Solar System Objects
The discovery and characterisation of exoplanet systems, comets, asteroids, near Earth objects and other Solar System objects is a key component of the NRT science case. The flexibility of the robotic Liverpool Telescope (LT) scheduler has shown that exoplanet transit monitoring programmes can be combined with other time critical observations to maximise telescope efficiency. The simple, low-cost instrumentation philosophy of the LT group has shown the importance of creating instrumentation to suit science cases. For example, the LOTUS UV spectrograph was designed and delivered in the space of 6 months for the study of the Churyumov-Gerasimenko comet.
The next generation of satellite surveys (e.g. TESS, PLATO) will find a zoo of new exoplanets that require ground-based characterisation. These surveys target bright host stars to maximise the potential for follow-up; providing a wider variety of time variable signatures to be explored for large numbers of exoplanets. The spectroscopic and polarimetric capabilities of the NRT can be exploited to explore the debris disks of these planetary systems.
Along with observing large samples of exoplanets around bright stars, a secondary aim of the exoplanetary community has been to target small stars with the motivation of discovering Earth-sized worlds. It has been recognised that the transit depth for an Earth-sized exoplanet around an M-dwarf is the same as a hot Jupiter orbiting a G-dwarf. The strategy of targeting late type stars has paid off immensely with the discovery of an Earth-sized world around Proxima Centauri, along with the characterisation of seven such planets in the TRAPPIST-1 system (a science programme in which the LT played and continues to play a prominent role). The difficulty is that host stars are extremely faint: TRAPPIST-1 has an Mv=18.4 despite being only 12 parsecs away. The TRAPPIST successor array SPECULOOS will probe over 1000 ultra-cool stars and brown dwarfs over the next decade for transits from Earth-sized planets, and NRT will be ideally placed to follow-up targets found with the northern array on Tenerife (Delrez+ 2018, SPIE, 10700, 21).
The TRAPPIST-I system shown in comparison to the Jupiter system. This and many more interesting infographics can be found on the TRAPPIST-I website.
Within our solar system, science is naturally dominated by the time domain. NRT will contribute to understanding the physics of individual Solar System objects (e.g. YORP effect in asteroids, simultaneous spectroscopy and polarimetry of small bodies in conjunction with rendezvous missions (e.g. Psyche, Lucy) for gas and dust composition and dynamics, and monitoring the post New Horizons encounter evolution of the surface chemistry of Pluto). It will also support population studies where fast non-sidereal tracking will enable spectroscopic observations of moving targets, an important tool for taxonomy. The robotic operations model will allow rapid follow-up of new discoveries (e.g. LSST, ZTF, Pan-STARRS) to extend the orbit arc and studies of transient events such as asteroid collisions and interstellar visitors.
The cadence and depth of new surveys have led to, for example, the first identifications of the first minor planets with interstellar origins (Meech+ 2017, Nature, 552, 378; MPEC 2019-R106). Photometry and spectroscopy of such systems can be used to constrain the physical and chemical processes involved in planetary formation in other extrasolar systems (Fitzsimmons+ 2019, ApJ, 885, 9). Small bodies inform our understanding of the composition of the protoplanetary disk and the evolutionary history of the Solar System. Near Earth asteroids are of additional interest due to their Earth impact potential, or as targets for sample collection or even economic exploitation in the medium to long term. Surveys such as ZTF and Rubin offer the possibility for a comprehensive census of such objects (see, e.g. Bolin+ 2020, arXiv:2008.05384), and the robotic operations model of NRT allows rapid follow-up of new discoveries to solve the orbit arc. It is a target requirement of the NRT to provide non-sidereal tracking with autoguiding, which is necessary for spectroscopy of Solar System bodies, and is a capability which the LT does not offer.