Exploration of the time domain - discovery and studies of objects and phenomena changing on time scales ranging from seconds to years - is now one of the most vibrant and rapidly developing fields of astronomy, touching on a broad and diverse spectrum of research areas, from the Solar system and discoveries of exoplanets to the distant quasars, and from stellar astrophysics to cosmology and extreme relativistic astrophysics. Time domain information is essential for understanding of some of the most interesting phenomena we observe; for example, we could not learn anything from a single picture of a Supernova, or a single snapshot of a gamma-ray burst; variability of stars aids to our understanding of their structure and evolution; motions of stars tell us about the structure of our Galaxy. We now study the universe and its major constituents as a dynamical, and always changing system. This change was enabled by the progress in information technology. For many years now, large digital sky surveys have been the main sources of data in astronomy. While they can be seen as panoramic cosmic photography, we are now moving into a panoramic cosmic cinematography, with a corresponding increase in information volumes and quality: digital synoptic sky surveys which cover the sky many times, detecting objects and phenomena which change or move. This trend will culminate in the Large Synoptic Survey Telescope (LSST) years from now, but we are already exploring the science and technology of time-domain astronomy with precursor surveys. They already have a significant potential for discovery, and will help us sharpen our questions and strategies for the larger surveys in the future. This project is a continuation and substantial expansion of the Catalina Real-Time Transient Survey (CRTS), an ongoing, productive synoptic sky survey that is producing a steady stream of astronomical transient events, and making them immediately available to the entire community; it is the only current sky survey that does so. It utilizes a data stream obtained in a search for near-Earth and planetary hazard asteroids, funded by NASA, and it leverages considerable existing investments in software and data services. We have established an extensive web of collaborations for the follow-up observations and data analysis. These substantial external resources come at no cost to the NSF, and provide for much greater scientific returns on investment than what could be done with a fully funded, new survey.
The overall scientific goal of CRTS is a systematic exploration of the faint, variable sky. CRTS has so far discovered ~6,500 distinct transient events, and > 13 million variable sources, including a wide variety of variable stars, active galactic nuclei, various cosmic explosions, stellar flares, etc. For at least 2 years in a row, CRTS has published more Supernovae (SNe) than any other survey, including the most luminous SNe ever seen, long-predicted SNe from AGN accretion disks, hundreds of dwarf novae and other interesting cataclysmic variables, planets around white dwarfs, new counterparts of x-ray sources, new tidal streams in the Galactic halo, etc. In addition to a plenty of known types of objects and phenomena, there is a real possibility of a discovery of previously unknown kinds. This project will continue these studies, and start a number of new ones, that touch on a variety of open astronomical challenges. The unique open data policy of CRTS enables the entire astronomical community to partake in these discoveries. All transient events are published electronically in real time, and all data (images, catalogs, etc.) are also made publicly available; they will enable a broad range of archival science. CRTS may be a showcase for the data sharing and re-use, that must become a standard practice in the 21st century.
This project will aid the entire astronomical community in making new discoveries and developing new scientific strategies. It is an example of a new generation of scientific experiments involving real-time mining of massive data streams, and dynamical follow-up strategies. We train undergraduate and graduate students and postdocs, the future science and technology leaders, and develop a broad variety of educational and public outreach materials, both for the new science and computation.
