---
title: "Astronomy Photo of the Day: 7/21/14 — M17"
description: "The stunning region seen here is known by many names — including Messier 17 (M17), the Swan Nebula, the Checkmark Nebula, or the Horseshoe Nebula — but perhaps [the \"Omega nebula\"]() is the most memorable."
date: "2014-07-21"
modified: "2014-07-21"
authors:
  - name: "Jaime Trosper"
    link: "https://futurism.com/authors/jaimefqtq"
url: "https://futurism.com/apotd-m17"
categories:
  - "From Quarks to Quasars"
---

# Astronomy Photo of the Day: 7/21/14 — M17

![](<https://futurism.com/wp-content/uploads/2015/11/Omega-Nebula.jpg>)

The stunning region seen here is known by many names — including Messier 17 (M17), the Swan Nebula, the Checkmark Nebula, or the Horseshoe Nebula — but perhaps [the "Omega nebula"](<http://en.wikipedia.org/wiki/Omega_Nebula>) is the most memorable.

[![M17](<https://futurism.com/wp-content/uploads/2014/07/M17-e1405933393384.jpg>)](<https://futurism.com/wp-content/uploads/2014/07/M17.jpg>)
**Image Credit: European Southern Observatory (See a larger image [here](<http://31.media.tumblr.com/c72e5b5efbc41c7c7ba974fc50837e00/tumblr_n4o1nsIJpp1s5ibd1o1_500.jpg>))**

This tremendously large region, which can be found about 5,000 light-years away from Earth in the Sagittarius constellation, is a small part of a large molecular cloud that spans at least 40 light-years across.

Spread throughout this appreciable region is more than 30,000 solar masses of material *(like gas and dust)*. Much of that material still permeates the interstellar medium, but some of it is now locked up in a plethora of massive and hot, blue-white stars *(with some belonging to an open cluster of 35 youngish stars)*. These stars now give life to the nebula by bombarding the surrounding gas with ultraviolet radiation, which strips atoms of their electrons. When they rejoin, they give off a brilliant glow, an effect [called ionization](<http://en.wikipedia.org/wiki/Ionizing_radiation>)

[![Image Credit: ESO (See a larger image)](<https://futurism.com/wp-content/uploads/2014/07/Omega-Nebula.jpg>)](<https://futurism.com/wp-content/uploads/2014/07/Omega-Nebula.jpg>)
**Image Credit: ESO ([See a larger image](<http://www.eso.org/public/archives/images/large/eso0925a.jpg>))**

Astronomers estimate that the region's focal point *(the Omega nebula)* extends about half way across the length of the nebula, or about 15 to 20 light-years in diameter *(one light-year alone is equal to 5,878,000,000,000 miles or* *9,461,000,000,000 km),* yet it only contains about 800 solar masses of material.

*See translation in french here.*

## Author
Jaime is a freelance writer, who finds great joy in sharing the wonders of universe with others. She used this passion to launch "From Quarks to Quasars" in 2012.