PhD Projects with Professor Chris Tinney

Our research group focuses on exoplanetary detection using "Doppler Wobble" and direct imaging techniques. We also pursue studies of brown dwarfs - objects somewhat more massive and brighter than exoplanets, but which we can actually see - in order to gain insight into exoplanetary properties. These areas encompass a large range of possible projects - to give a flavour of the sort of work involved, a few of them are spelled out in more detail below. But this is by no means an exhaustive list.

Our focus in supervising PhDs is to train students for a subsequent career as an independent, astronomical researcher. So you'll be travelling to telescopes in Australia and overseas to do observing, analysing data, writing papers, and presenting results at international conferences - and we have funds to support you in doing all that.

And of course, we can offer students a Doppler & Direct Top-up Scholarship of $6000 per annum, for students in our group.

There are two main requirements for becoming a UNSW graduate student,

1. • Being accepted in the Graduate Research School, and
   

2. • Accessing funding to support you while undertaking research full time for three years.
   

Australian students should see the Graduate Research School web pages for details on how to Apply for an Australian Post-graduate Award (deadlines are around end of October for Semester 1, around end of March for Semester 2) and how to Apply for Admission (deadline around mid-December and late-May).

Prospective students from overseas (in addition to Applying for Admission - deadlines around mid-December and late-May) will have to pay tuition fees. Again there are Scholarships available (see UNSW International Research Scholarships for details - deadlines are a few months earlier than for Australian scholarships). These scholarships are quite competitive. Your home country may also have scholarships available to support overseas study.

UNSW requires prospective students to have discussed possible projects and organised a prospective supervisor in advance of applying for admission or any of these awards. So, if the PhD experience outlined above sounds interesting to you, please contact me well in advance of these deadlines, so we can discuss possible projects.

Chris Tinney

July 2008

Finding Habitable Planets

One of the undeniable "holy grails" in astronomy is the search for habitable terrestrial planets - unfortunately detecting Earth-like planets in Earth-like orbits around Sun-like (ie. G-type) stars is some way off - their Doppler Wobble signatures are just too small, and they are also rediculously faint compared to their host stars.

However, fainter host-stars offer the prospect of making some headway. Faint and cool M-type and L-type stars (and brown dwarfs) have masses ~10 times smaller than the Sun. So a given Doppler Wobble precision can find a planet ten times smaller. Moreover, because these stars are much fainter and cooler, their "habitable zones" (ie. the orbital radii at which water can be liquid on the surface of a rocky planet - the current touchstone for "habitability") are at much smaller orbital radii - which means they have larger Doppler amplitude and so, again, are easier to detect.

Indeed, 1m/s precisions should fairly easily detect habitable planets around late-M and early-L dwarf stars. Unfortunately, these stars emit most of their flux in the near-infrared (ie. at wavelengths of 1-2µm) while current Doppler Wobble techniques operate in the visible (0.4-0.8µm) where these stars are much fainter. So the number of stars for which this experiment can currently be performed is very small.

The obvious solution is to move these Doppler Wobble techniques into the near-infrared, and this is the main science driver of the Gemini Observatory's Precision Radial Velocity Spectrograph, which is now in its design phase. However, before this spectrograph does into operation and detects its first planets, there are many scientific questions to be answered. What's the best way to structure its habitable planet survey? What will the selection effects of such a survey, and how will we extrapolate from habitable planet detections to their frequency throughout the Universe? How intrinsically stable are the velocities of these low-mass stars? How will the varying throughput and emission of the near-infrared sky be dealt with? Attacking these questions as a PhD project will put Australia and the Gemini partners in an excellent position to "hit the ground running" when PRVS goes into operation.

The Hunt for Free Floating Planets

Over 230 extra-solar planets are now known to orbit nearby stars. Most of these have been discovered by the Doppler wobble technique, and so have only been "indirectly" detected via their impact on their host star. So none of these planets has actually been seen directly. In this project you will use the recently developed technique of methane imaging to search for, and image, "unbound" planets (ie planets without a host star) and brown dwarfs (ie. stars too low in mass to burn nuclear fuel) in young southern star clusters.

The primary tool for this will be methane imaging. The coolest objects detected to date outside our solar system are "T-dwarfs" - star-like objects with temperatures of 800-1300 Kelvin that show pronounced features in their near-infrared spectra due to methane absorption. Methane imaging (ie near-infrared imaging in bands at 1.5-1.65 and 1.6-1.75um) can powerfully discriminate these rare objects from all other contaminating objects in the fields of young star clusters. Moreover, when used to detect young objects, it can reveal objects as low in mass as 1 Jupiter mass.

The observational tools for projects searching for methane T-dwarfs in star clusters are wide-field near-infrared spectrographs. Sixteen nights of observing with the IRIS2 instrument on with the Anglo-Australian Telescope has been used to date to target the cluster IC2391. In 2008, the Australian-built Gemini South Adaptive Optics Imager will go into operation on the 8m Gemini telescope in Chile, together with the Canopus Adaptive Optics system. Together these components will enable on of the largest telescopes in the world to deliver deep, wide-field, high-resolution images of star clusters and will be an unprecedented tool for the detection of free-floating planetary mass objects.

In 2009, the FourStar instrument will go into operation on one of the 6.5m Magellan telescopes (also in Chile). This instrument will have a massive field of view of 0.18x0.18 degrees, allowing it to complement Gemini searches by targeting nearer and larger star clusters. The University of NSW, together with the Carnegie Institution and MIT, is funding the purchase of methane filters for this new camera.

The Southern Hemisphere is the ideal location to undertake these studies, as it harbours many of the nearby Galactic star clusters. As a result there is lots of scope for additional students to join Stephen Parker, who began work in this area in 2008.

This page last updated by Chris Tinney, 8 July 2008