APOD: M45: The Pleiades Star Cluster (2019 Sep 01)

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APOD: M45: The Pleiades Star Cluster (2019 Sep 01)

Post by APOD Robot » Sun Sep 01, 2019 4:10 am

Image 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 featured exposure took over 12 hours 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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Re: APOD: M45: The Pleiades Star Cluster (2019 Sep 01)

Post by Boomer12k » Sun Sep 01, 2019 5:31 am

Very nice, and detailed...

Here is one from 1890!!! I think it is AMAZING!! You can see some "whispy" details...

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Re: APOD: M45: The Pleiades Star Cluster (2019 Sep 01)

Post by Ann » Sun Sep 01, 2019 6:05 am

APOD Robot wrote:

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.
So what other star cluster could be as famous as the Pleiades?
Wikipedia wrote:

The Pleiades are a prominent sight in winter in the Northern Hemisphere, and are easily visible out to mid-Southern latitudes. They have been known since antiquity to cultures all around the world,[12] including the Celts, Hawaiians (who call them Makaliʻi[13]), Māori (who call them Matariki), Aboriginal Australians (from several traditions), the Persians, the Arabs (who called them Thurayya[14]), the Chinese (who called them 昴 mǎo), the Quechua, the Japanese, the Maya, the Aztec, the Sioux, the Kiowa,[15][16] and the Cherokee. In Hinduism, the Pleiades are known as Krittika and are associated with the war-god Kartikeya. They are also mentioned three times in the Bible.[17]

The earliest-known depiction of the Pleiades is likely a Northern German bronze age artifact known as the Nebra sky disk, dated to approximately 1600 BC.[18] The Babylonian star catalogues name the Pleiades MULMUL (𒀯𒀯), meaning "stars" (literally "star star"), 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 Ancient Egyptians may have used the names "Followers" and "Ennead" in the prognosis texts of the Calendar of Lucky and Unlucky Days of papyrus Cairo 86637.[19] Some Greek astronomers considered them to be a distinct constellation, and they are mentioned by Hesiod's Works and Days,[20] Homer's Iliad and Odyssey,[21] and the Geoponica.[22] Some scholars of Islam suggested that the Pleiades (ath-thurayya) are the "star" mentioned in Sura An-Najm ("The Star") of the Quran.[23]
So the Pleiades are well-known and famous all right! :mrgreen: They are so unusual because the bright cluster members are relatively bright in our skies as about fourth magnitude, and all the dominant stars are blue, and the bright stars are close together and form the cutest little tiny "dipper" in the sky, like a child's toy version of the Big Dipper. The stars of M45 so extremely obviously belong together.

The lovely reflection nebulosity is quite invisible to the eye, even though the extended nebulosity around Merope might possibly, possibly be visible in an extremely dark sky. But I don't think that any of the ancient cultures that loved the Pleiades ever saw any "cloudiness" around them.

The Pleiades. Not today's APOD.
But today's APOD shows us the nebulosity around the Pleiades in a great way. I love the "streakiness" of the nebula. I read somewhere that magnetism might have something to do with the "combed hair" appearance of the nebulas, but I don't know if that is true. Note, however, that the obvious Merope Nebula curves down and to the left around the star, as if Merope was moving down and to the left. And that, indeed, is exactly what Merope and the rest of the Pleiades are doing.

I'm posting the picture at left because the stars are annotated, but please look at today's APOD as well. I dare not post the APOD here, because I think it is too large for me to be allowed to post it (over 500 KB), but please look at the APOD again and note the fantastic details in the dust. Also note that the blue nebula turns greyish some distance from the stars. In the picture at left, the blue nebulosity mostly disappears at the point where the dust turns grey in the APOD.

Beautiful APOD!

Ann
Last edited by Ann on Sun Sep 01, 2019 5:47 pm, edited 1 time in total.
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Re: APOD: M45: The Pleiades Star Cluster (2019 Sep 01)

Post by Ann » Sun Sep 01, 2019 6:16 am

APOD Robot wrote:

Also known as the Seven Sisters and M45, the Pleiades lies about 400 light years away toward the constellation of the Bull (Taurus).
There has been a lot of controversy regarding the true distance to the Pleiades. The figure "400 light years" comes from the parallax measured by the Hipparcos satellite, but that distance is generally regarded as being wrong.

Wikipedia wrote:

The distance to the Pleiades can be used as an important first step to calibrate the cosmic distance ladder. As the cluster is so close to the Earth, its distance is relatively easy to measure and has been estimated by many methods.
...
Measurements of the distance have elicited much controversy. Results prior to the launch of the Hipparcos satellite generally found that the Pleiades were about 135 parsecs (pc) away from Earth. Data from Hipparcos yielded a surprising result, namely a distance of only 118 pc by measuring the parallax of stars in the cluster—a technique that should yield the most direct and accurate results. Later work consistently argued that the Hipparcos distance measurement for the Pleiades was erroneous.
Today most measurements other than Hipparcos agree that the distance to the Pleiades is about 135 parsecs, or 440 light-years.

Ann
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Re: APOD: M45: The Pleiades Star Cluster (2019 Sep 01)

Post by orin stepanek » Sun Sep 01, 2019 12:26 pm

Whatever the distance; the Pleiades is always pleasing to look at! At times they appear really bright in the sky! 8-)
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Re: APOD: M45: The Pleiades Star Cluster (2019 Sep 01)

Post by E Fish » Sun Sep 01, 2019 1:13 pm

This is a beautiful image. The Pleiades is my favorite astronomical object and I look forward to its evening rising every year. Whenever I talk about star clusters in classes, it's always accompanied by pictures of the Pleiades.

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Re: APOD: M45: The Pleiades Star Cluster (2019 Sep 01)

Post by rstevenson » Sun Sep 01, 2019 1:28 pm

Ann wrote:
Sun Sep 01, 2019 6:16 am
APOD Robot wrote:

Also known as the Seven Sisters and M45, the Pleiades lies about 400 light years away toward the constellation of the Bull (Taurus).
There has been a lot of controversy regarding the true distance to the Pleiades. The figure "400 light years" comes from the parallax measured by the Hipparcos satellite, but that distance is generally regarded as being wrong.

Wikipedia wrote:

The distance to the Pleiades can be used as an important first step to calibrate the cosmic distance ladder. As the cluster is so close to the Earth, its distance is relatively easy to measure and has been estimated by many methods.
...
Measurements of the distance have elicited much controversy. Results prior to the launch of the Hipparcos satellite generally found that the Pleiades were about 135 parsecs (pc) away from Earth. Data from Hipparcos yielded a surprising result, namely a distance of only 118 pc by measuring the parallax of stars in the cluster—a technique that should yield the most direct and accurate results. Later work consistently argued that the Hipparcos distance measurement for the Pleiades was erroneous.
Today most measurements other than Hipparcos agree that the distance to the Pleiades is about 135 parsecs, or 440 light-years.

Ann
I wouldn't want to plan a trip without being a lot more certain than that when to turn off my warp drive. Forty light-years would be a big Oops!

Rob

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Re: APOD: M45: The Pleiades Star Cluster (2019 Sep 01)

Post by neufer » Sun Sep 01, 2019 1:44 pm

Boomer12k wrote:
Sun Sep 01, 2019 5:31 am

Very nice, and detailed...

Here is one from 1890!!!

I think it is AMAZING!! You can see some "whispy" details...
https://www.metmuseum.org/toah/works-of-art/10.64.13/ wrote: The Pleiades,1885

Elihu Vedder American

According to Greek mythology, the Pleiades were the seven daughters of Atlas and the nymph Pleione. Vedder used the Pleiades as his subject for the first illustration in the "Rubaiyat of Omar Khayyam". The seven female figures represent the horoscope of the astronomer-poet, Omar Khayyam. The two influences of Jupiter and the Pleiades, connected by the pleasure of the vine, are symbolized by the thread that entwines them. The central figure, whose thread is broken, is "the lost Pleiad."
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Re: APOD: M45: The Pleiades Star Cluster (2019 Sep 01)

Post by Chris Peterson » Sun Sep 01, 2019 1:46 pm

Ann wrote:
Sun Sep 01, 2019 6:16 am
Today most measurements other than Hipparcos agree that the distance to the Pleiades is about 135 parsecs, or 440 light-years.
Here's a summary. And most recently, Gaia places the distance at 136.2 ± 5.0 pc. (The Gaia DR2 data is such high resolution that the resultant value considers the different distances of each star inside the cluster. That is, it records the different distances of the different stars from the cluster center.)
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Re: APOD: M45: The Pleiades Star Cluster (2019 Sep 01)

Post by starsurfer » Sun Sep 01, 2019 4:40 pm

neufer wrote:
Sun Sep 01, 2019 1:44 pm
Boomer12k wrote:
Sun Sep 01, 2019 5:31 am

Very nice, and detailed...

Here is one from 1890!!!

I think it is AMAZING!! You can see some "whispy" details...
https://www.metmuseum.org/toah/works-of-art/10.64.13/ wrote: The Pleiades,1885

Elihu Vedder American

According to Greek mythology, the Pleiades were the seven daughters of Atlas and the nymph Pleione. Vedder used the Pleiades as his subject for the first illustration in the "Rubaiyat of Omar Khayyam". The seven female figures represent the horoscope of the astronomer-poet, Omar Khayyam. The two influences of Jupiter and the Pleiades, connected by the pleasure of the vine, are symbolized by the thread that entwines them. The central figure, whose thread is broken, is "the lost Pleiad."
I love this painting! :wink:

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Re: APOD: M45: The Pleiades Star Cluster (2019 Sep 01)

Post by starsurfer » Sun Sep 01, 2019 4:41 pm

I always look forward to seeing the Pleiades in the winter skies.

Also I wish Marco Lorenzi would return to astrophotography. :cry: