Title: The Omega Project: measuring the equation of state of the universe

Scientific program:

This programme is designed to find and follow ~200 Type Ia supernovae (SNe Ia) over a period of 5 years to determine the equation of state parameter of the universe. Light curves of these supernovae will be done within the ESSENCE project combining several observatories. The VLT part of this project is to provide the crucial spectroscopic classification of the SNe Ia. Checks on the reddening and possible evolution of the supernovae will be performed with IR observations from the VLT as well. We will find supernovae distributed evenly over the redshift range [0.15, 0.75].

The goal is to answer a simple, but very important, question: is the dark energy of the universe consistent with a cosmological constant (Omega=-1)? If not, this means the dark energy must be a more general energy field such as "quintessence." The survey is designed to determine Omega to +/-0.1. The spectroscopy is to classify the SNe Ia and separate them from other supernovae, hypernovae and variable AGN. This is an essential requirement for a successful experiment. With such a large set of spectral classifications, we will also be able to put strong constraints on the supernova rate as a function of lookback time to almost half the age of the universe. For a few core-collapse supernovae we will be able to derive distances through the expanding photosphere method, a critical cross-check for the distance measurements. The classifications will be announced immediately to allow other research teams to monitor the supernovae.