Starship Asterisk*

[float=right][img3="The inner part of NGC 7822 in Cepheus. Image: Mark Carter."]https://apod.nasa.gov/apod/image/2201/IMG_9447_1024.jpg[/img3][/float][float=left][img3="The full question mark shape of NGC 7822 along with small round nebula Sharpless 2-170 (bottom). Image: Yizhou Zhang."]https://apod.nasa.gov/apod/image/2110/NGC7822_Yizhou_960.jpg[/img3][/float]

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I find the inner part of NGC 7822 somewhat messy-looking, and I prefer the full, tantalizing cosmic question mark shape.

Me being me, I always want to know what hot blue stars are ionizing each particular emission nebula (except those that aren't ionized by stars but by shock waves... oh well...).

So for me, the problem with NGC 7822 is that the ionizing blue stars are very far from obvious. But it's not as if this nebula lacks them. Another picture might give you a better idea as to where to find them:


[float=left][attachment=0]NGC 7822 Neil Fleming annotated.png[/attachment][c][size=85][color=#0040FF]NGC 7822. Photo: Neil Fleming.[/color][/size][/c][/float]

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BD+66 1673 appears to be the hottest of the stars ionizing NGC 7822.

[quote][url=https://en.wikipedia.org/wiki/NGC_7822]Wikipedia[/url] wrote:

NGC 7822 is a young star forming complex in the constellation of Cepheus. The complex encompasses the emission region designated Sharpless 171, and the young cluster of stars named Berkeley 59. The complex is believed to be some 800–1000 pc distant, with the younger components aged no more than a few million years.[b][size=110][color=#0040FF]
The complex also includes one of the hottest stars discovered within 1 kpc of the Sun, namely BD+66 1673, which is an eclipsing binary system consisting of an O5V that exhibits a surface temperature of nearly 45,000 K and a luminosity about 100,000 times that of the Sun.[/color][/size][/b]
The star is one of the primary sources illuminating the nebula and shaping the complex's famed pillars of creation-type formations, the elephant trunks.[/quote]

If you check out the [url=http://simbad.u-strasbg.fr/simbad/sim-id?Ident=BD+%2B66+1673]Simbad info[/url] on BD+66 1673 (which is called V* V747 Cep over at Simbad), you can see in the accompanying image that the star appears to be just peeking out behind a dark dust lane. I think the star in question is the one I have marked with white lines on Neil Fleming's image. Berkeley 59 would be the young cluster.

BD+66 1673 is not visible in today's APOD.

Ann

[float=right][youtube]https://www.youtube.com/watch?v=kKVV23LAkRo[/youtube][/float][quote="APOD Robot" post_id=319996 time=1642655245 user_id=128559]

[b] Explanation: [/b] Hot, young stars and [url=http://www.eso.org/public/news/eso1518/]cosmic pillars[/url] of gas and dust seem to crowd into NGC 7822. At the edge of a giant molecular cloud toward the northern constellation Cepheus, the glowing star forming region lies about 3,000 light-years away. Within the nebula, bright edges and dark shapes stand out in this colorful [url=https://www.instagram.com/p/CY4FNczLdOy/]telescopic skyscape[/url]. The atomic emission is [url=https://apod.nasa.gov/apod/ap051223.html]powered by[/url] energetic radiation from the central hot stars. Their powerful winds and radiation sculpt and erode the denser pillar shapes and clear out a [url=https://apod.nasa.gov/apod/ap150225.html]characteristic[/url] cavity light-years across the center of the natal cloud. Stars could still be forming inside the pillars by [url=http://hyperphysics.phy-astr.gsu.edu/hbase/astro/gravc.html#c1]gravitational collapse[/url] but as the pillars are eroded away, any forming stars will ultimately be cutoff from their reservoir of [url=https://hubblesite.org/contents/news-releases/2015/news-2015-01.html]star stuff[/url].[/quote]
[c][url=https://en.wikipedia.org/wiki/Victor_Mature]Star stuff[/url][/c]

[attachment=0]IMG_9447.jpg[/attachment]
What a view! Great views often on APOD! 8-) :D

Which one is Bo?

[url=https://apod.nasa.gov/apod/ap220120.html] [img]https://apod.nasa.gov/apod/calendar/S_220120.jpg[/img] [size=150]NGC 7822 in Cepheus[/size][/url]

[b] Explanation: [/b] Hot, young stars and [url=http://www.eso.org/public/news/eso1518/]cosmic pillars[/url] of gas and dust seem to crowd into NGC 7822. At the edge of a giant molecular cloud toward the northern constellation Cepheus, the glowing star forming region lies about 3,000 light-years away. Within the nebula, bright edges and dark shapes stand out in this colorful [url=https://www.instagram.com/p/CY4FNczLdOy/]telescopic skyscape[/url]. The image includes data from [url=https://apod.nasa.gov/apod/ap060324.html]narrowband[/url] filters, mapping emission from atomic oxygen, hydrogen, and sulfur into blue, green, and red hues. The emission line and color combination has become well-known as the [url=https://hubblesite.org/contents/articles/the-meaning-of-light-and-color]Hubble palette[/url]. The atomic emission is [url=https://apod.nasa.gov/apod/ap051223.html]powered by[/url] energetic radiation from the central hot stars. Their powerful winds and radiation sculpt and erode the denser pillar shapes and clear out a [url=https://apod.nasa.gov/apod/ap150225.html]characteristic[/url] cavity light-years across the center of the natal cloud. Stars could still be forming inside the pillars by [url=http://hyperphysics.phy-astr.gsu.edu/hbase/astro/gravc.html#c1]gravitational collapse[/url] but as the pillars are eroded away, any forming stars will ultimately be cutoff from their reservoir of [url=https://hubblesite.org/contents/news-releases/2015/news-2015-01.html]star stuff[/url]. This field of view spans about 40 light-years at the estimated distance of NGC 7822.


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