APOD: The Hyades Star Cluster (2020 Jan 22)

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APOD: The Hyades Star Cluster (2020 Jan 22)

Post by APOD Robot » Wed Jan 22, 2020 5:08 am

Image The Hyades Star Cluster

Explanation: It is the closest cluster of stars to the Sun. The Hyades open cluster is bright enough to have been remarked on even thousands of years ago, yet is not as bright or compact as the nearby Pleiades (M45) star cluster. Pictured here is a particularly deep image of the Hyades which has brings out vivid star colors and faint coincidental nebulas. The brightest star in the field is yellow Aldebaran, the eye of the bull toward the constellation of Taurus. Aldebaran, at 65 light-years away, is now known to be unrelated to the Hyades cluster, which lies about 150 light-years away. The central Hyades stars are spread out over about 15 light-years. Formed about 625 million years ago, the Hyades likely shares a common origin with the Beehive cluster (M44), a naked-eye open star cluster toward the constellation of Cancer, based on M44's motion through space and remarkably similar age.

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sffilstagemusic

Re: APOD: The Hyades Star Cluster (2020 Jan 22)

Post by sffilstagemusic » Wed Jan 22, 2020 5:32 am

Good Evening: Noticed a dark cloud at the top center of the picture. Does it have a name? Is it a star-forming region?

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Ann
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Re: APOD: The Hyades Star Cluster (2020 Jan 22)

Post by Ann » Wed Jan 22, 2020 7:24 am

sffilstagemusic wrote:
Wed Jan 22, 2020 5:32 am
Good Evening: Noticed a dark cloud at the top center of the picture. Does it have a name? Is it a star-forming region?
Well spotted. Yes, it does look as if something rather tiny is forming in there, probably a red dwarf star or maybe just a brown dwarf.

The Taurus molecular cloud is, after all, the nearest star forming region to us. According to Wikipedia, the Taurus molecular cloud is located at about the same distance as the Pleiades, of some 430 light-years. So in all probability the small star forming region that we can see in today's APOD has nothing to do with the Hyades cluster, which is located at a distance of some 150 light-years.

Ann
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geckzilla
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Re: APOD: The Hyades Star Cluster (2020 Jan 22)

Post by geckzilla » Wed Jan 22, 2020 7:32 am

Ann wrote:
Wed Jan 22, 2020 7:24 am
Well spotted. Yes, it does look as if something rather tiny is forming in there, probably a red dwarf star or maybe just a brown dwarf.
If you can see the jets coming out of a molecular cloud, it's a sign that the object is still accreting and not yet in its final form. I always see them called YSOs (young stellar objects). I think you probably already know this, but the way you worded it made it sound like it was somehow all it was ever going to be. or maybe I'm just tired
Just call me "geck" because "zilla" is like a last name.

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Ann
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Re: APOD: The Hyades Star Cluster (2020 Jan 22)

Post by Ann » Wed Jan 22, 2020 8:36 am

geckzilla wrote:
Wed Jan 22, 2020 7:32 am
Ann wrote:
Wed Jan 22, 2020 7:24 am
Well spotted. Yes, it does look as if something rather tiny is forming in there, probably a red dwarf star or maybe just a brown dwarf.
If you can see the jets coming out of a molecular cloud, it's a sign that the object is still accreting and not yet in its final form. I always see them called YSOs (young stellar objects). I think you probably already know this, but the way you worded it made it sound like it was somehow all it was ever going to be. or maybe I'm just tired
Thanks for the correction, Geck. I'm sure you have seen a ton of pictures of young stars forming, so you are clearly familiar with their appearance. As for myself, my own interest in stars is in massive objects that are either blue already, or are in the process of formation. Low mass stars don't much interest me, sorry. So when I said that the object, to me, looks like a low-mass star forming, that was not an educated guess. It was just a guess.

I'll refrain from say anything else about this object.

Ann
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JimT in Canada

Re: APOD: The Hyades Star Cluster (2020 Jan 22)

Post by JimT in Canada » Wed Jan 22, 2020 10:05 am

I cannot rest from travel: I will drink
Life to the lees: All times I have enjoy'd
Greatly, have suffer'd greatly, both with those
That loved me, and alone, on shore, and when
Thro' scudding drifts the rainy Hyades
Vext the dim sea:
— Ulysses, by Alfred, Lord Tennyson

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Re: APOD: The Hyades Star Cluster (2020 Jan 22)

Post by orin stepanek » Wed Jan 22, 2020 11:39 am

Hyades_Mtanous_1080.jpg

What can I say? It is like this Hyades photo is like art! 8-)
It is why I keep coming to APOD every day!
Kudos to Jose
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Last edited by orin stepanek on Wed Jan 22, 2020 11:43 am, edited 1 time in total.
Orin

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Re: APOD: The Hyades Star Cluster (2020 Jan 22)

Post by starsurfer » Wed Jan 22, 2020 11:40 am

sffilstagemusic wrote:
Wed Jan 22, 2020 5:32 am
Good Evening: Noticed a dark cloud at the top center of the picture. Does it have a name? Is it a star-forming region?
This is Sh2-239 and LDN 1551. You can see a closer image here.

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Re: APOD: The Hyades Star Cluster (2020 Jan 22)

Post by starsurfer » Wed Jan 22, 2020 11:41 am

orin stepanek wrote:
Wed Jan 22, 2020 11:39 am
Hyades_Mtanous_1080.jpg


What can I say? It is like this Hyades photo is like art! 8-)
It is why I keep coming to APOD every day!
Vincent van Gogh would be proud! :D

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Re: APOD: The Hyades Star Cluster (2020 Jan 22)

Post by orin stepanek » Wed Jan 22, 2020 11:47 am

starsurfer wrote:
Wed Jan 22, 2020 11:41 am
orin stepanek wrote:
Wed Jan 22, 2020 11:39 am
Hyades_Mtanous_1080.jpg


What can I say? It is like this Hyades photo is like art! 8-)
It is why I keep coming to APOD every day!
Vincent van Gogh would be proud! :D
+++ :b:
Orin

Smile today; tomorrow's another day!

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Re: APOD: The Hyades Star Cluster (2020 Jan 22)

Post by Chris Peterson » Wed Jan 22, 2020 3:08 pm

A region like this almost impossible to image accurately. While today's image is very pretty, with both the imaging and the processing expertly done, the reality is that a large amount of what we're seeing is the result of optical artifacts. Almost all that color is artificial- the result of diffraction and optical scatter around stars that are orders of magnitude brighter than the surrounding dust that is being exposed for. Imaged from space with super clean optics, all we'd see is the brown dust and colored points of light for the stars.
Chris

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neufer
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Re: APOD: The Hyades Star Cluster (2020 Jan 22)

Post by neufer » Wed Jan 22, 2020 3:23 pm





Click to play embedded YouTube video.
Last edited by neufer on Wed Jan 22, 2020 4:39 pm, edited 1 time in total.
Art Neuendorffer

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Re: APOD: The Hyades Star Cluster (2020 Jan 22)

Post by Ann » Wed Jan 22, 2020 4:23 pm

neufer wrote:
Wed Jan 22, 2020 3:23 pm


Click to play embedded YouTube video.

I'm trying to understand that one, Art. You mean the Hyades cluster looks a little bit like a teddy bear? With Aldebaran as the bear's head?

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Re: APOD: The Hyades Star Cluster (2020 Jan 22)

Post by neufer » Wed Jan 22, 2020 5:04 pm

Ann wrote:
Wed Jan 22, 2020 4:23 pm
neufer wrote:
Wed Jan 22, 2020 3:23 pm


I'm trying to understand that one, Art. You mean the Hyades cluster looks a little bit like a teddy bear? With Aldebaran as the bear's head?
  • It is critical for your understanding that you are aware of the tragic Greek Myth:
https://en.wikipedia.org/wiki/Hyades_(mythology) wrote:
<<The Hyades (Ancient Greek: Ὑάδες, popularly "rain-makers" or "the rainy ones" from ὕω hyo "I fall as rain", but probably from ὗς hys "swine") are a sisterhood of nymphs that bring rain. The Hyades were daughters of Atlas (by either Pleione or Aethra, one of the Oceanides) and sisters of Hyas in most tellings, although one version gives their parents as Hyas and Boeotia. The Hyades are sisters to the Pleiades and the Hesperides.

Click to play embedded YouTube video.
The main myth concerning them is envisioned to account for their collective name and to provide an etiology for their weepy raininess: Hyas was killed in a hunting accident and the Hyades wept from their grief. They were changed into a cluster of stars, the Hyades, set in the head of Taurus. The Greeks believed that the heliacal rising and setting of the Hyades star cluster were always attended with rain, hence the association of the Hyades (sisters of Hyas) and the Hyades (daughters of ocean) with the constellation of the Hyades (rainy ones).

In Tennyson's poem, Ulysses recalls his travels of old:
  • I cannot rest from travel: I will drink
    Life to the lees: All times I have enjoy'd
    Greatly, have suffer'd greatly, both with those
    That loved me, and alone, on shore, and when
    Thro' scudding drifts the rainy Hyades
    Vext the dim sea: I am become a name;
Art Neuendorffer

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Ann
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Re: APOD: The Hyades Star Cluster (2020 Jan 22)

Post by Ann » Wed Jan 22, 2020 5:34 pm

Thanks, Art. I associate Pleione with the Pleiades, not the Hyades. Anyway, I have not bothered trying to learn any Greek myths about the Hyades, but it is good to know the story you told me.

Thanks again!

Ann
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elaphae

Re: APOD: The Hyades Star Cluster (2020 Jan 22)

Post by elaphae » Thu Jan 23, 2020 3:45 am

I wish I was better at this. Was trying to reconcile https://apod.nasa.gov/apod/ap121224.html with today's inmage https://apod.nasa.gov/apod/ap200122.html so I could name the stare. The newer image is more confusing to my decades old eyes.

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Re: APOD: The Hyades Star Cluster (2020 Jan 22)

Post by Ann » Thu Jan 23, 2020 5:29 am

elaphae wrote:
Thu Jan 23, 2020 3:45 am
I wish I was better at this. Was trying to reconcile https://apod.nasa.gov/apod/ap121224.html with today's inmage https://apod.nasa.gov/apod/ap200122.html so I could name the stare. The newer image is more confusing to my decades old eyes.
Good question. The pictures are indeed so different that it is hard to believe that they show you the same object. What we are seeing is the result of data acquisition and processing. In other words, the appearance of the pictures is a consequence of how the photographer photographed his object and what he then did to make the picture more interesting.

Let's start with Jerry Lodriguss' image. I hope I am allowed to copy it, because Jerry Lodriguss is one of those who is generally not happy about having his pictures copied. But if his picture disappears here, you can always look at it in the APOD from 2012.

The Hyades by Jerry Lodriguss.
When I first saw this picture I was delighted, because I love strong colors in stars, and I particularly like the color blue. But this is exactly where Jerry Lodriguss goes wrong.

The stars of the Hyades are not strongly colored. Yes, bright Aldebaran, which is not even a true member of the Hyades, is obviously orange-tinted. But the other stars, the true members of the Hyades, are pale.

Let's talk color indexes here. The larger the color index, the redder is the star. The color index of Aldebaran is 1.54, which is pretty red. But what about the true members of the Hyades? The reddest of them is Epsilon, ε, whose color index is 1.01. That's not very red for a red giant. But it gets even more interesting when you look at Jerry Lodriguss' image. Can you see that the star 𝛿1 looks redder than ε? But in reality, it's the other way round, because 𝛿1 is marginally redder than ε.

When it comes to the blue stars, it gets worse. First of all, there is not a single very blue star in the Hyades. The blue stars that certainly existed there when the Hyades cluster was really young have run through their brief life cycles and died. The bluest star in the Hyades is 𝛿3, and it isn't labelled in Jerry Lodriguss' image, but it is the blue-looking star to the left of 𝛿1 and 𝛿2.. 𝛿3 is a star of spectral class A2IV, with a color index of 0.04. That makes it "okay blue", but not remarkably so.

In some cases Jerry Lodriguss has obviously "imparted color differences" that don't exist. Look at the line of stars at the bottom of Jerry Lodriguss' image. Below Aldebaran is a blue double star, and to the right of this double star is another blue star, and to the right of that blue star is a beige-looking star, and to the right of that one is another blue-looking star. Can you see them?

Well, here's the deal. The beige-looking star is just marginally redder than the stars to its right and its left. The beige-looking star is an F0V-type star with a color index of 0.26. If the Sun suddenly turned as blue as this, the Earth would be inundated with a torrent of (to us) unbearably blue and ultraviolet light.

The star to the left of the beige-looking star in Jerry Lodriguss' picture has a spectral class of A8V and a color index of 0.25. Yes, that is a little bluer, but marginally, marginally so. The star to the right of the beige-looking star has a spectral class of A7V and a color index of 0.21. That's a little bluer still, but again only marginally so. Such a small difference should not show up in a well-calibrated color image.

Conclusion? Jerry Lodriguss has imparted colors and color differences to the stars of the Hyades that aren't really there.

The Hyades by Jose Mtanous.
What about yesterday's APOD? The photographer, Jose Mtanous, has allowed the light from the stars to "bleed" and create huge colored halos. Here too some colors look a little bit strange to me, for example the copper-like color of Gamma, ɣ, to the far right. But what is most interesting is all the nebulosity that we can see in this image. The photographer has clearly meant to make this dust visible, which is also why the stars have such big halos.

There really is quite a lot of dust in the direction of Taurus, the constellation where we find the Hyades. But most of the dust is probably located at a distance of about 400 light-years, and not so much of it is probably located at the distance of the Hyades, which is about 150 light-years.



I really recommend two pictures of Alson Wong, which I find splendid.

The Hyades and the Pleiades by Alson Wong.
The Hyades and the Pleiades by Alson Wong, version 2.


















Note in Alson Wong's pictures the paleness of the colors of the stars of the Hyades (lower left). Note how the blue color of the Pleiades (top right) stands out compared with the Hyades. And note, too, particularly in the picture at right, how the dust in this whole region becomes visible. You can spot some of the dusty features that are so visible in Jose Mtanous' image in Alson Wong's picture, too.

Hope my explanation helped you!

Ann
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