Other worlds in visible light.
The habitable zones of the nearest Sun-like stars are within reach of CELESTE coronagraphy. Each detection builds the sample that will guide the Habitable Worlds Observatory target list.
Imagery · ESO / J. C. Muñoz-Mateos
Key Science Topic
Exoplanet
Exoplanet
characterization.
Direct imaging and atmospheric spectroscopy of nearby exoplanets in reflected visible light — a near-term precursor to the Habitable Worlds Observatory.
The CELESTE coronagraphic mode achieves contrast ratios of 10⁻⁸ at angular separations of two diffraction widths from the host star. At these inner working angles, the habitable zones of dozens of nearby Sun-like stars become directly accessible in reflected visible light.
A spectroscopic mode samples R ≈ 70 over the full CELESTE band, sufficient to detect Rayleigh scattering, methane, water, and oxygen features in temperate-planet atmospheres. Yield is complementary to JWST's transit spectroscopy and to the future Habitable Worlds Observatory.
The Brief
i.
Science Objectives
Directly image planets in the habitable zones of nearby Sun-like stars. Characterise their atmospheres through low-resolution visible spectroscopy. Build the statistical sample of reflected-light spectra needed to inform the design of the Habitable Worlds Observatory.
ii.
Observables & Measurements
Coronagraphic images at contrast 10⁻⁸ at 2 λ/D inner working angle. R ≈ 70 spectra of candidate planets in the 0.4 – 1.0 μm band for detection of O₂, H₂O, CH₄, and Rayleigh scattering slope.
iii.
Key Functional Requirements
Vector vortex coronagraph (charge 4) with inner working angle of 2 λ/D ≈ 20 mas at 700 nm. Wavefront stability maintaining Strehl > 0.7 at 700 nm over science integrations. Raw contrast floor of 10⁻⁷ before post-processing.
iv.
CELESTE Uniqueness
Ground AO cannot reach the contrast or inner working angles needed for habitable-zone imaging without a space-borne reference. CELESTE delivers these capabilities at a fraction of the cost of a dedicated space coronagraph, and operates at the visible wavelengths where key atmospheric biosignatures are strongest.