Science with the Cherenkov Telescope Array

The Cherenkov Telescope Array, CTA, will be the major global observatoryfor very high energy gamma-ray astronomy over the next decade andbeyond. The scientific potential of CTA is extremely broad: fromunderstanding the role of relativistic cosmic particles to the searchfor dark matter. CTA is an explorer of the extreme universe, probingenvironments from the immediate neighbourhood of black holes to cosmicvoids on the largest scales. Covering a huge range in photon energy from20 GeV to 300 TeV, CTA will improve on all aspects of performance withrespect to current instruments. The observatory will operate arrays onsites in both hemispheres to provide full sky coverage and will hencemaximize the potential for the rarest phenomena such as very nearbysupernovae, gamma-ray bursts or gravitational wave transients. With 99telescopes on the southern site and 19 telescopes on the northern site,flexible operation will be possible, with sub-arrays available forspecific tasks. CTA will have important synergies with many of the newgeneration of major astronomical and astroparticle observatories.Multi-wavelength and multi-messenger approaches combining CTA data withthose from other instruments will lead to a deeper understanding of thebroad-band non-thermal properties of target sources. The CTA Observatorywill be operated as an open, proposal-driven observatory, with all dataavailable on a public archive after a pre-defined proprietary period.Scientists from institutions worldwide have combined together to formthe CTA Consortium. This Consortium has prepared a proposal for a CoreProgramme of highly motivated observations. The programme, encompassingapproximately 40% of the available observing time over the first tenyears of CTA operation, is made up of individual Key Science Projects(KSPs), which are presented in this document.