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Pelican, North America Nebulae and the Bajamar Star - IC5070, NGC7000, Sh2-117, 2MASS J205551.3+435225, Mau_Bard
Pelican, North America Nebulae and the Bajamar Star - IC5070, NGC7000, Sh2-117, 2MASS J205551.3+435225, Mau_Bard

Pelican, North America Nebulae and the Bajamar Star - IC5070, NGC7000, Sh2-117, 2MASS J205551.3+435225

Getting plate-solving status, please wait...
Pelican, North America Nebulae and the Bajamar Star - IC5070, NGC7000, Sh2-117, 2MASS J205551.3+435225, Mau_Bard
Pelican, North America Nebulae and the Bajamar Star - IC5070, NGC7000, Sh2-117, 2MASS J205551.3+435225, Mau_Bard

Pelican, North America Nebulae and the Bajamar Star - IC5070, NGC7000, Sh2-117, 2MASS J205551.3+435225

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Description

With this image I consider the difficult commissioning of my new "baby scope" (80mm, f/4.8 included reducer) completed. Now all the pieces are working, even if after this recording here I performed some adjustment that improved the guiding.
The image was exposed on 8 and 9 August 2022 from my Bortle 7 city backyard with good air conditions and nearly full moon.

In the annotated version, I highlighted the damped "Bajamar Star" that is responsible for the ionization of the whole Sh2-117 complex (see the Bajamar's interesting story here below!).

The Pelican Nebula
Also known as IC 5070, is an H II region associated with the North America Nebula in the constellation Cygnus. 
The prominent pedunculus hosts the Herbig–Haro object 555, a young star emitting two jets barely visible here due to the image scale.

The North America Nebula
Known also as NGC 7000 or Caldwell 20, has a shape that resembles that of the continent of North America, complete with a prominent Gulf of Mexico.

It was observed initially by William Herschel in 1786 as a “faint milky nebulosity scattered over this space, in some places pretty bright.” and was catalogued in the New General Catalogue as NGC 7000, where it is described as a "faint, most extremely large, diffuse nebulosity.” In 1890, the pioneering German astrophotographer Max Wolf noticed this nebula's characteristic shape on a long-exposure photograph, and dubbed it the North America Nebula.

In his study of nebulae on the Palomar Sky Survey plates in 1959, American astronomer Stewart Sharpless realised that the North America Nebula is part of the same interstellar cloud of ionized hydrogen (H II region) as the Pelican Nebula, separated by a dark band of dust, and listed the two nebulae together in his second list of 313 bright nebulae as Sh2-117. American astronomer Beverly T. Lynds catalogued the obscuring dust cloud as L935 in her 1962 compilation of dark nebulae. Dutch radio astronomer Gart Westerhout detected the HII region Sh2-117 as a strong radio emitter, 3° across, and it appears as W80 in his 1958 catalogue of radio sources in the band of the Milky Way.

The North America Nebula covers a region more than ten times the area of the full moon, but its surface brightness is low, so normally it cannot be seen with the unaided eye.
The portion of the nebula resembling Mexico and Central America is known as the Cygnus Wall. This region exhibits the most concentrated star formation.

At optical wavelengths, the North America Nebula and the Pelican Nebula IC 5070 appear distinct as they are separated by the silhouette of the dark band of interstellar dust LDN935. The dark cloud is however transparent to radio waves and infrared radiation, and these wavelengths reveal the central regions of Sh2-117 that are not visible to an ordinary telescope, including many highly luminous stars.

The distances to the North America and Pelican nebulae were controversial, because there are few precise methods for determining how far away an HII region lies. Until 2020, most astronomers accepted a value of 2,000 light years, though estimates ranged from 1,500 to 3,000 light years.

But in 2020, the Gaia astrometry spacecraft measured the distances to 395 stars lying within the HII region, giving the North America and Pelican nebulae a distance of 2,590 light years (795±25 parsecs). The entire HII region Sh2-117 is estimated to be 140 light years across, and the North America nebula stretches 90 light years north to south.

The Bajamar Star
HII regions shine because their hydrogen gas is ionised by the ultraviolet radiation from a hot star. In 1922, Edwin Hubble proposed that Deneb may be responsible for lighting up the North America Nebula, but it soon became apparent that it is not hot enough: Deneb has a surface temperature of 8,500 K, while the nebula's spectrum shows it is being heated by a star hotter than 30,000 K. In addition, Deneb is well away from the middle of the complete North America/Pelican nebula complex (Sh2-117), and by 1958 George Herbig realised that the ionizing star had to lie behind the central dark cloud L935. In 2004, European astronomers Fernando Comerón and Anna Pasquali searched for the ionizing star behind LDN935 at infrared wavelengths, using data from the 2MASS survey, and then made detailed observations of likely suspects with the 2.2 m telescope at the Calar Alto Observatory in Spain. One star, catalogued J205551.3+435225, fulfilled all the criteria. Lying right in the centre of Sh2-117, with a temperature of over 40,000 K, it is almost certainly the ionising star for the North America and Pelican nebulae.

Later observations have revealed J205551.3+435225 is a spectral type O3.5 star, with another hot star (type O8) in orbit. J205551.3+435225 lies just off the “Florida coast” of the North America Nebula, so it has been more conveniently nicknamed the Bajamar Star ("Islas de Bajamar," meaning "low-tide islands" in Spanish, was the original name of the Bahamas because many of them are only easily seen from a ship during low tide).

Although the light from the Bajamar Star is dimmed by 9.6 magnitudes (almost 10,000 times) by the dark cloud LDN935, it is faintly visible at optical wavelengths, at magnitude 13.2. If we saw this star undimmed, it would shine at magnitude 3.6, almost as bright as Albireo, the star marking the swan's head.

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  • Final
    Pelican, North America Nebulae and the Bajamar Star - IC5070, NGC7000, Sh2-117, 2MASS J205551.3+435225, Mau_Bard
    Original
  • Pelican, North America Nebulae and the Bajamar Star - IC5070, NGC7000, Sh2-117, 2MASS J205551.3+435225, Mau_Bard
    B

B

Title: Bajamar Star and Annotation

Description: Partially hidden Bajamar Star highlighted, responsible for the whole Sh2-117 emission

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Pelican, North America Nebulae and the Bajamar Star - IC5070, NGC7000, Sh2-117, 2MASS J205551.3+435225, Mau_Bard