# Wormhole Shadows

## TL;DR

This paper introduces a method to detect Ellis wormholes by analyzing their images surrounded by dust, focusing on brightness contrasts that distinguish them from black holes using high-resolution observations.

## Contribution

The study derives steady dust solutions around wormholes and demonstrates how image brightness contrasts can differentiate wormholes from black holes.

## Key findings

- Bright ring appears due to photon orbits, similar to black holes.
- Intensity contrast inside and outside the ring differs between wormholes and black holes.
- High-resolution imaging can potentially identify Ellis wormholes.

## Abstract

We propose a new method of detecting Ellis wormholes by use of the images of wormholes surrounded by optically thin dust. First, we derive steady solutions of dust and more general medium surrounding the wormhole by solving relativistic Euler equations. We find two types of dust solutions: one is a static solution with arbitrary density profile, and the other is a solution of dust which passes into the wormhole and escapes into the other side with constant velocity. Next, solving null geodesic equations and radiation transfer equations, we investigate the images of the wormhole surrounded by dust for the above steady solutions. Because the wormhole spacetime possesses unstable circular orbits of photons, a bright ring appears in the image, just as in Schwarzschild spacetime. This indicates that the appearance of a bright ring solely confirms neither a black hole nor a wormhole. However, we find that the intensity contrast between the inside and the outside of the ring are quite different. Therefore, we could tell the difference between an Ellis wormhole and a black hole with high-resolution very-long-baseline-interferometry observations in the near future.