A Capacity for Opacity

Ha Sun 

2007 08 26, 1700-1928 UT

PCW Memorial Observatory, Zanesville, Ohio

Equipment used:

Internally Double stacked Maxscope 60mm, WO Binoviewers, 20mm WO EP’s, LXD75.

Meade ETX70-AT, 21-7mm Zhumell, glass white light filter.

Seeing above average with only a few moments of quivering, transparency above average.

Temps 80.1 °F / 26.7 °C to 78.1 °F / 25.6 °C over course of observation.

Winds 4.6 mph – 6.9mph NNE/ 11.1 km/h.

Clear progressing to mostly cloudy by the end of the session.

Humidity 54%

Sketching media: The white light sketch was done on copy paper with a number 2 pencil.

The Ha sketch color sketch was done using black strathmore paper with color Prang pencils.
 

Word for the day:  Opacity

According to my heavy, red, weathered Merriam-Webster’s Collegiate Dictionary (tenth
edition), opacity is defined as:

“n, .1: the quality or state of a body that makes it impervious to the rays of
light; broadly: the relative capacity of matter to obstruct the transmission of
radiant energy..2b: the quality or state of being mentally obtuse: Dullness.”

I kind of got a kick out this.  It appears that with one word, I can attempt to
discuss opacity of the Sun and yet at the same time try not to create opacity while
doing it.

Studying the Sun, as well as anything worthwhile, can be very confusing and
sometimes overwhelming.  It helps to understand the basics such as knowing that the
Sun is a giant ball of gas.  It has several layers starting at the inner most called
the core. The majority of the Sun’s core consists of hydrogen.  By nuclear fusion,
the hydrogen is converted into helium.  The key here is that in doing so, energy is
created. Energy equals heat.  All in all, when we think of the Sun, we think of
radiation, or electromagnetic radiation to be more specific.  Radiation is a process
that transports energy.  Electromagnetic radiation is a radiation that carries
energy through empty space by means of waves at the speed of light. 

You see, atomic particles (created by the nuclear reactions in the core) speed up
and grow from the exchange of varying flows of electrical and magnetic fields, which
is where electromagnetic radiation originates.  Following me so far?  Here’s where I
start to get back on topic.  Electromagnetic radiation has both wavelength and
frequency.  When you multiply the two together, you get the velocity of light.  If
one of the variables increases, the other has to decrease for the velocity of light
to stay constant.

Oh, how easily it would be to dive in further with all this.  But I need to stay on
track with the first definition of opacity.  Wavelengths are compiled in what we
call a spectrum.  And this is when we get into means possible for us to view the
Sun. 

Imagine the energy being transported through a few more layers of the Sun, each
layer quite a bit hotter than the previous as it extends away from the core.  We
finally reach the layer that most call the “surface” of the Sun, the Photosphere.
Does that look Greek to you?  Well, not to worry.  It is Greek.  The Greek word
“phot” stands for light and “sphere” of course stands for round ball. 

In the photosphere, the gas is heated so much that it burns bright giving off most
of its energy close to the middle of the spectrum, creating visible light.  And it
doesn’t end there.  Reaching out from that thin layer of burning gas is the
chromosphere, meaning round ball of color.  After a brief pass through the
transition region, the energy enters the corona and then outwards as solar wind.
Each layer is visible through specialized means.  Each layer involves our word for
the day, opacity.

One evening, quite a few years back, my brother in law and I were cooking supper
together. I was in charge of the chip pan and cutting up the potatoes.  I could see
him very clearly across the room and the air was transparent and had a zero optical
thickness.

As we were talking to each other from different ends of the kitchen, we soon noticed
that we were getting harder for the other to see. In other words, the optical
thickness was getting thicker.  By the time we became alarmed to this fact, the
smoke was nearly opaque with an optical thickness of close to 9.  I could hardly see
him anymore.  As he walked toward me, I could see him more clearly and by the time
he reached me the optical thickness was perhaps a 3.

We removed the smoking chip pan that caused the smoke from the stove, opened the
kitchen windows, grabbed the dog and a bottle of wine, and sat out on the steps of
the flat, watching the smoke roll out of the kitchen window.  I don’t recall what we
ever did for supper that night, but I suppose that’s beside the point. It was a
perfect example of opacity and how I measured it. The same is done when viewing the
Sun.

The further into the Sun we look, the higher the opacity. We can only see up to
approximately an optical thickness of between 0.5 and 2.  The photosphere is said to
have an optical thickness range of close to 3/4, and it includes all the light that
we can muster from the Sun, meaning white light.  If I wanted to view through a
narrowband filter such as a hydrogen alpha filter, the optimal optical thickness
would be reached before I even gazed into the Sun as far as the photosphere.  I
would in fact start at the Chromosphere.  This is wonderful news for us in that by
using special filters, it changes the opacity from a zero to us being able to
actually see the color of the light in this layer of gas, blocking out all the other
colors that would have hidden this color otherwise.

Well now, I’ve come full circle with opacity!  And what does this have to do with my
observations today?  Well everything to be honest.  Opacity is what strives us to
find new filters for trying to tease out as much detail as we can.  And there’s
information to be had if we can look at different layers of the sun.  In my
observations today, I viewed in both the photosphere and the chromosphere.  Two
different gas layers with a temperature difference of over 4000 degrees Kelvin
(chromosphere at 10,000 K and photosphere at 5780 K).  Each will allow us to see
slightly different details on the Sun and each are important to consider while
studying it.

This first observation was recorded in hydrogen alpha.  You can see the effects of
the magnetic fields through the long fingers of the filaments holding the cooled
dense gas in place.  Although this observation is mainly in the chromosphere and
lower parts of the corona, the filaments are generally held in place by regions of
opposing magnetic polarity within the photosphere.  Of course this is also the case
for the prominences, as prominences are filaments above the limb where the gas is
set in front of the black sky instead of the disk.  Although the filaments were very
impressive on the disk itself, they were not so impressive on the limb today.
Having said that, take a look at the faint section of prominence that appears to be
floating off the limb in the WNW region.

NOAA 10969’s plage intertwined and reached out with crooked fingers. 

White light 

The next observation was using a white light filter where over 99.999% of the Sun’s
light is blocked out, making it possible for me to view the photosphere.  This is
called white light.  You can see NOAA 10969 in the cooler layer.  The chromosphere
becomes invisible to me again.  The two dark sections of umbrae within the penumbra
of this action region were very prominent.  I could see a darkened outline of the
penumbra and it had an almost rectangular shape with curved corners.  Of particular
interest was the very faint darkened area to the right of the sunspot.  This happens
to me fairly often, seeing little bonus features like this.  I’m still not sure what
causes it.  Normally I would think it was contrast from faculae that I was unable to
discern.  Normally we can only see faculae closer to the darker limb regions. But
often I can see an outline of contrast suggesting faculae present when the active
region is toward the center of the disk.

This time it is a little different.  If I didn’t know any better, it looked like a
thick triangular cooler region next to the sunspot.  By this I mean cooler than the
photosphere, hotter than the umbra, and only just slightly hotter than the
penumbrae.

With so much to learn concerning the sun, at least we learned one new word.  It’s a
start in the right direction anyway. 

Erika Rix

Two views of the nearest star

 Colored Ha Sun

You can see the effects of the magnetic fields through the long fingers of the
filaments holding the cooled dense gas in place. Although this observation is mainly
in the chromosphere and lower parts of the corona, the filaments are generally held
in place by regions of opposing magnetic polarity within the photosphere. Of course
this is also the case for the prominences, as prominences are filaments above the
limb where the gas is set in front of the black sky instead of the disk. Although
the filaments were very impressive on the disk itself, they were not so impressive
on the limb today. Having said that, take a look at the faint section of prominence
that appears to be floating off the limb in the WNW region.

NOAA 10969’s plage intertwined and reached out with crooked fingers.

Sun white light

The next observation was using a white light filter where over 99.999% of the Sun’s
light is blocked out, making it possible for me to view the photosphere.  This is
called white light.  You can see NOAA 10969 in the cooler layer.  The chromosphere
becomes invisible to me again.  The two dark sections of umbrae within the penumbra
of this action region were very prominent.  I could see a darkened outline of the
penumbra and it had an almost rectangular shape with curved corners.  Of particular
interest was the very faint darkened area to the right of the sunspot.  This happens
to me fairly often, seeing little bonus features like this.  I’m still not sure what
causes it.  Normally I would think it was contrast from faculae that I was unable to
discern.  Normally we can only see faculae closer to the darker limb regions. But
often I can see an outline of contrast suggesting faculae present when the active
region is toward the center of the disk.

This time it is a little different.  If I didn’t know any better, it looked like a
thick triangular cooler region next to the sunspot.  By this I mean cooler than the
photosphere, hotter than the umbra, and only just slightly hotter than the
penumbrae.

2007 08 26, 1700-1928 UT

PCW Memorial Observatory, Zanesville, Ohio
Equipment used:

Internally Double stacked Maxscope 60mm, WO Binoviewers, 20mm WO EP’s, LXD75.

Meade ETX70-AT, 21-7mm Zhumell, glass white light filter.

Seeing above average with only a few moments of quivering, transparency above average.

Temps 80.1 °F / 26.7 °C to 78.1 °F / 25.6 °C over course of observation.

Winds 4.6 mph – 6.9mph NNE/ 11.1 km/h.

Clear progressing to mostly cloudy by the end of the session.

Humidity 54%
H-alpha sketch was rendered using Prang colored pencils and Black Strathmore
Artagain paper.  White light sketch was created with photocopy paper and a number 2
pencil.

Erika Rix

Prom Dance

Prom Sequence 
Western prominence sequence and animation

I used the normal black Strathmore Artagain with a combination of Prang white
pencil, Conte’ white pencil and Conte’ crayon.

The Prang is waxy, more precise, and lighter markings. The Conte’ pencil is very
white heavy markings, but not as precise.

I’ve made a little animation to go with it.
http://www.sflorg.com/member_gallery/solar_images/20070804_animation

Erika Rix
Zanesville, Ohio USA

White Light Delight

White light sketch 

Solar Photosphere: The Beginning of NOAA 10966

Faculae were on both the eastern and western limbs, showing up with nice contrast
against the limb darkening. Within the eastern facula, the spot in NOAA 10966 was
hiding so well that I nearly missed it all together. After scanning the entire disk,
I finally picked up this little pore. No signs of penumbra. Faint granulation was
observed, though.

I’ve been using copy paper and a #2 pencil for my multiple white light filter
observations. Blending done with my finger.

Erika Rix
Zanesville, Ohio USA

Sunny Hawaii

 Sunny Hawaii

A unique sunspot grouping, AR963, emerged this week and has been dubbed by some “the
Hawaiian Islands”. The large ‘island’ is about the size of Neptune and all the little ones are each about the size of Earth. Atmospheric conditions prevented anything but brief glimpses at the Sun through heavy clouds and gusty winds.

This grouping is definitely one to keep an eye on!

The Sun with AR963
100mm acromat refractor at 48x (25mm Plossl + 2x Barlow).
Graphite pencil on white paper, blending stumps.

Andrew English

Splash in the water

Prom sequence 

This erupting prominence sequence reminded me of a rock plopping in the water. It
was brilliant to watch. This observing session nearly made me late for my brother’s
wedding, but I just couldn’t tear my eyes away from the view to to give myself ample
time to look presentable for the special occasion. As a last minute idea to add to
their wedding present, I framed the first sketch of this sequence with the date for
them….starting their new lives together with a bang, so to speak. Number 963 for
the sun, day one for my brother and his new wife. Sketches done with black
Strathmore paper and white Conte’ crayon.

Erika Rix
Zanesville, Ohio

This is a link to an animated sequence of the same session that Erika produced herself!

One prom times twelve

prom sequence
The flare activity this morning (June 9th, 2007) had pretty much subsided by the time my session took place.  Yes, I was disappointed, but AR0960 was still showy
with AR0959 accessorizing it nicely.  There was a thin little plage
marking 959 as well as plage just East of the center of the disk, and
plage also very thinly following the path of a long slender filament just
inside the Eastern limb.  Add the remarkable plage details in AR0960 to
that, and you have a straight line of interrupted plage going from East to
West.

The two spots within 960 were easy to spot as black dots.  There was a
third dot just North of them that I first thought was another spot to that
region. But I’m pretty sure it was a little piece of filament having
compared my sketches to other images afterward.

When tuning, I could easily pick out several other filaments across the
disk even though they were very slender and short, almost like little
crooked crosshairs of an eyepiece.  There were five definite prominences
with a few little hints of others on the limb.  The huge prominence that
was evident on the NW limb earlier this morning was no longer there that I
could see.  However, the “pick of my pleasure” prominence was the presence
of an “m” shaped faint one on the NE limb.  And this, my friends, became
the start of a three and a half hour project for me today.  It made no
matter that I had lots of chores to do.  Astronomy comes first…at least
today.

The series for this one prom was rendered in two sessions.  An hour with 1
minute intervals, an hour and a half break so that I could at least get
the riding mower part of the grass cutting done, and then another hour
session with 10 minute intervals again.  I would have loved to spend the
entire day doing this, but I was starting to get sunburn on my farmer’s
tan legs and feet that today sported sandals instead of sneakers.
Nevertheless, perhaps 12 sketches of the same prominence were enough to
show how dynamic the Sun is over such a short period of time.  Or could I
have really stopped because I didn’t want to be known as the eccentric
prom lady that latched on to only one prom, sketching it over and over
again with a strange fixation…you can chose, if you like.

Sketches were done with black Strathmore paper and colored Conte’ crayons
for the full disk, white Conte’ for the prominence sequence.

Erika Rix
Zanesville, Ohio

This is a delightful video version of full disk and the prom sequence sketches that Erika created: http://www.photoshow.com/watch/gA4ky6wN   check it out!
 

Four days in the life of a sunspot

sunspot 0953 

Here is a small sequence of observations of sunspot 0953 made during 4 days. 0953
turned out to be one of the bigger sunspots of recent time.

Time : see sketches
Scope : ETX 105/1470
Vixen LV Zoom eyepiece at 8mm
Power : 183
Filter : Baader AstroSolar filter.
Seeing : 2/5

Sketch Orientation : N up, W right.
Digital sketch made with a digital tablet and PhotoPaint, based on a raw pencil sketch.
 
Rony De Laet

http://www.geocities.com/rodelaet, my personal website.