Expert: Tom Whiting - 5/23/2009

Question
QUESTION: Hi Tom,
I recently saw an amazing photo of the Cat's Eye Nebula and read that it is considered to be one of the least understood and amazing phenomena so far photographed in space (Mind you, the magazine I saw it in was over 5 years old, so things may have changed). Could you tell me what exactly the Cat's Eye Nebula is (e.g. is it a star) and is it true that it is one of the least understood phenomena in space and, if so, why? What is so unique about it and, if we understood it better what could it tell us or give us an insight into (i.e. what would it's legacy be if it's mystery was unravelled)?
Finally, is it also true that the Cat's Eye Nebula is dying and, if so, does that make it less significant a discovery?
I am really intrigued about this because there is just something quite incredible about that photo that I can't quite put my finger on!
Thanks for your time
Gary

ANSWER: Hi Gary,
Ironically we were out observing tonight, and once it's dark, NGC
6543 is one of the first deep sky objects I like to go to with my 30 inch portable scope.

In the general sense, the Cat Eye (NGC 6543 in Draco) is not unique...it is just one of thousands of planetary nebula in our
night sky...the Owl Nebula (M-97), the Ring Nebula (M-57), the Dumbbell Nebula (M-27), the Eskimo Nebula (NGC 2392), the Blue Flash Nebula (NGC 6905), and I can name off hundreds more. And by definition, ALL planetary nebulae are dying stars.
  
Of course the word 'planetary' is a mis-nomer....they have nothing to do with planets. (Or do they? See farther down)... The ancient astronomers thought that those little bluish-green disks were new planets forming up, especially since Uranus (discovered in 1781) had a greenish disk and Neptune is slightly bluish. So the name stuck.  Today we know that the planetary nebula stage is simply the stage between a normal solar-type star moving from the Red Giant stage to the white dwarf stage.  And that's why there are thousands of planetary nebulae out there. {Our own sun will do the same someday,
after the red giant stage.} Eventually the dust and gas dissipate,
and you are left with a white dwarf star in the center.

What is strange specifically about NGC 6543 is the helix structure
and wide outer irregular envelopes surrounding the central star (which is the core of a former red giant on it's way to being a white dwarf- like all the other planetary nebulae).  What caused the spiraling helix structure and the irregular outer envelopes?  One popular theory is that perhaps this solar-type star had a 'solar system' of planets around it, which were far enough away to survive the red giant phase.  As the red giant stage came to an end, and the star began to expel the dust and gas to form a planetary nebula, perhaps giant planets were still revolving about the star, and caused the spiral or helix structure in the dust and gas we see today.  Surviving outer giant planets could also explain the irregular outer envelope lobes of gas too....but no one knows for sure, as yet.
In any case, perhaps outer giant planets, in the survival mode, may account for some of the varied and unusual structures that we see in a lot of the planetary nebulae.  So perhaps.....the term is not a misnomer after all. But perhaps its planets at the END of their life causes the irregular structures we see, not the beginning of their life, as was originally thought by the...old timers of the 18th
and 19th century.
But in reality, no one yet really knows why the unusual structures
that we see in the planetaries.  Planetaries happen to be my favorite of all the deep sky objects.
Hope this helps,
Clear skies,
Tom Whiting
Erie, PA


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

QUESTION: Hi Tom,
thank you very much for your help in explaining the science behind the Cat's Eye Nebula. It really is fascinating stuff. Out of interest, would I be able to observe it here in the UK and if so, what would be a good telescope to get, in order to see it or, is it too far away to see with a conventional telescope?
Finally, in your opinion, is there any other phenomena that has been observed/photographed in space that could be labelled unique in the respect that it is still not well understood?
Thanks for your time
Gary

ANSWER: Hi Gary,
Last question first....there are a lot of things that are still
unknown in space...What is the dark matter and dark energy that make
up 96% of our Universe (normal matter only constitutes 4% of the
Universe!).  What dark body causes the star Epsilon Aurigae to
undergo a 2 year partial eclipse every 27.1 years...starting in Sept 2009 by the way...(google Epsilon Aurigae near the bright star Capella.)  How do the quasars out there 5-10 billion lightyears
put out so much energy?  How did the initial stars and galaxies
form up right after the Big Bang?  The light we see from the Big
Bang 380,000 years after Big Bang, the remnant radiation, as the
Universe finally became transparent, how did this effect the
expansion rate and did small temperature variations explain the
initial formation of the galaxies, and how?
These questions, and others, are why the ESA just launched the
Herschel space telescope (far-infrared) and piggy-backed to that
is the Planck Surveyor to detect the light from the Big Bang,
which of course is red-shifted down into the microwave portion
of the radio spectrum.  Also there are plans for the James Webb
telescope to be launched in 2014 or thereabouts. If we knew all
these answers, there would probably be no need for astronomers!

First question, Oh yes, the Cat eye nebula is easily visible from
anywhere in the N. hemisphere at 9th magnitude, which technically
makes it barely visible as a little fuzzy dot with only 10 x 50
binoculars, IF you know exactly were it is in Draco.  (So naturally,
any small telescope can view NGC 6543, and it has a pretty high
surface brightness too, so you can throw some magnification to it.
(Unlike some of the other planetary nebulae that are very faint
and diffuse...high magnification, which requires lots of light,
ruins the view of most faint, diffuse planetaries. The challange on
these planetaries... is to view the central star for us amateurs,
which in some cases is very very difficult to do.  I think it takes
at least an 8 inch glass to view the central star in NGC 6543.

The hard part, of course, is the knowledge of exactly where the
Cat Eye is in the sky.  For that, you need to step back and decide
whether or not you want to go into observational astronomy in the
first place, otherwise just contact an amateur who already knows
the night sky and has a scope.
In our great hobby, equipment comes LAST, knowledge of the night sky
comes FIRST.  First you need to learn your 40 or so northern
constellations and learn the naked-eye night sky first. This is
not as hard as it sounds....if you can learn and memorize 4 adjoining
counties...Cornwall, Devon, Dorset, Hampshire; then you can also
learn and memorize Gemini, Cancer, Leo, Virgo...4 adjoining constellations, or area's of the sky. It just takes the self-motivation to want to do it, that's all.  All this has to be done
first, for a foundation...you can't build a house without a foundation first.  So make your first 'scope' a pair of binoculars
and a good star chart (map of night sky) and go outside at night
and start learning your areas of the sky. Find a local club, there
are hundreds of them in the UK now...or start your own astronomy
club in your local region like I did.  This is not an activity
that you just jump into for one night's viewing...there is a process
and procedure to follow to do it correctly. Suggest, if you're interested, you punch up our club website and punch on "Tom Whiting's
Sound Advice for the New Observer", and read how to do it correctly, at
http://www.velocity.net/~bwhiting
and read about the correct procedure of how to get into our great
hobby.

Clear Skies,
Tom Whiting
Erie, PA USA

PS...By the way, NGC 6543 is NOT a beginner's object due to it's small size and location...it's out in the middle of no-where in
Draco, with no bright naked-eye stars nearby to sight in on, so
for that reason, it's considered an advanced amateur object as it's
not that easy to find, even if you know your night sky.  So don't
plan on running outside at night and be able to find it with
little or no knowledge of the night sky.  It's even tricky for
an advanced amateur...I have to cross-hatch about 4 distant stars
to find it thru my Telrad finderscope...and I even know exactly
where it's located! But I've been doing this for over 50 years now.
And sometimes it even takes me 30-60 seconds to get it in my scope, whereas I can find and acquire the easy stuff (Like the Ring Nebula planetary (M-57) in less than 5 seconds. Just an example of why
NGC 6543 is considered an "advanced" object, not super easy like
other brighter, bigger, Messier deep sky objects.

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

QUESTION: Wow. Thank you Tom. Before I was intrigued. Now, you've got me hooked on the subject. I will take your advice and read your webpage (Thanks for the link). Once I've learnt the basics (which I understand will take time), perhaps I could get back to you regarding advice on which telescope to get! My initial goal is to see NGC 6543
Thanks again Tom. Your enthusiasm for the subject has rubbed off on me. Looking forward to reading the article you wrote. In the meantime, are there any books you recommend for a beginner like me?
Best Regards
Gary

Answer
Hi Gary,
Like our webpage says, since astronomy is a learning hobby, and
not a flashy visuals hobby, read all you can about it.  It would
be nice if you lived near a college which teaches astronomy, and
they might have a college book store, so you could go in there an
purchase an Astronomy 101 beginners textbook. Or just raid your
public library for astronomy books.  Realize that stuff like books,
computer research, planetariums, courses in astronomy...these are
all good incentives. BUT they don't give you what you need right
now.--  A good star chart of the heavens and go outside at night
to a relatively dark sky and self-teach yourself (That's right, just like Abe Lincoln did)!...the night sky and the constellations and the identification and the names of the stars.  It isn't that difficult as it sounds...it's all self-motivation and the desire to want to learn it, that's all. If you're fairly competent in map reading and compass directions, you find it's quite easy to learn...self teach yourself...the night sky.

Well, you have to figure out first what you want to specialize in
before a telescope...lunar/planetary, deep sky objects, comet hunting, splitting close doubles/multiples (which make up nearly
half the stars)....there is a scope out there that maximizes each
of these activities.  If you pick (and it seems you are tending
toward) deep sky objects (DSO's), then you want a standard Newtonian
Reflector, DOB mounted (alt-azimuth) with as big a mirror as you
can afford.  Normally our DSO new people go for a 10 inch Newtonian
DOB mounted reflector from either Orion or Discovery.
(I don't know their brand names in the UK).
 
AVOID....equatorially mounted scopes for your first scope. Only
astrophotographers need those heavy, bulky, equatorial mounts.
AVOID....clock driven scopes; only astrophotographers need those.
AVOID....goto telescopes, with batteries, servers, computers, etc. too much to carry and transport to a dark sky site, and besides, if you spend 6 months learning the night sky, you'll know from your star atlas where everything is anyway.  Besides, a goto makes people lazy and nonchalant...it takes away the interest in actually learning the night sky, which is half the fun of it...discovering things out there on your own.
Then, with the money you've saved by NOT buying a clock
driven goto equatorially mounted scope, use that money to get a scope with a still bigger mirror. Like in real estate, the 3 biggest things with a scope are...aperture, aperture, aperture! The bigger the mirror, the more light coming in and the more you'll see.
DSO people like me want a large mirror reflector, and not a refractor
scope...those are for the lunar/planetary and double star observers,
with a long focal ratio (f10 and higher) and no central obstruction of a secondary mirror for better contrast. We DSO people want a large a mirror as possible, with a short focal ratio (say f4.5) to keep the length of scope to a minimum.  (See my 30 inch portable
scope on our club webpage).

There are some general rules you want to follow:
Anything less than 6 inch diameter mirror is nearly worthless for
DSO's. Plan on your purchase of the equivalent of $500 USD as a bare minimum, otherwise you may end up with a piece of junk (the optics
are very critical....in fact, with scopes, you always have to go
"First Class"...there is no such thing as a good, cheap scope
because of the laws of optics, which you can read about on our club
website that I furnished you).  On the other hand, I wouldn't go any
bigger than a 10 inch mirror for your first scope either.  Above 10
is for advanced amateurs, requiring the purchase of much better
star charts costing nearly $100 USD plus who really knows ahead of
time whether they'll really like our nighttime outdoor hobby or not.
Generally 6, 8 and 10 inch scopes are easy to re-sell, but the larger
sizes, 12.5, 16 and 18's aren't so easy to sell because your starting
to talk some real money now, at least a thousand dollars USD for
those 12.5 inchers.
So take it slow...there is a lot to learn about this hobby before
you make the plunge into buying a scope...just a for instance, do
you know how to collimate (line up the optical axis) of a scope?
YOu should know that before buying a scope, and whether or not it
CAN be collimated, as they all have to be occasionally. Did you know
that you want to set up outside an hour before sunset to let the
mirror and optics cool down to the air temperature? That's right,
mirrors and the air in the tube have to be very close to ambient
temperature, otherwise its a horrible image with heat waves in the
scope. (We're talking a couple millionths of an inch on the figure
of your mirror and optics).  This is a very precision hobby!
NO looking out a window (which the glass in not optically pure) and
the temperature difference in the room compared to the outside air
if different, renders a horrible image. No looking over a neighbor's
asphalt roof or tile roof where heatwaves destroy your image. You
have to get into relatively dark skies, otherwise light pollution
kills off all the DSO's. Stuff like that...that you haven't even
considered...and there are another million little things you have
to learn. Like, are you right eye or left eye dominant? If left eye
like me, then you want the eyepiece on the right hand side of the
tube for comfort, but if you're right eye dominant, then you want
the eyepiece holder on the left side of the tube! Little things like
that.  They all add up to comfort and knowing what you are doing
out there.
So join a club, go out observing with other astronomers,
see what equipment they use and recommend, learn the ropes...takes
about 6 months, but no hurry, NGC 6543 will still be there in our
lifetime.
Clear Skies, and Good luck,
Tom Whiting
Erie, PA USA
PS...sure, you can contact me anytime off site, as I am retired, at
bwhiting@velocity.net

FOLLOW UP:
Oh, two other things you should be aware of...use a red light at
night to read your star charts or atlas. White light night blinds
you, so we all use red light to read. We all wear these red lights
on our foreheads, like coal miners lights, but they are red light
so it doesn't destroy our night vision at night when we refer to
our sky maps.
And I hope this next one isn't too devastating to you..you've probably seen all those pretty colored pictures of DSO's like the
Cat Eye...with all the color. Sorry, but that's ONLY the way film, CCD's and computers record the photograph. Then they get it into the
dark room, or the computer, and they intentionally saturate the
color to brighten it up. But with the naked eye, at night, using only
our rods on our retina's, there is very little color seen. Most of the objects are just a creamy white with just a tinge of color.
All the color receptors are in our cones on the retina, (daylight
vision) and require lots of light to see color. We don't see all
that color using our night vision thru a scope!  I've had many a new-comer at the scope ask, "Where's all the color?"  Sorry, but it
doesn't work that way.
With NGC 6543 I see a cream white with just a tinge of blue-green color, and that's it. All planetary nebula radiate most of their light at 5007 Angstroms (doubly ionized oxygen atoms) with is in the
blue-green part of the spectrum, so all planetaries have just a
hint of blue or green color, and that's it. There are no reds, yellows, oranges...all those bright colors that you may have seen in the pictures.  And that's true for most objects in the night sky because we use our rods on the retina, not the cones.
The light is too dim, so there is hardly any color.
(That's why a nebular filter is a good buy for a telescope...it allows that one wavelength of light thru, blocking all others, so
you get to see the nebulosity at 5007 angstroms only, so it brings
up the nebulosity in the blue-green part of the spectrum...but at a price because that same filter knocks out the light from the central star which radiates mainly in the deep blue and UV part of the spectrum in most cases.  So most of the time, I don't use a nebular
filter...only for the Veil and the Crescent Nebula's in Cygnus because they are so faint, you have to use a nebula filter just to see them.
So I hope I haven't devastated you too much with no, or very little, color to the naked-eye. See, there is much to learn, and what to expect from your equipment before you go tearing off.... down to the local pub.
Clear Skies,
Tom