The Case of the Missing Pleiad

Once upon a time (if memory serves) there was a discussion on saa
concerning the missing Pleiad.

Back in the days before beef stew (or somewhat more recently) the
average eye, on an average night, could see 6 naked eye stars in the
Pleiades star cluster. Since this cluster was also referred to as the
*Seven Sisters*; there was speculation concerning the fate of the
missing Pleiad.

In my own experience, either 6 or 9 of the named stars can be seen
with the naked eye. If conditions are good enough to see 7, I'll also
see two more.

Fast forward to today. I recently read about the Pleiades in yet
another book. An illustration showed the 9 brightest stars along with
their names. The text pointed out the seven sisters as well as the
two parents. At that point a thought crossed my mind.

On those nights when I could see 9 stars I was seeing the seven
sisters and the two parents. Might it be that before the
proliferation of outdoor lighting, on a good night, the average
observer could see the nine named stars? Might it also be that those
observers were aware of the distinction between the seven sisters and
the two parents? If so, when they spoke of seeing seven Pleiades they
were referring only to the sisters since the parents, though present
and visible, were not sisters. Might this clear up the case of the
(not so) missing Pleiad?

Willie R. Meghar

Willie R. Meghar wrote:
Once upon a time (if memory serves) there was a discussion on saa
concerning the missing Pleiad.

Back in the days before beef stew (or somewhat more recently) the
average eye, on an average night, could see 6 naked eye stars in the
Pleiades star cluster. Since this cluster was also referred to as the
*Seven Sisters*; there was speculation concerning the fate of the
missing Pleiad.

In my own experience, either 6 or 9 of the named stars can be seen
with the naked eye. If conditions are good enough to see 7, I'll also
see two more.

Fast forward to today. I recently read about the Pleiades in yet
another book. An illustration showed the 9 brightest stars along with
their names. The text pointed out the seven sisters as well as the
two parents. At that point a thought crossed my mind.

On those nights when I could see 9 stars I was seeing the seven
sisters and the two parents. Might it be that before the
proliferation of outdoor lighting, on a good night, the average
observer could see the nine named stars? Might it also be that those
observers were aware of the distinction between the seven sisters and
the two parents? If so, when they spoke of seeing seven Pleiades they
were referring only to the sisters since the parents, though present
and visible, were not sisters. Might this clear up the case of the
(not so) missing Pleiad?

Willie R. Meghar

Also keep in mind that some eyes are better than others.

Historical Perspective
http://www.ast.cam.ac.uk/~ipswich/Ob...g_Proj/POP.htm

Many of the great observers of history counted the number of Pleiads
visible to the naked eye. Some of these observers had exceptional
eyesight, and of course observed without the curse of light pollution
that we suffer from so badly today. The most impressive historical
observers of the Pleiades are as follows:


Maestlin (1550-1631; Kepler's tutor) claimed to see 14 and mapped 11
before the invention of the telescope.

Carrington (1826-1875) & Denning (1848-1931) counted 14.

Miss Airy (daughter of G B Airy) counted 12.

William Dawes (1799-1868) counted 13.

One record of the modern era is by O'Meara who claimed to discern 17
Pleiads by naked eye in 1978 at Cambridge, MA, USA.

Many of the great observers of history counted the number of Pleiads
visible to the naked eye. Some of these observers had exceptional
eyesight, and of course observed without the curse of light pollution
that we suffer from so badly today. The most impressive historical
observers of the Pleiades are as follows:


Maestlin (1550-1631; Kepler's tutor) claimed to see 14 and mapped 11
before the invention of the telescope.

Carrington (1826-1875) & Denning (1848-1931) counted 14.

Miss Airy (daughter of G B Airy) counted 12.

William Dawes (1799-1868) counted 13.

One record of the modern era is by O'Meara who claimed to discern 17
Pleiads by naked eye in 1978 at Cambridge, MA, USA.

I would say that any really experienced observer with fairly good
eyesight and excellent skies, should be able to see at least a dozen
Pleiads naked eye. When I enjoyed very good skies back in the 60's and
70's, I saw 14 stars repeatedly and suspected several more. Likewise,
on the best nights long years ago, I could often detect the enveloping
nebulosity surround the cluster without optical aid.

It's also very true that light pollution has taken so much away from
the extreme visual limits commonplace a century and more ago that few
observers today realize just how much "should" be visible without
optical aid.

JBortle

"CNJ999" wrote:

I would say that any really experienced observer with fairly good
eyesight and excellent skies, should be able to see at least a dozen
Pleiads naked eye.

Agreed. I would have to dig a bit to find my naked eye observations;
but I can recall seeing something in the neighborhood of 12 cluster
members on my better nights.

Unfortunately I wear eyeglasses; and optometrists in my neck of the
woods have been quite good at ignoring the desire to see sharply at
low light levels. On the plus side, I have an older pair of glasses
that are sharper for night work than my newer ones. The night sky
difference between these eyeglasses is quite substantial.

In the context of my initial posting I was referring to the nine named
members -- the seven sisters and the two parents; but upon rereading
that posting it seems to make little sense in connection to the 'case
of the missing Pleiad'. Oh well, it still provides something to
discuss :-)

When I enjoyed very good skies back in the 60's and
70's, I saw 14 stars repeatedly and suspected several more. Likewise,
on the best nights long years ago, I could often detect the enveloping
nebulosity surround the cluster without optical aid.

I can't positively state that I've ever detected the nebulosity naked
eye; but I don't doubt your statement.

In the context of optical aid: It wouldn't surprise me if more than a
few modern observers have mistaken scattered light either in their
optics or in a not so transparent atmosphere for the nebulosity. The
Merope Nebula's distinctive shape is in my opinion the key to knowing
whether or not an inexperienced observer has made a positive
detection. It can also be helpful to check out nearby stars of
similar brightness for false (instrumental or atmospheric) nebulosity.

It's also very true that light pollution has taken so much away from
the extreme visual limits commonplace a century and more ago that few
observers today realize just how much "should" be visible without
optical aid.

Yes, light pollution is a very unfortunate fact that most of us have
to deal with in one form or another. It literally consumes the night
sky. Other forms of atmospheric pollution contribute as well,
especially in the presence of lights.

Willie R. Meghar

Willie R. Meghar wrote:

Once upon a time (if memory serves) there was a discussion on saa
concerning the missing Pleiad.

The thread was called "Why Seven Pleiades?" -- you can look it up
in Google. Unfortunately, it splintered rapidly into a bunch of
side-issues
(partly my fault for a rather careless initial post), so it's hard to
sort the
substance out of the responses.

In my own experience, either 6 or 9 of the named stars can be seen
with the naked eye. If conditions are good enough to see 7, I'll also
see two more.

That's rather unusual. From the admittedly rather small sample of
responses, it seems that the most common numbers of Pleiads
seen in ideal conditions were six, seven, and eight. Nine wasn't
rare, but not much more common than ten.

Curiously, among those who see seven, it's pretty much a tie
between the seventh being Pleione (28 Tau) and Caelano (16 Tau).
Pleione is significantly brighter, but it's also a good deal closer
to its nearest partner.

Personally, I see six when wearing my normal glasses, with
optimal daytime correction, and eight when using an extra 0.5
or 0.75 diopters correction for optimal nighttime viewing. I've
never seen nine -- and not for want of trying.

Fast forward to today. I recently read about the Pleiades in yet
another book. An illustration showed the 9 brightest stars along with
their names. The text pointed out the seven sisters as well as the
two parents.

The assignment that we now use of specific names to specific Pleiades
dates from the early telescopic era, when people were already aware
that there are (at least!) several dozen Pleiads. It's unclear whether
the ancient Greeks assigned specific names to specific stars. But it
is pretty clear that they considered the stars that we now name as
parents (Atlas and Pleione) to be sisters, not parents.

On Mon, 07 Aug 2006 18:34:15 -0600, Willie R. Meghar
wrote:

On those nights when I could see 9 stars I was seeing the seven
sisters and the two parents. Might it be that before the
proliferation of outdoor lighting, on a good night, the average
observer could see the nine named stars? Might it also be that those
observers were aware of the distinction between the seven sisters and
the two parents? If so, when they spoke of seeing seven Pleiades they
were referring only to the sisters since the parents, though present
and visible, were not sisters. Might this clear up the case of the
(not so) missing Pleiad?

An interesting idea, although I doubt anything will ever clear the
matter up.

I too see 6 stars under average conditions, and 9 under good conditions
(with additional, fainter ones drifting in and out, on the edge of my
perception). I don't remember ever counting 7- just 6 or 9. I know a few
people claim to see 7 fairly commonly, but nobody I know personally.

My own view is that historically there were never 7 stars commonly
visible, but the idea of the Seven Sisters came from a more complicated
relationship with myth (something like what you suggest, for example).
Certainly, the number 7 has powerful symbolism in many cultures.

_________________________________________________

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

On Tue, 08 Aug 2006 15:28:37 GMT, Chris L Peterson
wrote:

My own view is that historically there were never 7 stars commonly
visible, but the idea of the Seven Sisters came from a more complicated
relationship with myth (something like what you suggest, for example).
Certainly, the number 7 has powerful symbolism in many cultures.

Greek star lore was consistent in having only 6 of the 7 sisters
shining in the sky.

Bud
--
The night is just the shadow of the Earth.

Willie R. Meghar wrote:
Once upon a time (if memory serves) there was a discussion on saa
concerning the missing Pleiad.

Willie, would you be so kind as to e-mail me? Thanks!

--
Brian Tung
The Astronomy Corner at http://astro.isi.edu/
Unofficial C5+ Home Page at http://astro.isi.edu/c5plus/
The PleiadAtlas Home Page at http://astro.isi.edu/pleiadatlas/
My Own Personal FAQ (SAA) at http://astro.isi.edu/reference/faq.html