How big is Orion Nebula? | Scale of the Universe

The Orion Nebula is a cloud of glowing gas and dust where new stars are forming, about 1,300 light-years from Earth. A light-year is the distance light travels in one year, about 9.46 trillion kilometers. The nebula spans about 24 light-years, or 230 trillion kilometers. It is the closest large star-forming region to Earth, and it can be seen without a telescope as a fuzzy patch in the sword of the constellation Orion.

Size

The Orion Nebula is an H II region, a cloud of hydrogen that glows because ultraviolet light from hot young stars inside it has stripped electrons from its atoms. Like other clouds of gas, it fades out gradually instead of ending at a sharp edge. Its size depends on how faint a glow is counted. The European Southern Observatory (ESO) gives a span of about 24 light-years.

On the sky, the nebula covers about 66 arcminutes, a little more than a degree, where an arcminute is 1/60 of a degree. Radio telescopes measured its distance in 2007 at about 1,350 light-years, and a 2017 measurement put it slightly closer, at about 1,270 light-years. At those distances, 66 arcminutes is 24–26 light-years.

Size comparisons

The Orion Nebula is about twice as wide as the Crab Nebula, the cloud left by an exploded star, which averages about 11 light-years across.
It spans almost six times the distance from the Sun to Proxima Centauri, the nearest star, 4.2 light-years away.
On the sky, the nebula is about twice as wide as the full Moon.
If the Orion Nebula were shrunk to the length of a marathon, 42.195 kilometers (26.2 miles), the orbit of Neptune would be a circle about 1.7 meters (5.5 feet) across. Earth's orbit would be about 5.6 centimeters (2.2 inches) across.

The stars that light it

The bright center of the nebula holds its four most massive stars, called the Trapezium after the four-sided shape they make. Ultraviolet light from these stars is carving a hollow in the cloud they formed from. Because the stars have blown away most of the nearby dust and gas, astronomers have a clear view into the nebula.

A Hubble Space Telescope picture released in 2006 shows more than 3,000 stars in the nebula. Among them are brown dwarfs, objects too small to shine by nuclear fusion the way the Sun does. In 2016, infrared images from ESO's Very Large Telescope revealed about ten times as many brown dwarfs and lone planet-mass objects as were known before.

Where planets begin

Near the Trapezium, Hubble found young stars surrounded by disks of gas and dust, called protoplanetary disks. Planets can form in disks like these, and the Solar System probably formed from one about 4.5 billion years ago. Most of the known disks of this kind that are lit up by nearby stars lie in the Orion Nebula.

Astronomers think the Sun itself was born in a cloud like this one. People have watched the nebula for a long time: NASA notes that the Maya of Mesoamerica saw it as the cosmic fire of creation.