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General Astronomy >> General Observing and Astronomy

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Plan9
professor emeritus


Reged: 01/28/08

Loc: Northern VA
Re: unlearning the constellations new [Re: drollere]
      #5485730 - 10/23/12 05:32 PM

Bruce,

I'm late to the party - just checked out the Observing forum and spotted your thread.

Your subject line and first post grabbed me - while I accept the usefulness of the constellations (at least it's a map and you can kind of find your way around the sky with it), they don't provide a framework for any deep knowledge. I'm keen to continue this discussion (maybe more future threads to keep from being unwieldy ?).

A couple of things I found in a few minutes of surfing that might be of use/interest (all wikipedia):

Local Bubble
Orion-Cygnus Arm
Perseus Arm

These talk about Milky Way structures that surround us; I wasn't actually familiar with these terms/structures.

Also, more software:
3D Galaxy Map

BTW, no need to be down on Java, esp for applications rather than applets - the Mac is the only platform I'm aware of that provides Java out of the box (and Apple just handed over support of it to Oracle - previously it had been rather neglected and behind the curve compared to the Windows version, which was always maintained by Sun then Oracle).

Quote:

i claim there is a general lack of single and compact resources to anchor the average amateur astronomer's understanding of our place in the galaxy, its broad structure and processes.




Bravo! How can we help this to happen?

Bill


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GlennLeDrew
Postmaster
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Reged: 06/18/08

Loc: Ottawa, Ontario, Canada
Re: unlearning the constellations new [Re: Plan9]
      #5485802 - 10/23/12 06:11 PM

Bruce,
Fine work on your galaxy map, based on the CO chart by Dame et al. I note the you missed two really nice OB groups; Cep OB 3 and 4. And it's worth pointing out that the Local and Per arm clouds, etc., between Cep and Gem are superimposed. The high latitude features tend to reside in our arm, while much of the stuff near the galactic equator is in the Per arm.


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cadfour
member
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Reged: 07/26/12

Loc: Melbourne, Florida
Re: unlearning the constellations new [Re: Doc Willie]
      #5486803 - 10/24/12 11:04 AM

As a beginner in this hobby, last night rather than gaze at objects though the scope, I decided to take Bruceís "big picture" approach. I looked at Sagittarius and thought...'Thatís the center of our galaxy'....arced toward Vega and Cygnus and thought.....'Thatís the direction our sun is moving'...then arced from Cygnus toward Orion and thought....'Thatís the direction of the galactic arm that we reside'.

I think I might have gotten my first glimpse of the forest though the trees.


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uniondrone
Carpal Tunnel
*****

Reged: 12/05/09

Loc: Streetlight Archipelago
Re: unlearning the constellations new [Re: cadfour]
      #5487448 - 10/24/12 06:26 PM


Despite the contentions brought up in a few of the replies, I think that Bruce makes some fascinating points about how we look at the night sky and how this creates certain biases to our perspective of the universe. Although constellations can be useful navigational aids and have some historical and cultural relevance, we shouldn't overlook the fact that they are totally artificial constructs, lest we lose sight of the real shape and scale of our galaxy.


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Dennis_S253
Pooh-Bah


Reged: 11/22/11

Loc: West Central Florida
Re: unlearning the constellations new [Re: uniondrone]
      #5487687 - 10/24/12 09:28 PM

Cadfour, I think the center is in Scorpius. Between the arrow of Sagittarius and Scorpius's heart. And don't forget Ophiuchus, it's right there also.

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Dennis_S253
Pooh-Bah


Reged: 11/22/11

Loc: West Central Florida
Re: unlearning the constellations new [Re: Dennis_S253]
      #5487736 - 10/24/12 10:04 PM

I always wondered though, is the center the same in Africa or Russia or where ever you are? I suppose it must be.

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tedbnh
scholastic sledgehammer


Reged: 11/14/07

Loc: New Hampshire
Re: unlearning the constellations new [Re: Dennis_S253]
      #5487748 - 10/24/12 10:15 PM

I have not seen mention yet in this very interesting discussion of Guy Ottewell's "Astronomical Companion" in which he demonstrates with gorgeous hand-painted illustrations the 3D arrangement of nearby stars and DSO's.

So I will mention it! :-)

Also: When I explain the Messier objects to the public (what they are in general) I always try to point out that those hundred or so objects contain examples of almost every stage of stellar evolution and cluster life cycle in the rest of the Milky Way. It is just that we are lucky to have these examples close enough to see in small amateur telescopes. The message I try to convey is that they should try to understand that in the 95% of the Milky Way where we can't see such objects because they are too far away, it is almost certain that the same classes of objects occur everywhere. We got a nice random sample close to home, and since it's random it should be representative.


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derangedhermit
Pooh-Bah


Reged: 10/07/09

Loc: USA
Re: unlearning the constellations new [Re: drollere]
      #5488067 - 10/25/12 05:30 AM

Quote:

ptolemy represents a floor, not a standard. the point isn't that ptolemy is especially admirable ... it's that he at least saw the milky way as worth looking at, and that nobody since has looked at it with a comparable level of detail. (excepting things like the barnard survey photos ... one can find hundreds of lovely images, but a dearth of explanation of what we are looking at.)


There is often enough information to at least let inquiring minds take off in independent study - for example, each APOD photo, like today's Medusa Nebula, has a pithy summary of what we are seeing, with sufficient links to dig in further. But I suspect this is not what you mean.

Quote:

i claim there is a general lack of single and compact resources to anchor the average amateur astronomer's understanding of our place in the galaxy, its broad structure and processes.


I think you mean "broad" here quite literally, except limiting it to intra-galaxy size. Yet if I compare the scope of Shu, for example, in his textbook, then he spends a small fraction of his time on objects and processes focused on in this thread. He spends most of his time on smaller things (e.g. stellar development and evolution) and larger things (e.g. galactic dynamics). To me those other topics also deserve attention (or Shu seems to think so), and you are simply saying that the "average amateur astronomer" needs to have the equivalent of a year's worth of university-level coursework.

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Dennis_S253
Pooh-Bah


Reged: 11/22/11

Loc: West Central Florida
Re: unlearning the constellations new [Re: derangedhermit]
      #5488675 - 10/25/12 01:51 PM

We really don't even know what our galaxy looks like. It is people guessing. They don't know if there are 4 arms or 6 or 8. What size is it? Oh maybe 100000 to 120000 ly across and maybe 1000 ly thick. So, what do I do? I view the wonders of the universe with my small telescope and use my imagination. I personally don't care where it is. I'll never get to go there in person in this life. But as long as I know it's RA/Dec I can find it. We've come a long way I guess. Just how far, well your guess is as good as anybody's. In a very good dark sky you can see the galactic bulge. Well, thats what they think it is anyway. Has anyone or anything ever been there? NO

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csrlice12
Postmaster
*****

Reged: 05/22/12

Loc: Denver, CO
Re: unlearning the constellations new [Re: uniondrone]
      #5488837 - 10/25/12 03:32 PM

Quote:


Despite the contentions brought up in a few of the replies, I think that Bruce makes some fascinating points about how we look at the night sky and how this creates certain biases to our perspective of the universe. Although constellations can be useful navigational aids and have some historical and cultural relevance, we shouldn't overlook the fact that they are totally artificial constructs, lest we lose sight of the real shape and scale of our galaxy.




and the skies are not static, they are forever changing, albeit slowly. The sky of 100,000 years ago are not the skies we have today, and today's skies won't be the skies 100,000 years from now (and it may even be a lot shorter time period).


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Tony Flanders
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Reged: 05/18/06

Loc: Cambridge, MA, USA
Re: unlearning the constellations new [Re: Dennis_S253]
      #5488889 - 10/25/12 04:04 PM

Quote:

We really don't even know what our galaxy looks like.




True.

Quote:

It is people guessing.




No, that's grossly overstating the case. We don't know precisely how our galaxy is constituted -- or any other galaxy, for that matter. But we have a pretty darned good idea. We do know it's a spiral, we're essentially certain that it has a central bar, and we have very tight constraints on the shapes on the arms and how stars inside them move. There's no doubt at all where the core is, nor is there any doubt about the central bulge.

This isn't guesswork; it's all based on solid observations.

As for the size of our galaxy, the uncertainty is as much a matter of definition as lack of data. Galaxies don't have sharp edges!

We can never know ANYTHING precisely, but that's no excuse for ignoring what we do know. If you don't want to learn, that's your own choice -- and your own loss. But don't blame it on lack of knowledge.

As for me, I find it odd when people aren't interested how they fit into the larger scheme of things, be that their family, their company, their city, their country, the planet, the solar system, the galaxy, or the universe at large.


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Dennis_S253
Pooh-Bah


Reged: 11/22/11

Loc: West Central Florida
Re: unlearning the constellations new [Re: Tony Flanders]
      #5488956 - 10/25/12 05:04 PM

True true and true. I for one does not have all the equipment one needs for sure. And if I were a younger man and knew what I know now, I may have had a totally different life. Most professional astronomer's spend very little time at a telesscope. Yes, I believe them when they tell me an object is X amount of LY's away. This universe is ever changing. Even our own asterism "the Big Dipper" is changing everyday. Yes, do I try to learn something everyday? Of course I do. But, I'll stick to being an amateur astronomer. I'll look for things in the night sky. Maybe I'll be the first to see a super nova or a comet or some other special thing. And when I do, I'll want to tell them what constellation it was in and what my RA/Dec was.

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GlennLeDrew
Postmaster
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Reged: 06/18/08

Loc: Ottawa, Ontario, Canada
Re: unlearning the constellations new [Re: Dennis_S253]
      #5489072 - 10/25/12 06:45 PM

Dennis,
By "sticking to being an amateur astronomer"', do you mean limiting yourself to looking skyward by peering into an eyepiece? Nothing at all wrong with that, but the definition of an amateur is in no way restricted to just gazing.


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Dennis_S253
Pooh-Bah


Reged: 11/22/11

Loc: West Central Florida
Re: unlearning the constellations new [Re: GlennLeDrew]
      #5489142 - 10/25/12 07:29 PM

True, there are amateur astronomers that do more than just gaze at the sky. Maybe there is no exact definition to use for myself. Back yard gazer who likes to look at a number of different objects?

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drollere
Pooh-Bah
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Reged: 02/02/10

Loc: sebastopol, california
Re: unlearning the constellations new [Re: GlennLeDrew]
      #5490006 - 10/26/12 10:57 AM

Quote:

Fine work on your galaxy map, based on the CO chart by Dame et al. I note the you missed two really nice OB groups; Cep OB 3 and 4. And it's worth pointing out that the Local and Per arm clouds, etc., between Cep and Gem are superimposed. The high latitude features tend to reside in our arm, while much of the stuff near the galactic equator is in the Per arm.




thanks for the kudos, glenn. the exclusion of CEP OB3 and OB4 follows de zeeuw & alia (query "de zeeuw 1999" at SAO/NASA), who couldn't identify a moving group based on hipparcos data, which of course has a limited resolution of distant proper motions. apparently for that reason they don't address associations in CAS, GEM, AUR and CYG which i've excluded as well. (see also the RASC guide to the gould belt HERE, which similarly excludes CEP OB3 and OB4 and was written by ... glenn ledrew!)

however, to the earlier post about wanting to see the stars in an association, it's important to emphasize the associations that are visually striking or clearly related to other visible landscape features.

i mentioned earlier that the milky way is actually "transparent" in many directions, and for that reason we can see distant features in the perseus arm through features in the local arm. for me this is a major difficulty in helping someone visualize the structures presented to the eye only as a mottled "flat" band of light.


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drollere
Pooh-Bah
*****

Reged: 02/02/10

Loc: sebastopol, california
Re: unlearning the constellations new [Re: derangedhermit]
      #5490097 - 10/26/12 11:57 AM

Quote:

Yet if I compare the scope of Shu, for example, in his textbook, then he spends a small fraction of his time on objects and processes focused on in this thread. He spends most of his time on smaller things (e.g. stellar development and evolution) and larger things (e.g. galactic dynamics). To me those other topics also deserve attention (or Shu seems to think so), and you are simply saying that the "average amateur astronomer" needs to have the equivalent of a year's worth of university-level coursework.



first off, i have to highlight your mention of frank shu's FABULOUS TEXTBOOK and my strong recommendation that anyone interested in the fundamentals of astronomy (and comfortable skipping over any unfamiliar calculus to follow the main story) should definitely snag a copy. it appears to be back in print.

i think you underestimate how closely my proposal complements shu, or at least would try to anchor his chapters 8, 9, 11 and 12 in visible structures. as i said earlier, the amateur astronomer can greatly benefit from the "landscape" awareness that our galaxy ("The Galaxy" as it's often called) has a certain size, shape, basic structure and motion, our place in that structure and motion, and the bright stars, asterisms or distinctive milky way features that locate all that in the sky.

all that is taxonomic: the real point is that we reside in an enormous machine for making stars, or more accurately star systems -- double stars and planetary systems. this is a *process* story that comes naturally out of the landscape. as i said, the whole story is laid out in almost any seasonal quadrant of the milky way -- silhouetted giant molecular clouds, bok gobules or barnard objects; illuminated H-II regions; massive OB stars and smaller T Tauri stars emerging from dust clouds or H-II regions; hot young star clusters like the double cluster or pleiades, cool old clusters like the hyades or praesepe, the rich mixture of main sequence, giant and white dwarf stars they contain -- what the difference between the clusters illustrates about their age and stellar life cycles -- supernovae remnants and planetary nebulae.

if all that stimulates questions of "why?" or "how?" then there is a firm basis to dig into shu's two protagonists, universal gravitation and the second law of thermodynamics, and how their fierce struggle plays out in structure and process. the foundation is laid.


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drollere
Pooh-Bah
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Reged: 02/02/10

Loc: sebastopol, california
Re: unlearning the constellations new [Re: Dennis_S253]
      #5490150 - 10/26/12 12:37 PM

Quote:

I for one does not have all the equipment one needs for sure. ... Yes, I believe them when they tell me an object is X amount of LY's away. This universe is ever changing. Even our own asterism "the Big Dipper" is changing everyday. Yes, do I try to learn something everyday? Of course I do. But, I'll stick to being an amateur astronomer. I'll look for things in the night sky.



i'd emphasize that the necessary equipment assumed here is your naked eye observation or, even better, a good binocular -- and a reasonably dark observing location, which for many is the most difficult bit of "equipment" to obtain.

of course the equatorial coordinate system is useful to align your telescope: i'm offering the galactic coordinate system, which is useful to align your insight. it's simply the center line of the milky way band; you can mark off the compass points positions with bright stars: N is the teapot, NW is altair, W is deneb, SW is the double cluster, S is beta aurigae, SE is sirius, E is lambda velorum, NE is alpha centauri. where is the galaxy center? N. where is the orion arm? from W to SE. where is the sun headed? W by NW. where is the scorpius-centaurus association? from N to NE. and so on.

it's perfectly fine to learn that "M45 or the seven sisters is an object in the messier catalog, located in the shoulder of the Bull, an ancient zodiacal constellation that appears in the art of minos and the myths of babylon."

i'm suggesting that you can with no more difficulty learn that "M45 is a very young star cluster located in a nearby area of the galaxy where stars are still being formed, probably a sibling to the cluster of stars around alpha persei and out of dark clouds of interstellar gas that are still visible in the milky way between betelgeuse and capella."

these alternative bits of "lore" have this effect: the question "how do we know, in the myths of *babylon*?" takes your curiosity in a very different direction from the question "how do we know, a *young* star cluster?" it's my contention that one question takes you further into the heart of astronomy, and the other question takes you ... somewhere else.


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auriga
Pooh-Bah


Reged: 03/02/06

Re: unlearning the constellations new [Re: drollere]
      #5490638 - 10/26/12 05:58 PM

Sky Safari Pro shows the galactic equator very well.

How do you know the Teapot is North? On Earth what we have decided to call North is defined by the North Pole (rotational north) or by the North Magnetic Pole.

Isn't the direction you designate as North, namely near the Teapot, arbitrary for our galactic system? Why not call it South, East or West?

If one means the pole around which our galaxy rotates, the North Galactic Pole, on my maps it is in Coma Berenices, not near the Teapot in Sagittarius.

Please say more on these topics.

I am interested in learning more about thinking in terms of galactic coordinates, but I consider the history of the constellations in various cultures to be a very interesting part of astronomy.

Given the intellectual power manifested in your web site, you might enjoy Jacques Ellul's book, "La Technique" (title mistranslated as "The Technological Society.")

Thanks


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GlennLeDrew
Postmaster
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Reged: 06/18/08

Loc: Ottawa, Ontario, Canada
Re: unlearning the constellations [Re: auriga]
      #5490724 - 10/26/12 07:00 PM

Auriga,
Bruce was indeed transposing an arbitrary compass face onto the galactic equator, as seen from galactic north, or 'above.'

Bruce,
I'm quite familiar with the work of deZeeuw, et al, and have the paper you mentioned. (One of the investigators sent me a copy of the fine book he produced as his PhD thesis summarizing this and related material.)

In my RASC article I omitted all associations not believed to belong to the Gould Belt (as the latter was the subject.) But Cep 3 and 4, as well as Gem 1, are eminently observable and interesting with small instruments. Eventually my own web site will feature, among other stuff, an observer's guide to the Gould Belt and other associations.


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drollere
Pooh-Bah
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Reged: 02/02/10

Loc: sebastopol, california
Re: unlearning the constellations [Re: GlennLeDrew]
      #5490976 - 10/26/12 10:28 PM

Quote:

In my RASC article I omitted all associations not believed to belong to the Gould Belt (as the latter was the subject.) But Cep 3 and 4, as well as Gem 1, are eminently observable and interesting with small instruments.



you raise an interesting point, namely -- which stars are in an association? setting aside that things sorta change as new methods are applied, i don't know of a "viewer's guide" to association members. you *can* find academic papers with exhaustive lists, but many members are lost in the field stars. what's needed is a star chart with group members labeled.

also, i've looked for but haven't found a finder chart for the hyades, praesepe and pleiades ... perhaps you know of one.

of course your paper was limited to the gould belt; i was tweaking you. but to the substance, i omitted associations not in de zeeuw because of their failure to confirm 6 nearby associations grandfathered in the literature. (i made one exception for the far group CYG OB2.) that was an insight into the status of associations that gave me pause.


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