Stars – Page 4 – Semper Iuvenis Photography

Sadr – Gamma Cygni Nebula

This image contains several distinct features.

NGC 6910 – Inchworm Cluster / Rocking Horse Cluster. It is a small open cluster located near Gamma Cygni (Sadr) in the constellation of Cygnus. It lies approximately 3700 light years away, near the galactic plane. It is embedded in IC 1316, a much larger emission nebula.

Sadr, Gamma Cygni (γ Cyg) is a yellow-white supergiant star. With an apparent magnitude of 2.23, it is the constellation’s second brightest star, after Deneb. Sadr lies at an approximate distance of 1,800 light years from Earth. It is the star that marks the intersection of the Northern Cross, a bright asterism that dominates the summer sky in the northern hemisphere. Sadr lies in a rich field of the Milky Way and is surrounded by the diffuse emission nebula IC 1318, also known as the Gamma Cygni Nebula or Sadr Region.

IC 1318 – Sadr is surrounded by the emission nebula IC 1318, one of the several nebulous regions at the centre of the Northern Cross. IC 1318 is known as the Gamma Cygni Nebula, Sadr Region or the Butterfly Nebula. It is not physically related to Sadr, but merely lies in the same line of sight. The nebula is located much farther away than the star, at a distance of 4,900 light years. The star that illuminates IC 1318 is a hot, blue O9-class star obscured by interstellar dust.

Sadr is the central star of the Northern Cross, also formed by the bright Deneb (Alpha Cygni), Albireo (Beta Cygni), Aljanah (Epsilon Cygni) and Fawaris (Delta Cygni). Deneb, Sadr and Albireo form the pole of the cross, while Aljanah and Fawaris mark the crossbeam.

The name Sadr (pronunciation: /ˈsædər/) comes from the Arabic ṣadr, meaning “chest.” It has the same etymology as the name of Alpha Cassiopeiae, Schedar. The name has also been spelled Sadir or Sador. It refers to the star’s position in the constellation, marking the Swan’s chest. The name was officially approved by the International Astronomical Union’s (IAU) Working Group on Star Names (WGSN) on August 21, 2016. It formally applies only to Gamma Cygni A.

Sadr is very easy to find because it lies at the intersection of the bright, large Northern Cross asterism. The Northern Cross is easy to spot on a clear night. It lies within the larger Summer Triangle, a brighter summer asterism formed by Deneb with Vega in the constellation Lyra and Altair in Aquila.

Sadr is located in the vicinity of several interesting deep sky objects. The Rocking Horse Cluster (NGC 6910) is an open cluster located only half a degree east and a little north of the star. It is at a similar distance as the Gamma Cygni Nebula and may be physically associated with it. The cluster has an apparent magnitude of 7.4 and occupies an area of 10’. The neighbouring open cluster Collinder 419 (Cr 419) is only slightly fainter, with a visual magnitude of 7.60.

Sadr is located in the constellation Cygnus. Representing the celestial Swan, Cygnus is one of the larger northern constellations, stretching across 804 square degrees of the apparent sky. It is known mainly for the Northern Cross and its bright stars Deneb, the 19th brightest star in the sky, and Albireo, a famous contrasting double.

The constellation contains a number of well-known deep sky objects, among others the bright open clusters Messier 29, Messier 39 and NGC 6910, the Fireworks Galaxy (NGC 6946), and several bright nebulae, including the North America Nebula (NGC 7000), the Pelican Nebula (IC 5070), the Veil Nebula (NGC 6960, 6962, 6979, 6992 and 6995), the blinking planetary nebula (NGC 6826), and the nebulae near Sadr: the Gamma Cygni Nebula (IC 1318) and the Crescent Nebula (NGC 6888).

The best time of year to see the stars and deep sky objects in the constellation is during the month of September.

Key Facts & Summary

Sadr is located at around 1,800 light-years / 560 parsecs away from the Sun.

Sadr is the second brightest star in the constellation of Cygnus, after Deneb. This star is also among the brightest stars in the night sky.

Its location marks the intersection of the Northern Cross, a bright asterism that dominates the summer sky in the northern hemisphere.

In comparison to our Sun, Sadr is around 33,023 times brighter, yet it is several times younger, having an estimated age of around 12 million years.

Sadr has around 12.11 solar masses and a radius of 150 times that of our Sun.

Sadr is a supergiant star of spectral type FB8 lab, appearing yellowish-white in color.

The star is surrounded by a diffuse nebula called IC 1318, or the Gamma Cygni region.

The star’s name, Sadr, is derived from Arabic and it translates to “chest.” The same word gave rise to the name of the star Schedar – Alpha Cassiopeiae.

Sadr formed at around 12 million years ago from an interstellar medium of gas and dust. Gravity pulled the swirling gas and dust together until it reached the critical temperature, giving birth to the second-brightest star in Cygnus, named Sadr.

It is quite a young star and the interstellar medium from which it was born was probably abundant in elements such as hydrogen, thus the reason for its short lifespan, as Sadr will eventually go supernova.

Sadr has reached the supergiant stage of its stellar evolution and thus its radius has expanded and it will probably continue to expand several times its former size.

Since Sadr is so massive, it will one day go supernova and illuminate a big portion of the night sky, despite being such a young star.

Elephant’s Trunk Nebula

The Elephant’s Trunk Nebula is a concentration of interstellar gas and dust within the much larger ionized gas region IC 1396 located in the constellation Cepheus about 2,400 light years away from Earth. The piece of the nebula shown here is the dark, dense globule IC 1396A; it is commonly called the Elephant’s Trunk nebula because of its appearance at visible light wavelengths, where there is a dark patch with a bright, sinuous rim. The bright rim is the surface of the dense cloud that is being illuminated and ionized by a very bright, massive star (HD 206267) that is just to the east of IC 1396A.

The Elephant’s Trunk Nebula is now thought to be a site of star formation, containing several very young (less than 100,000 yr) stars that were discovered in infrared images in 2003. Two older (but still young, a couple of million years, by the standards of stars, which live for billions of years) stars are present in a small, circular cavity in the head of the globule. Winds from these young stars may have emptied the cavity.

The combined action of the light from the massive star ionizing and compressing the rim of the cloud, and the wind from the young stars shifting gas from the center outward lead to very high compression in the Elephant’s Trunk Nebula. This pressure has triggered the current generation of protostars.

Very happy to have captured this piece of our night sky from Burke County, NC. A very peaceful night here in the hills of the blue Ridge. Any questions or comments, we’d love to hear from you.

North America Nebula

My first target in Astrophotography was the North America Nebula framed with the Pelican Nebula. The name is obvious as this dust cloud really looks like the continent. There has been a lot of stuff to learn in photographing objects in our dark sky. The initial image is as you might expect – black with a few white dots! This version of the nebula is comprised of 48 images or 2 1/2 hours of exposure obtained over two nights of imaging. My first night was not very productive (learning curve is steep).

Once the images have been obtained they have to be debayered, aligned, registered and stacked. While PixInsight (PI) can do this, I prefer DeepSkyStacker (DSS) and feel it does a better job than my manual workings in PI. After stacking I do switch to PI for most of the processing and then Photoshop(PS) for the final tweaks.

All of this is run from my Acer Netbook, which I remotely manage from my home office (about 40 yards away). Image acquisition is totally performed with Astro Photography Tool (APT). Everything is intergrated via ASCOM drivers. It took over a month to understand all of the technology involved. I learned that capturing the photograph is only half the job! Truly looking forward to mastering this over the years.

As always my images can be seen in the Semper Iuvenis Galleries.

Astrophotography

As a result of the Covid-19 stuff I looked for an avenue of photography that did not involve travel or people. I had always wanted to photograph the moon or the Milky Way but lacked the equipment to to do it right and honestly didn’t think it achievable. I sought help on Youtube! Trevor Jones at Astrobackyard.com is awesome and his tutorials convinced me that I could photograph the night sky after all – and the investment is less than a single dive trip!

Stay tuned for images as clear night skies allow. As always my images are presented in the Semper Iuvenis Galleries. Cheers!