Introduction of coherence in astrophysical spectroscopy

TL;DR

This paper introduces the concept of coherence in astrophysical spectroscopy, challenging previous assumptions and proposing a simple model that aligns well with astronomical observations, potentially simplifying the study of complex astrophysical systems.

Contribution

It demonstrates the importance of coherence in light-matter interactions in astrophysics and presents a simple model that reproduces observed spectra using classical physics.

Findings

Coherent interactions are significant in astrophysical media.

A simple model reproduces spectra of objects like SNR1987A and quasars.

Standard laser spectroscopy theories can model complex astrophysical phenomena.

Abstract

By confusing the radiance of a single mode light beam, constant in a transparent medium, with the irradiance which decreases away from the source, Menzel purports to show that coherent interactions of light with the diluted media of astrophysics, are negligible. Therefore, to study the interaction of light with gases, astrophysicists use Monte Carlo computations which work to study nuclear systems, but not optics: optical modes which may be defined in inhomogeneous media or for the emissions of single atoms interact coherently with these systems: a unique formula represents, according to the sign of a parameter, absorption and coherent emission. The optical and spectroscopic properties of a very simple model, an extremely hot source in an isotropic cloud of pure, low pressure, initially cold, huge hydrogen cloud are studied using Planck's and Einstein's theories. The similarities of the images and the spectra of this simple model with astronomical observations, for instance of SNR1987A, Einstein cross, lyman break galaxies, quasars,... is so large that this model may be an elementary first step in the study of many astrophysical objects. Adaptations of the model to complex astrophysical systems could represent them using only the old, standard theories of physics commonly used in laser spectroscopy.