Posts Tagged ‘NASA’

Aurora Australis – Earth’s Green Ribbon

June 9th, 2010 No comments

Hi everyone

Last week I uploaded some amazing images NASA took of the sun using their STEREO Ahead spacecraft. (See “Shooting Star” – Stereo Photography? blog posting).

Those “solar storms” are incredibly powerful, and yet the distance between the earth and sun (approximately 93,000,000 miles) is just right for life on earth. In fact, the solar storms have a really cool “side affect” that is truly spectacular. Once the stream of electrons and other charged particles reach earth they interact with gases in the atmosphere to generate colorful aurora.

When the charged particles from May’s solar storms reached Earth, they caused no damage, but they did generate sheets of colored light dancing across polar skies. This shot was taken by astronauts onboard the International Space Station.

Aurora Australis

Credit: ISS Expedition 23 Crew, ISAL, NASA
Taken on May 29, looking southward from about 350 km’s above the southern Indian Ocean
(The photograph was taken with a Nikon D3 digital camera).

Aurora Australis

It is hard to imagine the feeling of the astronauts as they watched this enormous, green ribbon shimmering below them. What a truly amazing moment to capture on camera!

As you may know, these “light shows” of ever-shifting colored bands are most visible near the North (aurora borealis or northern lights) and South (aurora australis or southern lights) Poles. Apparently though, severe storms impacting the Earth’s magnetic field can shift them towards the equator.

So how is the spectacular colour of an aurora produced?

The short answer:
Auroras happen when energy charged particles streaming from the Sun interact with Earth’s magnetic field.

The longer answer:
Auroras happen when energy charged particles (ions) from the sun (known as the solar wind) collide with atoms of oxygen and nitrogen in the upper atmosphere. The atoms are excited by these collisions, and they typically emit light as they return to their original energy level. The light creates the aurora that we see.

The most commonly observed color of aurora is green, caused by light emitted by excited oxygen atoms at wavelengths centered at 0.558 micrometers, or millionths of a meter. (Incidentally, visible light is reflected from healthy (green) plant leaves at approximately the same wavelength.) Red aurora are generated by light emitted at a longer wavelength (0.630 micrometers), and other colors such as blue and purple are also sometimes observed.

So there you have it. … As you might have guessed already, I find this stuff fascinating! I hope you did too. 🙂

Thankfully, light and how we see it will continue to stimulate our sight and the imagination. And of course, photography will continue to capture light in it’s various forms for our enjoyment.

Catch you next time.


Categories: Links of Interest Tags: , , ,

“Shooting Star” – Stereo Photography?

June 2nd, 2010 No comments


Did you realize that the word stereo has a photographic connection?

Likely when most of us hear the word we automatically think of that thing we play our music on. (Or perhaps the thing our neighbour’s play their music on late at night). Up until recently that was true of me. No, I don’t mean the noisy neighbour bit, I mean the connecting the word stereo with music.

Anyhow, if you look the word stereo up in the dictionary (just click on the word if you want the easy way), you will note that it can be linked to Stereoscopy (also called stereoscopic or 3-D imaging). Which as I understand it, is any technique capable of recording three-dimensional visual information or creating the illusion of depth in an image.

What I thought was kind of cool, and something else that I didn’t know until just recently, was that NASA has a spacecraft called STEREO Ahead. It’s full name, by the way, is Solar Terrestrial Relations Observations Ahead. … Hmmm … strange acronym. What do the E’s stand for I wonder? Oh wait, they are there next to the other ones .. dah … Hang on, shouldn’t it be STeReO then?

Anyway, I digress. Are you still with me? … You are. Awesome! Thought for a moment you got bored and left. Glad you stayed because here comes the neat part. Check out the images that STEREO Ahead captured . . .

NASA Images of the Sun

Stereo Sun #1

Stereo Sun #2

In the top image, a bright mass of charged particles loops from the Sun’s atmosphere. (NASA calls them a “coronal mass ejection” otherwise know as a “solar storm”). Two hours later, the looped mass had expanded and was moving away from the Sun.

What is that black bit in the middle of the photograph I hear you ask? Well, even with all the advances in technology, a photographer can still leave the lens cap on, can’t he? Hey, we are human you know. … Actually, I’m just kidding (you didn’t really believe me did you?).

The images show only the Sun’s corona, the outermost layer of the atmosphere. A dark disk covers the rest of the Sun, and a white circle represents the Sun’s surface. Cool huh! Brings new meaning to the phrase “shooting star” doesn’t it?

According to the NASA website, a large solar storm, can expel a billion tons of matter at a million miles per hour or more. The strongest solar storms have the potential to interfere with communications, power grids, and satellites. When the charged particles from this solar storm reached Earth, they caused no damage, but there was an amazing “side affect” of these solar flares.

I’ll tell you more about that in my next posting. 😉

Happy shooting.