How big is North America Nebula? | Scale of the Universe

The North America Nebula is a cloud of glowing gas in the constellation Cygnus, named for its outline, which looks like the continent of North America. It is about 2,560 light-years from Earth. A light-year is the distance light travels in one year, about 9.46 trillion kilometers. At its longest, the nebula is about 90 light-years, or 850 trillion kilometers, across.

Size

Like any cloud of gas, the nebula has no sharp edge, so its size depends on how faint a glow is counted. Two catalogs of nebulae give its longest dimension as 120 arcminutes, or 2 degrees of sky. An arcminute is one-sixtieth of a degree.

Turning an angle on the sky into a width needs the distance. The Gaia space telescope has measured the distances of hundreds of young stars in the nebula. Together they put it about 2,560 light-years away, give or take about 50 light-years. At that distance, 2 degrees is about 90 light-years.

The North America Nebula and the Pelican Nebula are two parts of one larger glowing region. Seen from Earth, a dark lane of dust and cold gas lies between them and gives the North America Nebula its shape, including the part called the "Gulf of Mexico". The whole region is about 3 degrees across, or about 130 light-years.

Size comparisons

Seen from Earth, the nebula is about four times as wide as the full Moon. It looks faint against the stars of the Milky Way, and binoculars show it only as a subtle glow.
The Orion Nebula, another cloud where stars are forming, is about 24 light-years across. The North America Nebula is nearly four times as wide.
The nebula is about 21 times as wide as the distance from the Sun to Proxima Centauri, the nearest star, 4.2 light-years away.
If the orbit of Neptune around the Sun were shrunk to the width of a U.S. penny, 19 millimeters (0.75 inches), the nearest star would be about 85 meters (280 feet) away. The nebula would be about 1.8 kilometers (1.1 miles) across.

The star that lights it

Light from a very hot star knocks electrons off the atoms in the gas, and this makes the gas glow. The gas is mostly hydrogen, which gives the nebula its reddish color.

The main star lighting both the North America and Pelican nebulae is called the Bajamar Star. It is actually a pair of massive, very hot stars of the kind astronomers call O-type. It sits behind the dark cloud of the "Gulf of Mexico", which dims its visible light about 7,000 times. It was not identified until 2005.

Where stars are forming

New stars are still forming in the region, mostly inside the dark lane of dust and gas. Measurements from Gaia sort the young stars into at least six groups. Three of the groups are spreading apart, with stars moving outward at up to about 8 kilometers per second.

The Bajamar Star is moving quickly compared with the young stars around it. Astronomers think it escaped from one of the groups about 1.5 million years ago. William Herschel discovered the nebula in 1786, and it is listed as NGC 7000 in the New General Catalogue of nebulae and star clusters.