APOD: M45: The Pleiades Star Cluster (2013 Sep 18)

[APOD Robot]

M45: The Pleiades Star Cluster

Explanation: Have you ever seen the Pleiades star cluster? Even if you have, you probably have never seen it as dusty as this. Perhaps the most famous star cluster on the sky, the bright stars of the Pleiades can be seen without binoculars from even the depths of a light-polluted city. With a long exposure from a dark location, though, the dust cloud surrounding the Pleiades star cluster becomes very evident. The above exposure took about 20 minutes and covers a sky area several times the size of the full moon. Also known as the Seven Sisters and M45, the Pleiades lies about 400 light years away toward the constellation of the Bull (Taurus). A common legend with a modern twist 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 Pleiades stars visible, however, may be more or less than seven, depending on the darkness of the surrounding sky and the clarity of the observer's eyesight.

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[Boomer12k]

oooooo....Pretty!!!! Awesome Job!!!!

:---[===] *

[keerthi2kiran]

The number of hours of exposure provided in the APOD description may be wrong.
I saw the photo in Astrobin www.astrobin.com/55798/
It looks like the total exposure was 20 minutes and not 30 hours as mentioned in the APOD description.

Thanks and Regards,
Keerthi

[Ann]

Today's APOD is a totally lovely portrait of the Pleiades and the interstellar cloud that this gem of a cluster has accidentally blundered into.

That yellow star at about 2.30 is a background object, or so I think.

Ann

[bystander]

The number of hours of exposure provided in the APOD description may be wrong.
I saw the photo in Astrobin http://www.astrobin.com/55798/
It looks like the total exposure was 20 minutes and not 30 hours as mentioned in the APOD description.

Thanks and Regards,
Keerthi

Thanks. It would seem you are correct. The PTBs have been notified.

[fausto.lubatti]

A really wonderful work!

[bentsn]

Over the years I have enjoyed counting the Pleiades. In poor seeing I have generally gotten six stars. In better seeing I have been able to count anywhere from eight to eleven or so stars. I have never encountered conditions where the count stopped at seven. Thus I have long been puzzled by the name "seven sisters".

[francescodib]

I think there is a mistake in the description, as already held by the author on Facebook and confirmed on Astrobin data it comes to 20min (0.3h) exposure and not 30h
2*300" luminance + 1*300" R + 1*300" B (+ synthetic G)
http://www.astrobin.com/55798/

[Robert L.Grisham]

Dear Reader.
I do observe the Astronomy Pictures of the day ,almost every day,Its a astonishment of the beauty and amazement
of the existence of Gods creation for the being to see and be involved with.
The picture of the seven sister's so to say, if observed closely ,if an picture was drawn around it would look like a
dancer in a skirt.
Some being is just trying to have a little fun out of the observer.
Robert L.Grisham/09/18/13

[neufer]

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Over the years I have enjoyed counting the Pleiades. In poor seeing I have generally gotten six stars. In better seeing I have been able to count anywhere from eight to eleven or so stars. I have never encountered conditions where the count stopped at seven. Thus I have long been puzzled by the name "seven sisters".

<<The nine brightest stars of the Pleiades are named for the Seven Sisters of Greek mythology: Sterope, Merope, Electra, Maia, Taygeta, Celaeno, and Alcyone, along with their parents Atlas and Pleione.>>

[neufer]

[b][color=#0000FF]The Nebra sky disk, dated c. 1600 BC. The cluster of dots in the upper right portion of the disk is believed to be the Pleiades.[/color][/b]

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[b][color=#0000FF]Animation of proper motion in 400,000 years (cross-eyed viewing Stereogram).[/color][/b]

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<<The Pleiades are a prominent sight in winter in both the Northern Hemisphere and Southern Hemisphere, and have been known since antiquity to cultures all around the world, including the Māori, Aboriginal Australians, the Persians, the Chinese, the Japanese, the Maya, the Aztec, and the Sioux and Cherokee. In Tamil culture this star cluster is attributed to Lord Murugan (Lord Murugan raised by the six sisters known as the Kārththikai Pengal and thus came to be known as Kārtikeyan). In Sanskrit he is known as Skanda.

The Babylonian star catalogues name the Pleiades MUL.MUL or "star of stars", and they head the list of stars along the ecliptic, reflecting the fact that they were close to the point of vernal equinox around the 23rd century BC. The earliest known depiction of the Pleiades is likely a bronze age artifact known as the Nebra sky disk, dated to approximately 1600 BC. Some Greek astronomers considered them to be a distinct constellation, and they are mentioned by Hesiod, and in Homer's Iliad and Odyssey. They are also mentioned three times in the Bible (Job 9:9 and 38:31, as well as Amos 5:8). The Pleiades (Krittika) are particularly revered in Hindu mythology as the six mothers of the war god Murugan, who developed six faces, one for each of them. Some scholars of Islam suggested that the Pleiades (ath-thurayya) are the star mentioned in the sura (chapter) Najm of the Quran.

In Japan, the constellation is mentioned under the name Mutsuraboshi ("six stars") in the 8th century Kojiki and Manyosyu documents. The constellation is also known in Japan as Subaru (“unite”) and is depicted in the logo and name of the Subaru automobile company. The Persian equivalent is Nahid (pronounced "Naheed").

The rising of the Pleiades is mentioned in the Ancient Greek text Geoponica. The Greeks oriented the Hecatompedon temple of 1150 BC and the Parthenon of 438 BC to their rising.

They have long been known to be a physically related group of stars rather than any chance alignment. The Reverend John Michell calculated in 1767 that the probability of a chance alignment of so many bright stars was only 1 in 500,000, and so correctly surmised that the Pleiades and many other clusters of stars must be physically related. When studies were first made of the stars' proper motions, it was found that they are all moving in the same direction across the sky, at the same rate, further demonstrating that they were related.

Charles Messier measured the position of the cluster and included it as M45 in his catalogue of comet-like objects, published in 1771. Along with the Orion Nebula and the Praesepe cluster, Messier's inclusion of the Pleiades has been noted as curious, as most of Messier's objects were much fainter and more easily confused with comets—something that seems scarcely possible for the Pleiades. One possibility is that Messier simply wanted to have a larger catalogue than his scientific rival Lacaille, whose 1755 catalogue contained 42 objects, and so he added some bright, well-known objects to boost his list.>>

[Chris Peterson]

Over the years I have enjoyed counting the Pleiades. In poor seeing I have generally gotten six stars. In better seeing I have been able to count anywhere from eight to eleven or so stars. I have never encountered conditions where the count stopped at seven. Thus I have long been puzzled by the name "seven sisters".

Your experience is typical. In almost all cases, people see either six stars or they see eight or more. There isn't a set of seven in the cluster sharing brightness characteristics making them stand out from the others.

No doubt the "seven" aspect comes from the mystical connotations most cultures associate with that number, and not any actual observation. It has been suggested that in the past the brightnesses were somewhat different, but I'm skeptical that this was the case over just the last few thousand years.

[pferkul]

Great image of a beautiful cluster. The dust is interesting, but I like the image enhanced to bring out more colors and a darker background.

Click to view full size image

[geckzilla]

pferkul: Well, the colors were definitely saturated for that version, but it makes the intricate dust structures farther from the stars nigh impossible to see. That said, selectively revealing detail definitely has an aesthetic value. I find that it sometimes conflicts with astronomical imaging. On the one hand, some very cluttered, noisy star fields are useful for showing just how many stars there really are, but on the other it tends to be visually harsh.

[RJN]

The number of hours of exposure provided in the APOD description may be wrong.
I saw the photo in Astrobin http://www.astrobin.com/55798/
It looks like the total exposure was 20 minutes and not 30 hours as mentioned in the APOD description.

Thanks and Regards,
Keerthi

Oops. Thanks! Fixed it. - RJN

[Coil_Smoke]

There are three dark spots in this image that look to be associated with three stars in the cluster. Down loading and blowing up the high resolution(3.6Mb) image reveals something in the glow of the three bright outer stars at approximately the 4, 10 and 11 o'clock position of the cluster. At first I thought there was a flaw it the image. Then I noticed a similar 'dark companion' close to the adjacent star. The fact that three of the stars seem to have this feature tends to rule out photographic artifacts. Please have a look for your selves and tell me what you think
http://apod.nasa.gov/apod/image/1309/m4 ... i_2645.jpg

[geckzilla]

There are three dark spots in this image that look to be associated with three stars in the cluster. Down loading and blowing up the high resolution(3.6Mb) image reveals something in the glow of the three bright outer stars at approximately the 4, 10 and 11 o'clock position of the cluster. At first I thought there was a flaw it the image. Then I noticed a similar 'dark companion' close to the adjacent star. The fact that three of the stars seem to have this feature tends to rule out photographic artifacts. Please have a look for your selves and tell me what you think

I'd guess some sort of processing relating to hot pixels. They're certainly anomalies and not actual objects.

[Anthony Barreiro]

The Pleiades are in beautiful view before dawn these days, high overhead for those of us at mid-northern latitudes. You won't see nebulosity with your unaided eyes or through binoculars, but they're a lovely cluster nonetheless.

[Sharkey377]

Is it true that Alexander the Great used this star cluster to test the eyesight of his archers?

[neufer]

Is it true that Alexander the Great used this star cluster to test the eyesight of his archers?

Don't know... but it's a Great story

In modern Olympic archery the distance from the archer to the 122 cm target is 70 metres.

The average good eye resolution is about 3 arc minutes or 6 centimeters at 70m
or about the diameter of the target's gold inner most 10 ring.

The Pleiades are about 110 arc minutes across or almost twice the diameter of the full 122 cm target.

[b][color=#0000FF][size=125]The Pleiades are about 110 arc minutes across (~ twice the diameter of an Olympic archery target)[/size][/color][/b]

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Pleiades As A Test Of Eyesight
from "The Book Of Woodcraft", by Ernest Thompson Seton.

<<I once asked a group of boys in camp how many of the Pleiades they could count with the naked eye. A noisy, forward boy, who was nicknamed "Bluejay," because he was so fond of chattering and showing off, said, "Oh, I see hundreds".

"Well, you can sit down," I said, "for you can do nothing of the kind".

Another steadier boy said, "I believe I see six," and he proved that he did see them, for he mapped them out properly on a board with six pebbles. That boy had good eyes, because poor eyes see merely a haze, but another boy present had better eyes, for he saw, and proved that he saw, seven. This is considered first-class. The Indians as a rule see seven, because they call them the Seven Stars. But, according to Flammarion, it is possible to exceed this, for several persons have given proof that they distinguished ten Pleiades. This is almost the extreme of human eyesight. There is, however, according to the same authority, a record of thirteen Pleiades having been actually seen by the unaided human eye.

COUNT THE PLEIADES ...by Mel Bartels

<<The Pleiades Star Cluster, known as Messier 45, often called the "Seven Sisters", is the most famous galactic star cluster in the heavens, revered from antiquity. According to Richard Allen's "Star-Names and their Meanings", the Pleiades seem to be the among the first star mentioned in astronomical literature, appearing in Chinese annals of 2357 B.C. Job is thought to refer to them twice in his word Kimah. The Egyptians called them Chu and said that they represent the goddess Nit. Burnham's Celestial Handbook relates an interesting American Indian legend connecting the Pleiades to Devil's Tower. The Kiowa say that the Tower was raised by the Great Spirit to protect seven Indian maidens pursued by giant bears, the maidens afterwards being placed in the heavens for protection, and the bears' claw marks seen today in the vertical striations on the Tower's sides.

Burnhams states that, "There are at least 20 star in the group which might be glimpsed under the finest conditions, having a brightness just below usual unaided-eye range;" This is true, but the next clause is not true, where he goes on to say, "the crowded massing of the stars, however, makes this impossible."

Actually, the star separations are far greater than the unaided-eye resolution of 1-2 arc minutes. You can test your own unaided-eye resolution by looking at Epsilon Lyrae. You should see two adjoining specks of light. If you see clear black inbetween, your resolution limit is closer to 1 arc minute, if you see the specs as an elongated star, you resolution limit is closer to 3 arc minutes. The average resolution is supposed to be 2 arc minutes, but I have found when asking people at star parties to tell me what they see, most of them do not see clear black inbetween, indeed many do not see an elongation.

Probably the biggest problem in going for faint stars in the Pleiades is the nebulosity. In good dark skies, you should see the Pleiades enveloped in a fairly bright solid glow. The Pleiades are embedded in an interloper cloud of gas, not their birth gas. This is similar to the problem of the central star in the Ring Nebula, where it too is embedded in a faint glow of the ring's interior. The central star in the ring is supposedly at 15.5 to 16 magnitude, but it is more difficult to see than a stand alone 15.5 star. You can see faint stars in nebulosity, but it takes more effort and time.

In dark skies, you should catch 13-14 stars, in very dark skies, up to 17 stars, and in exception skies over the years, more than 20 stars.>>