The extragalactic explosive Universe: the new era of transient surveys and data-driven discovery

ESO-HQ, Garching near Munich, Germany

September 16-19, 2019

At the turn of the decade, in 2010 a number of moderate-sized telescopes were equipped with digital cameras of around 10 square degrees. The relative cost of detectors and computing had reduced to a level where rapid, real-time processing of the imaging data provided monitoring of large sky areas every few days. This revolutionised the field of time domain astronomical surveys and we have witnessed a vast array of new discoveries.  The global community have mapped the solar system, star forming regions in our galaxy, local group galaxies, and the local and high-redshift Universe leading to the discovery of new types of transients.  We have discovered low luminosity stellar explosions in nearby galaxies and the most luminous supernovae beyond a redshift of 3, exotic transients in the nuclei of galaxies including tidal disruption events, stellar mergers, unusual novae and previously unknown species of stellar outbursts. The diversity in the explosive Universe is remarkable.

Type Ia supernovae have long been renowned for their homogeneity and use as standardisable candidates, but we now know thermonuclear supernovae show a wide diversity in explosion energies and composition of radioactive elements. How a white dwarf explodes, exactly what is the critical mass (Chandrasekhar or not), and what is the most common progenitor channel are all still unknowns. Explosions that we assume are from the core-collapse in massive stars are also stretching our understanding of how the explosion mechanism works. Many supernovae have explosion energies greater than a few times 1051 erg and are difficult to physically explain by neutrino driven core-collapse. The likely candidates are magnetar driven explosions, black hole and jet formation (as in GRBs), circumstellar interaction and pair-instability driven stellar deaths. Discoveries by revolutionary wide-field surveys such as the Palomar Transient Factory, Pan-STARRS, Catalina Sky Survey, La Silla QUEST, OGLE, Skymapper, Gaia, DES, ASAS-SN and ATLAS have changed the field. The extreme physics has come from rapid and detailed follow-up from X-ray to radio domains. ESO has played a major part in this through the swift reaction of the VLT and its extensive instruments combined with the Public ESO Survey of Transient Objects (PESSTO). Many of these surveys have now entered their second phase with upgraded detectors and even more ambitious goals. 

These new data-driven initiatives are joined by the exciting prospect of routine detections of gravitational wave sources and electromagnetic follow-up. The spectacular discovery in August 2017 of the first merging neutron star system detected in gravitational waves and at almost every wavelength from gamma-rays to the radio has truly opened this new field. By September 2019, the third LIGO-Virgo run will have been running for 6 months and we may have new discoveries by the time of the meeting. The coming decade will have larger data sets that require public access for full scientific exploitation. The meeting will discuss how we will manage these large data sets. The conference will focus on the rich physics that has arisen from these discoveries and multi-wavelength follow-up programmes. Theory and modelling experts will also be a key part of the meeting, with a focus on how we can provide open data products to enhance model and data testing. 

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