Warwick Astronomy and Astrophysics Consolidated Grant 2020-2023

How do stars, galaxies and planets form? What are they made of? How do they die? These are some of the questions addressed by the research programme of the Warwick Astronomy and Astrophysics group. Answering them is becoming possible in ways not imagined just 5 years ago. We now know of thousands of planets outside our Solar system, many of them exotic worlds closer to their stars than even Mercury is to the Sun. These planets are seen against overwhelming glare from their host stars, but remarkably it is now possible to tease out information on their compositions imprinted in their star's light as it passes through their atmospheres. The Solar system contains not just planets, but debris in the form of comets, asteroids and dust left-over from their formation. Other solar systems do too, but again the glare from stellar hosts makes it hard to see this material. A cutting-edge technique called interferometry allows us to see faint sources close to the star; we will use this to study remnant planetary material. The same planetary material can survive the entire lifetime of the stars until all that remains of the stars are hot, ultra-dense remnants known as white dwarfs. White dwarfs have extraordinary gravities, 200,000 times that of Earth, so high that only the lightest elements, hydrogen or helium, are typically visible in their atmospheres. How then do some of them show heavier elements? We believe that we are actually seeing recent or even present-day accretion of their remnant planetary disks. It is remarkable that this happens at all because just before turning into white dwarfs, stars swell by one hundred times in size, and should clear all planetary material out to a distance corresponding to Earth's orbit and beyond. Nevertheless, this gives us a unique insight into the composition of extra-solar planets and planetesimals, and is work that will be pursued in this grant. White dwarfs themselves are sites of exotic physics, allowing us to test quantum mechanics in dense fluids and to see matter in magnetic fields far stronger than can be generated on Earth. They are archaeological remnants of the history of our Galaxy, which betray their ages not through radio-carbon dating, but temperature, as they cool so slowly that they can still be detected over 10 billion years after formation. As a result of the Gaia satellite, we now know of more than 250,000 white dwarfs; we will carry out theoretical research to map the history of our Galaxy through its star formation. We will search these stars for pulsars, stellar lighthouses driven by rotating magnetic fields. Star formation and how it evolves crucial to our understanding of other galaxies, and how they build up chemical elements, right back to the most distant galaxies visible in the far Universe. We have developed models which account for the unusual evolutionary pathways made possible in binary star systems (close pairs of stars). We aim to build a consistent model of the build up of chemical elements which will be needed to interpret the observations soon to flow from the next great mission of astronomy, the James Webb Space Telescope (JWST). Looking far outside our Galaxy, we can encompass millions of other galaxies, allowing us to see events that may only occur once in 100,000 years in our own Galaxy. This has recently allowed the detection of ripples in space-time from the violent merger of black-holes and the super-dense neutron stars, processes that may form much of the heavy element content of the Universe. We will pursue the detection of such events in visible light through rapid-alert observation of wide areas of the sky. Finally, returning closer to home, the same wide-field observations have found many of the most interesting known exo-planets by seeing them pass in front of their host stars. We will follow such systems found near bright stars by NASA's TESS satellite in order to probe planet formation and planetary atmospheres.

The Astronomy and Astrophysics group at Warwick has developed considerable expertise in the deployment and operation of, and the analysis and curation of data from, wide-field survey telescopes. We have used these to search for exoplanets and more recently to search for the electromagnetic counterparts of gravitational wave transients. during our current consolidated grant, we have begun to employ these skills in a very different arena, which is the security of the near-Earth environment populated by artificial man-made satellites. The immediate beneficiaries of this work are our collaborators the Defence Science and Technology Laboratory (DSTL), the US Air Force (USAF), and the European Office of Aerospace Research and Development (EOARD), but the security of the satellite network is critical to the functioning of the modern world and of immense national and international significance. In this new application, we apply to continue and extend the wide-field astronomical survey work from which the satellite work emerged. The two strands of work will cross-fertilise each other other in terms of software infrastructure and technologies.

Technology Development: During the development of the NGTS detectors we worked closely with engineers at Andor Technology. The deep-depleted technology of these chips needed new developments and testing and has now become a product listed on their website. In the new grant we will continue to push the limits of what these devices can deliver, and to feed data back to Andor. More recently, we have engaged at a similar level with the manufacturers of our GOTO telescopes which include novel optics and mount. The companies involved APL Professional Telescopes and JTW Astronomy have secured orders for products that have benefitted from our input, and this will continue as the project progresses. Our work with high-speed detectors will similarly be of mutual benefit to us and from interaction with the ATC Edinburgh, the European Southern Observatory (ESO) and CCD manufacturer e2v, who were all involved in the design and building of the most recently-developed camera, the five-band HiPERCAM.

Inspiration: During the current grant, our travelling planetarium has gone from strength to strength and is the centrepiece of our schools programme. We will maintain this as as a link from the University to schools in the local area, particularly to those catering for the most disadvantaged children. The astronomy group itself is a beneficiary of this effort as it places our PhD students into very different circumstances from their day-to-day research work. We are finding that similar mutual benefit and exchanges come from social media activity connected to our research. We will continue to pursue both of these avenues of public engagement which reach non-traditional audiences, and to encourage out students to engage with them. We will also continue our long-standing work in collaboration with our university press office to publicise our research. This is a more traditional use, but still one of enormous potential impact, particularly when it feeds on-line media.