, and we have been observing the spectra of the Solar-system giant planets using the Gemini GNIRS spectrometer. These observations are being used to study the Jupiter aurora in observations coordianted with the NASA Juno spacecraft. 

Our Models:   We interpret these observations using state-of-the-art models that we have developed. Our VSTAR (Versatile Software for Transfer of Atmospheric Radiation) is a highly versatile atmospheric code that can be applied to a range of cool (< 3000K) objects including the Earth and other Solar-system planets, exoplanets and ultracool stars. It can be used to predict the spectra of these objects, and the emission (eclise) and transmission (transit) spectra of exoplanets. It has now been upgraded to include full polarization, and in this mode can predict how the polarization of a planet varies across the disk, with wavelength, and with changing orbital phase angle.

For our stellar work we have recently developed a new code to model the polarization in stellar atmospheres by modifying the SYNSPEC stellar spectral syntehsis code, to do fully polarized radiative transfer. 

Projects:  We can set up Honours or PhD projects to suit your interests. Do you prefer a project that concentrates on instrument science and engineering? Do you want to get involved in observing at the telescope? Are you more interested in modelling and analysis of observations? Or some some combination of these?