Overview
Just after the Big Bang the Universe contained only hydrogen, helium and a trace of lithium. Today it holds every element in the periodic table, from the carbon, oxygen and phosphorus that life depends on to the silicon, iron and uranium on which our civilisation is built. Where, when and how were these elements made? How much of the trans-iron elements comes from supernovae, and how much from mergers of neutron stars such as those now seen in gravitational waves? Which elements are forged in stellar furnaces, what role do binary and higher-order systems play, and how are the products spread across a galaxy? And when did the Universe become enriched enough to form planets and, possibly, life?
Why the TDT?
The TDT will combine a response to external alerts within minutes with the depth to reach g ≈ 25 in 30 minutes, and will cover the full optical to near-infrared spectrum at R ≈ 5000, so that transients and their progenitor systems can be followed on the timescales on which they evolve. Next-generation gravitational-wave detectors such as the Einstein Telescope are expected to find well-localised (< 10 deg²) binary neutron-star mergers out to 1.5 Gpc (z ≈ 0.3) at a rate of about one per week. Scaled from GW170817, their counterparts will peak at g ≈ 24: within reach of current and upcoming imaging surveys, but beyond any spectrograph except the TDT.
Science themes
Gravitational-wave mergers
Supernovae and gamma-ray bursts
Stellar furnaces
Observing requirements
| Requirement | Value |
|---|---|
| Target classes and magnitude range | Kilonovae from binary neutron-star mergers (peak g ≈ 24), supernovae, gamma-ray bursts and their progenitors |
| Spectral resolution | R ≈ 5000 |
| Wavelength coverage | 350–1800 nm (u to H), simultaneously |
| Response time to alerts | Minutes |
| Number of unit telescopes per target | Up to the full array (100 units) for the faintest events |
White papers
- Multi-messenger and time-domain astronomy in the 2040s arXiv:2512.14546
- GRBs and Relativistic Transients in the 2040s arXiv:2512.15010
- Luminous Fast Blue Optical Transients in the 2040s arXiv:2512.14832
- Shedding visible light on the origin of Fast Radio Bursts
- Core-Collapse Supernovae in the 2040s
- Underluminous Thermonuclear Supernovae arXiv:2512.17404
- Asteroseismology of white dwarfs in the 2040s arXiv:2512.15814
See all TDT publications.