Explanation: Fantastic shapes lurk in clouds of glowing hydrogen gas in NGC 6188. The emission nebula is found near the edge of a large molecular cloud, unseen at visible wavelengths, in the southern constellation Ara, about 4,000 light-years away. Massive, young stars of the embedded Ara OB1 association were formed in that region only a few million years ago, sculpting the dark shapes and powering the nebular glow with stellar winds and intense ultraviolet radiation. The recent star formation itself was likely triggered by winds and supernova explosions, from previous generations of massive stars, that swept up and compressed the molecular gas. Joining NGC 6188 on this cosmic canvas is rare emission nebula NGC 6164, also created by one of the region's massive O-type stars. Similar in appearance to many planetary nebulae, NGC 6164's striking, symmetric gaseous shroud and faint halo surround its bright central star at the upper right. The field of view spans about two full Moons, corresponding to 70 light years at the estimated distance of NGC 6188.
This is a very beautiful picture of a truly fascinating part of the sky.
A lovely thing about today's APOD is that the photographer has used the blue-green OIII filter to such great effect. The star surrounded by the ethereal blue shell is HD 148937, a massive O-typ star which is on its way to becoming a Wolf-Rayet star. A Wolf-Rayet star is what you get when a massive O-type star really starts blowing off its outer layers. The process is similar to a red giant blowing off its outer layers to become a white dwarf, surrounded by a planetary nebula.
The blue nebula surrounding HD 148937...
...is somewhat similar to a planetary nebula, and like a planetary nebula, its bluish color comes fromdoubly ionized oxygen.
Photo, HD 148937: Don Goldman.
Photo, Abell 39: George Jacoby.
The central star of a planetary nebula is every bit as hot as a Wolf-Rayet star, and it is typically hotter than a "normal" O-type star. The difference is that a Wolf-Rayet star is a lot more massive and luminous than a white dwarf, which is always very tiny. Wolf-Rayet stars are believed to end up as supernovae.
HD 148937 is one of the fantastic stars in today's APOD. But the star responsible for most of the ionization in this picture - the star responsible for "setting these masses of hydrogen gas aglow in red", as it were - is HD 150136, the blue star at 8 o'clock. HD 150136 is a very young O-type star, probably no more than one million years old. (By contrast, HD 148937 is on its way to saying good-bye to its status as an O-type star, so it must be several million years old.) Young HD 150136 may actually be an O3 star, which would make it a truly rare beast indeed. Off hand, I can only think or one other O3 star in our galaxy, HD 93128 in cluster Trumpler 14 near Eta Carina.
Stars lose a lot of mass. This NASA solar eclipse image from Antarctica, 2008 (where a female friend of mine was present to look at the eclipse) gives you an idea of how mass is flowing away from the Sun in a solar wind. But hot, massive stars have much, much stronger winds.
Space isn't empty. There is hydrogen everywhere, and stars are born in gas clouds, where the density of gas is very high. Newborn hot stars consume a lot of gas and blow away still more gas, leaving a cavity close to themselves. But remnants of the original gas cloud may still be found in the vicinity of the hot young stars. When the strong stellar winds from hot stars hit the gas that remains of the original nebula, this gas may be compressed so much that it leads to more star formation.
<<In illustrations (e.g., Johann Elert Bode's illustration of Ara, from his Uranographia (1801) shown right) Ara is usually depicted as an altar with its smoke 'rising' southward. In ancient Greek mythology, Ara was identified as the altar, made by the Cyclops, where the gods first made offerings and formed an alliance when they were about to fight the Titans. The northwest corner of Ara is crossed by the Milky Way and contains several open clusters, notably NGC 6200 and diffuse nebulae. The brightest of the globular clusters, sixth magnitude NGC 6397, at a distance of 8,200 light-years might be the closest of all globular clusters in the sky.>>
Re: APOD: NGC 6188 and NGC 6164 (2011 Jul 28)
Posted: Thu Jul 28, 2011 2:13 pm
by Chris Peterson
Ann wrote:The blue nebula surrounding HD 148937...is somewhat similar to a planetary nebula, and like a planetary nebula, its bluish color comes from triply ionized oxygen
The common nomenclature is a bit confusing. In fact, the color is primarily the 500.7 nm doubly ionized oxygen line, which is also called O III.
Re: APOD: NGC 6188 and NGC 6164 (2011 Jul 28)
Posted: Thu Jul 28, 2011 2:15 pm
by Chris Peterson
garry wrote:"Star formations triggered by winds"? Errr you cannot have a wind in a vacuum! Less artistic licence and correct terminology!
Very true. But since these regions are certainly not vacuums, there is no problem with having winds.
Re: APOD: NGC 6188 and NGC 6164 (2011 Jul 28)
Posted: Thu Jul 28, 2011 2:56 pm
by moonstruck
garry wrote:"Star formations triggered by winds"? Errr you cannot have a wind in a vacuum! Less artistic licence and correct terminology!
This is the second negative comment you've made in two days where you used the words (artistic licence). What does licence mean?
moonstruck wrote:This is the second negative comment you've made in two days where you used the words (artistic licence). What does licence mean?
Obviously it's just a bit of artistic license in orthography.
It seems licence is the accepted spelling in the Queen's English,
while license seems to be the preferred American spelling.
Just one of those things, like the British -ise vs American -ize.
"None can love freedom heartily, but good men; the rest love not freedom, but licence." ~ John Milton
Re: APOD: NGC 6188 and NGC 6164 (2011 Jul 28)
Posted: Thu Jul 28, 2011 8:53 pm
by Ann
Chris Peterson wrote:
Ann wrote:The blue nebula surrounding HD 148937...is somewhat similar to a planetary nebula, and like a planetary nebula, its bluish color comes from triply ionized oxygen
The common nomenclature is a bit confusing. In fact, the color is primarily the 500.7 nm doubly ionized oxygen line, which is also called O III.
Oooops!!!!
Ann
Re: APOD: NGC 6188 and NGC 6164 (2011 Jul 28)
Posted: Thu Jul 28, 2011 9:00 pm
by Ann
Nice videos, Orin!
So Adam was made out of dust pillars in emission nebula NGC 6188, eh? Well, it fits with the description that Adam was made of dust!
And nice Star Wars reference! It's fitting that Princess Leia wore an apparently OB-colored dress (blue-white) when she was calling for Obi!
Ann
Re: APOD: NGC 6188 and NGC 6164 (2011 Jul 28)
Posted: Fri Jul 29, 2011 1:21 am
by neufer
Ann wrote:
A lovely thing about today's APOD is that the photographer has used the blue-green OIII filter to such great effect. The star surrounded by the ethereal blue shell is HD 148937, a massive O-typ star which is on its way to becoming a Wolf-Rayet star. A Wolf-Rayet star is what you get when a massive O-type star really starts blowing off its outer layers. The process is similar to a red giant blowing off its outer layers to become a white dwarf, surrounded by a planetary nebula.
http://apod.nasa.gov/apod/ap060606.html wrote:
Explanation: How did a star form this beautiful nebula? In the middle of emission nebula NGC 6164-5 is an unusually massive star nearing the end of its life. The star, visible in the center of the above image and catalogued as HD 148937, is so hot that the ultraviolet light it emits heats up gas that surrounds it. That gas was likely thrown off from the star, possibly by its fast rotation, like a rotating lawn sprinkler. Expelled material might have been further channeled by the magnetic field of the star, creating the symmetric shape of the bipolar nebula. NGC 6164-5 spans about four light years and is located about 4,000 light years away toward the southern constellation Norma.
http://en.wikipedia.org/wiki/List_of_people_with_bipolar_disorder wrote:
Many people involved with creativity and Arts are believed to have suffered from bipolar disorder (formerly known as "manic depression"), such as Vincent van Gogh, Edgar Allan Poe, Georg Cantor, Ludwig Boltzmann, Edvard Munch, Ernest Hemingway, Graham Greene, and Jack London.
Re: APOD: NGC 6188 and NGC 6164 (2011 Jul 28)
Posted: Fri Jul 29, 2011 6:53 pm
by MarekX
Why isn't 6188 called the Dragon nebula? Or am I the only one who sees it there? It punched me in the face in first second though, so I think it must be obvious
Re: APOD: NGC 6188 and NGC 6164 (2011 Jul 28)
Posted: Sat Mar 03, 2012 9:08 am
by WolfgangW
I read about a photometric optical survey of NGC 6167 and NGC 6193 and their neighbourhood field with the result that they produce a uniform photometric catalogue and estimate robustly the fundamental parameters of NGC 6167 and NGC 6193, in addition to the IRAS 16375-4854 source. So all of them are located at approximately the same distance from the Sun in the Sagittarius-Carina Galactic arm. ...
NGC 6188 and NGC 6164
