Exploring the transient Universe

A novel mission - to understand how the Universe began and what it is made of – involves Professor Paul O'Brien from our Department of Physics and Astronomy.

The project, called Theseus, is now to be considered for ESA’s fifth medium class mission in its Cosmic Vision science programme, with a planned launch date in 2032.

Theseus is the Transient High Energy Sky and Early Universe Surveyor and is one of three new mission concepts - selected from 25 proposals put forward by the scientific community - that will be studied in parallel before a final decision is expected in 2021.

Theseus will monitor transient events in the high-energy Universe across the whole sky and over the entirety of cosmic history. In particular, it promises to make a complete census of gamma-ray bursts from the Universe’s first billion years, to help shed light on the life cycle of the first stars.

Professor O’Brien said: “Theseus will reveal the origin of high-energy transient sources over the entirety of cosmic history. It will probe the early Universe to determine when the first stars were born and probe the nearby Universe to locate the sources of gravitational waves.”

Carrying a unique combination of instruments on a rapid response spacecraft, Theseus will provide an unprecedented combination of:

  • wide and deep sky monitoring in a broad energy band (0.3keV -20 MeV);
  • focusing capabilities in the soft X-ray band providing very large sky coverage and high angular resolution
  • on board near-IR capabilities for immediate transient source identification and redshift determination

The X-ray instrument team is led from the University of Leicester, UK, the gamma-ray instrument is led from INAF, Italy and the IR telescope is led from CEA, France.

The Theseus mission was proposed to ESA in 2016 and is under study as the fifth medium-sized mission (M5) in ESA’s ‘Cosmic Vision’ programme. Theseus has been selected along with two other missions for study out of an original 25 proposals. The final decision on which mission to select for launch as M5 will be taken in 2021.