A new high-resolution spectrograph has begun operations on the Southern Astrophysical Research (SOAR) Telescope in Chile. The instrument, known as the SOAR Telescope Echelle Spectrograph (STELES), recorded first light in August with observations of Eta Carinae and 13 other targets.
SOAR, located on Cerro Pachón and operated by NSF NOIRLab’s Cerro Tololo Inter-American Observatory, is a 4.1-metre facility run in partnership with US and Brazilian institutions. STELES was installed on 30 July 2025 and achieved its first observations on 6 August.
A Long Path to First Light
Development of STELES began in Brazil, led by the Laboratório Nacional de Astrofísica and the University of São Paulo. The optical design was provided by Bernard Delabre of the European Southern Observatory. It was delivered in Chile in 2016, and engineers carried out years of building and trials, facing logistical barriers, pandemic delays, and repeated travel between Brazil and Chile. The project reflects a trend at major Chilean observatories such as the Vera Rubin Observatory, where international collaboration and diverse teams sustain long-term science.
Eta Carinae was chosen as the inaugural target in recognition of Brazilian astronomer Augusto Damineli. He was the first to propose the star system’s binary nature and played a central role in securing funding for the instrument. The system itself is highly luminous but heavily obscured by the Homunculus Nebula, material expelled during the 1837 “Great Eruption”. Astronomers continue to track its unpredictable brightening and dimming cycles.
Capabilities and Research Goals
STELES divides light into separate blue and red paths, working across a spectral range from 300 to 890 nanometres. Each arm uses echelle gratings to fan out the light into spectra, which are used to study chemical content, movement, and spatial placement.. The design allows a broad capture, able to gather nearly all available visible photons in one observation.
With these capabilities, scientists will examine stars with very low heavy-element content within and outside the Milky Way. A central aim is the search for Population III stars, considered the very first stars, lacking metals heavier than helium. These earliest stars have never been observed directly.
Researchers also expect data from STELES to advance studies of stellar formation, hot stars, and the long-term chemical history of the of the galaxy. Early science operations are scheduled to begin in 2026 once final engineering checks are complete.
