APOD: North America and the Pelican (2021 Sep 16)

[APOD Robot]

North America and the Pelican

Explanation: Fans of our fair planet might recognize the outlines of these cosmic clouds. On the left, bright emission outlined by dark, obscuring dust lanes seems to trace a continental shape, lending the popular name North America Nebula to the emission region cataloged as NGC 7000. To the right, just off the North America Nebula's east coast, is IC 5070, whose avian profile suggests the Pelican Nebula. The two bright nebulae are about 1,500 light-years away, part of the same large and complex star forming region, almost as nearby as the better-known Orion Nebula. At that distance, the 3 degree wide field of view would span 80 light-years. This careful cosmic portrait uses narrow band images combined to highlight the bright ionization fronts and the characteristic glow from atomic hydrogen, sulfur, and oxygen gas. These nebulae can be seen with binoculars from a dark location. Look northeast of bright star Deneb in the constellation Cygnus the Swan.

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[Ann]

After all these years, I still think that Hubble palette images of nebulas look strange because of their colors.

That said, I must admit that today's APOD does a splendid job at showing us that the dark dividing line between the North America Nebula and the Pelican Nebula is really a long and thick foreground dust lane, which is getting some reinforcement by another dust lane crossing it at the "Gulf of Mexico".

It really looks as if the North America Nebula and the Pelican Nebula are in fact one and the same large region of emission nebulosity. So the one million dollar question is, what and where is the star ionizing it all?

Ann

[ZJPBJ]

I’m sorry, but the big black dust lane is a little reminiscent of something else to me...

[orin stepanek]

Nice; a good photo of the North America and Pelican! I happened to
notice what looks to me like a dog's face between the two!

Thanks for the annotation! I have trouble reading a star map!

[neufer]

It really looks as if the North America Nebula and the Pelican Nebula are in fact one and the same large region of emission nebulosity. So the one million dollar question is, what and where is the star ionizing it all?

North America and Pelican Nebulae viewed in optical (top left) and successively longer infrared wavelengths, which penetrate the dust cloud between them.

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Click to play embedded YouTube video.

<<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 L935 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 L935, 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.

[Ann]

It really looks as if the North America Nebula and the Pelican Nebula are in fact one and the same large region of emission nebulosity. So the one million dollar question is, what and where is the star ionizing it all?

North America and Pelican Nebulae viewed in optical (top left) and successively longer infrared wavelengths, which penetrate the dust cloud between them.

---

<<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 L935 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 L935, 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.

Photo: jgraham/Cloudy Nights

1) HD 199956

2) HD 199547

3) J205551.3+435225? Ionizing star of the North America Nebula and the Pelican Nebula? An O3.5 star, terrifically reddened and dimmed by 9.6 magnitudes, almost 10,000 times?

Ann

[eshy76]

This is great narrowband image of NGC7000 and IC5070, very detailed! I recent captured an OSC version of this region and there is a really dense star field above the North America Nebula which I also find breathtaking.

[Knight of Clear Skies]

<<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 L935 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.

Thanks for that. I knew that Deneb might not be the star ionising the nebula (or nebulae) but not that it had been definitely ruled out as its surface temperature isn't high enough. Many sources still quote Deneb as the ionising source.

[TheZuke!]

Inkednebclust.gif (60.9 KiB) Viewed 3343 times

So, I've added blue lines to Orin's .gif, marking voids between rows of stars.
Is that how the different arms of The Milky Way are determined?