M35 is the only Messier open cluster in Gemini. It was discovered byJean-Philippe Loys de Chéseaux in 1745 and independently discovered by John Bevis before 1750. This star cluster is large and covers an area the approximate size of thefull Moon. M35 is located 2,200 light-years from Earth. M35’s Trumpler classification as III,3,r according to all reference sources.
With an age of approximately 100 million years, M35 is an intermediate age open cluster, and contains several yellow and orange giants of spectral type late G to early K. Its hottest main sequence star is given as of spectral class B3. With a blue Doppler shift, it is approaching Earth at a rate of 5 km/sec.
The compact open cluster NGC 2158 is directly southwest of M35. NGC 2158 is also an open cluster in Gemini.
The two clusters are unrelated, as NGC 2158 is around 9,000light years further away than M35.
Observing this Cosmic Duet definitely benefits from a dark and moonless night, where M35 is easily seen, but the dimmer NGC 2158 appears as a faint smudge. Although within reach and observable through my 4” apochromat refractor, the dimmer NGC 2158 was more apparent and observable in the my 130 mm apochromat refractor and my 9.25” SCT.
This cosmic duet is not only a binocular pair, but under dark skies can be seen with the naked eye.
Both M6 and M7 are open clusters in the Scorpius. The M7 is detectable without optical aid and is located near to the tail stinger of Scorpius, the Scorpion. M7 is the southernmost object in the Messier catalog. M6, being slightly dimmer, can also be seen with the naked eye nearby. Dark country locations will enable naked eye sittings of M6 and M7. Suburban and urban observers need not apply.
The ancient Greeks knew of M7. It was first recorded by the 2nd-century Greek-Roman astronomer Ptolemy, who described it as a nebula in 130 AD.This is how M7 gained the nickname of Ptolemy’s Cluster. Some astronomy historians think that Ptolemy may have also observed M6, but he did not record that observation.
Italian astronomer Giovanni Batista Hodierna observed M7 before 1654 and recorded it containing 30 stars. In 1654, Hodierna observed and recorded the Butterfly Cluster. Hodierna published in 1654 a book that contained his catalog of non-stellar objects, but this work apparently was unknown to Charles Messier. In 1764, the Butterfly Cluster and the Ptolemy Cluster became the sixth and seventh members of Charles Messier’s famous catalog.
There is some disagreement on the Trumpler classification of M6. Trumpler has classified M6 as II,3,m, while the Sky Catalog 2000.0 gives its Trumpler type as III,2,p. Other sources have listed M6 as II,3,r.
M6 is estimated to be around 100,000 million years old. Most of the bright, visible stars in it are hot, young, blue stars belonging to the spectral class B4-B5. However, the brightest star in the cluster is an orange giant belonging to the spectral class K.
The brightest star in M7 is a yellow G8-type giant with an apparent magnitude of 5.6.
Observations of M7 reveal about 80 stars within a field of view of 1.3° across. M7’s estimated distance of 980 light-years, and approximately 25 light years across. The age of the cluster is around 200million years while the brightest member star is of 5.6 magnitude. M7 is classified as of Trumpler type I,3,m or I,3,r.
The two Messier clusters can be easily observed through 2.1×42, 7×50, and 10×50 binoculars, even under slightly light-polluted suburban skies. M6 and M7 are separated by 6º, making telescopic duet observing virtually impossible.
As a special added attraction, a dark nebula can be detected under dark skies in the M6/M7 region. The famous Pipe Nebula on the Scorpius / Ophiuchus border, lies north of M6 and M7. The Pipe Nebula is also known as Barnard 59, 65–67, and 78. The Pipe Nebula is a dark nebula of light obscuring dust and gases in the Ophiuchus and is part of the larger Dark Horse Nebula. It is a large but readily apparent pipe shaped dust lane that obscures the Milky Way star clouds behind it. Clearly visible to the naked eye in the southern United States under clear dark skies, it is best viewed with 7×50 or 10×50 binoculars. Observing dark nebulae requires the special skill that is opposite of a sky observer’s normal observing process. Instead of recognizing where stars and nebulosity is, the goal is recognizing where stars aren’t.
This latest entry is somewhat of a departure from my regular postings.
Like most of my readers, my wife and I have been stuck at home waiting out this Covid-19 pandemic. Fortunately, my many hobbies and interests have kept me busy.
This time has also allowed me to reassess my astronomy hobby, and in particular my current lineup of telescopes. My telescopes are mostly refractors ranging in apertures from 80mm to 130mm. But at the head of the collection was my Celestron NexStar 11 GPS.
My 11” served as my “Big Eye”, my deep sky telescope. With its substantial aperture (no snickering from you large aperture Dobsonian users) and GoTo capabilities, I’ve been able to hunt down and observe all the Messier objects, and a large number of faint NGC and Caldwell deep sky targets.
But I just turned 68 years old, and my youthful vigor and strength have given way to an older person’s struggle. When I turned 65, I would describe myself as “the wheels aren’t falling off, but the lug nuts need tightening.” As I turned 68, the wheels are falling off. A combination of osteoarthritis in my foot and achilles tendonitis, plus the slow diminishing of upper body strength has made it challenging for me to use some of my telescope collection. You can’t use a telescope if it has become an immoveable object sitting in the corner of your living room.
My 11” SCT had become an immoveable object. A look at my logbooks of the past two years proved to me that I had to make an adjustment. My binoculars, 80mm, 94mm, and 102mm refractors were getting the bulk of my observing time. My 130mm apo and the 11” gathered dust, each getting only four observing sessions over two years. The reason for the 130mm lack of use was diagnosed to a faulty controller cable that has been since remedied. But the 11” lack of use was due to its weight and bulkiness. With the NexStar 11” weighing in at 92 pounds, the struggle to get the telescope out to my deck has proven too much for my aging body.
Yes, I know there are wheely bars and various dollies for sale to move overweight telescopes. But they all have one drawback, the wheely bars and telescope dollies are too big for most domestic doors. A local middle school, which has two Meade 16” SCTs mounted on wheely bars had to install new doors on the rear of the school in order to get their telescopes out to the observing pad.
So that option is not available to me.
But in keeping with my fourth book and fifth book, I have found my solution. For those avid readers of my books, you will recall my fourth book is a users guide for using the Celestron Evolution series of telescopes. These telescopes are revolutionary in their use of WiFi connected control using apps on iPhone, iPad, or Android devices to control the telescopes. Genius!
My fifth book is of particular interest for those who share my particular affliction, growing old. Astronomy for Older Eyesis a survival guide for late 50’s or older backyard astronomers. One of the book’s recommendations is to downsize the telescopes being used. The rule of thumb is that the telescope that gets used more will see more.
With these two books at hand, I decided to heed my own advice. The 11” GPS needed to be replaced with a lighter, easier to set up telescope. I still needed a larger aperture “Big Eye” for deep sky observing, but something more moveable. I still wanted the GoTo function, since it saves time in searching for objects (as you know, time becomes precious as you grow older). And I own a lot of SCT accessories.
The opportunity presented itself in the form of the Celestron Evolution 9.25” SCT. GoTo. Check. Aperture. Somewhat smaller and less light gathering but still ample. Check. Lighter and easier to move. 40 pounds lighter. Definitely check!
So my beloved NexStar 11 GPS is gone. My new Evolution 9.25” is here, sans a tripod. The tripod is on order. Soon, I will be tripping the faint starlight fantastic with my new telescope.
In the meantime, I have to read my own book on how to use the Evolution 9.25”. Its been a few years since I used the Celestron Evolution 6” to write the book, so I definitely need a refresher.
M46 and M47 (Illustration courtesy of Jon Talbot. Used with permission.)
M46
Alternate: NGC 2237
Puppis
RA 7h 41.8 m
Dec -14º 49′
Magnitude 6.1
M47
Alternate: NGC 2422
Puppis
RA 7h 36.6 m
Dec -14º 30′ 00′
Magnitude 4.2
M46 and M47 open clusters in Puppis offer vastly different styles of clusters in the binocular view. M46 is about a degree east of M47 in the sky, so the two fit well in a binocular or wide-angle telescope field. This pair of clusters sets before 2:00am this time of year.
Details of M46 can be seen in a previous blog post. M46 is classified as of Trumpler type II,2,r.
M47 was discovered by Hodiernabefore 1654 and independently discovered by Charles Messier on February 19, 1771. It was later independently discovered again, under the nomenclature NGC 2422.
M47 was considered a lost Messier Object. There is actually no cluster in the position indicated by Messier. Messier located the open cluster in terms of right ascension and declination with respect to the star 2 Puppis. However,further examination determined M47 and NGC2422 one and the same, The discovery that M47 and NGC2422 were the same cluster only came in 1959 with a realization by Canadian astronomer T. F. Morris.
M47 is at a distance of about 1,600 light-years from Earth with an estimated age of about 78 million years.There are about 50 stars in this cluster,the brightest one being of magnitude +5.7. As with many open clusters, M47’s Trumpler type ranges from II,3,m to I,3,m and III,2,m. M46 is much older and much further away than M47.
M47 is one of the least densely populated open clusters known. The cluster contains many luminous blue stars and a few older red giants. The brightest stars in M47 have a visual magnitude of 5.7. The single brightest star in the cluster is of the spectral type B2. The cluster also contains two K-type orange giants, each about 200 times more luminous than the Sun.
Like M46, M47 holds an additional treasure within its cluster. The double star at the center of M47 is Struve 1121, with components of magnitude 7.4 and 7.9. Struve 1121 can be cleanly split with a 20×80 or 25×100 binocular or better yet a 102 mm refractor. M46 is a very faint fuzzy spot in a 10×50, with M47 appearing as a much brighter star cluster.
M77 (at the top left) and NGC 1055 (near center) (Jon Talbot)
M77 is an SB barred spiral galaxy and is about 47 million light-years distant in the Cetus. M77 has a diameter that is estimated at 170,000 light-years.
M77 was discovered by Pierre Méchain in 1780, who originally described it as a nebula. Méchain then communicated his discovery to Charles Messier, who subsequently listed the object in his famed catalog. Both Messier and William Herschel described this galaxy as a star cluster, although Herschel’s description of it changed as he observed it with larger telescopes. After seeing it in his 6”, 7-foot focal length telescope in 1783, he described M77 as an “ill defined star, surrounded by nebulosity.” Between 1801 and 1810, he observed it in his 9”, 10-foot focal length telescope and noted that it had “almost the appearance of a large stellar nebula.” He later observed the galaxy in his large 18”, 30-foot focal length telescope and remarked, “A kind of much magnified stellar cluster; it contains some bright stars in the centre. With 171 its diameter is 1′ 17″; with 220 it is 1′ 36″.”
Admiral William Henry Smyth observed M77 in October 1836 and described the galaxy with the following description: “A round stellar nebula, near Delta in the Whales’s lower jaw, and about 2 1/2 deg from Gamma on the line towards Epsilon, or s. by w. This was first classed by M. [Messier] in 1780 as a mass of stars containing nebulosity. It is small, bright, and exactly in a line with three small stars, one preceding and two following, of which the nearest and largest is a 9th-magnitude to the sf [south following, SE]. There are other minute companions in the field; and the place is differentiated from Gamma Ceti.This object is wonderfully distant and insulated, with presumptive evidence of intrinsic density in its aggregation; and bearing indication of the existence of a central force, residing either in a central body or in the centre of gravity of the whole system. Sir William Herschel, after repeatedly examining it, says, – “From the observations of the large ten-feet telescope, which has a gauging power of 75.82, we may conclude that the profundity of the nearest part is at least of the 910th order.” That is, the 910 times as far off as the stars of the first magnitude!”
Today, however, the object is known to be a galaxy.
M77 is an active galaxy. It is classified as a type 2 Seyfert galaxy and is the brightest galaxy of this type in the sky. Named after the American astronomer Carl Seyfert, who was the first to identify the class in 1943, Seyfert galaxies are characterized by hot, highly ionized gas around an extremely active centre. M77 serves as the prototype for the class. The galaxy’ active galactic nucleus (AGN) is hidden from view by dust and cannot be seen in visible light.
From 1940 to 1942 as a National Research Council Fellow at Mt. Wilson Observatory, Carl Seyfert did pioneering research, while at Mt. Wilson Observatory, of nuclear emission in spiral galaxies: In 1943, he published a paper on galaxies with bright nuclei that emit light with emission line spectrum, and exhibit characteristically broadened emission lines. These galaxies are since called Seyfert Galaxies; the most prominent example, identified as such by Seyfert, is M77. Since, the class of Seyfert galaxies has been shown to be a subclass of a much wider group, the galaxies with Active Galactic Nuclei (AGNs).
M77 is also the nearest Seyfert galaxy to the solar system, and one of the most studied galaxies in the sky. Classified as a barred spiral, M77 has loosely wound spiral arms, dotted with countless star forming regions, and a small central bulge. The supermassive black hole at the galaxy’s core has an estimated mass of around 15 million times that of the Sun and is less than 12 light years in diameter. The galaxy itself has a mass of about 1 billion solar masses.
The galaxy’s spectrum shows broad emission lines, indicating that large gas clouds are rapidly moving out of the galaxy’s central region at velocities of several 100 km/s. The energy source responsible for the high velocities is found in the nucleus of M77, which is a strong source of radio emissions. The source is known as Cetus A and 3C 71.
NGC 1055 is an Sb edge-on spiral galaxy also in Cetus, and displays a prominent central bulge with a distinct lumpy dark lane of dust and gas. NGC 1055 was discovered by William Herschel on December 19, 1783.
M77, NGC 1055, NGC 1073,and five other small irregular galaxies form a gravitationally linked galaxy group. M77 and NGC 1055 are the largest galaxies of this small galaxy group.
NGC 1055 is 52 million light-years distant, with a diameter of about 115,800 light-years. The separation between NGC 1055 and M77 is about 442,000 light-years.
M77 and NGC 1055 can be seen through an 8” SCT or 8” Newtonian using a moderate low magnification and wide field eyepiece with a field-of-view of 68°or more. M77 is an easy target in dark country skies. Dark skies and dark adapted eyes are necessary to spot NGC 1055. I have sighted this Cosmic Duet through my 130 mm apochromat refractor (the benefits of great optics and high contrast) in the dark Virginia country skies of my backyard..
M65, M66, and NGC 3628 are part of a group of galaxies known as the Leo Galaxy Group. This group of galaxies also includes another trio of galaxies M95, M96, and M105. M65 and M66 are a popular pair of galaxies for backyard astronomers to observe, second to only to M81 and M82.
Whereas M95, M96, and M105 can be readily observed with the smaller 4” refractor, M65, M66, and NGC 3628 are a challenge in a 4” because of the difficulty of seeing the edge-on NGC 3628. With an 8” aperture, NGC 3628 can be seen to have a large dark dust lane that extends through the galaxy’s profile, which gives the galaxy its Hamburger Galaxy moniker. The dust lane has the effect of lowering the surface brightness of the object. The 8” aperture of a SCT or Newtonian helps overcome the lower surface brightness.
M65 and M66 are separated by only 21′, with NGC 3628 only 35′ away from M66. Chose an eyepiece that produces a true field of view of 1º, and all three galaxies will fit comfortably in the same eyepiece view. For example, a 28 mm 68ºFOV eyepiece will produce a 0.95ºtrue field of view at 71x in an 8” SCT.
M65 is an Sa galaxy that was discovered by Charles Messier in March 1, 1780. He described M65 as a :
“…nebula discovered in Leo: It is very faint and contains no star.”
M66 is an Sab galaxy discovered by Charles Messier on the same night in 1780 as his discovery of M65. Messier’s description of M66 was:
“…its light is very faint & it is very close to the preceding (M65). They both appear in the same field in the refractor. The comet of 1773 & 1774 has passed between these two nebulae on November 1 to 2, 1773. M. Messier didn’t see them at that time, no doubt, because of the light of the comet.”
Admiral William Henry Smyth described M66 as follows:
“A large elongated nebula, with a bright nucleus, on the Lion’s haunch, trending np [north preceding, NW] and sf [south following, SE]; this beautiful specimen of perspective lies just 3deg south-east of Theta Leonis. It is preceded at about 73s by another of a similar shape, which is Messier’s No. 65, and both are in the field at the same time, under a moderate power, together with several stars.”
NGC 3628 is an unbarred Sa spiral galaxy that was discovered by William Herschel. NGC 3628 was discovered on April 8, 1784, when William Herschel used a larger telescope than that used by Messier. The one month later discovery of NGC 3628 just adds fuel to the old astronomer adage: “Aperture rules!”
Sometime in the distant past, all three of these Leo galaxies, sometimes referred to as the Leo Triplet, had a close gravitational encounter with each other. As a result, M65 is suspected of actually having a central bar, although this is difficult to detect because of its oblique angle to astronomers. Gravitational interaction from its past encounter with neighboring NGC 3628 has resulted in M66 having an extremely high central mass concentration.
Some astronomers include the nearby lenticular galaxy NGC 3593 as a possible member of the M66 Group. NGC 3593 is a starburst galaxy and known to contain two populations of stars that are rotating in opposite directions. With an apparent magnitude of 12.6, the galaxy is fainter than the Leo Triplet, and is on the hairy edge of visibility in an 8” SCT, but visible in larger apertures. NGC 3593 can be viewed as part of this galaxy group by owners of 10” or larger apertured telescopes and very wide field eyepieces.
With a tip of the hat to astronomer Phil Platt in his column for SyFy Wire, and an assist from Star Gaze Hawaii, this month’s corner looks at a little known star cluster that is a fun deep sky object to track down. Along with asterisms such as “The Hanger”, and “Kemble’s Kite”, the “37” Cluster is a unique arrangement of stars.
NGC 2169, commonly called the “37” Cluster from its appearance as letters or numbers written in the stars, is a little known cluster in the constellation Orion. Unlike most open star clusters that are arranged in random patterns, NGC 2169 appears as the number “37”. Smaller telescopes see the letters “XY” and larger telescopes and astro-images see the number “37” as dimmer stars become visible with increased apertures. The winter months are the optimum time to observe NGC 2169 with Orion high in the sky and the wintery months transparent night skies. NGC 2169 is a good alternative to observing M42 and M43.
Historically, the cluster may have been discovered by Hodierna prior to 1654. Our old friend William Herschel discovered and documented his discovery of the cluster on October 15, 1784. The cluster has since be studied and is composed of componentsCollinder 38, a I3pn open cluster, and Collinder 83, a III3m open cluster.
Open star clusters are formed from hydrogen molecular clouds that have condensed into stars and are loosely gravitationally bound into groups. The “37” Cluster is an open cluster made up of about 30 stars of 6thmagnitude and dimmer. It is not naked eye visible. NGC 2169 is located north of Betelgeuse near Nu and Xi Orionis. The estimated age of NGC 2169 is approximately 8 million years old. The brightest member is a type B star which has a projected life of less than 1 billion years. There are various colors visible in images indicating various masses and spectral types. There is a yellow star of type G2 that would be an analog of our Sun with a projected life of about 10 billion years. One of the dimmer members is a red giant of type B6 which has already run out of Hydrogen and is between 4 and 8 times the mass of our Sun. The dim star that makes the top bar of the “7” is 11thmagnitude and requires larger apertures to be seen at all and is white in color.
In refractors and Schmidt-Cassegrain telescopes, the view of the cluster will be mirror reversed, so the “37” will need some interpretation. Newtonian telescopes will display the true arrangement and reveal directly the 37. The letters “YX” may be easier to decipher in reversed telescopes. An image corrector can reduce brightness by about 20% and are not recommended for small telescopes. My SCT 11″ telescope that have enough light grasp to see the mirrored image through a 2” diagonal, and a corrected image through an 1-1/4” erecting diagonal. My 102mm apo with a regular 2” diagonal shows the “YX” formation. The cluster is only 7′ across, so moderate to moderately-high power maybe needed to see this cluster.
The Great Orion Nebula, M42 and M43, with the Flame Nebula NGC 2024 and the Horsehead Nebula Barnard 33 (Photo by Jon Talbot)
M42
Alternate: NGC 1976, the Great Orion Nebula
Orion
RA 5h 35.3 m
Dec -5º 23′
Magnitude 3.7
M43
Alternate: NGC 1982
Orion
RA 5h 35.6 m
Dec -5º 16′
Magnitude 6.8
With the cold winter months upon us, our old cosmic friend Orion the Hunter has returned to our night skies. And with the presence of this most famous constellation is the arrival of its most famous deep sky object, the Great Orion Nebula.
Many readers are probably unaware that when viewing the Great Orion Nebula they are actually observing a cosmic duet. The proximity of M43 to M42 often goes unnoticed due the spectacular nebulosity exhibited by the region overall. The Great Orion Nebula is easily detectable with binoculars. A 4-inch refractor can easily split M42 and M43 at 35x, with more detail revealed when higher powers and larger aperture telescopes are used. No need for wide-angle, super-wide-angle, or ultra-wide-angle eyepieces, a 50º AFOV Plossl will get the job done.
The first discovery of the nebula clouds of the Orion Nebula is generally credited to French astronomer Nicolas-Claude Fabri de Peiresc. Peiresc recorded his observations on November 26, 1610, while observing the nebula through his patron’s refracting telescope.
The first published details of the nebula were provided by the Jesuit mathematician and astronomer Johann Baptist Cysatus in his 1619 monograph on comets. He wrote of observations of the nebula dating back to 1611. Cysatus described the nebula as “one sees how in like manner some stars are compressed into a very narrow space and how round about and between the stars a white light like that of a white cloud is poured out.”
Galileo observed the Trapezium on February 4, 1617, but he did not observe the nebula itself. This oversight was probably caused by the poor optics and the small aperture of his telescope.
All of these discoveries were lost or the knowledge was not well distributed. Historically, Christian Huygens was credited with the discovery in 1656:
“There is one phenomenon among the fixed stars worthy of mention, which as fas as I know, has hitherto been noticed by no one and indeed, cannot be well observed except with large telescopes. In the sword of Orion are three stars quite close together. In 1656 as I changed viewing the middle one of these with the telescope [a 23-foot FL refractor], twelve showed themselves – not an uncommon circumstance, Three of these almost touched each other and, with four others, shone through a nebula so that the space around them seemed brighter than the rest of the heavens which was entirely clear and appeared quite black, the effect being that of an opening in the sky through which a brighter region was visible.”
Christian Huygens was a Dutch mathematician and scientist of the 1600’s whose impact is still felt today in astronomy. Not only is he credited with the discovery of the Orion Nebula, which is the Winter showcase deep sky object for backyard observers and astronomers, but was the originator of the Huygens eyepiece found as standard equipment in many beginner telescopes.
Charles Messier listed the Orion Nebula as Messier 42 in his first catalog, with his comments:
“I have examined a large number of times the nebula in the sword of Orion, which Huygens discovered in the year 1656, & of which he has given a drawing in the work which he has published in 1659, under the title Systema Saturnium[Saturnian System]. It has been observed since by different Astronomers. M. Derham, in a Memoir printed in the Philosophical Transactions, no. 428, page 70, speaks of that nebula which he has examined with a reflecting telescope of 8 feet. Here is the translation [actually here, the text] of what he has reported in this Memoir. ” only that inOrion, hath some Stars in it, visible only with the Telescope, but by no Means sufficient to cause the Light of the Nebulosethere. But by these Stars it was, that I first perceived the Distance of the Nebulosaeto be greater than that of the Fix’d Stars, and put me upon enquiring into the rest of them. Every one of which I could very visibly, and plainly discern, to be at immense Distance beyond the Fix’d Stars near them, whether visible to the naked Eye, or Telescopick only; yea, they seemed to be as far beyond the Fix’d Stars, as any of those Stars are from Earth.” M. le Gentil also examined this nebula with ordinary refractors of 8, of 15 & of 18 feet length; as well as a Gregorian telescope of 6 feet, which belongs to Mr. Pingré. He has published his observations in a Memoir which can be found printed in the Volumes of the Academy, year 1759, page 453. There is a joint of the drawings which he had made of it at that time, as well as those of Huygens & of Picard; these drawings differ from each other, so that one may suspect that this nebula is subject to sort of variations. Here is what I have reported about that nebula in the Journal of my Observations. On March 4, 1769, the sky was perfectly serene, Orion was going to pass the meridian, I have directed to the nebula of this constellation a Gregorian telescope of 30 pouces focal length, which magnified 104 times; one saw it perfectly well, & I drawed the extension of the nebula, which I compared consequently to the drawings which M. le Gentil has given of it, I found some differences. This nebula contains eleven stars; there are four near its middle, of different magnitudes & strongly compressed to each other; they are of an extraordinary brilliance: here is the position of the brightest of the four stars, which Flamsteed, in his catalog, designated by the greek letter Theta, of fourth magnitude, 80d 59′ 40″ in right ascension, & 5d 34′ 6″ in southern declination: this position has been deduced from that which Flamsteed has given in his catalog. [p. 458] 1769.Mar. 4. RA: 80.59.40, Dec: 5.34. 6.A. Position of the star Theta in the Sword of Orion, which is situated in the middle of the nebula in that constellation.”
In 1731, Jean-Jacques Dortous de Mairan was the first to notice M43 as an independent part of the Orion Nebula:
“Finally I will add that close to the luminous space in Orion [M42], one sees the star d of Huygens [NU Orionis] currently (1731) surrounded by a brilliance very similar to that which produces, as I believe, the atmosphere of our Sun, if it were dense enough and extensive enough to be visible in Telescopes at a similar distance. See it in the form and the situation [given by] D, according to what was determined with the Reticule.”
On March 4, 1771, Charles Messier would also come to the same conclusion as he states in his observing notes:
“The star which is above, and has little distance from that nebula, and of which is spoken in the Traite de l’Aurore boreale [Treat of the Northern Light] by M. de Mairan is surrounded, and equally by a very thin light; the star doesn’t have the same brilliance as the four of the great nebula: its light is pale, and it appears covered by fog. I determined its position; its right ascension was 81d 3′ 0″, and its declination 5d 26′ 37″ south.”
M42 is the showpiece deep sky object visible in the Northern Hemisphere. This diffuse nebula is located approximately 1,344 light years away.M42 has a radius of 12 light-years.
The Orion Nebula is part of a much larger cloud of dust and gas, called the Orion Molecular Cloud Complex, which encompasses a large part of the Orion constellation. This nebulous cloud encompasses features such as M43, Barnard’s Loop, the reflection nebula Messier 78, the NGC 2024 Flame Nebula, and the famous B33 Horsehead Nebula.
Both M42 and M43 are emission nebulae, with their light emitted from atoms being excited by the high-energy radiation of massive, very hot young stars within them. Wisps of the Orion Molecular Cloud in the neighborhood of M42 and M43 constitute the fainter reflection nebulae elements. The Orion Nebula is a star nursery, with approximately 700 stars at various stages of early development. These young stars are the main source of energy that illuminates the Orion Nebula.
Backyard astronomers always look for the Trapezium asterism within M42. The Trapezium is group of very young energetic stars, with the appearance in smaller telescopes of four stars. Two of the Trapezium stars can be resolved into double stars on good seeing nights and larger telescope apertures. The Trapezium stars are part of the larger cluster of young stars energizing the HII the Orion Nebula.
Visually, the M42/M43 complex appears as a faintly greenish -white color through the telescope eyepiece. Photographically, the more illuminated regions of the nebula appear red. The green hue is caused by a low probability electron transition in doubly ionized oxygen, known to astrophysicists as the forbidden transition. Normally in astro-spectroscopy, a forbidden transition is a spectral line associated with the absorption or emission of light by H II regions, a result that cannot be observed under laboratory conditions because the gases cannot be rarefied sufficiently. In the laboratory, an excited atom tends to bounce off another particle or the walls of the gas container before it emits a photon, thus interfering with the experiment.
Forbidden is an odd term in this case, since the more accurate description is that the transition is highly improbable. The emissions result from electrons transitioning from an upper energy level to a lower energy level which requires a long time to take place. In an H II region, such as the Orion Nebula, the excited atom remains undisturbed long enough to emit a photon. Adding to this is the transparency of the H II region ionized gases to visible light, which permits the photons given off to contribute to detectable spectral lines. In the case of the Orion Nebula, the O III spectral lines of 495.9 nm and 500.7 nm are highly prominent. This explains the success the using of O III nebula filters for observing M42 and M43.
The red hue seen in astro-images is the result of the hydrogen-alpha recombination line radiation at the wavelength of 656.3 nm. The red hue is not observable to the visual observer because of the human eye is not sensitive to low-level red light. There is a reason why backyard astronomers use red flashlights at night!
The blue-violet hues seen in astro-images are actually reflections originating from O-class stars within the core of the Orion Nebula.
M42 and M43 are one of the most studied and photographed areas of the night sky by both professional and amateur astronomers. Every backyard astronomer with a camera has taken an astro-photograph of M42 and M43.
This month’s Jim’s Corner is what I submitted to Springer’s blog for World Space Week 2019. My publisher asked for some amusing Apollo Program stories, since the theme of this year’s World Space Week was “Back to the Moon”.
In the process of research for my first book, How to Find The Apollo Landing Sites, I came upon a few of humorous behind-the-scenes anecdotes related to the Apollo 11, Apollo 13 and Apollo 17. These stories are not well known, but are so interesting and funny that I feature them in all my speaking engagements concerning the Apollo Program.
The U.S. Customs regulations collided with NASA’s Apollo 11 mission as the quarantined Neil Armstrong, Buzz Aldrin, and Michael Collins were returning from their ocean landing to Honolulu, Hawaii. In typical government bureaucratic fashion, the U.S. Customs required the Apollo 11 crew to fill out a declaration form for the moon rocks and lunar samples returned from the Sea of Tranquility. According to U.S. Customs regulations, the Apollo 11 crew had definitely left the United States to a foreign soil and was returning to the United States with items procured at said foreign soil.
The U.S. Customs declaration form was signed by all three astronauts, declaring moon rocks and moon dust samples, and their destination was the Moon. There was no monetary value claimed for the Moon rocks and Moon dust samples. Clearly an example of bureaucracy gone wrong.. The declaration form was never repeated for successive Apollo missions.
Another funny behind-the-scenes anecdote concerned the failed Moon landing but safe return of the astronauts of Apollo 13. The rescue of astronauts Jim Lovell, Fred Haise, and Jack Swigert is now legendary, and is perhaps as famous as the Apollo 11 first landing on the Moon. Books have been written, documentaries aired on television, and a very successful theatrical movie have been produced about this ill-fated mission. Apollo 13 is often described as NASA’s finest moment as the agency successfully returned the astronauts safely home. It is a testament to the many NASA engineers and scientists who brought astronauts Jim Lovell, Fred Haise and Jack Swigert to a safe return and landing.
The anecdote centers on the designers and engineers of GrummanAerospace Corporation, who built the Lunar Module turned lifeboat Aquarius and North American Rockwell, designers and builders of the Apollo 13 Command and Service Module Odyssey.
After the safe return of Apollo 13, Grumman engineers on the LM program sent a spoof invoice A441066 to North American Rockwell, the builders of Odyssey, for towing Apollo 13 around the moon and home to Earth. The bill was submitted by Sam Greenberg, a pilot for Grumman Aerospace, and was written by workers at Grumman’s Flight Control Integration Lab in 1970. A higher level Grumman manager with no sense of humor, fired Greenberg for spoof invoice. Fortunately for Greenberg, Lou Evans, president of Grumman , found the invoice hilarious, reinstated Greenberg, signed the invoice and sent it to Rockwell. It included towing at $4.00 first mile, $1.00 each additional mile, battery charge, oxygen and addition guest at $8.00/night. Water and baggage handling was free. With a 20% commercial discount and 2% cash discount (net 30 days), the total bill came to $417,421.24, including a $100,000 charge for keeping the invoice confidential. Rockwell responded in a press conference that they still had not received payment for shipping four of Grumman’s LMs previously delivered to Earth orbit and to the Moon!
A humorous footnote to the Apollo 17 mission was mankind’s first fender bender in space and first car repair in space. During the first scheduled lunar activity, astronaut Gene Cernan brushed against the Lunar Rover, and a hammer in his spacesuit shin pocket caught the right rear fender and knocked off half of it. The half fender allowed a dust plume to kick up as the Lunar Rover moved. The dark lunar dust covered the astronauts, which absorbed the sunlight and could potentially cause overheating problems for Cernan and Harrison Schmitt. The abrasive moon dust could also cause scratching of the astronauts’ visors, and hinder the operation of the various latches, hinges, and joints of the Lunar Rover. Before the second lunar excursion, using a roll of duct tape, Cernan was able to re-attach the fender piece. This repair didn’t last long. The taped fender lasted for only four of the seven hour second lunar activity. The duct tape lost some of its stickiness because of the ubiquitous moon dust. For the remaining three hours, the astronauts stopped frequently use a dust brush to clean off the vehicle, equipment and themselves. Before the third and final lunar excursion, Cernan and Schmitt fashioned a makeshift fender out of four laminated maps and duct tape while inside the relatively cleaner LM. The duct ape worked better this time, and the new fender was attached by using clamps from from the optical alignment telescope lamp. The makeshift fender lasted for the rest of the Apollo 17 mission..
And finally, afew years ago, the three Lunar Rovers were an auction item on eBay as an April Fool’s Day joke, with the auction removed the next day. The Lunar Rover was listed as having very low mileage and driven very little for the past four or five decades. A quantity of three were available. The listing described the vehicles as four-wheel drive lunar utility vehicles, namely in today’s terms a moon SUV! Tires were described as in great shape. The items were possibly little dusty, but a good car wash would make it look like new. A real collector’s car. No rust and mint condition. No UPS, or FedEx delivery was available. The items were available for local pickup. A reminder to whoever won the eBay auction for the Apollo 17 lunar rover, the vehicle does need some bodywork!
NGC 3226 is a E2 dwarf elliptical galaxy that is interacting with the Sab spiral galaxy NGC 3227. The two galaxies are one of several examples of a spiral with a dwarf elliptical companion that are listed in HaltonArp’s Atlas of Peculiar Galaxies. Both galaxies are identified as Arp 94.
For those unfamiliar with Halton Arp’s Atlas of Peculiar Galaxies, it is a catalog of 338 galaxies first published in 1966. The primary goal of the Atlas of Peculiar Galaxieswas to present photographic examples of the different kinds of peculiar structures found among nearby galaxies. At the time, the reason why galaxies formed into elliptical, lenticular, spiral, or barred spiral shapes was not well understood. Halton Arp perceived peculiar galaxies as small examples that astronomers could use to understand the physical processes that distort spiral or elliptical galaxies. With this atlas, astronomers had a sample of peculiar galaxies that they could study in more detail. The atlas was not meant to present a complete catalog of every peculiar galaxy in the sky but instead provides examples of the different phenomena as observed in nearby galaxies. The atlas provided the seed for astronomers to understand the physics of galaxy formation and today, the physical processes that lead to the peculiarities seen in the Arp atlas are well understood.
William Herschel discoveredboth NGC 3226 and 3227 and described the pair as a double nebula. NGC 3227 has since been identified as a Seyfert galaxy.
10”+ aperture telescopes can resolve NGC 3226 and NGC 3227 at a magnification of 100x. They are situated 50′ east of the well-known double star system Algieba. Again, as in last month’s article, a large aperture and moonless dark nights are needed to spot Arp 94. A mild sky glow may inhibit the observation of Arp 94, but a mild LPR filter may help. Don’t use a UHC, hydrogen-beta, or OIII filter as these will not filters are too severe in their filtering characteristics to help.
