Thursday, October 27, 2011

Sunspot 1319 Movie

Just Missed An Energy Flare

This is one of the movies I promised in my last post. The movie begins with some bright white energetic eruptions already in progress. The eruptions fade away while gases swirl. Too bad I didn't start recording about 20 minutes sooner! Then I could have captured both the rise and fall of the eruption. One of these days I'll get lucky and timing will be better. 

Here is a still image of sunspot 1319 showing its complicated structure and some areas of bright emission.

Sunspot 1319 in center. Sunspot neighbors above and below. (Click for full detail.)
The movie below shows 33 minutes of activity in sunspot 1319 from 11:22 AM to 11:55 AM EDT on October 16, 2011. It takes a while for the movie to load and play at normal speed, so please be patient. 

Even though I took meticulous care in the manual alignment of each frame in this movie, there is still a bit of jiggle in the final result. Apparently it takes only a few slightly misaligned frames to cause the annoying effect.

Watch this movie for a few minutes. You'll notice the hot, white, energetic interior underneath the cooler, darker, continuously churning gas plumes above. It looks like the hot white stuff wants to break out from the Sun. It ominously tests its bonds by brightening in several locations, including a winding network in the lower left.

I wish I had recorded the action for more than 33 minutes. What happened next? In my next post I'll have a 64-minute movie including this sunspot along with some others nearby. Maybe this 64-minute movie will capture more action!

Wednesday, October 19, 2011

Splendid Sun!

October 16, 2011

Solar imaging improves! Cloudless sky and pleasantly cool temperature made observing comfortable on October 16th. Absolute perfection is hard to achieve, however. It was a bit breezy, sometimes enough to shake the telescope. Nevertheless, I was able to get my best whole disk solar image so far. The following image is a mosaic of seven individual images, each made at the prime focus of my Lunt 100mm h-alpha telescope with a DMK41 camera. The Sun's disk contained a good number of sunspots, dark filaments, and even a few bright white eruptions! Too bad there weren't a few more dramatic prominences. Still, this is the kind of image I hoped to achieve when I bought my solar scope.
(Click for full detail.)
After capturing images at prime focus I used a 2X Barlow lens to magnify some of the sunspots. Here is an image of sunspot 1312, the one at the bottom of the whole disk image near the prominence.
Sunspot 1312 and prominence (Click for full detail.)
Finally, here is an image of the two sunspots slightly below and to the left of the disk center.
Sunspot 1314 bottom left, sunspot 1319 top center (Click for full detail.)
Sunspot 1319 at top center had a beautiful complicated structure seething with bright white energetic eruptions. I recorded 34 minutes of activity in sunspot 1319 and hope to make a good movie for my next post a few days from now.

I also recorded 60 minutes of activity at prime focus showing activity in more than one sunspot. That movie will take much longer to construct and will not appear for a while.

In this productive observing session I recorded 112 videos, each about 27 seconds long. (This amounts to 51 GB of data! Thank goodness for big hard drives!) Each video contains 400 still frames. The 400 somewhat blurry still frames in each video get combined by magical Registax6 software to produce one single detailed still image. Then I enhance and colorize these 112 detailed still images to make movies, mosaics, or individual images. I'm really enjoying this!

Tuesday, October 11, 2011

October 5th Sun Movie

Beautiful Clear Sky!

A spectacular giant erupting sunspot moved across the Sun's disk in late September. Uncooperative completely cloudy weather here in Virginia prevented observation of the fireworks. A stretch of excellent weather arrived soon after with mild temperature, low humidity, and not one cloud in the sky. Several sunspots were present on October 5. Here is sunspot 1309:
Sunspot 1309 with sunspot 1312 in upper left. (Click for full detail.)
Changing the view slightly shows sunspot 1312 on the left and 1309 on the right with spicules along the Sun's rim:
Sunspots 1312 and 1309 (Click for full detail.)
Here's another pair of sunspots on the opposite side of the Sun:
Small sunspot 1306 on left, larger spot 1305 on right. (Click for full detail.)
I spent most of the observing session trying to record a small eruption near sunspot 1313. Here's an image of emerging sunspot 1313:
Sunspot 1313 is in the upper left. (Click for full detail.)
One 400-frame video was recorded every minute for one hour. Each video eventually produced one still frame. Hours of tedious manual alignment of these 61 still frames produced the following movie showing one hour in the life of sunspot 1313 from 11:39 AM to 12:39 PM EDT. This will take some time to load before it plays at normal speed. Please be patient!
Look at the spray of gas erupting in the upper left! Some movement is also visible along the snake-like filament on the right. Sadly, the movie continually jiggles because, even after hours of manual alignment, I could not get the individual frames perfectly aligned. Almost every feature on the Sun is continually moving, so it's hard to find fixed reference points to align. Although the dark sunspot umbra here stays fairly constant, it is small and not very distinct. The solar rim should also be a fixed feature. Unfortunately, the exact position of the rim seems to depend on the exposure settings of the camera which changed automatically as the image drifted due to imperfect tracking. In the future I need to improve image alignment.

Sunday, October 2, 2011

Eclipsing Stars

Observing an eclipse of RW Geminorum

This is the final example of my not widely shared observations made at Winfree Observatory at Randolph Macon Woman's College (now called Randolph College).

A total solar eclipse, when our Moon passes in front of the Sun, is a spectacular and somewhat rare event! People travel all over the globe to watch. So far I've been fortunate to see only one total solar eclipse in my life, on July 10, 1972 on Prince Edward Island, Canada.
With C at the 1972 eclipse site on Prince Edward Island
A total solar eclipse looks roughly like the image below when viewed with ordinary binoculars during totality. Notice the pink flame-like prominences which become visible on the Sun's rim!
A view similar to what I saw from Prince Edward Island with unfiltered binoculars
As wonderful as a solar eclipse is, it must be tame compared to one star eclipsing another! Wouldn't it be amazing to watch one star pass in front of another? Actually, this happens frequently in the heavens when two stars orbit each other. These are called binary stars. If a distant planet happened to orbit a binary star, it might experience double sunsets like Luke Skywalker observed from the planet Tatooine in this memorable scene from the first Star Wars film:

There are a great number of binary stars with orbital planes oriented edge-on to our line of sight. As these stars orbit they regularly pass in front of one another and produce eclipses from our point of view. One such eclipsing binary star is called RW Geminorum (meaning the variable star system RW in the constellation Gemini). The red X locates the position of RW Geminorum in the constellation Gemini below:
(click to enlarge)
What if, from our point of view, two orbiting stars completely overlap during the orbit? The light from the system should then vary like this:
A more detailed, but somewhat different, illustration is:
Notice how the brightness curve of the binary system is flat and horizontal during the deeper primary (1st minimum) and shallower secondary (2nd minimum) eclipses. These flat and horizontal portions of the light curve happen when a smaller star fits completely in front of or behind a larger star. This is the situation for the two stars, A and B, in RW Geminorum. Brighter star A has a mass of 4.97 Solar Masses, a radius of 3.69 Solar Radii, a surface temperature of 12,390K, and a bolometric luminosity of 285.25 Solar Luminosities. Dimmer star B has a mass of 2.24 Solar Masses, a radius of 4.67 Solar Radii, a surface temperature of 6,200K, and a bolometric luminosity of 28.47 Solar Luminosities. (Bolometric means including all wavelengths of light.) During the primary eclipse of RW Geminorum the smaller diameter, brighter star A is entirely behind the larger diameter, dimmer star B. This primary eclipse totality time lasts for more than an hour.

During the fall of 2003 senior physics major, Sarah Priester (class of 2004), and I decided to observe the primary eclipse of RW Geminorum. Since the complete orbital period of RW Geminorum is 2.8654972 days, we decided there would not be enough observing time in the fall semester to capture the light curve for the entire orbit. Therefore, we set out to observe only the primary eclipse. This required about 15 hours of observing.

During October and November of 2003 we observed RW Geminorum on 3 different nights. We made 189 V-filter CCD images, one every 5 minutes during each session. The exposure times varied between 60 seconds, and 240 seconds. After many hours carefully measuring and analyzing all 189 images we obtained the light curve shown below which clearly shows the primary eclipse.
This is one of the most beautiful light curves I ever achieved at Winfree Observatory!
The vertical scale is an astronomer's (logarithmic) scale of brightness measured through a photometric green filter (also known as a visual, or V, filter). The smaller the magnitude, the brighter the star. The horizontal scale, orbital phase, is a portion of the time for a complete orbit. The time for a complete orbit is 2.8654972 days. This is 1.00 cycle. The horizontal scale runs from 0.400 (40 percent) of the orbital cycle to 0.650 (65 percent) of the orbital cycle with the center of the primary eclipse located halfway through at 0.500 (50 percent) of the orbital cycle.

The duration of the flat total eclipse portion is one hour, 22 minutes with an uncertainty of about 5 minutes. The two unfortunate gaps in the otherwise beautiful curve are caused by the annoying inability of our German equatorial telescope mount to continuously follow celestial objects as they cross the meridian. At two meridian crossings no images could be taken while the telescope slewed from one side of the pier to the other.

We didn't observe the entire eclipse continuously, rather we watched like we would watch a long movie with several intermissions! There's a good chance we were the only people on Earth observing this particular eclipse at this particular time!

People say I'm crazy doing what I'm doing
Well they give me all kinds of warnings to save me from ruin
When I say that I'm o.k. well they look at me kind of strange
Surely you're not happy now you no longer play the game

People say I'm lazy dreaming my life away
Well they give me all kinds of advice designed to enlighten me
When I tell them that I'm doing fine watching shadows on the wall
Don't you miss the big time boy you're no longer on the ball

I'm just sitting here watching the wheels go round and round
I really love to watch them roll
No longer riding on the merry-go-round
I just had to let it go

John Lennon