# What is a typical mass density for inter-galactic gas in a cluster?

• I
• timjdoom
In summary, the conversation discusses the use of X-ray emission detections, particularly the famous bullet cluster images, to analyze the density of intergalactic gas. The first discovery of this was found through a Google search for "the density of intergalactic gas" which yielded results focused on electron density rather than mass density.
timjdoom
TL;DR Summary
As far as I'm aware, galaxy clusters typically have some level of hot gas permeating the entire cluster, which the galaxies within these cluster orbit each other within. What is the typical mass density of that gas?
I assume we can work it out from X-ray emission detections, such as shown with the famous bullet cluster images.

OMG, thank you. I tried searching for "mass density of galaxy cluster gas" and variations but never intergalactic gas. The results I found focused on electron density and I struggled to understand the papers e.g. https://academic.oup.com/mnras/article/457/1/281/989241

Clearly I need google my exact question before posting it. Thank you again!

Tom.G and berkeman

## 1. What is mass density?

Mass density is a measure of the amount of mass per unit volume of a substance or object. It is typically expressed in units of kilograms per cubic meter (kg/m^3) in the International System of Units (SI).

## 2. What is inter-galactic gas?

Inter-galactic gas refers to the gas that exists between galaxies in a cluster. It is primarily made up of hydrogen and helium, with small amounts of other elements such as carbon, oxygen, and nitrogen.

## 3. What is a cluster?

A cluster is a large group of galaxies that are gravitationally bound together. They can range in size from a few dozen to thousands of galaxies.

## 4. What is the typical mass density for inter-galactic gas in a cluster?

The typical mass density for inter-galactic gas in a cluster is very low, averaging around 10^-27 kg/m^3. This is much lower than the density of air at sea level on Earth, which is around 1.2 kg/m^3.

## 5. How is the mass density of inter-galactic gas in a cluster measured?

The mass density of inter-galactic gas in a cluster is typically measured through observations using telescopes and other instruments. Scientists can also use computer simulations to estimate the mass density based on the known properties of the gas and the cluster as a whole.

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