Starship Asterisk*

In New Zealand the Pleiades is known as 'Matariki' and it's rising here signifies the Maori New Year. I love that we are one of the few countries to have a cultural holiday based on an astronomical event!

[quote="bert"]There are a very large number of stars in this photograph that form definite strings. It that due to the time delayed photographic process, or do stars actually form in strings accross space?[/quote]

More often than not, long strings of stars are probably chance alignments.

[float=right][img]http://outreach.atnf.csiro.au/education/senior/astrophysics/images/stellarevolution/pleiadesuks018c.jpg[/img][/float]Take a look at this David Malin/Anglo-Australian Observatory/Royal Observatory of Edinburgh image of the Pleiades: :arrow:

A good thing about it is that it is labelled.

One of the more obvious "strings" of stars in the Pleiades seems to start some distance below Alcyone and extend downward and to the left, passing Merope. However, this string is partly a chance alignment.

The topmost star in this string, HD 23631, is probably a true Pleiad. Its parallax would seem to be wrong, but it hasn't been well measured, and its proper motion agrees well with the average proper motion of the Pleiades. Its color and brightness is also right for a member of the Pleaides of spectral class A.

The second star from the top, HD 23632, is definitely a Pleiad. Its parallax has been well measured and agrees very well the average parallax of the Pleiades. Its proper motion is just right, as is its color, brightness and measured spectral class, A1V.

The third star from the top, HD 23609, is [b]not[/b] a Pleiad. Its parallax has been well measured, and it is only about half as far away as the true members of the Pleiades. Unsurprisingly, its proper motion also disagrees with the Pleiades, and its color and brightness is wrong for a star at the distance and general reddening of the Pleiades.

The fourth star from the top, HD 23643, is a Pleiad. Its parallax does not make sense, but it has not been well measured. Its proper motion is just right, as is its color and brightness for a member of the Pleaides of spectral class A.

The fifth star from the top, HD 23654, is not a Pleiad. Its measured parallax is unrealiable, but its proper motion is wrong, as is its color and brightness.

The sixth star, HD 23665, is also not a Pleiad. Again its parallax is unreliable, but again its proper motion is wrong, as is its color and brightness.

[float=left][img2]http://homepage.mac.com/andjames/Fig030b004.png[/img2][/float]How do we know what the color and brightness of a star belonging to the Pleiades cluster "ought" to be? We can figure that out by constructing a color-magnitude graph, where we plot the color and the brightness of all the members of the Pleiades. In this graph, the vertical axis measures the brightness (or V magnitude) of the members of the Pleiades, and the horizontal axis measures the B-V color index of the stars.

We can see from this graph that the brightest stars of the Pleiades are the bluest, and the fainter a member of the Pleiades is, the redder it is. Not only that, but we can tell from this graph exactly how bright a member of the Pleiades ought to be if it is a certain color, and in the same way, we can say what color it ought to be if it is of a certain brightness.

If we find stars which appear to be located in the Pleiades cluster, but whose position in the color-magnitude graph is wrong, and if we can determine that their proper motion is also wrong, then we can be sure that these stars are not members of the Pleiades. Instead, they are either background or a foreground stars.

Therefore, many long strings of stars are really chance alignments.

Ann

Stellar picture of my favorite stars! I can usually make out 8 of them on a clear night... I never understood why they were the "7" either and always found myself wondering which one was considered the seventh lol... maybe that's what always keep me looking... :-)

Looking at the center of the star field, I can see the outline of a woman
standing tall, looking to her left. There is the outline of a face,
arms, hands, body and a flowing dress. Never noticed this before!!
Maybe the false color imaging of the dust cloud is making the
"image" appear. At any rate I think it is just beautiful!!

[quote="Joel N"]

why wouldn't that dust cloud be considered a nebula?[/quote]
Those dust clouds are considered reflection nebulae:
[quote=" http://messier.seds.org/m/m045.html"]

<<The Pleiades nebulae are blue-colored, which indicates that they are reflection nebulae, reflecting the light of the bright stars situated near (or within) them. The brightest of these nebulae, that around Merope, was discovered on October 19, 1859 by Ernst Wilhelm Leberecht (Wilhelm) Tempel at Venice (Italy) with a 4-inch refractor; it is included in the NGC as [url=http://apod.nasa.gov/apod/ap990301.html]NGC 1435[/url]. Leos Ondra has made the biography of Wilhelm Tempel available online together with a drawing of the Merope Nebula, and has agreed to include it in this database. The extension to Maia was discovered by the brothers Paul and Prosper Henry in Paris on a photographic plate taken on November 16, 1885; this is NGC 1432 or the Maia Nebula. The nebulae around Alcyone, Electra, Celaeno and Taygeta were found on photographs in the later 1880s. The full complexity of the Pleiades nebulae was revealed by the first astro cameras, e.g. by that of the brothers Henry in Paris and Isaac Roberts in England, between 1885 and 1888. In 1890, E.E. Barnard discovered a starlike concentration of nebulous matter very close to Merope, which found its way into the IC as IC 349. The analysis of the spectra of the Pleiades nebulae by Vesto M. Slipher in 1912 reveiled their nature as reflection nebulae, as their spectra are exact copies of the spectra of the stars illuminating them. Physically, the reflection nebula is probably part of the dust in a molecular cloud, unrelated to the Pleiades cluster, which happens to cross the cluster's way. It is not a remainder of the nebula from which the cluster once formed, as can be seen from the fact that the nebula and cluster have different radial velocities, crossing each other with a relative velocity of 6.8 mps, or 11 km/sec.>>[/quote]

Excuse the newbie question, but why wouldn't that dust cloud be considered a nebula?

[quote="bert"]There are a very large number of stars in this photograph that form definite strings. It that due to the time delayed photographic process, or do stars actually form in strings accross space?[/quote]

I'm always perceiving "strings" of stars in astroimages. I'm sure many times it's just a chance alignment, put together into a pattern by our wonderful brains, but I've always wondered whether "ribbons" of interstellar stuff sometimes form stars. Just glance at a not-too-deeply exposed image of the M4 cluster some time to see some good examples of visual strings of stars...

[attachment=0]M4.jpg[/attachment]

-Noel

Gotta love it when the stuff that's so dim others have trouble imaging it is so bright in this image that it's all but washed out.

I really, REALLY like alternate perspectives on things. The universe never ceases to provide more and more beauty.

Well done!

-Noel

[quote="bert"]do stars actually form in strings accross space?[/quote]

Short answer, yes.
Longer answer: GMC's (Giant Molecular clouds) are the dark nebulae like M42 in Orion. These are considered stellar nurseries from which stars are born. They may exist somewhat stably for a while, but then a dying star in the neighborhood will explode in a supernova explosion. It is the shockwave from this explosion that triggers the gravitational collapse of various segments in the cloud, each of which can become an new star.

This is my best understanding of it, less several "if's, but's, and what-have-you's."
I urge other bloggers to correct me. (not my grammer though) :P

There are a very large number of stars in this photograph that form definite strings. It that due to the time delayed photographic process, or do stars actually form in strings accross space?

[quote="starstruck"]Much better than 'the seven sisters', from now on I'm calling the Pleiades 'the blue lagoon'[/quote]
Hmm... do you know which one is Brooke Shields :?: :?:

[quote="Indigo_Sunrise"]

*Oh, and to those of you driving a [url=http://en.wikipedia.org/wiki/Pleiades_in_folklore_and_literature#Japan]Subaru automobile[/url] - how fortuitous!
:D[/quote]
My neighbor drives a Suburu; the logo shows 6 of the sisters. :mrgreen: 8-) The Pleiades has become a favorite of mine! :D 8-)

[quote="Indigo_Sunrise"]

*Oh, and to those of you driving a [url=http://en.wikipedia.org/wiki/Pleiades_in_folklore_and_literature#Japan]Subaru automobile[/url] - how fortuitous! :D[/quote]
[img3=""]http://www.skitheeast.net/user_media/864343010/img_5756_large.jpg[/img3]

[quote]A [url=http://arxiv.org/ftp/arxiv/papers/0810/0810.1592.pdf]common legend[/url] with a [url=http://kencroswell.com/GD50.html]modern twist[/url] is that one of the brighter stars faded since the cluster was named, leaving only six stars visible to the unaided eye. The actual number of [url=http://www.youtube.com/watch?v=p6prI0Zfw80]Pleiades[/url] stars visible, however, may be more or less than seven, depending on the [url=http://apod.nasa.gov/apod/ap010827.html]darkness[/url] of the surrounding sky and the [url=http://en.wikipedia.org/wiki/File:Snellen_chart.svg]clarity[/url] of the observer's eyesight.[/quote]

This has always been a kind of problem for me: I could never find the elusive seventh sister! :oops: As long as I can remember (or at least since I've been smitten by the stars!), when I would look at images of M45, I would think, 'so which ones are the seven?' I always appreciate when any of these images include some type of list or have labeling.

Very beautiful image!

8-)

*Oh, and to those of you driving a [url=http://en.wikipedia.org/wiki/Pleiades_in_folklore_and_literature#Japan]Subaru automobile[/url] - how fortuitous!
:D

Note how the blue dust clouds appear to be superimposed on beige dust features that are farther away from us. I wonder how much farther away the beige dust is. Perhaps the difference is small. The blue Pleiades dust "is lit up" by the bright B-type stars of this famous cluster, but the beige dust "is eclipsed", as it were. In many places the blue and the beige dust features appear to be very well separated, but in other places they appear to be mixed, gradually changing from one hue to another. I'd sure love to know exactly how the "color optics and chemistry" are working here!

Ann

WOW!!!

Reckon they picked today's APOD especially with you in mind Ann . . that sure is blue!

Much better than 'the seven sisters', from now on I'm calling the Pleiades 'the blue lagoon'

Beautiful picture Stanislav!

Neat to see such a deep exposer of M45.
Compare that to an earlier APOD by Rob Gendler back in 2003:
[url]http://apod.nasa.gov/apod/ap031227.html[/url]
Another nice view of the Pleiades, but not nearly as long of an exposure as this one!

I do like the eye chart. I can read the whole thing. Of course my screen is set at 150% magnification. :mrgreen:

[b][size=200][color=#4080FF]OOOOOHHH!!!![/color][/size][/b]

Lovely, lovely, lovely!!!! :D :clap: :D :clap: :D :clap: :D

Ann

[url=http://apod.nasa.gov/apod/ap110921.html][img]http://apod.nasa.gov/apod/calendar/S_110921.jpg[/img] [size=150]Pleiades Deep Field[/size][/url]

[b] Explanation: [/b] Have you ever seen the Pleiades star cluster? Even if you have, you probably have never seen it like this: all dusty. Perhaps the most famous star cluster on the sky, the bright stars of the [url=http://www.seds.org/messier/m/m045.html]Pleiades[/url] can be seen without binoculars from even the depths of a [url=http://antwrp.gsfc.nasa.gov/apod/image/0208/earthlights02_dmsp_big.jpg]light-polluted city[/url]. With a long exposure from a dark location, though, the dust cloud surrounding the [url=http://apod.nasa.gov/apod/ap091205.html]Pleiades[/url] star [url=http://asterisk.apod.com/viewtopic.php?f=24&t=18009]cluster[/url] becomes very evident. The [url=http://i056.radikal.ru/1109/e5/305680a6d131.jpg]above exposure[/url] took about 30 hours and covers a sky area several times the size of the full moon. Also known as the [url=http://www.ras.ucalgary.ca/~gibson/pleiades/pleiades_myth.html]Seven Sisters[/url] and [url=http://apod.nasa.gov/apod/ap960423.html]M45[/url], [url=http://en.wikipedia.org/wiki/Pleiades_%28star_cluster%29]the Pleiades[/url] lies about 400 light years away toward the constellation of the Bull ([url=http://en.wikipedia.org/wiki/Taurus_%28constellation%29]Taurus[/url]). A [url=http://arxiv.org/ftp/arxiv/papers/0810/0810.1592.pdf]common legend[/url] with a [url=http://kencroswell.com/GD50.html]modern twist[/url] is that one of the brighter stars faded since the cluster was named, leaving only six stars visible to the unaided eye. The actual number of [url=http://www.youtube.com/watch?v=p6prI0Zfw80]Pleiades[/url] stars visible, however, may be more or less than seven, depending on the [url=http://apod.nasa.gov/apod/ap010827.html]darkness[/url] of the surrounding sky and the [url=http://en.wikipedia.org/wiki/File:Snellen_chart.svg]clarity[/url] of the observer's eyesight.

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