Posts

150 Billion Pixels, 1 Billion Stars

Ok, have a look at this image — if you click on it, it gets really, really big:

That’s our Milky Way.  The image below here represents the material within the white square on the left — a star-forming region called G305 to astronomers and astrophysicists — again, a click makes it bigger:

That cutaway image above?  Only ten thousand stars.  SLACKERS!  (Of course I jest)

Scientists from the UK, Chile, and Europe have created the initial 150 billion pixel image by combining ten years’ worth of data into a monster survey of the Milky Way region.  From the University of Edinburgh website:

Astronomers have today released a picture containing more than one billion stars in our Milky Way galaxy. It combines data from two near-infrared1 telescopes – the UK Infrared Telescope (UKIRT) in Hawaii and the VISTA telescope in Chile –  and is the result of a decade-long collaboration by astronomers at the University of Edinburgh and the University of Cambridge to process, archive and publish the prodigious quantities of sky survey data generated by these two telescopes.

Dr Phil Lucas from the University of Hertfordshire leads the UKIRT study of the Milky Way, and co-leads the VISTA study. He said: “The combined data on over a billion stars represent a scientific legacy that will be exploited for decades in many different ways. They provide a three-dimensional view of the structure of our spiral galaxy, the Milky Way, while also mapping several hundred nebulae where stars are being born. The VISTA data, in particular, is breaking new ground by showing how several hundred million stars vary in brightness over time.”

The full image contains 150 billion pixels, and the detail it contains is only revealed by the three zoom levels, centred on G305, a large and complex star-formation region: the innermost zoom covers a tiny fraction of the full image, but still contains more than ten thousand stars.

Presenting the image at the UK-German National Astronomy Meeting in Manchester, Dr Nick Cross of the University of Edinburgh said: “This remarkable image is only one of the many outputs from the VISTA Data Flow System (VDFS) project2. VDFS data is being used by astronomers around the world and has led to great discoveries in many fields of astronomy, from the coolest known stars to the most distant quasars.”

Something pretty cool:  you can view the monster image with a custom viewer at the University of Edinburgh’s website.  You have to check this out, it is  amazing.

Thanks, Space, HuffPo, PhysOrg, and Science Daily

Moonlight Mini-Lesson

The above photo by Andrew Tallon was taken at 10:30 pm! What I love about this image is it perfectly exemplifies that our moon is just a reflector for sunlight.

So why don’t we see our night landscape this way, if a camera can capture it?

A number of fascinating factors!

Our moon’s albedo (the measurement of amount of light reflected by astronomical objects) is 0.12, which means about 12% of light which hits the moon is reflected. This amount is subject to fluctuation by numerous factors, including the phase of the moon. The amount which hits the earth’s surface can be–and frequently is–significantly less.

To capture the above image, the shutter was open for 30 seconds. Our eyes have our own tricks for seeing in low-light scenarios, which involve our fantastic friends the rods and cones. The outer segment of rods contain the photosensitive chemical rhodopsin (you might know this as visual purple). Cones contain color pigments in their outer segment. Our rods predominantly help us in low light level environments, which means that we have significantly decreased color perception in moonlight.

Cones are located in the center of the eye and are high-density. Rods meanwhile are located around the cones, so in extreme darkness, a 1° blind spot is developed in the central region of the eye where there are only cones. Rods reach their maximum concentration around 17° each direction from the center line, so sneaking some sideways glances actually improves your nighttime perception.

Our rods are not equally sensitive to all wavelengths of light. They are far more sensitive to blue light, and at around 640 nm, are pretty much useless! Click this graph from the University of New Mexico to check it out:

This means that the color of light the moon is actually reflecting appears significantly different to us because of its low intensity.

A neat example I found on the American Optometric Association’s Website which caught my interest was:

For example, in a darkened room, if one looks at two dim lights of equal illumination (one red and one green) that are positioned closely together, the red light will look brighter than the green light when the eyes are fixating centrally. If one looks to the side of the dim lights about 15-20 degrees, the green light will appear brighter than the red.

If you’re planning on shooting your own moonlight landscapes, be a light geek! It is hard to find focus at night, so place a luminous object near your focus, whether it’s a lantern, or a friend with their cell phone! If you want to be super geeky, tape a laser pointer to the top of your camera, then manually focus on the dot.

 

So, with all of this science in mind, how would you replicate moonlight now, vs how you did previously?

My God, It’s Full of Stars! What You See When Your Eyes are Closed – Phosphenes

As much as I love light, I love to close my eyes and stare at the back of my eyelids.  Have you ever noticed how amazing, how beautiful the events that occur are when you rub your eyes and notice the instant star and explosion show that occurs in your vision?  I always imagine it as I’m looking into the birth of a universe – each time I stare at my eyelids I see little exploding stars that each take about 2-3 seconds to fully ignite, explode, and become part of the other stars waiting for me to focus my gaze on them.  Try it, it’s a lot of fun!  It is for me, at least.  Perhaps I’m nutso.  Still, AWESOME!

These little events are called entopic phenomena, meaning that they come directly from the eye itself.  I’m pretty sure everyone’s experienced the most common form of entopic phenomena, eye floaters.  Right?

 

Eye floaters, whether or not they have a sarcastic retort like the ones in Family Guy, are entopic phenomena.

The light that you see when you don’t see any light – whether it’s the random star birth and death that I see when I close my eyes, or if I rub my eyes, or any of a few things that trigger it for me – are called phosphenes.  That word is from two greek words, phos (light) and phainein (to show), and goes to explain most of the “hey there is light in my vision but there’s no source” mysteries.  The phrase “seeing stars,” like from getting whacked in the head or from being dizzy is phosphenic.  When people are deprived of light for long periods of time, phosphenes occur in the person’s vision as well – this is referred to as “the prisoner’s cinema.”  Isn’t that just creepy and horrible?  Apparently phosphenes can occur through several methods, from strong magnetic fiends, to just rubbing your eyes, to reports of astronauts seeing them when exposed to radiation in space.

Here’s a good account of the Prisoner’s Cinema, which also happens apparently to truck drivers, pilots, and other folk who have to concentrate on something for very long periods of time:

It has been widely reported that prisoners confined to dark cells often see brilliant light displays, which is sometimes called the “prisoner’s cinema.” Truck drivers also see such displays after staring at snow-covered roads for long periods, and pilots may experience phosphenes, especially when they are flying alone at high altitudes with a cloudless sky. In fact, whenever there is a lack of external stimuli, these displays can appear. They can also be made at will by simply pressing your fingertips against closed eyelids. In addition, they can also be produced by an electrical shock. In fact, reportedly, it was high fashion in the eighteenth century to have a phosphene party. It is noted that Benjamin Franklin once took part in such an encounter where a circle of people holding hands would be shocked by a high-voltage electrostatic generator, so that phosphenes were created each time the circuit was completed or broken.

The earliest account of phosphenes is given by the Bohemian physiologist Johannes Purkinje in 1819. These subjective images are called phosphenes (from the Greek phos, light, and phainein, to show). Oster (1970) suggests that, because phosphenes originate within the eye and the brain, they are a perceptual phenomenon common to all mankind. The visual areas of the brain at the back of the head (occipital lobe) can also be stimulated to produce phosphenes.

I find these very fascinating, these entropic events.  Do you have them?  How would you describe them?  Please, leave a message in the comments, I am very interested in your phosphene experiences!

Check out this beautiful video representation of phosphene events portrayed artistically.  So pretty!

Thanks to Wikipedia, and again, and Multiple Sclerosis Info, WiseGeek, MadSci, and MotiFake!   

Hubble Images – The Heavens are Stunning

When I was a kid, I used to love to stare up at the sky at night, trying to focus my eyes on the light that I discovered around age 8 was reaching Earth from thousands of years ago.  I knew all of the constellations, and I was always thrilled when I found a multi-colored star, or found a shooting star.  In 1999, I discovered the Leonids (although I was in college at the time, not a kid) while sitting in the middle of some corn field in rural IL with a telescope and a bottle of Wild Turkey.  Oh, college…

I ran into a Hubble telescope gallery last night.  I looked at it for nearly an hour.  There are hundreds of images there, video, detailed explanations, and other stuff to get lost in.

But of course I mean “in which to get lost.”

All images are courtesy of The Hubble Site.  I hope you like them, these are some of my favorites.

hb1

Planetary Nebula NGC 2818

hb4

hb5

hb6

hb3

hb7

hb8