The central objective of PEPSI is to understand the structure and dynamics of the surface magnetic fields of solar-type stars and its impact on stellar formation and evolution. The magnetic field of the Sun is the source of a large variety of dynamic phenomena with impact onto Earth and the other planets. Observations of stars of different mass, rotational period and evolutionary stage help to better understand the Sun and will, e.g., place tight constraints on solar-based theories of stellar dynamos. A better understanding of stellar magnetic fields thus has also a profound effect on understanding the formation and evolution of stars and their environment, including solar and extrasolar planets. Other areas in astrophysics are just now slowly exploiting the effects of magnetic fields, e.g. accreting black holes or cosmological gamma-ray bursters. The combination of the enormous light-gathering power of the LBT and the polarimetric capability at the high spectral resolution and large wavelength coverage of PEPSI will, for the first time, provide direct measurements of magnetic structures on a spatial scale previously only possible for the Sun. These measurements will address problems in solar, stellar, and extragalactic physics alike and will cover many other fields of interest as well.

The paper on the scientific objectives published in AN (The science case of the PEPSI high-resolution echelle spectrograph and polarimeter for the LBT. K. G. Strassmeier et al. AN 325, 27 (2004)) can be downloaded from the public documentation repository .

	Wind structure in hot stars
	Nuclear structure, winds, and jets in AGNs
	Variability in Quasar and Blazar emission and absorption lines
	Surface fields of white dwarfs and central stars of planetary nebulae
	Stellar flares and prominences
	Magnetospheric mass accretion in binaries with degenerate components
	Interstellar and intergalactic magnetic fields
	Supernovae in nearby galaxies
	Polarization of stars near the galactic centre
	Helium and deuterium abundance studies
	Oxygen abundances of metal-poor dwarfs and subdwarfs
	Radial velocities of planetary candidates in old clusters
	Polarization signatures from extra-solar planets
	Asteroseismology of solar-type stars
	Rotational velocities of very low-mass stars and brown dwarfs