North America Nebula

Lore & Background

William Herschel first noted the nebula on October 24, 1786, from Slough, England, describing a 'faint milky nebulosity scattered over this space, in some places pretty bright.' His son John Herschel catalogued the most prominent region on August 21, 1829, and it was later listed in the New General Catalogue as NGC 7000, a 'faint, most extremely large, diffuse nebulosity.' In 1890, German astrophotographer Max Wolf recognized its characteristic shape on a long-exposure photograph and named it the North America Nebula. In 1959, American astronomer Stewart Sharpless determined that the North America Nebula and the Pelican Nebula are part of the same interstellar cloud of ionized hydrogen, separated by a dark band of dust, and listed them together as Sh 2-117. American astronomer Beverly T. Lynds catalogued the obscuring dust cloud as L935 in 1962. Dutch radio astronomer Gart Westerhout detected the H II region as a strong radio emitter, 3° across, catalogued as W80 in 1958.

Reader's Guide

The North America Nebula covers an area more than ten times that of the full moon, but its low surface brightness makes it invisible to the unaided eye under normal conditions. Binoculars or telescopes with a wide field of view (about 3°) can show it as a foggy patch under dark skies; a UHC filter allows it to be seen without magnification. Its reddish color, from hydrogen Hα emission, appears only in photographs. The portion resembling Mexico and Central America is called the Cygnus Wall, the region of most concentrated star formation. The nebula's distance was long uncertain, with estimates ranging from 1,500 to 3,000 light years, until 2020 when the Gaia spacecraft measured distances to 395 stars within the H II region, yielding 2,590 light years. The ionizing star was long debated: Edwin Hubble proposed Deneb in 1922, but Deneb is too cool (8,500 K) to heat the nebula, which requires a star hotter than 30,000 K. In 2004, European astronomers Fernando Comerón and Anna Pasquali identified the star J205551.3+435225 behind the dark cloud L935, with a temperature over 40,000 K. This star, now called the Bajamar Star, is of spectral type O3.5 with an O8 companion, and lies off the 'Florida coast' of the nebula. Its light is dimmed by 9.6 magnitudes by L935, but it is faintly visible at magnitude 13.2; undimmed it would shine at magnitude 3.6. The Bajamar Star and another O-type star, HD 199579 (the Toronto star), are escaping from a group called the Bermuda cluster, apparently ejected about 1.5 million years ago.

Did You Know?

• Its ionizing star, the Bajamar Star, is dimmed by nearly 10,000 times by the dark cloud L935.
• The nebula and the Pelican Nebula are part of the same H II region, Sh 2-117, separated by a dark dust band.
• The Cygnus Wall, resembling Mexico and Central America, is the region of most concentrated star formation.

From Faint Glow to a Continent's Silhouette

William Herschel first recorded a vague, milky smudge in the Cygnus sky on October 24, 1786, while observing from Slough, England. He described it as a faint nebulosity that brightened in patches, but no one gave it a distinctive name for over a century. His son John formally catalogued the brightest portion on August 21, 1829, and it entered the New General Catalogue as NGC 7000 with the note that it was a faint, extremely large, diffuse nebulosity. The breakthrough in public recognition came in 1890, when German astrophotographer Max Wolf examined a long-exposure plate and saw the unmistakable outline of a continent. He christened it the North America Nebula, a name that stuck. In the mid-twentieth century, the object's context expanded dramatically. Stewart Sharpless recognized in 1959 that the nebula and the nearby Pelican Nebula were actually one vast ionized hydrogen cloud split by a dust lane, listing them together as Sh 2-117. Beverly Lynds added the obscuring dust band to her 1962 dark-nebula catalogue as L935, and Dutch radio astronomer Gart Westerhout identified the whole complex as a powerful radio source, W80, in his 1958 catalogue.

A Continent Written in Hydrogen Light

The North America Nebula sprawls across a patch of sky more than ten times the apparent area of the full moon, yet its glow is so diffuse that the naked eye cannot pick it out against the Cygnus background. Under truly dark skies, wide-field binoculars or a low-power telescope with roughly a three-degree field will reveal a soft, foggy patch of light. A UHC filter, which blocks certain unwanted wavelengths, can make the nebula visible even without magnification. The iconic continental outline and the characteristic reddish hue produced by hydrogen alpha emission, however, remain visible only in long-exposure photographs. The region that corresponds to Mexico and Central America on the map is called the Cygnus Wall, and it hosts the most intense star formation within the complex. At optical wavelengths, the North America and Pelican nebulae look like two separate objects because the dark dust band L935 cuts between them. But that same dust is transparent to radio and infrared radiation, and observations at those wavelengths expose the hidden central regions of Sh 2-117, including many extremely luminous stars that no ordinary optical telescope can reveal.

The Star Behind the Wall

For decades, astronomers puzzled over what powered the North America Nebula's glow. In 1922, Edwin Hubble suggested Deneb, the bright star at the swan's tail, might be the ionizing source. The idea quickly collapsed: Deneb's surface temperature of roughly 8,500 kelvin is far too cool, while the nebula's spectrum demands a star exceeding 30,000 kelvin. Deneb also sits outside the center of the full complex. By 1958, George Herbig reasoned that the true ionizing star must hide behind the central dust cloud L935. The answer emerged in 2004, when Fernando Comerón and Anna Pasquali used infrared data from the 2MASS survey to shortlist candidates behind the dust, then followed up with detailed observations on the 2.2-meter telescope at Calar Alto Observatory in Spain. One object, catalogued J205551.3+435225, met every criterion: it sits at the center of Sh 2-117 and burns at over 40,000 kelvin. Later work classified it as an O3.5 star with an O8 companion in orbit. The IAU approved its nickname, the Bajamar Star, on April 18, 2026. Despite being dimmed by 9.6 magnitudes by L935, the star is faintly detectable at magnitude 13.2; undimmed, it would shine at magnitude 3.6, nearly rivaling Albireo at the swan's head.

Measuring the Distance and the Wider Complex

Determining how far the North America Nebula lies was long a source of disagreement among astronomers, because there are few reliable methods for pinning down the distance to an HII region. For years, the consensus settled on roughly 2,000 light years, though individual estimates stretched from 1,500 to 3,000 light years. That uncertainty was finally resolved in 2020, when the Gaia astrometry spacecraft measured the positions and parallaxes of 395 stars embedded within the HII region. The result placed the North America and Pelican nebulae at 2,590 light years, or 795 ± 25 parsecs. At that distance, the entire Sh 2-117 complex spans about 140 light years, while the North America portion alone stretches 90 light years from north to south. The complex also has a dynamic stellar neighborhood. The Bajamar Star and another O-type star in the region, HD 199579 (nicknamed the Toronto Star), are both escaping from a group of stars called the Bermuda cluster, following the same Caribbean geographical nomenclature. Both appear to have been ejected from that cluster roughly 1.5 million years ago, carrying the seeds of the nebula's illumination far from their birthplace.