[Paper Review] The CODEX-ESPRESSO experiment: Cosmic dynamics, fundamental physics, planets and much more...

S. Cristiani, G. Ávila+37 more|arXiv (Cornell University)|Sep 1, 2007

Astronomy and Astrophysical ResearchPhysics and Astronomy1 citations

TL;DR

The CODEX-ESPRESSO experiment proposes using a high-resolution, super-stable spectrograph on the Extremely Large Telescope (E-ELT) to directly measure the time evolution of the Universe's expansion rate, enabling breakthroughs in cosmology, fundamental physics, and exoplanet detection. A precursor instrument, ESPRESSO, is being developed for the VLT to validate key technologies and observational strategies.

ABSTRACT

Summary. — CODEX, a high resolution, super-stable spectrograph to be fed by the E-ELT, the most powerful telescope ever conceived, will for the first time provide the possibility of directly measuring the change of the expansion rate of the Universe with time and much more, from the variability of fundamental constants to the search for other earths. A study for the implementation at the VLT of a precursor of CODEX, dubbed ESPRESSO, is presently carried out by a collaboration including ESO, IAC, INAF, IoA Cambridge and Observatoire de Genève. The present talk is focused on the cosmological aspects of the experiment.

Motivation & Objective

• To directly measure the time variation of the Hubble parameter, enabling a direct test of cosmic acceleration.
• To investigate potential variations in fundamental physical constants over cosmic time.
• To search for Earth-like exoplanets through radial velocity measurements with unprecedented precision.
• To develop and validate instrumentation and observational techniques via the ESPRESSO precursor at the VLT.
• To advance cosmological constraints using high-precision spectroscopy of distant quasars and stars.

Proposed method

• Utilize the Extremely Large Telescope (E-ELT) as a primary collector for high-throughput, high-resolution spectroscopy.
• Implement a super-stable spectrograph design to minimize instrumental drift and achieve sub-meter-per-second radial velocity precision.
• Employ laser frequency comb calibration to enable absolute wavelength calibration and long-term stability.
• Observe high-redshift quasars to measure redshift drift and probe cosmic expansion history.
• Conduct radial velocity monitoring of solar-type stars to detect low-mass, Earth-like exoplanets.
• Integrate data from the ESPRESSO instrument at the VLT to test and refine observational procedures and calibration techniques.

Experimental results

Research questions

• RQ1 Can the time variation of the Hubble parameter be measured directly using high-precision spectroscopy?
• RQ2 Do fundamental constants such as the fine-structure constant vary over cosmic time?
• RQ3 What is the radial velocity stability required to detect Earth-mass exoplanets in habitable zones?
• RQ4 How can instrumental stability and calibration be maintained over long observation timescales?
• RQ5 To what extent can the ESPRESSO precursor at the VLT validate the scientific and technical feasibility of CODEX?

Key findings

• CODEX will enable the first direct measurement of the time derivative of the Hubble parameter, offering a new probe of cosmic acceleration.
• The instrument's super-stable design and laser frequency comb calibration will achieve sub-meter-per-second radial velocity precision.
• ESPRESSO, as a precursor, is expected to validate key calibration and stability techniques for the full CODEX system.
• High-redshift quasar absorption lines will be used to test for variations in the fine-structure constant with high sensitivity.
• The experiment will significantly improve the detection threshold for Earth-mass exoplanets in habitable zones.
• The synergy between E-ELT and CODEX will open new frontiers in cosmology, fundamental physics, and planetary science.