Isotropic Gamma-Ray Background: Cosmic-Ray Induced Albedo from Debris in the Solar System?

TL;DR

This paper explores how cosmic-ray interactions with debris in the solar system's outer regions could produce a gamma-ray background detectable by Fermi, offering insights into the distribution of small bodies in the Oort Cloud and beyond.

Contribution

It introduces a model for gamma-ray albedo from solar system debris, suggesting a significant contribution to the extragalactic gamma-ray background and proposing a method to measure debris mass in the solar system.

Findings

Gamma-ray albedo from debris could account for part of the extragalactic gamma-ray background.

Detection of this gamma-ray emission can reveal the total column density of debris in the Oort Cloud.

The same process applies to other small body populations, enabling mass constraints.

Abstract

We calculate the gamma-ray albedo due to cosmic-ray interactions with debris (small rocks, dust, and grains) in the Oort Cloud. We show that under reasonable assumptions a significant proportion of what is called the "extragalactic gamma-ray background" could be produced at the outer frontier of the solar system and may be detectable by the Large Area Telescope, the primary instrument on the Fermi Gamma-Ray Space Telescope. If detected it could provide unique direct information about the total column density of material in the Oort Cloud that is difficult to access by any other method. The same gamma ray production process takes place in other populations of small solar system bodies such as Main Belt asteroids, Jovian and Neptunian Trojans, and Kuiper Belt objects. Their detection can be used to constrain the total mass of debris in these systems.