Please adjust your monitor's brightness and contrast so you can see a shade difference between the Black and Black #2
above. This will assure good viewing of the images below.
Full moon taken October 7th, 2003 @ f3. The 1004X camera typically does not do well with bright objects, but because
of the short focal lenght (f3), and a full image, the AGC on the camera was fooled into low gain.
Called Luna by the Romans, Selene
and Artemis by the Greeks, and many other names in other mythologies.
The Moon, of course, has been known since prehistoric times. It is the second brightest object in the sky after the Sun. As the Moon orbits around the Earth
once per month, the angle between the Earth, the Moon and the Sun changes; we see this as the cycle of the Moon's phases.
The time between successive new moons is 29.5 days (709 hours), slightly different from the Moon's orbital period (measured
against the stars) since the Earth moves a significant distance in its orbit around the Sun in that time.
Due to its size and composition, the Moon is sometimes classified as a terrestrial
"planet" along with Mercury, Venus, Earth
The Moon was first visited by the Soviet spacecraft Luna
2 in 1959. It is the only extraterrestrial body to have been visited by humans. The first
landing was on July 20, 1969 (do you remember where you were?); the last was in December 1972. The Moon is also the only body
from which samples have been returned to Earth. In the summer of 1994, the Moon was very extensively mapped by the little
spacecraft Clementine and again in 1999 by Lunar Prospector.
The gravitational forces between the Earth and the Moon cause some interesting effects. The most obvious is the tides.
The Moon's gravitational attraction is stronger on the side of the Earth nearest to the Moon and weaker on the opposite side.
Since the Earth, and particularly the oceans, is not perfectly rigid it is stretched out along the line toward the Moon. From
our perspective on the Earth's surface we see two small bulges, one in the direction of the Moon and one directly opposite.
The effect is much stronger in the ocean water than in the solid crust so the water bulges are higher. And because the Earth
rotates much faster than the Moon moves in its orbit, the bulges move around the Earth about once a day giving two high tides
per day. (This is a greatly simplified model; actual tides, especially near the coasts, are much more complicated.)
But the Earth is not completely fluid, either. The Earth's rotation carries the Earth's bulges slightly
ahead of the point directly beneath the Moon. This means that the force between the Earth and the Moon is not exactly along
the line between their centers producing a torque on the Earth and an accelerating force on the Moon. This causes a
net transfer of rotational energy from the Earth to the Moon, slowing down the Earth's rotation by about 1.5 milliseconds/century
and raising the Moon into a higher orbit by about 3.8 centimeters per year. (The opposite effect happens to satellites with
unusual orbits such as Phobos and Triton).
asymmetric nature of this gravitational interaction is also responsible for the fact that the Moon rotates synchronously,
i.e. it is locked in phase with its orbit so that the same side is always facing toward the Earth. Just as the Earth's rotation
is now being slowed by the Moon's influence so in the distant past the Moon's rotation was slowed by the action of the Earth,
but in that case the effect was much stronger. When the Moon's rotation rate was slowed to match its orbital period (such
that the bulge always faced toward the Earth) there was no longer an off-center torque on the Moon and a stable situation
was achieved. The same thing has happened to most of the other satellites in the solar system. Eventually, the Earth's rotation
will be slowed to match the Moon's period, too, as is the case with Pluto and Charon.
Actually, the Moon appears to wobble a bit (due to
its slightly non-circular orbit) so that a few degrees of the far side can be seen from time to time, but the majority of
the far side (left) was completely unknown until the Soviet spacecraft Luna 3 photographed it in
1959. (Note: there is no "dark side" of the Moon; all parts of the Moon get sunlight half the time (except for a few deep
craters near the poles). Some uses of the term "dark side" in the past may have referred to the far side as "dark" in the
sense of "unknown" (eg "darkest Africa") but even that meaning is no longer valid today!)
The Moon has no atmosphere. But evidence from Clementine
suggested that there may be water ice in some deep craters near the Moon's south pole which are permanently shaded. This has
now been confirmed by Lunar Prospector. There is apparently ice at the
north pole as well. The cost of future lunar exploration just got a lot cheaper!
The Moon's crust averages 68 km thick and varies from essentially 0 under Mare Crisium
to 107 km north of the crater Korolev on the lunar far side. Below the crust is a mantle and probably a small core (roughly
340 km radius and 2% of the Moon's mass). Unlike the Earth, however, the Moon's interior is no longer active. Curiously, the
Moon's center of mass is offset from its geometric center by about 2 km in the direction toward the Earth. Also, the crust
is thinner on the near side.
There are two primary types of terrain on the Moon: the heavily cratered and
very old highlands and the relatively smooth and younger maria.
The maria (which comprise about 16% of the Moon's surface) are huge impact craters that were later flooded by molten lava.
Most of the surface is covered with regolith, a mixture of fine dust and rocky debris produced by meteor impacts. For some unknown reason, the maria are concentrated on the near side.
Most of the craters on the near side are named for famous figures in the history
of science such as Tycho, Copernicus, and Ptolemaeus.
Features on the far side have more modern references such as Apollo, Gagarin and Korolev (with a distinctly Russian bias since
the first images were obtained by Luna 3). In addition to the familiar features on the near side, the Moon also has the huge craters South Pole-Aitken on the
far side which is 2250 km in diameter and 12 km deep making it the the largest impact basin in the solar system and Orientale
on the western limb (as seen from Earth; in the center of the image at left) which is a splendid example of a multi-ring crater.
A total of 382 kg of rock samples were returned to the Earth by the Apollo
and Luna programs. These provide most of our detailed knowledge of the Moon. They are particularly
valuable in that they can be dated. Even today, more than 30 years after the last Moon landing, scientists still study these
Most rocks on the surface of the Moon seem to be between 4.6 and 3 billion years
old. This is a fortuitous match with the oldest terrestrial rocks which are rarely more than 3 billion years old. Thus the
Moon provides evidence about the early history of the Solar System not available on the Earth.
Prior to the study of the Apollo samples, there was no consensus about the origin
of the Moon. There were three principal theories: co-accretion which asserted that the Moon and the Earth formed at
the same time from the Solar Nebula; fission which asserted that the Moon split off of the
Earth; and capture which held that the Moon formed elsewhere and was subsequently captured by the Earth. None of these
work very well. But the new and detailed information from the Moon rocks led to the impact theory: that the Earth collided
with a very large object (as big as Mars or more) and that the Moon formed from the ejected material. There are still details
to be worked out, but the impact theory is now widely accepted.
The Moon has no global magnetic field. But some of its surface rocks exhibit remanent
magnetism indicating that there may have been a global magnetic field early in the Moon's history.
With no atmosphere and no magnetic field, the Moon's surface is exposed directly
to the solar wind. Over its 4 billion year lifetime many hydrogen ions from the solar wind have
become embedded in the Moon's regolith. Thus samples of regolith returned by the Apollo missions proved valuable in studies
of the solar wind. This lunar hydrogen may also be of use someday as rocket fuel.
M42 taken in March of 2003. Five-5 second exposures stacked.
Discovered 1610 by Nicholas-Claude Fabri de Peiresc.
Located at a distance of about 1,600 (or perhaps 1,500) light years, the Orion Nebula
is the brightest diffuse nebula in the sky, visible to the naked eye, and rewarding in telescopes of every size, from the
smallest glasses to the greatest Earth-bound observatories and the Hubble Space Telescope.
It is the main part of a much larger cloud of gas and dust
which extends over 10 degrees well over half the constellation Orion. The linear extend of this giant cloud is well several
hundreds of light years. It can be visualized by long exposure photos (see e.g. Burnham) and contains, besides the Orion nebula
near its center, the following objects, often famous on their own: Barnard's Loop, the
Horsehead Nebula region (also containing NGC 2024 = Orion B), and the reflection nebulae around M78.
Already impressive in deep visible light photographs, the Orion Cloud is particularly gorgeous in the infrared
The Orion Nebula itself is still a big object in the sky, extending some
66x60 arc minutes, thus covering four times the area of the full Moon. This corresponds to a linear diameter of about 30 light
years. It is also one of the brightest Deep Sky objects, well visible to the naked eye, so that the present author is wondering
that its nebulous nature was apparently not documented before 1610, when Nicholas-Claude Fabri de Peiresc
(1580-1637), a French lawyer, turned his telescope to this region of the sky (although Ptolemy,
as well as later Tycho Brahe and Johann Bayer had cataloged the brightest stars within it as one bright star - the latter
cataloging it as Theta Orionis, and Galileo had detected a number of faint stars when first looking
at this region with his telescope earlier in 1610). It was independently rediscovered in 1611 by the Jesuit astronomer Johann Baptist Cysatus (1588-1657) of Lucerne who compared it with a comet he had observed in the same
year. The first known drawing of the Orion nebula was created by Giovanni
Batista Hodierna. All these discoveries apparently got lost for some time, so that eventually
Christian Huygens was longly credited for his independent rediscovery in 1656, e.g. by Charles
Messier when he added it to his catalog on March 4, 1769.
As the drawings of the Orion Nebula known to him did so poorly represent Messier's
impression, he created a fine drawing of this Object, in order to "help to recognize it again,
provided that it is not subject to change with time" (as Messier states in the introduction to his catalog).
This gorgeous object continued influence astronomers since. It was the first deepsky
observation by William Herschel with a self-constructed reflecting telescope of 6-foot focal length
in 1774. In 1789, with some prophetic touch, he described his observations with his 48-inch aperture, 40-inch FL scope as
"an unformed fiery mist, the chaotic material of future suns." In 1880, M42 was the first nebula to be successfully photographed,
by Henry Draper.
The small northeastern portion was first reported by de Mairan,
and was given an extra number by Charles Messier, M43 (see below also). In the very neighborhood,
to the north, there are also fainter reflection nebulae, partially reflecting the light of the Great Nebula. They were not
notable for Charles Messier, but labeled later with the NGC numbers 1973-5-7. Here we have a collection of more
images of M42, M43, and more images of M42, M43 and NGC 1973-5-7.
M42 itself is apparently a very turbulent cloud of gas and dust, full of interesting
details, which C.R. O'Dell compares to the rich topography of the Grand Canyon in his HST photo caption. The major features
got names on their own by various observers: The dark nebula forming the lane separating M43 from the main nebula extends
well into the latter, forming a feature generally nicknamed the "Fish's Mouth". The bright regions to both sides are called
the "wings", while at the end of the Fish's Mouth there's a cluster of newly formed stars, called the "Trapezium cluster".
The wing extension to the south on the east (lower left in our image) is called "The Sword", the bright nebulosity below the
Trapezium "The Thrust" and the fainter western (right) extension "The Sail". Here we have a small collection of Images
of detail in M42, including another nomenclature for the brightest region in the nebula by historic visual observers,
as well as a pictorial study of the Trapezium cluster and region by Lowell Observatory images.
The Trapezium cluster is among the very youngest clusters known, with new stars
still forming in this region. The cluster was first depicted as triple star apparently by Hodierna
before 1654 (see his drawing), and first described by Christian Huygens in 1656 when he indepedently
rediscovered the Orion nebula. These first three stars are often labelled "A", "B", and "C". At this time, this was apparently
the second recognized multiple star (after Mizar in Ursa Major which had been found to be a telescopic double in 1650). The
fourth Trapezium star, "D", was first found by Abbe Jean Picard in 1673 (according to de Mairan),
and independently by Huygens in 1684. The fifth cluster star "E" was discovered by Friedrich Georg Wilhelm
Struve in 1826 with a 9.5-inch refractor in Dorpat, the sixth, "F", by John Herschel on
February 13, 1830, the seventh, "G", by Alvan Clark in 1888 when testing his 36-inch refractor of Lick Observatory, and the
eighth, "H" by E.E. Barnard later in 1888 with the same telescope. Barnard later found that "H"
is double, with two 16th-magnitude components. Today we know that stars "A" and "B" are both eclipsing variables of Algol
type: A varies between magnitudes 6.73 and 7.53 with a period of 65.4325 days, while B varies between mag 7.95 and 8.52 in
The Orion Nebula is also one of the easiest and most rewarding target for amateur astrophotographers.
The past decades of research on the Orion Nebula have revealed that the visible
nebula, M42, the blister of hot, photo-ionized, luminous gas around hot Trapezium stars, is only a thin layer lying on the
surface of a much larger cloud of denser matter, the Orion Molecular Cloud 1 (OMC 1). We happen to see this structure approximately
face-on. The idea for this model came originally from Münch (1958) and Wurm
(1961) and fully elaborated by several authors around 1973-1974 (Zuckerman (1973), Balick et.al. (1974), soon supported by evidence, and is still studied in detail, see e.g. O'Dell (2001) for a recent review, and references cited therein. The San Diego Supercomputer
Center (SDSC)'s VisLab has created a 3-dimensional visualization of the Orion Nebula based
on this model (see side-view model image of M42).
The Orion nebula was, continuously since the early times
before its refurbishment, a preferred target for the Hubble Space Telescope. One major discovery was that of protoplanetary
disks, the socalled "Proplyds" (planetary systems in formation) in these HST images of M42
(these images were used for an animation simulating the approach to a protostar [caption].
HST images of November 1995 have revealed further insight into the complicated process taking place
in this "star factory". Hubble investigations of January 1997 have revealed interesting interactions
of the young hot Trapezium cluster stars with the protoplanetary disks: Their violent radiation tends to destruct the discs,
so that the lower-mass stars forming here may loose the material needed to form planetary systems.
It is very easy to find the Orion Nebula, as it surrounds the Theta Orionis multiple
star or cluster, seen to the naked eye in the middle of the sword of Orion. Already under fairly good conditions, the nebula
itself can be glimpsed with the naked eye as a faint nebulosity around this star.
It is somewhat unusual that the Orion Nebula has found its way into Messier's
list together with the bright star clusters Praesepe M44 and the Pleiades
M45; Charles Messier usually only included fainter objects which could be easily taken for comets. But in this one
night of March 4, 1769, he determined the positions of these wellknown objects, (to say it with Owen Gingerich) `evidently
adding these as "frosting" to bring the list to 45', for its first publication in the Memoires de l'Academie for 1771
(published 1774). One may speculate why he prefered a list of 45 entries over one with 41; a possible
reason may be that he wanted to beat Lacaille's 1755 catalog of southern objects, which had 42
entries. Messier measured an extra position for a smaller northeastern portion, reported by de Mairan previously, which therefore
has the extra Messier number: M43.
M17 taken August 10th 2003 @ f3. Five-20 second exposures stacked.
Discovered by Philippe Loys de Chéseaux in 1745-46.
The Omega Nebula M17, also called the Swan Nebula, the Horseshoe Nebula, or (especially
on the southern hemisphere) the Lobster Nebula, is a region of star formation and shines by excited emission, caused by the
higher energy radiation of young stars. Unlike in many other emission nebulae, however, these stars are not obvious in optical
images, but hidden in the nebula. Star formation is either still active in this nebula, or ceased very recently. A small cluster
of about 35 bright but obscurred stars seems to be imbedded in the nebulosity.
The color of the Omega Nebula is reddish, with some graduation to pink. This color
comes from the hot hydrogene gas which is excited to shine by the hottest stars which have just formed within the nebula.
However, the brightest region is actually of white color, not overexposed as one might think. This phenomenon is apparently
a result of a mixture of emission light from the hottest gas, together with reflections of the bright star light from the
dust in this region. The nebula contains a large amount of dark obscuring material, which is obvious in its remarkable features.
This matter has been heated by the hidden young stars, and shines brightly in infrared light.
The mass of the gas has been estimated to amount about 800 times that of the Sun,
enough for forming a conspicuous cluster, and a good deal more than that of the Orion nebula M42.
While the bright nebula seems to be roughly 15 light years in extension, the total gaseous cloud, including low-luminosity
material, seems to extend to at least 40 light years. Distance estimates are spread over a wide range, but modern values are
between 5,000 and 6,000 light years, thus little less than that of its apparent neighbor, M16 with
the Eagle nebula - apparently, these two star forming regions are indeed close together, in the same spiral
arm (the Sagittarius or Sagittarius-Carina arm) of the Milky Way galaxy, and perhaps part
of the same giant complex of cosmic clouds of interstellar matter.
As for many diffuse nebulae, the overall brightness of this object is difficult
to estimate, and is given discordantly in the sources. While older sources give estimates around 7.0 magnitudes, probably
because these were performed at northern observatories, modern compilations list its visual magnitude brighter: Don Machholz
lists it at 6.6 mag, the Sky Catalogue 2000.0 at 5.0 mag, and the Deep Sky Field Guide to Uranometria 2000.0 gives a value
of 6.0 mag (which we adopt here); anyway, it is visible to the naked eye under good observing conditions from not too northern
The discovery of M17 by De Chéseaux didn't get widely
known, so Charles Messier independently rediscovered it and cataloged it
on June 3, 1764.
The Omega or Swan Nebula M17 can be found quite easily, and similar and simultaneously
to its apparent neighbor, M16. The first way to find it is locating the white giant star Gamma
Scuti, of magnitude 4.70 and spectral type A2 III, e.g. from Altair (Alpha Aquilae) via Delta and Lambda Aql; M16 is slightly
more than 2 degrees to the southwest of this star. Alternatively, in particular with a pair of binoculars, locate star cloud
M24 and move northward via a pair of stars of 6th and 7th mag in the north-eastern edge of M24,
followed by small open cluster M18 1deg north, and M17 another 1deg to the north.
M27 taken September 2nd, 2003 @ f3. Six-20 second exposures stacked.
Discovered on July 12, 1764 by Charles Messier.
- "Nebula without star, discovered in Vulpecula, between the two forepaws, & very near the star 14 of that constellation,
of 5th magnitude according to Flamsteed; one can see it well with an ordinary telescope of 3.5-foot [FL]; it appears of oval
shape, & it contains no star. M. Messier has reported its position on the chart of the Comet of 1779, which was engraved
for the volume of the Academy of the same year. Observed again January 31, 1781." (diam. 4')
Mars taken August 15th, 2003 @ f20. Again, the 1004X is too sensitive for imaging
planets. In this image the scope was stopped down to 50mm and a 96% filter was added with poor results.
M51 taken June 3rd 2003 @ f3. Ten-20 second exposures stacked.
The famous Whirlpool galaxy M51 was one of Charles Messier's
original discoveries: He discovered it on October 13, 1773, when observing a comet, and describe it
as a "very faint nebula, without stars" which is difficult to see. Its companion, NGC 5195, was
discovered in 1781 by his friend, Pierre Méchain, so that it is mentioned in
Messier's 1784 catalog: `It is double, each has a bright center, which are separated 4'35". The two "atmospheres" touch
each other, the one is even fainter than the other.' NGC 5195 was assigned an own number by William Herschel:
Occasionally, there is some confusion what is meant with the designation
M51: The pair (justified by Messier's mention of both "nebulae") or the larger galaxy, NGC 5194. If the pair is meant, NGC
5194 is sometimes called "M51A", and NGC 5195 is then "M51B".
M51 is the dominating member of a small group of galaxies.
As it is about 37 million light years distant and so conspicuous, it is actually a big and luminous galaxy. The value of M51's
(and the whole group's) distance is still not very well known. Our value, of 37 Mly, is based on photometric methods and e.g.
given by Kenneth Glyn Jones. Some authors give significantly lower values (less than 20 Mly), but a recent (2001) STScI Press
Release gave 31 million light years.
This galaxy was the first one where the spiral structure was discovered, in spring
1845 by Lord Rosse, who made a very careful and acurate painting. Therefore, M51 is sometimes referenced
as Rosse's Galaxy or Lord Rosse's "Question Mark" - he is cited with this name (see, e.g., NED).
According to our present understanding, the pronounced spiral structure is a result
of M51's current encounter with its neighbor, NGC 5195 (the fainter one in Messier's description). Due to this interaction,
the gas in the galaxy was disturbed and compressed in some regions, resulting in the formation of new young stars. As is common
in galactic encounters, spiral structure is preferably induced in the more massive galaxy. Halton Arp has included M51 as
No. 85 in his Catalogue of Peculiar Galaxies as "Spiral with Large High-Surface-Brightness Companion".
For the amateur, M51 is easy and a showpiece if the sky is dark, but is quite sensitive
for light pollution which easily makes it fade in the background. Under very good conditions, even suggestions of its spiral
arms can be glanced with telescopes starting from 4-inch. Low magnification is best for viewing this pair.
M106 taken June 3rd 2003 @ f3. Ten-20 second exposures stacked.
Discovered by Pierre Méchain in July 1781.
Independently rediscovered by William
Herschel on March 9, 1788.
M104 taken June 3rd, 2003 @ f3. Eight-15 second exposures stacked.
M104 is numerically the first object of the catalog which was not included in Messier's
originally published catalog. However, Charles Messier added it by hand to his personal copy on
May 11, 1781, and described it as a "very faint nebula." It was Camille Flammarion
who found that its position coincided with Herschel's H I.43, which is the Sombrero Galaxy (NGC 4594), and added
it to the official Messier list in 1921. This object is also mentioned by Pierre Méchain
as his discovery in his letter of May 6, 1783. William Herschel found
this object independently on May 9, 1784.
This brilliant galaxy was named the Sombrero Galaxy because of its appearance. According
to de Vaucouleurs, we view it from just 6 degrees south of its equatorial plane, which is outlined by a rather thick dark
rim of obscuring dust. This dust lane was probably the first discovered, by William Herschel in his great reflector.
This galaxy is of type Sa-Sb, with both a big bright core, and as one can see in
shorter exposures, also well-defined spiral arms. It also has an unusually pronounced bulge with an extended and richly populated
globular cluster system - several hundred can be counted in long exposures from big telescopes.
Recent very deep photographs from the Anglo-Australian Observatory show that this
galaxy has a very extended faint halo.
This galaxy was the first one with a large redshift found, by Vesto M. Slipher at
Lowell Observatory in 1912. Its redshift corresponds to a recession velocity of about 1,000 km/sec (it is caused by the Hubble
effect, i.e. the cosmic expansion). This was too fast for the Sombrero to be an object in our Milky Way galaxy. Slipher also
detected the galaxy's (then the nebula's) rotation.
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from the Cedar Glen Observatory