APOD: Messier 45: The Daughters of Atlas... (2019 Nov 07)

Comments and questions about the APOD on the main view screen.
User avatar
APOD Robot
Otto Posterman
Posts: 3751
Joined: Fri Dec 04, 2009 3:27 am

APOD: Messier 45: The Daughters of Atlas... (2019 Nov 07)

Post by APOD Robot » Thu Nov 07, 2019 5:07 am

Image Messier 45: The Daughters of Atlas and Pleione

Explanation: Hurtling through a cosmic dust cloud a mere 400 light-years away, the lovely Pleiades or Seven Sisters open star cluster is well-known for its striking blue reflection nebulae. It lies in the night sky toward the constellation Taurus and the Orion Arm of our Milky Way Galaxy. The sister stars and cosmic dust cloud are not related though, they just happen to be passing through the same region of space. Known since antiquity as a compact grouping of stars, Galileo first sketched the star cluster viewed through his telescope with stars too faint to be seen by eye. Charles Messier recorded the position of the cluster as the 45th entry in his famous catalog of things which are not comets. In Greek myth, the Pleiades were seven daughters of the astronomical Titan Atlas and sea-nymph Pleione. Their parents names are included in the cluster's nine brightest stars. This deep and wide telescopic image spans over 20 light-years across the Pleides star cluster.

<< Previous APOD This Day in APOD Next APOD >>

User avatar
Ann
4725 Å
Posts: 9967
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Messier 45: The Daughters of Atlas... (2019 Nov 07)

Post by Ann » Thu Nov 07, 2019 6:41 am

Who isn't happy to see the Pleiades as an APOD? :D

And I for mine am very happy to see Adam Block get another APOD! :D

This particular picture of the Pleiades is very deep and wide, and it reveals lots of nebulosity outside the most recognizable outline of the Pleiades. The nebulosity comes in different colors, yellowish, faintly reddish, and blue. Most of the blue nebulosity that is disconnected from the recognaizable outline of the Pleiades is seen to the left of the Pleiades in this picture (actually to the north of this iconic cluster).

Fascinatingly, though, the star that is most deeply immersed in blue nebulosity outside the Pleiades (a star at 8 o'clock) has a much larger parallax than the stars of the Pleiades. Judging from its parallax, this star, HD 23985, is less than half as far away as the Pleiades, less than 200 light-years for this star versus more than 400 light-years for the Pleiades!

Fascinating! Do I take this to mean that the dust cloud that the Pleiades are immersed in is more than 200 light-years deep? So that the Pleiades and HD 23985 are immersed in different ends of one admittedly somewhat broken huge dust cloud?

Apart from HD 23985, most of the blue stars in Adam Block's picture have similar parallaxes and similar proper motions as the most iconic Pleiades. So the actual Pleiades cluster extends well beyond its most iconic outline.

The Pleiades small.png
You do not have the required permissions to view the files attached to this post.
Color Commentator

User avatar
orin stepanek
Plutopian
Posts: 5168
Joined: Wed Jul 27, 2005 3:41 pm
Location: Nebraska

Re: APOD: Messier 45: The Daughters of Atlas... (2019 Nov 07)

Post by orin stepanek » Thu Nov 07, 2019 1:03 pm

7 Sisters; my favorite cluster! 8-)
Orin

Smile today; tomorrow's another day!

GeoX

Re: APOD: Messier 45: The Daughters of Atlas... (2019 Nov 07)

Post by GeoX » Thu Nov 07, 2019 1:06 pm

Nice uncommon view instead of the usual tight closeup!

sillyworm 2

Re: APOD: Messier 45: The Daughters of Atlas... (2019 Nov 07)

Post by sillyworm 2 » Thu Nov 07, 2019 1:17 pm

Was just viewing this cluster in the deep ink black skies of upper lower Michigan.No street lights or light pollution on our block .Stunning.

TheZuke!
Ensign
Posts: 55
Joined: Fri Mar 22, 2019 2:19 pm

Re: APOD: Messier 45: The Daughters of Atlas... (2019 Nov 07)

Post by TheZuke! » Thu Nov 07, 2019 2:34 pm

Subaru!

BDanielMayfield
Don't bring me down
Posts: 2183
Joined: Thu Aug 02, 2012 11:24 am
AKA: Bruce
Location: East Idaho

Re: APOD: Messier 45: The Daughters of Atlas... (2019 Nov 07)

Post by BDanielMayfield » Thu Nov 07, 2019 3:10 pm

sillyworm 2 wrote:
Thu Nov 07, 2019 1:17 pm
Was just viewing this cluster in the deep ink black skies of upper lower Michigan.No street lights or light pollution on our block .Stunning.
As you look at them with unaided eyes, how many of them can you see? Then, look at them with binoculars or a small telescope.

I've heard that most people see less than 7 these days. Has one of the sisters faded or is it just modern light pollution?
"Happy are the peaceable ... "

User avatar
Chris Peterson
Abominable Snowman
Posts: 14682
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA

Re: APOD: Messier 45: The Daughters of Atlas... (2019 Nov 07)

Post by Chris Peterson » Thu Nov 07, 2019 3:17 pm

BDanielMayfield wrote:
Thu Nov 07, 2019 3:10 pm
sillyworm 2 wrote:
Thu Nov 07, 2019 1:17 pm
Was just viewing this cluster in the deep ink black skies of upper lower Michigan.No street lights or light pollution on our block .Stunning.
As you look at them with unaided eyes, how many of them can you see? Then, look at them with binoculars or a small telescope.

I've heard that most people see less than 7 these days. Has one of the sisters faded or is it just modern light pollution?
I don't think the asterism has changed since people have been observing it. People picked "seven" because that's a number most cultures placed mystical significance on. Most people under typical observing conditions see six stars. Under good, dark skies and with excellent vision, most people see eight or nine stars. But few see seven.
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

sillyworm 2

Re: APOD: Messier 45: The Daughters of Atlas... (2019 Nov 07)

Post by sillyworm 2 » Thu Nov 07, 2019 3:32 pm

I see it pretty clearly with unaided eyes.Sure I have to squint and I know there are at least 7 or 9 by it's apprearance...I actually did pull out a pair of binoculars a week ago.I could see the individual stars. It's a beautiful cluster.The space station flew right overhead back in Aug.

User avatar
Joe Stieber
Science Officer
Posts: 164
Joined: Tue Aug 18, 2009 1:41 pm
Location: Maple Shade, NJ

Re: APOD: Messier 45: The Daughters of Atlas... (2019 Nov 07)

Post by Joe Stieber » Thu Nov 07, 2019 3:38 pm

BDanielMayfield wrote:
Thu Nov 07, 2019 3:10 pm
sillyworm 2 wrote:
Thu Nov 07, 2019 1:17 pm
Was just viewing this cluster in the deep ink black skies of upper lower Michigan.No street lights or light pollution on our block .Stunning.
As you look at them with unaided eyes, how many of them can you see? Then, look at them with binoculars or a small telescope.

I've heard that most people see less than 7 these days. Has one of the sisters faded or is it just modern light pollution?
With unaided eyes from the New Jersey Pines (reasonably dark) on a moon-free night, I typically see five or six stars with casual observation. The most I've seen and counted with concentration on a good night is nine (9). I've actually seen more than that using averted vision, but couldn't count them -- as soon as I start to count, I involuntarily disrupt my averted vision. I suspect the vagaries of light pollution, atmospheric transparency and human vision could in themselves account variations in the number visible.

User avatar
Ann
4725 Å
Posts: 9967
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Messier 45: The Daughters of Atlas... (2019 Nov 07)

Post by Ann » Thu Nov 07, 2019 3:45 pm

Chris Peterson wrote:
Thu Nov 07, 2019 3:17 pm
BDanielMayfield wrote:
Thu Nov 07, 2019 3:10 pm
sillyworm 2 wrote:
Thu Nov 07, 2019 1:17 pm
Was just viewing this cluster in the deep ink black skies of upper lower Michigan.No street lights or light pollution on our block .Stunning.
As you look at them with unaided eyes, how many of them can you see? Then, look at them with binoculars or a small telescope.

I've heard that most people see less than 7 these days. Has one of the sisters faded or is it just modern light pollution?
I don't think the asterism has changed since people have been observing it. People picked "seven" because that's a number most cultures placed mystical significance on. Most people under typical observing conditions see six stars. Under good, dark skies and with excellent vision, most people see eight or nine stars. But few see seven.
Well, seven "planets" in the night sky - the Sun, the Moon, Venus, Mars, Jupiter and Saturn - and therefore seven sisters of the Pleiades.

Ann
Color Commentator

TheZuke!
Ensign
Posts: 55
Joined: Fri Mar 22, 2019 2:19 pm

Re: APOD: Messier 45: The Daughters of Atlas... (2019 Nov 07)

Post by TheZuke! » Thu Nov 07, 2019 5:17 pm

BDanielMayfield wrote:
Thu Nov 07, 2019 3:10 pm
As you look at them with unaided eyes, how many of them can you see? Then, look at them with binoculars or a small telescope.

I've heard that most people see less than 7 these days. Has one of the sisters faded or is it just modern light pollution?
As I am near sighted, all I see is a blur! :)

If one uses Orion's Belt as a line reference, Aldebaran is on the line to the west, with Subaru a bit beyond. and if they follow the "Belt line" to the East, Sirius awaits.

TheZuke!
Ensign
Posts: 55
Joined: Fri Mar 22, 2019 2:19 pm

Re: APOD: Messier 45: The Daughters of Atlas... (2019 Nov 07)

Post by TheZuke! » Thu Nov 07, 2019 5:23 pm

Ann wrote:
Thu Nov 07, 2019 3:45 pm
Well, seven "planets" in the night sky - the Sun, the Moon, Venus, Mars, Jupiter and Saturn - and therefore seven sisters of the Pleiades.

Ann
And 7 days is approximately 1/4 of a Moon (month) cycle.
In the Old Testament, 7 was symbolic of "completeness", and 6 therefore, was "incomplete".
Which later, in the New Testament, 666 means "very incomplete".

TheZuke!

BDanielMayfield
Don't bring me down
Posts: 2183
Joined: Thu Aug 02, 2012 11:24 am
AKA: Bruce
Location: East Idaho

Re: APOD: Messier 45: The Daughters of Atlas... (2019 Nov 07)

Post by BDanielMayfield » Thu Nov 07, 2019 6:23 pm

Ann wrote:
Thu Nov 07, 2019 3:45 pm
Well, seven "planets" in the night sky - the Sun, ...

Ann
Seeing the Sun in the night sky, my oh my. :lol2:
"Happy are the peaceable ... "

User avatar
neufer
Vacationer at Tralfamadore
Posts: 16552
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Messier 45: The Daughters of Atlas... (2019 Nov 07)

Post by neufer » Thu Nov 07, 2019 7:15 pm

TheZuke! wrote:
Thu Nov 07, 2019 5:23 pm
Ann wrote:
Thu Nov 07, 2019 3:45 pm

Well, seven "planets" in the night sky - the Sun, the Moon, Venus, Mars, Jupiter and Saturn - and therefore seven sisters of the Pleiades.
And 7 days is approximately 1/4 of a Moon (month) cycle.

In the Old Testament, 7 was symbolic of "completeness", and 6 therefore, was "incomplete".
Which later, in the New Testament, 666 means "very incomplete".
  • That explanation is "very incomplete" :!:
    (I've been told that 6 is a perfect number)
https://en.wikipedia.org/wiki/6#In_religion wrote:
<<God took six days to create the world in the Old Testament Book of Genesis; humankind was created on day 6.

In the City of God, Augustine of Hippo suggested (book 11, chapter 30) that
God's creation of the world took six days because 6 is a perfect number.>>
  • The age of the universe in Planck time ~ 8.08 x 1060
    The largest perfect number proven by hand: 2126(2127-1) ~ 1.4474 x 1076
    The approximate number of atoms in the observable universe ~ 8.68 x 1079
https://en.wikipedia.org/wiki/Observable_universe#Matter_content_%E2%80%93_number_of_atoms wrote:
Assuming the mass of ordinary matter is about 1.45×1053 kg and assuming all atoms are hydrogen atoms (which are about 74% of all atoms in our galaxy by mass, calculating the estimated total number of atoms in the observable universe is straightforward. Divide the mass of ordinary matter by the mass of a hydrogen atom (1.45×1053 kg divided by 1.67×10−27 kg).
https://en.wikipedia.org/wiki/%C3%89douard_Lucas wrote:
<<François Édouard Anatole Lucas (4 April 1842 – 3 October 1891) worked in the Paris observatory and later became a professor of mathematics in Paris. In the meantime he served in the army. In 1857, at age 15, Lucas began testing the primality of 2127 − 1 by hand, using Lucas sequences. In 1876, after 19 years of testing, he finally proved that 2127 − 1 was prime; this would remain the largest known Mersenne prime for three-quarters of a century. This may stand forever as the largest prime number proven by hand. Later Derrick Henry Lehmer refined Lucas's primality tests and obtained the Lucas–Lehmer primality test.

In 1875, Lucas posed a challenge to prove that the only solution of the Diophantine equation:


with N > 1 is when N = 24 and M = 70. This is known as the cannonball problem, since it can be visualized as the problem of taking a square arrangement of cannonballs on the ground and building a square pyramid out of them. It was not until 1918 that a proof (using elliptic functions) was found for this remarkable fact, which has relevance to the bosonic string theory in 26 dimensions.>>
https://en.wikipedia.org/wiki/Number_of_the_Beast wrote:
<<In Greek isopsephy and Hebrew gematria, every letter has a corresponding numeric value. Summing these numbers gives a numeric value to a word or name. "Nero Caesar" in the Hebrew alphabet is נרון קסר‎ NRON QSR, which when used as numbers represent 50 200 6 50 100 60 200, which add to 666, and was used to secretly speak against the emperor.>>
Art Neuendorffer

TheZuke!
Ensign
Posts: 55
Joined: Fri Mar 22, 2019 2:19 pm

Re: APOD: Messier 45: The Daughters of Atlas... (2019 Nov 07)

Post by TheZuke! » Fri Nov 08, 2019 9:03 pm

Thanks Neufer,
I can always count on you
to shoot me out of the saddle!
B^)

TheZuke!
Ensign
Posts: 55
Joined: Fri Mar 22, 2019 2:19 pm

Re: APOD: Messier 45: The Daughters of Atlas... (2019 Nov 07)

Post by TheZuke! » Fri Nov 08, 2019 9:06 pm

BDanielMayfield wrote:
Thu Nov 07, 2019 6:23 pm
Ann wrote:
Thu Nov 07, 2019 3:45 pm
Well, seven "planets" in the night sky - the Sun, ...

Ann
Seeing the Sun in the night sky, my oh my. :lol2:
You just need to know where to look for it.
It is tougher to see when it is turned off. :)