Our Research

Artists impression of the 5 Earth mass planet

Extra-solar planets

The detection and study of extra-solar planetary (exoplanet) systems is a relatively new and exciting field of astrophysics. Since 1995 more than 500 extra-solar planets have been discovered and the rate of detection is accelarating as methods improve.

At JBCA we are engaged in the detection and study of exoplanets using two complementary detection methods: gravitational microlensing and the transit method. We also have more general interests in the architecture of exoplanetary systems, planet formation theories and how these can be directly tested by exoplanet observations.

A time lapse of the night sky over the Danish Telescope at La Silla during MiNDSTEp observations by the JBCA exoplanets group. The Galactic Centre comes into view over head towards the end of the movie.

Staff at JBCA are leaders in theoretical and observational aspects of exoplanet detection using microlensing. In the context of exoplanet detection microlensing describes the temporary magnification of background stars by the passage of foreground planetary systems across the line of sight. The plantary host star produces a magnification signal which typically lasts for weeks to months, whilst its planets may induce brief distortions of this signal lasting for around a day (for a Jupiter mass planet) down to hours (for Earth mass planets). Microlensing is especially good for detecting low-mass planets at large separations from the host star, a regime that is difficult to explore with other detectiion methods. JBCA staff have close links with the main microlensing survey groups (OGLE and MOA). We are also members of the MiNDSTEp follow-up network which uses telescopes based in Chile, South Africa and the USA to look for signals due to exoplanets down to Earth masses. Staff at JBCA have pioneered both the theory behind extra-solar planet detection with microlensing, as well as the theory and application of the technique beyond the Milky Way. Research programmes in this area at JBCA span observations, data reduction techniques, analysis and theory.

Kerins is a co-leader of the ESA Euclid Exoplanets Working Group. ESA has recently selected Euclid as a medium-class mission in its Cosmic Vision programme. Euclid's primary science is the study of dark energy but it is also expected to undertake other science programmes including a high cadence near-infrared search for exoplanets towards the Galactic bulge using microlensing. Such a survey would allow the distribution function of exoplanets to be determined down to Earth masses over exoplanet host separations ranging from 0.5 AU out to the free-floating exoplanet regime, providing the ideal complementary dataset to Kepler. Manchester is a World leader in simulations of space-based microlensing surveys and we are leading the design of the Euclid exoplanet survey.

Members of JBCA are also engaged in the detection of exoplanets using the transit method. If a planet passes directly in front of its parent star then the brightness of the host star will temporarily decrease. The decrease is typically very small: the brightness of a Sun-like star will drop by only 1% due to the passage of a Jupiter-like planet across it. To date over one hundred planets have been detected in this way. The transit method is especially sensitive to planets closer to their host star, where the probability of transit is hightest, and so provides excellent complementarity with the microlensing method described above. JBCA members are involved in MiNDSTEp which uses both microlensing and transits to detect exoplanets.

Our interest in planet formation stems from involvment in the PEBBLES collaboration, together with colleagues from St Andrews and Edinburgh universities. PEBBLES will use eMerlin and ALMA to image planet growth in the 'missing link' size range between tiny dust grains and planets large enough to be detected by microlensing, transit observations, or other methods.

Current research in this area

Research activities currently include:

Interested in doing a PhD in this area? Why not get in touch by emailing: exoplanets@jb.man.ac.uk

The JBCA exoplanet group:

Eamonn Kerins Dr Eamonn Kerins, academic staff: I am always amazed at what we can discover with microlensing. Today we are using it to find distant planets with masses not much larger than that of the Earth. I have also previously used it to probe the three-dimensional structure of our Galaxy and to measure the abundance of dark matter in astrophysical forms (e.g. stellar remnants and brown dwarfs). Currently I am working on the prospect of space-based microlensing surveys which could be carried out by the ESA EUCLID or NASA WFIRST missions (or even by both!). These missions will complete the census of Earth-mass planets now underway with the Kepler transit mission by focussing on more distant planets, including planets ejected from their host systems during formation. This should provide us with a much clearer picture of exoplanetary architectures which in turn can be used to calibrate planet formation theories. I am also a member of the MiNDSTEp team which is detecting exoplanets using both the microlensing and transit techniques. Aside from exoplanet research I lead the Angstrom Project, which is a microlensing survey of the bulge of the Andromeda Galaxy employing a network of 2m-class telescopes. In future we should be able to detect planets even in Andromeda using the microlensing technique. I am also involved in the VVV survey, an infrared variability survey of up to a billion stars in the inner Galaxy. VVV, which uses the VISTA telescope at Paranal observatory in Chile, will catalogue up to 10 million variable sources - making it the largest infrared variability survey ever undertaken.

Shude Mao Prof Shude Mao, academic staff: Prof Mao's research interests include the theory of exoplanet detection and exoplanet modelling using microlensing. He first suggested the idea of using microlensing to find exoplanets in a paper he wrote with Bohdan Paczynski in 1991.

Anita Richards Dr Anita Richards, UK ALMA Regional Centre support staff: Stars are born when huge interstellar clouds collapse and the leftover material forms a disc of gas and dust. We don't yet know the relative importance of turbulent instabilities in the disc, or gravitational attraction, in the early stages of planet formation. Temperature/density gradients in the disc promote different chemical reactions which determine whether the young planets are rocky and oxygen-rich or whether they become hydrogen-rich gas giants. Very fine details can be resolved by combining the signals from telescopes many kilometres apart, which is needed to separate the different regions in these protoplanetary discs. The Atacama Large Millimetre Array (ALMA), being built in the Chilean Andes, will show how the dust distribution develops as planets form. It will also use spectroscopic imaging to investigate chemical evolution and differentiation in the discs. The UK e-MERLIN array observes at centimetre wavelengths sensitive to pebbles in this size range. We will investigate a range of protoplanetary discs within a few hundred light-years and witness the first stages in planet growth.

Iain McDonald Dr Iain McDonald, post-doctoral researcher: Though I spend most of my time investigating evolved stars and their dust production, I also moonlight (no pun intended) as an extrasolar planet hunter. Most of my publications in planets have been helping the SuperWASP team find "hot Jupiters" — planets which are massive gas giants like Jupiter, but which orbit their parent stars every few days, rather than Jupiter's twelve years. Finding these planets is only the first step — we also want to know what they are made of. We can't see these planets directly, because of the glare from their parent stars, so measuring the light emitted from their surfaces requires extraordinarily high-precision spectroscopy: it's a bit like trying to work out the colour of a candle which is next to a searchlight at the distance of the Moon. This is only possible with the very largest and most-sensitive telescopes, so this work is only in its infancy. The techniques we are developing here to measure the composition of Jupiter-like planets are the same as those we will eventually use for our "Holy Grail": detecting alien life on Earth-like planets.

Matthew Penny Matthew Penny, PhD Astrophysics student: I am in the third year of my PhD at JBCA working on microlensing and exoplanets. My work has ranged from the theoretical, simulating the effects of orbital motion in microlensing events and space based microlensing surveys, to observational, performing follow-up observations of microlensing events at the 1.54m Danish telescope at La Silla, Chile, and analyzing data, reducing images and modelling lightcurves. I generally work quite independently, but I have valued the opportunity to work collaboratively, both within JBCA with fellow students and academics, and internationally as part of the MiNDSTEp consortium. I have also had the chance to talk about and present my work around the world, from internal seminars at Jodrell bank and Manchester, to conferences in Auckland, New Zealand.

Rieul Gendron Rieul Gendron, MSc Astrophysics student: I started my Masters in the School of Physics and Astronomy at the University of Manchester in September 2009. I chose to do my Masters here because I heard that it was possible to study extrasolar planets via the method of gravitational microlensing. I was fascinated by this topic because no one on Earth knew of the existence of worlds orbiting other stars like our Sun before 1995! This is a fast-moving area of research with new techniques being developed all the time. Over 500 extrasolar planets have been discovered to date and it's amazing what we can learn about the diversity of planets in our Galaxy. My work uses planet formation models to predict how often we should detect extrasolar planets in surveys of the night sky. The results should help scientists figure out how good the current planet formation models are so it's great to know that I'm contributing in some way to our understanding of the alien worlds that orbit the stars in our Galactic neighbourhood. I've had a chance to work with world-class physicists (both theoretical and experimental) in the field. Some of the ultimate aims of extrasolar planet research are to determine if Earth-like planets exist around other stars, whether they could potentially harbour life and how unique our Solar System is among the 300 billion stars or so that reside in our Galaxy.

Scot Hickinbottom Scot Hickinbottom, MSc Astrophysics student: I have just started my MSc by Research in the department working with the Exoplanet group. My research project revolves around trying to optimize how incoming microlensing datasets from multiple observing sites can be aligned prior to fitting physical models. When looking for brief signals from possible exoplanet systems it is useful to be able to gauge how an event is unfolding whilst it is ongoing. This is not always obvious from the datasets due to the heterogeneous nature of the different telescope, filter and camera systems employed. Whilst detailed modelling of an event is the most reliable way to align the data this is usually a very complex and time-intensive process which is often completed only after the event has occurred. I am really enjoying the fact that my research will have a real scientific application, and that it will be used within the Exoplanet community. The idea of being involved in searcingh for other worlds that orbit other stars, and the sheer vastness of the universe that is implied by this, is quite awe-inspiring. I would like to continue researching in this field in the future, as I would love to be involved with some of the space missions currently being developed that will greater improve our understanding of other planets outside of our solar system, which is a very exciting prospect indeed.

For further information on research opportunities in this area contact the JBCA exoplanets group via email at exoplanets@jb.man.ac.uk