Tag: nebula

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Bode’s Nebula – a rose by any other name

In Shakespeare’s Romeo and Juliet, Juliet affirms that she would love Romeo just as much if he had a different name; “That which we call a rose by any other name would smell as sweet”.  Surely this applies to Bode’s Nebula, a wonderful example of a spiral galaxy.

I had the rare treat of going to the library the other day and looking in a dictionary.  I was looking for the etymology of the word “nebula”.  The Oxford English Dictionary says the word is from Latin, meaning mist or vapor.  Universe Today has a great article on Bode’s Nebula, where its discovery is discussed.  In 1774, the German astronomer Johann Elert Bode described “two small nebulous patches” near Ursa Major.  The French astronomer Charles Messier added these objects to his catalog as M 81 and M 82.  The larger of these two objects, M 81, became known as Bode’s Nebula.

Over the next hundred years, advances in telescopes allowed thousands of deep sky objects to be discovered.   These were cataloged in 1888 by the Danish astronomer Johan Ludvig Emil Dreyer. Still, most of these objects appeared as nebulous patches, and were therefore categorized as nebula.  About this time, William Huggins, an English astronomer, determined that some nebulae were characterized by large amounts of gases, principally hydrogen, while other nebula were mostly large groups of stars.  The objects in this latter group were called galaxies, after our own Milky Way.  By the way, according to the Barnhart Dictionary of Etymology, the word galaxy has its root in ancient Latin and Greek and means milky.  Chaucer, in his 1380 House of Fame, records that “galaxy” referred to the milky white band seen in the night sky.  This became known as the Milky Way.  It wasn’t until the mid-1800’s that it was discovered that the Milky Way was composed of billions of stars, and that ours wasn’t the only galaxy.  Thus, the term “galaxy” changed from meaning the milky white object in the sky to a large organized group of stars.

We now know that Bode’s Nebula is in fact a spiral galaxy about 12 million light years distant.  As the largest galaxy in the M 81 Galaxy Group, it contains over 250 billion stars and a supermassive black hole.  Today, the deep sky object M 81 is often still referred to as Bode’s Nebula to honor Johann Bode and his “nebulous patches”. Whether you call it M 81, Bode’s Galaxy or Bode’s Nebula, it’s a beautiful wonder of the night sky, shining down on us from the Great Bear, Ursa Major.

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This Pac-Man is ready for Halloween

In 1883, American astronomer E. E. Barnard discovered a large faint nebula in the constellation Cassiopeia.  While it’s officially designated NGC 281, it’s most commonly known as the Pacman Nebula.  While the nebula normally appears in shades of red, a mistaken setting during processing yielded this eerie green version, which seems perfect for Halloween.

While the video game Pac-Man is almost 40 years old, the nebula is several million years old.  The nebula is 9200 light years from Earth, so the light used to make this image is 9200 years old!  The Pacman Nebula is so large that it takes light 48 years to travel from one side to the other.

The red glow (green in this image) is caused by ionized hydrogen gas.  The stars within the nebula energize the gas, which causes it to glow.  The small dark “eye” in the middle of the nebula is a Bok globule.  Bok globules are small areas of dust and gas.  They are very dense, often having a mass of up to 50 suns.  The dust and gasses are collapsing under the force of gravity and may eventually form new stars.  The “mouth” is caused by relatively cool, dark gas and dust obscuring the glowing gasses behind it.

The Pacman Nebula is located near the brightest star in the constellation Cassiopeia. The constellation itself looks like a W high in the northern sky near Polaris.  It is part of the Perseus Family of constellations, which includes the constellations Cepheus, Andromeda and Perseus.  In Greek mythology, Cassiopeia is the wife of Cepheus and the mother of Andromeda.  Perseus is the hero who saved Andromeda and later married her.

Pac-Man is the most successful video game in history.  Introduced in 1980, it’s been estimated that more than 10 billion quarters were fed into arcade games over the next 20 years in pursuit of higher scores.  The Pac-Man character became so famous it’s been featured in several movies, including Pixels (2015) and Guardians of the Galaxy 2 (2017).

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Capturing the miracle of the Western Veil Nebula

The Western Veil Nebula is aptly named. It’s a wondrous lace of magenta and green spread among the stars of the constellation Cygnus. It’s a large emission nebula about 2600 light years from Earth.  The nebula was formed by the explosion of a star between 5000 and 8000 years ago.  The Western Veil Nebula is what remains from that supernova.  As I described in a previous blog, the magenta color is due to ionized hydrogen gas, while the bright green light is given off by ionized oxygen.

In the rest of this blog, I’ll walk you through how I captured this image.  While the night skies in southeast Arizona are usually extraordinarily clear, summer is monsoon season, and on most nights the night sky is too cloudy for astrophotography.  But in early July I caught a break and had a cloudless night sky. 

My observatory is equipped with an 8” Schmidt-Cassegrain Advanced VX 8 from Celestron.  Because the Western Veil Nebula is so large, I was able to use the Hyperstar 8 lens system, developed and produced by Starizona.  The Hyperstar makes the telescope much faster, so I can get an image of the nebula within a minute.  I captured 40 one-minute exposures with a ZWO ASI 294 MC Pro ccd camera, and combined them to make the final image. Because the Moon was out that night, it was too bright to take pictures without a special filter.  I used the Optolong eNhance filter which blocks moonlight, and only lets red and green light through. 

Have you ever just sat out at night and watched as the stars wheel across the sky?  Nebulae move across the sky in the same way.  To get a sharp image, the telescope must move with the nebula.  The telescope I use has a German equitorial mount that allows it to track deep-space objects. First, however, there’s an involved alignment process.  After aligning and focusing the telescope, I start capturing images using the SharpCap software program. 

At this point, I have 40 images of the nebula, each about 24 Mb – that’s almost a gigabyte of data!  If you look at these images, they’re in shades of gray.  I use a second program, PixInsight, to process the images and extract the color information.  The software combines these 40 images into a single full-color image.  At this point, the image is just about done.  All that remains is to adjust the brightness, crop the image and set the file type.  I use Photoshop and Lightroom for these final steps and either publish it to the web or print it.

While it only took 40 minutes to get the data, it took hours of preparation and processing to turn that data into amazing wisps of magenta and green floating across a starry sky.  When that image appeared, I realized I was looking at the remnants of a supernova explosion that happened more than 5000 years ago.  I was seeing the universe in all its wonder and beauty!

Alan Biel – Thanks for joining me as I ponder the hidden wonders of the deep-sky.  Until next time!

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