Expert: Tom Whiting - 1/10/2011

Question
QUESTION: Hello!  I am a fellow expert over in the animals section.  I am a Biology teacher by trade and for some strange reason my principal has me teaching (or trying to teach) Earth Space Science this year.  Anyway, I have the kids started on a project in which they need to make a 3-d model of a constellation.  I assumed, (yeah, yeah, I know), that finding info about the stars and their distances from each other and from the Earth would be easy...  It has not been easy to find anything about distances.  

So, I am hoping you might be able to direct me to a website or other source which would have this info.  

Thanks!

ANSWER: Hi Brian,
Unfortunately, your basic premise is corrupt... constellations, BY DEFINITION, are only 2-dimensional as they simply define an area (like a state in the USA) of the sky, and that is all.
(Are states in the USA, 3 Dimensional?  Of course not.) Constellations, like states, are simply areas of the sky for identification purposes only.
But that being said, there are several sources for distance to the stars, which is the most difficult value to find... just type into google "list of stellar distances" and the first one you come up with is the nearby stars, at
http://en.wikipedia.org/wiki/List_of_nearest_stars
Personally, I would drop that whole idea, since constellations are not MEANT to be 3-D in the first place, and change the assignment to something more 'truthful' and meaningful... like say an accurate scale model of the Solar System by either size or distance, or both... something like that.  Or take the nearest 50 stars, and determine how many are small red dwarfs, solar type, and giants...  what percentage or proportion are represented in the 50 closest stars, something like that.
Clear Skies,
Tom Whiting
Erie, PA USA
PS.. oh, and no stellar distance is from the "Earth".. it's from the sun, our central star.
But the difference is so minor, because the Earth is only 8.3 light-minutes from the sun.
But the sun contains 99.86% of the mass of the Solar System, so it's our 'standard' when talking interstellar distances to the other stars, and not the Earth, technically.

FOLLOW UP:
It is true that the different stars (and other bodies like very distant galaxies) in a constellation are at different distances (that's a given)... just like mountains, trees, valleys, buildings, etc. in a top view of a state of the USA are at different elevations, But like a state, that doesn't change the area, shape, or size of a constellation.  And we who learn and study the 88 constellations, could care less about the 'depth' of same, because we know with a deep time exposure, you will photograph galaxies out there billions of light-years distant, but they are "in" that same constellation as are the relatively nearby stars. Because constellations represent an area, and NOT a volume!   The brighter stars are like "cities" in a state, and the lines we picture are the interstate highways connecting those 'cities' on a 2 dimensional plane. We don't memorize the boundaries (which are not visible in the sky) of a constellation, we memorize those interstate highways connecting the stars, as that's much easier to picture. It's simply a glorified game of connect-the-dots.
Clear Skies,
Tom  
FOLLOW UP:
In 1930, the IAU (International Astronomical Union) FIXED the boundaries of all 88 constellations. They are carved in granite. No more need to throw a man or animal into the constellations, as they are now simple areas. So if you can learn and memorize Pennsylvania, Ohio, Indiana, Illinois - 4 adjoining states, then you can also learn and memorize Gemini, Cancer, Leo, Virgo - 4 adjoining constellations.  It's that simple today.
tom



---------- FOLLOW-UP ----------

QUESTION: We did the solar system scale model before Christmas break.  This project was to encompass the concepts of apparent and absolute magnitude, star types, fusion, and the vastness of space.  I wanted the kids to realize that one star in a constellation might be say 8 light years away from us while that other one which appears to be right next to it is 3000 light years away.

We are "muddling through" finding the names of the stars in each constellation (seasky.org has been helpful there) and are having about a 60% success rate at finding their distances once we know their names.  I was very surprised to learn that so many stars don't have proper names or if they do how hard they are to find (especially so many that are actually part of a constellation).

Also, I would disagree that states are 2 dimensional.  If that were true hiking through say Grand Tetons National Park in WY would be no more challenging than The Ocala National Forest in Central FL.  In fact, we might need to add a 4th dimension-time!  Even if you planned on a challenging hike in the Tetons it might not be possible in Feburary.

Answer
The Earth is smoother than a billiard ball by comparison. Those few miles of elevation (Everest or the Marianna Trench) are nothing compared to the millions of light years out to a galaxy, or even 20 light years to a nearby star.
Yes, that is a very good idea to cover the different magnitudes, distances, spectral classification, composition, and H-R diagram with the students... and also the various fusion reactions in the various stars, along with their mass... the one factor that controls all other physical characteristics of a star. (But I wouldn't use 'constellation depth' as a control mechanism.)  I kept all those physical factors separate from learning the constellations when I taught the subject.
Actually, every star does have a name... if no lower case Greek letter, or Flamsteed number, or
SAO number. or other dimmer catalog number, etc etc., as you get dimmer and dimmer, than it's position on the celestial sphere in RA and Declination, becomes it's name (and position); like 023031+251822 as a made up... example.
Happy hunting,
Clear Skies,
Tom