Astrophotography Blogs

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The Eye of God Nebula and the Age of Aquarius

As the sun appears to move through the ecliptic, it moves into the region of the constellation Aquarius in mid-January.  According to astrologers, those of you born between January 20 and February 18 are said to be kind, friendly and generous.  Aquarians are true humanitarians and care about the welfare of all people.  As all of us baby-boomers know, the Age of Aquarius is supposed to usher in an era of “harmony and understanding; sympathy and trust” Age of Aquarius/Let the Sunshine In.

The symbol for Aquarius is water, and the constellation represents the water-bearer.  In Greek mythology, Aquarius is identified with the beautiful Ganymede, the son of King Tros of Troy.  Zeus takes him to Mount Olympus to serve as the cupbearer to the gods.

Located within the constellation Aquarius, the Helix or Eye of God Nebula is one of the most well-known and beautiful deep-sky objects.  About 10,600 years ago, a dying star expanded rapidly to become a red giant.  When it collapsed, the outer layers of that star were ejected as a ball of gas and dust.  The star became a white dwarf.  The intense radiation from that star heated the ejected gases and caused them to glow.  The red color that forms the outer ring of the nebula is caused by ionized hydrogen gas, while the inner eye of the nebula glows green due to ionized oxygen gas.  This type of nebula is known as a planetary nebula because the generally have a shape similar to giant gas planets.  By the way, our Sun is expected to become a red giant in about 5 billion years.

The Eye of God Nebula was discovered sometime before 1824 by German astronomer Karl Ludwig Harding.  The Gaia space telescope, launched by the European Space Agency in 2013, determined that the Eye of God Nebula is 655 light years from Earth.  This makes it one of the closest planetary nebulae discovered.

Formally known as NGC 7293, this nebula has several different common names.  Wider images of the nebula show fainter outer bands, which has given rise to the name, Helix Nebula.  With its bright red ring and central green core, it is often referred to as the Eye of God Nebula or the Eye of Sauron Nebula, a reference to The Lord of the Rings trilogy written by J. R. R. Tolkien.

Next post:  The Pinwheel Galaxy in Pisces

Take care and be safe!

Alan

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The Zodiac Collection

At an art festival last fall, a customer was reading the information on the back of an image of the Trifid Nebula.  She came across the fact that the nebula is located in the constellation Sagittarius and exclaimed, “That’s my sign”!  From that remark was born the Zodiac Collection of images.  This collection consists of a single galaxy or nebula for each of the constellations of the zodiac.  For example, since the Trifid Nebula is located in the constellation Sagittarius, it became the deep-sky object for that zodiac sign.  In other words, the Trifid Nebula is the deep-sky object for everyone born between November 22 and December 21.  Since that time, the images of the Zodiac Collection have become my best-selling items.  Especially popular are the 5 x 7 matted images and the art magnets.  People are both for themselves and as unique birthday gifts for friends and relatives.

I thought I might take your mind off the Coronavirus for a few moments by bringing you posts on each of the images in the Zodiac Collection.  Before we get into that, I’m going to spend the rest of today’s post talking about the Zodiac itself.

It was the ancient Babylonians, in about 400 BC, who first marked the path of the Sun throughout the course of a year (the ecliptic).  They divided the sky into 12 equal portions and assigned a constellation to each portion.  These same constellations are the ones we use today.

Here are the zodiac constellations and the modern dates, along with the deep-sky objects that I’ve assigned to each one.  Each deep-sky object is in or near the constellation to which it is assigned.

CONSTELLATION             DATES                               DEEP-SKY OBJECT

Aquarius                           Jan 20 – Feb 18                Eye of God Nebula

Pisces                                Feb 19 – Mar 20              Pinwheel Galaxy

Aries                                  Mar 21 – Apr 19              Pleiades

Taurus                               Apr 20 – May 20              Crab Nebula

Gemini                              May 21 – Jun 20              Jellyfish Nebula

Cancer                               Jun 21 – Jul 22                 Medusa Nebula

Leo                                     Jul 23 – Aug 22                Leo Trio Galaxies

Virgo                                  Aug 23 – Sep 22               Sombrero Galaxy

Libra                                  Sep 23 – Oct 22               Southern Pinwheel Galaxy

Scorpio                              Oct 23 – Nov 21               (Not available yet)

Sagittarius                        Nov 22 – Dec 21              Trifid Nebula

Capricorn                         Dec 22 – Jan 19                (Not available yet)

By the way, birthdays in the US aren’t evenly spread throughout the year.  The most common signs are Cancer, Leo and Virgo.

Head to https://hiddenskies.com/astrophotography-gallery/ to see (and purchase!) images of each of deep-sky objects listed here.

Next Post:  The deep-sky object of Aquarius – The Eye of God Nebula.

Stay safe!

Alan

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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!

©2019 Hidden Skies

https://hiddenskies.com

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Why is the Dumbbell Nebula so spectacularly colorful?

Have you ever wondered about the amazing colors in pictures of nebulae?  The reds and greens in the Dumbbell nebula are amazing!   The best part is these are the real colors I see in the telescope – they aren’t photoshopped.  Today, I’m going to explore why nebulae have such fantastic colors.  There are several types of nebulae, but this blog is only about emission and planetary nebulae.  Those are the nebulae that are spectacular shades of red and green.

First, you need to know what nebulae are.  They’re clouds of gas and dust floating in the space between stars – the interstellar space.  The gas and dust is called interstellar medium (ISM).  Some nebulae form because gravity causes the gases and dust in the ISM to clump together.  Others form by supernova explosions. The dust and gas thrown out by the explosion become the clouds we can see.  Still other nebulae are formed from the material given off by red dwarf stars.  Most of the gas in nebula is hydrogen, but there are small amounts of other gases, including oxygen, nitrogen, helium and sulfur.

So, we have these clouds of gases and dust, but why can we see them?  After all, our atmosphere has a lot of oxygen, nitrogen and hydrogen, but we don’t see bright clouds of red and green in our sky.  It turns out that when these gases are energized, they absorb the energy and turn into a form of the gases called ions.  These ionized gases give off the energy they’ve absorbed in the form of light.  Hydrogen gives off a red light, and oxygen emits a greenish-blue light.  Those two gases account for most of the color we see in nebulae.

Now, we’re going to get a bit technical. When you look at a rainbow, you see all the colors of the spectrum; from red through orange, yellow, green, all the way to blue.  Light can be described as a wave, and each color of light has a specific wavelength.  The wavelengths of light are measured in nanometers (nm).  Red light is about 400 nm, and blue light is on the other end of the spectrum at around 800 nm. But there are other colors we can’t see.  For example, infrared light has a wavelength that’s too small for the human eye to see, and ultraviolet has a wavelength that’s too long for us to see.  It turns out that both ionized hydrogen and oxygen give off light that the human eye can see.  Hydrogen gives off light at both 486 nm and 656 nm and oxygen gives off light at 501 nm.  Those are the colors of light you can see in my nebula images.

But I have a problem in making these wonderful images.  I live in Sierra Vista, AZ.  It’s a small town, so the light pollution isn’t too bad, but it’s nowhere near as dark as out on a mountaintop or in the middle of the desert.  Also, on nights when there is a lot of moonlight, the sky can be so bright that you can’t see many stars at all.  So how is it that I get images of these colorful nebulae when there’s all this light in the sky?  I use a filter from Optolong, called the L-eNhance filter.  This filter only lets light around 500 nm and about 660 nm through, while it blocks all the other light.  That means that the red and green light from the nebula gets through to the camera, while the light from the Moon and nearby streetlamps is blocked!

The Dumbbell Nebula is a tight cloud with lots of oxygen and hydrogen gas.  That’s why it’s such a spectacular display in green and red. 

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

©2019 Hidden Skies
https://hiddenskies.com

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Andromeda Galaxy – 7 fun facts you need to know

The Andromeda Galaxy with two satellite galaxies, M 32 and M 110. Taken July 5, 2019.
Andromeda Galaxy

This image of the Andromeda Galaxy and two satellite galaxies, M 32 and M 110, was taken in my backyard observatory on July 5, 2019.

1. The Andromeda Galaxy is named after a heroine in Greek mythology. In the Greek myth, Perseus first spied Andromeda on his way back home from killing Medusa. The sea-god Poseidon had chained the beautiful maiden to rocks overlooking the sea.  Her mother had foolishly boasted that Andromeda was more beautiful than even the Nereids.  This boast so enraged Poseidon that he chained Andromeda there to be devoured by a sea monster.  Perseus slew the sea monster, rescued Andromeda and married her.  According to the myth, they had nine children – seven sons and two daughters.  After Andromeda’s death, the goddess Athena honored her by putting her in the sky as a constellation. She resides forever near her mother Cassiopeia, and her beloved husband Perseus.  The galaxy earned its name because of its location near one of the legs of the constellation.

2. Andromeda is becoming a much more popular girl’s name. Until recently, Andromeda was not a popular girl’s name.  With the advent of the Harry Potter series, we’re seeing many more Andromeda’s being born.  For you fans, Andromeda Tonks was Nyphadora’s mother. Andromeda met Harry in the final book of the series, The Deathly Hallows.  She was the cousin of both Sirius Black and Bellatrix Lestrange. Her family disowned her for the sin of marrying a muggle, Ted Tonks.

3. Andromeda is a popular name in syfy literature.  In 1969, Michael Chrichton wrote The Andromeda Strain, a novel about an extraterrestrial microorganism that contaminated a military satellite.  When the satellite crashed to Earth in Piedmont, AZ, the microorganism killed almost everyone in the town.  Scientists had to race to kill the microorganism, codenamed “Andromeda”, before it destroyed all life on earth.  The novel was made into a blockbuster movie in 1971 and a television miniseries in 2008.

Andromeda Ascendant was the name of the ship captained by Dylan Hunt in the 2000-2005 television series.  In this series, the mission of the captain and crew was to restore the Commonwealth that had been destroyed 300 years before.

4. Early astronomers thought the Andromeda Galaxy was just a nuisance. Charles Messier was one of the most famous early astronomers.  He used a 4” telescope from his hotel room in downtown Paris to search the skies for comets. While conducting his search, he made a list of things he saw that weren’t comets. In 1764, Charles Messier listed the Andromeda Galaxy as object 31 in his catalog of things that were not comets. That list of nuisance objects became the first great catalog of deep-sky objects!

5. The Andromeda Galaxy is going to collide with the Milky Way. The Andromeda Galaxy is not the closest galaxy to us, but it is the closest large galaxy. It’s large and bright enough that it can be seen as a smudge in the sky on very dark nights even without a telescope.  It’s moving ever closer to us on a collision course with our own Milky Way! 

6. The Andromeda Galaxy might not exist anymore. The Andromeda Galaxy was born about three billion years ago when two smaller galaxies crashed and merged. The galaxy is 2.5 million light years from us, making this image a snapshot of a time two and a half million years in the past.  It’s strange to think that if the Andromeda Galaxy exploded, we wouldn’t know anything about it for millions of years. 

7. The Andromeda Galaxy has its own swarm of satellite galaxies. If you look closely at the image, you can see a small galaxy, designated M 110, slightly above and to the right of the central bulge of Andromeda.  There’s a somewhat larger satellite galaxy, M 32, below and to the left of the bulge.  These two satellite galaxies are among the more than 30 small galaxies which cluster around Andromeda.

Until the next blog, take a little time to ponder all the hidden wonders around us.

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