What happened when the comet swept past Mars

Animated GIF showing the comet belting past Mars on October 19, one frame every 17 seconds, from the High Resolution Stereo Camera (HRSC) on ESA’s Mars Express. Resolution is 17 km / 11 miles. Bright star at top might be the dying orange giant star Arcturus. From Mars, the comet appeared to pass close to this star. Image via ESA Mars Express/HRSC/DLR/FU Berlin.

On October 19, 2014, Comet C/2013A1 Siding Spring passed only 140,000 kilometers / 87,000 miles of Mars, closer than any known comet in recorded history. It was moving at a speed of 203,000 kilometers / 126,000 miles per hour. At closest approach, the comet swept over the predawn side of Mars after passing over the day side. The comet is orbiting the sun in the opposite direction to the planets in our solar system. It’s making its first foray into the inner solar system after a seven-million-year journey from the postulated Oort Cloud, some one-light year from the sun. There were observations from the surface of Mars, and from orbit. There is a potential twist to this story, with this comet potentially even more remarkable than first suspected. Plus there was a meteor shower as seen from Mars’ surface. All of this is described below.

The several spacecraft now orbiting Mars were not designed to study passing comets. Yet they all observed the comet around closest approach, with the orbiters all ‘taking cover’ over the opposite side of Mars when the coma and the tail of the comet swiped Mars.

That’s how we know that Mars was indeed enveloped by the huge coma of this tiny comet. That was one of the first results. Mars was, for a short period, totally enveloped by the outer coma.

These two infrared images were taken of Comet Siding Spring by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) camera on NASA’s Mars Reconnaissance Orbiter. CRISM used all 107 infrared channels to image the comet; in these images three color channels were used. The images yielded information about the comet’s inner and outer coma. Image via NASA/JPL-Caltech/JHUAPL/CRISM.

A fully resolved image of Comet Siding Spring nucleus in crescent phase as seen by MRO HiRISE. This image is a screen dump from a video of a NASA broadcast. Image via NASA/JPL/University of Arizona.

This image of comet C/2013 A1 Siding Spring was taken by NASA’s Mars Atmosphere and Volatile EvolutioN / MAVEN spacecraft, from a distance of 8.5 million kilometers / 5.3 million miles, two days before the comet’s close flyby of Mars and the spacecraft. This is an ultraviolet hydrogen image showing the hydrogen distribution within the coma. Image via NASA / UoC / LASP. Mars Atmosphere and Volatile EvolutioN / MAVEN spacecraft

Potential twist to the story of the nature of the comet. Comet C/2013A1 Siding Spring approached the solar system from the direction in our sky of constellation Lepus the Hare, near the border with the constellation Columba the Dove.

As our solar system orbits the center of the Milky Way once every 250 million years at a speed of approximately 829,000 kph / 515,000 mph (230 kps / 143 mps), we are traveling towards a point in the constellation Hercules, near the constellation Lyra the Lyre. That point is called the Solar Apex by astronomers.

The opposite point in Columba the Dove is called the Solar Antapex.

Comet C/2013A1 Siding Spring approached the solar system from a point very close to the north of the Antapex, and at a speed and direction which meant the comet overtook the solar system.

Those facts raise questions. Is indeed Comet C/2013A1 Siding Spring from the Oort Cloud? Or might it be an interstellar object ejected from another solar system entirely? The official line is that this is still an Oort Cloud comet, but the trajectory and speed of the comet remain too interesting to ignore.

Meteor shower as seen from Mars’ surface. As mentioned earlier, Mars was completely enveloped in the coma of Comet Siding Spring for a short period. The NASA Mars Reconnaissance Orbiter and MAVEN spacecraft along with the ESA Mars Express all observed a huge rise in the mineral content of the upper atmosphere on Mars as Mars experienced the mother of all meteor showers.

Comet C/2013A1 Siding Spring delivered in particular large quantities of sodium, magnesium, potassium, chromium, manganese, iron, nickel and zinc to the atmosphere of Mars.

Levels over a 24-hour period dropped back to normal as the heavy particles settled out. These observations represent the first every direct chemical measurements of an Oort Cloud comet by spacecraft.

Comet Siding Spring seen by Mars MER B Opportunity at the Meridiani Planum on Mars. Image via NASA.

Comet Siding Spring, under a dark sky at around the beginning of Martian morning twilight. At this time, the comet appeared among the stars of the constellation of Cetus the Sea Monster. Image via NASA’s Opportunity rover on Mars.

Comet Siding Spring is a fuzzy streak to the upper right of the bright streak, as captured by the MastCam on the Mars Science Laboratory Curiosity, at the Gale Crater on Mars. Image via NASA.

On the surface of Mars … two Mars rover – the veteran Mars Exploration Rover Opportunity and the Mars Science Laboratory Curiosity – both observed Comet C/2013A1 Siding Spring. These rovers are located at the Meridiani Planum and Gale Crater, respectively.

Opportunity had the best views as was able to observe the comet under a very dark sky at around the beginning of martian morning twilight with the comet among the stars of the constellation of Cetus the Sea Monster. See images above.

Curiosity has a vastly more difficult job as from Gale Crater. The speed of the comet meant that the comet was visible only under a much brighter sky. But MSL Curiosity was still successful in observations. See image above.

Early images from High Resolution Imaging Science Experiment (HiRISE) camera on NASA’s Mars Reconnaissance Orbiter.

The High Resolution Imaging Science Experiment (HiRISE) camera on NASA’s Mars Reconnaissance Orbiter captured views of comet C/2013 A1 Siding Spring while that visitor sped past Mars. The images are the highest-resolution views ever acquired of a comet coming from the Oort Cloud at the fringes of the solar system (or possible interstellar comet). The comet’s nucleus turned out to be tiny, barely 400 meters wide. The two sets of images were taken nine minutes apart. Top set the actual nucleus, bottom set including the inner coma. Image via NASA/JPL-Caltech/University of Arizona. HiRISE.

From the Indian Mangalyaan Mars Orbiter Mission (MOM) Mars Color Camera. Via ISRO.

Back in Mars orbit … the Mars orbiter Mars Reconnaissance Orbiter using the hugely powerful HiRISE (High Resolution Imaging Science Experiment) observed the comet prior to the spacecraft’s duck behind Mars. In this way, it actually imaged the nucleus of the comet, the very first time that a nucleus of an Oort Cloud comet has been seen.

The nucleus turned out to be smaller than expected. It turned out to have a maximum diameter of only 400 meters.

The observations using the HiRISE camera had been going on for several days leading up to closest approach and not only was the nucleus seen, but also the comet’s rotational period on its axis was detected to be nearly eight hours.

The shape of the nucleus using light curves as well as the images was determined to be roughly spherical.

Unlike other Kuiper Belt comets in short period orbits seen up close and even recently landed on which are dark as the carbon rich surface ices have become mostly dust, this comet was very bright, reflecting over 80% of the light that hits it. The CRISM (Compact Reconnaissance Imaging Spectrometer for Mars) also onboard the Mars Reconnaissance Orbiter imaged the comet in all 107 infrared channels and these confirm the elements that led to the temporary enrichment of the Martian atmosphere by detecting the same elements in the comet’s inner coma. CRISM could not image the nucleus as the field of view is wider.

The Indian Space Research Organisation Mangalyaan spacecraft also got some nice observations with the Mars Colour Camera monitoring the activity levels in the inner coma, before joining the NASA and ESA orbiters to duck behind Mars.

Bottom line: It took many weeks for the story of Comet Siding Spring’s close pass of Mars to emerge. Dazzling spacecraft imagery never came. Still, the images are fascinating, and the story of Comet Siding Spring’s exceedingly close pass of Mars might surprise you. See the images, and read the story, here.

from EarthSky http://ift.tt/1rMWdSj

Animated GIF showing the comet belting past Mars on October 19, one frame every 17 seconds, from the High Resolution Stereo Camera (HRSC) on ESA’s Mars Express. Resolution is 17 km / 11 miles. Bright star at top might be the dying orange giant star Arcturus. From Mars, the comet appeared to pass close to this star. Image via ESA Mars Express/HRSC/DLR/FU Berlin.

On October 19, 2014, Comet C/2013A1 Siding Spring passed only 140,000 kilometers / 87,000 miles of Mars, closer than any known comet in recorded history. It was moving at a speed of 203,000 kilometers / 126,000 miles per hour. At closest approach, the comet swept over the predawn side of Mars after passing over the day side. The comet is orbiting the sun in the opposite direction to the planets in our solar system. It’s making its first foray into the inner solar system after a seven-million-year journey from the postulated Oort Cloud, some one-light year from the sun. There were observations from the surface of Mars, and from orbit. There is a potential twist to this story, with this comet potentially even more remarkable than first suspected. Plus there was a meteor shower as seen from Mars’ surface. All of this is described below.

The several spacecraft now orbiting Mars were not designed to study passing comets. Yet they all observed the comet around closest approach, with the orbiters all ‘taking cover’ over the opposite side of Mars when the coma and the tail of the comet swiped Mars.

That’s how we know that Mars was indeed enveloped by the huge coma of this tiny comet. That was one of the first results. Mars was, for a short period, totally enveloped by the outer coma.

These two infrared images were taken of Comet Siding Spring by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) camera on NASA’s Mars Reconnaissance Orbiter. CRISM used all 107 infrared channels to image the comet; in these images three color channels were used. The images yielded information about the comet’s inner and outer coma. Image via NASA/JPL-Caltech/JHUAPL/CRISM.

A fully resolved image of Comet Siding Spring nucleus in crescent phase as seen by MRO HiRISE. This image is a screen dump from a video of a NASA broadcast. Image via NASA/JPL/University of Arizona.

This image of comet C/2013 A1 Siding Spring was taken by NASA’s Mars Atmosphere and Volatile EvolutioN / MAVEN spacecraft, from a distance of 8.5 million kilometers / 5.3 million miles, two days before the comet’s close flyby of Mars and the spacecraft. This is an ultraviolet hydrogen image showing the hydrogen distribution within the coma. Image via NASA / UoC / LASP. Mars Atmosphere and Volatile EvolutioN / MAVEN spacecraft

Potential twist to the story of the nature of the comet. Comet C/2013A1 Siding Spring approached the solar system from the direction in our sky of constellation Lepus the Hare, near the border with the constellation Columba the Dove.

As our solar system orbits the center of the Milky Way once every 250 million years at a speed of approximately 829,000 kph / 515,000 mph (230 kps / 143 mps), we are traveling towards a point in the constellation Hercules, near the constellation Lyra the Lyre. That point is called the Solar Apex by astronomers.

The opposite point in Columba the Dove is called the Solar Antapex.

Comet C/2013A1 Siding Spring approached the solar system from a point very close to the north of the Antapex, and at a speed and direction which meant the comet overtook the solar system.

Those facts raise questions. Is indeed Comet C/2013A1 Siding Spring from the Oort Cloud? Or might it be an interstellar object ejected from another solar system entirely? The official line is that this is still an Oort Cloud comet, but the trajectory and speed of the comet remain too interesting to ignore.

Meteor shower as seen from Mars’ surface. As mentioned earlier, Mars was completely enveloped in the coma of Comet Siding Spring for a short period. The NASA Mars Reconnaissance Orbiter and MAVEN spacecraft along with the ESA Mars Express all observed a huge rise in the mineral content of the upper atmosphere on Mars as Mars experienced the mother of all meteor showers.

Comet C/2013A1 Siding Spring delivered in particular large quantities of sodium, magnesium, potassium, chromium, manganese, iron, nickel and zinc to the atmosphere of Mars.

Levels over a 24-hour period dropped back to normal as the heavy particles settled out. These observations represent the first every direct chemical measurements of an Oort Cloud comet by spacecraft.

Comet Siding Spring seen by Mars MER B Opportunity at the Meridiani Planum on Mars. Image via NASA.

Comet Siding Spring, under a dark sky at around the beginning of Martian morning twilight. At this time, the comet appeared among the stars of the constellation of Cetus the Sea Monster. Image via NASA’s Opportunity rover on Mars.

Comet Siding Spring is a fuzzy streak to the upper right of the bright streak, as captured by the MastCam on the Mars Science Laboratory Curiosity, at the Gale Crater on Mars. Image via NASA.

On the surface of Mars … two Mars rover – the veteran Mars Exploration Rover Opportunity and the Mars Science Laboratory Curiosity – both observed Comet C/2013A1 Siding Spring. These rovers are located at the Meridiani Planum and Gale Crater, respectively.

Opportunity had the best views as was able to observe the comet under a very dark sky at around the beginning of martian morning twilight with the comet among the stars of the constellation of Cetus the Sea Monster. See images above.

Curiosity has a vastly more difficult job as from Gale Crater. The speed of the comet meant that the comet was visible only under a much brighter sky. But MSL Curiosity was still successful in observations. See image above.

Early images from High Resolution Imaging Science Experiment (HiRISE) camera on NASA’s Mars Reconnaissance Orbiter.

The High Resolution Imaging Science Experiment (HiRISE) camera on NASA’s Mars Reconnaissance Orbiter captured views of comet C/2013 A1 Siding Spring while that visitor sped past Mars. The images are the highest-resolution views ever acquired of a comet coming from the Oort Cloud at the fringes of the solar system (or possible interstellar comet). The comet’s nucleus turned out to be tiny, barely 400 meters wide. The two sets of images were taken nine minutes apart. Top set the actual nucleus, bottom set including the inner coma. Image via NASA/JPL-Caltech/University of Arizona. HiRISE.

From the Indian Mangalyaan Mars Orbiter Mission (MOM) Mars Color Camera. Via ISRO.

Back in Mars orbit … the Mars orbiter Mars Reconnaissance Orbiter using the hugely powerful HiRISE (High Resolution Imaging Science Experiment) observed the comet prior to the spacecraft’s duck behind Mars. In this way, it actually imaged the nucleus of the comet, the very first time that a nucleus of an Oort Cloud comet has been seen.

The nucleus turned out to be smaller than expected. It turned out to have a maximum diameter of only 400 meters.

The observations using the HiRISE camera had been going on for several days leading up to closest approach and not only was the nucleus seen, but also the comet’s rotational period on its axis was detected to be nearly eight hours.

The shape of the nucleus using light curves as well as the images was determined to be roughly spherical.

Unlike other Kuiper Belt comets in short period orbits seen up close and even recently landed on which are dark as the carbon rich surface ices have become mostly dust, this comet was very bright, reflecting over 80% of the light that hits it. The CRISM (Compact Reconnaissance Imaging Spectrometer for Mars) also onboard the Mars Reconnaissance Orbiter imaged the comet in all 107 infrared channels and these confirm the elements that led to the temporary enrichment of the Martian atmosphere by detecting the same elements in the comet’s inner coma. CRISM could not image the nucleus as the field of view is wider.

The Indian Space Research Organisation Mangalyaan spacecraft also got some nice observations with the Mars Colour Camera monitoring the activity levels in the inner coma, before joining the NASA and ESA orbiters to duck behind Mars.

Bottom line: It took many weeks for the story of Comet Siding Spring’s close pass of Mars to emerge. Dazzling spacecraft imagery never came. Still, the images are fascinating, and the story of Comet Siding Spring’s exceedingly close pass of Mars might surprise you. See the images, and read the story, here.

from EarthSky http://ift.tt/1rMWdSj

What’s the birthstone for December?

December has two birthstones, turquoise and zircon.

Turquoise

Turquoise is considered by some to be a symbol of good fortune and success, believed to bring prosperity to its wearer.

In the language of chemists and geologists, turquoise is known as “copper aluminum phosphate.” Turquoise is often found in weathered igneous rock that contains copper minerals, where it crystallizes in veins and nodules. The gemstone usually develops in rock near water tables, located in semiarid and arid environments. The chemicals in turquoise come from adjacent rock, leached out by rain and groundwater.

Turquoise is a relatively soft gemstone, and can be easily scratched and broken. This porous opaque stone is easily discolored by oil and pigments, and changes color when it loses some of its water content. A sky blue shade in turquoise is due to the presence of copper, while iron gives it a greener tone. Ochre and brown-black veins in the stone occur during the formation of turquoise, caused by inclusions from nearby rock fragments or from oxide staining. The most valued variety of turquoise is an intense sky blue color, like the color of a robin’s egg. Hard, relatively non-porous compact stones have the best appearance because the stone can be finely polished. Pale and chalky varieties however are sometimes impregnated with oil, paraffin, liquid plastic and glycerin to give it a good polish.

This stone can be found in Armenia, Kazakhstan, China, Australia, Tibet, China, Mexico, Brazil, and Egypt. In Iran, where some of the best stones are found, turquoise is the national gem. The American southwest-Nevada, Arizona, Colorado, New Mexico and California-are primary producers of turquoise. Much of the specimens have a light color, and are porous and chalky-only about 10% is of gem quality.

Its name is believed to originate from the French phrase “pierre turquoise” meaning “Turkish stone” because turquoise was brought to Europe by Venetian merchants who first acquired it in Turkish bazaars. It is also considered by some as a love charm. When received as a gift, the turquoise symbolizes a pledge of affection. Shakespeare used this lore in “The Merchant of Venice’. In it, Leah gave a turquoise ring to Shylock when he was a bachelor, hoping it would win his affections so he would ask her to marry him. In Russia, the turquoise is popularly used in wedding rings.

Turquoise is one of the earliest known stones to be used in jewelry. Pharaohs of Early Egypt wore them. A tomb excavated in 1900 contained the mummified remains of Queen Zer, who ruled in 5500 B.C.; found on her arm were four magnificent turquoise bracelets. Beads dating back to 5000 B.C. have been found in Mesopotamia (now Iraq). In Iran, turquoise was the national gemstone, adorning thrones, daggers, sword hilts, horse trappings, bowls, cups, and ornamental objects. Senior officials wore turquoise seals decorated with pearls and rubies. In the 7th century A.D., turquoise pieces inscribed with passages from the Koran and Persian proverbs were valued amulets. It was used as jewelry in ancient Siberia, around the Fifth and Sixth century B.C. During the Middle Ages, they were popularly used as decoration of vessels and covers for manuscripts. And it was again popular as jewelry during the Renaissance. It has also been found in ancient burial sites in Argentina, Bolivia, Chile, Peru, Mexico and Central America. The Incas crafted beads and figurines out of it, and the Aztecs made pendants and ritual masks.

Turquoise has a rich history in the American southwest. Native Americans have been using this gemstone to create magnificent jewelry and ornamental pieces for the past several thousand years. It was called “Chal-cui-hui-tal”, meaning “the highest and most valued thing in the world”. The Zuni, Hopi, Pueblo and Navajo Indians made magnificent necklaces, ear pendants and rings. The blue in turquoise symbolized the Heavens, and green symbolized the Earth. The stones were used by medicine men to work charms. The Navajo believed that turquoise pieces, thrown into a river while offering a prayer to the rain god, would bring much needed rain. Apache lore held that a turquoise attached to a bow or gun would ensure accurate aim.

There are many superstitions associated with the turquoise. In the Third century, it was believed to protect its owner from falling off a horse. A change in color revealed the infidelity of a wife. Twelfth century Arabian writings said “The turquoise shines when the air is pure and becomes pale when it is dim.” They also believed that its color changed with the weather. Persians said that the reflection of the new moon on a turquoise stone brought good luck, and guarded against evil. It was said to have a healing effect on the eye-merely looking at it strengthened the eye, while placing it on an inflamed eye brought a cure. A 15th century philosopher attributed its change of color to its ability to attract poisons. It was a barometer of its user’s health, turning pale in illness and losing color in death, yet regaining its original beauty in the hands of a new and healthy owner.

Photo credit: Rob Lavinsky

Zircon

The alternate birthstone for December is the zircon.

Zircon, in its unchanged natural form appears colorless to pale yellow, or green. These colors are caused by minute quantities of thorium and uranium that replaces zircon in the crystal structure. But over the vast spans of geologic time, other forces work within the zirconium silicate crystals. The uranium and thorium inclusions emit radiation that alters the original crystal structure. A glass-like material is formed, with colors of red to brown, orange and yellow.

The mineral zircon, known as zirconium silicate, is commonly found as a minor constituent in igneous rock such as granites and some kinds of metamorphic rock. Gem quality zircon stones are usually rare. These gemstones are formed mainly in pegmatites (coarse-grained igneous rock) and in fissures. But due to weathering of the gem-bearing rocks, most zircons are found in alluvial and beach deposits.

A new blue color for zircon, called “starlight blue,” was created by heating golden brown or yellow zircon in the 1920s. From Gems and Crystals by Anna S. Sofianides and George E. Harlow:

In the 1920s, a new blue gemstone suddenly appeared in the market. Endowed with spectacular brilliance, it was an immediate hit.

The gems were zircons, normally brown to green – but not blue. George F. Kunz, the legendary Tiffany gemologist, immediately suspected trickery; not only were there extraordinary stones available in abundance but available all over the world! Upon Kunz’s behest, a colleague made inquiries during a trip to Siam (Thailand) and learned that a large deposit of unattractive brown zircon had stimulated color- improvement experimentation by local entrepreneurs. Heating in an oxygen-free environment had turned the drab material into “new” blue stones, which were sent to outlets worldwide. When the deception was revealed, the market simply accepted the information, and the demand for the new gems continued unabated.

The most prized zircon is the red gemstone, which is rare. The pure intense blue and sky blue varieties are also highly valued, while the colorless, orange, brown and yellow stones are less expensive. Many zircons on the market are heat treated, and sold as blue, golden brown or colorless stones. Colorless zircons are the best imitators of diamonds, in appearance only, with a brilliant fire that is almost as dazzling as the real thing. However, the resemblance is superficial. Zircon is a brittle stone, easily broken with a well-placed knock, due to internal stresses in the crystal caused by radiation damage and heat treatment. But despite its frail disposition, the stone is still highly valued because of its stunning beauty.

Major sources of zircon are the Chanthaburi area of Thailand, the Palin area of Cambodia and the southern part of Vietnam near the Cambodian border, where gemstones are found in alluvial deposits. Bangkok is well-known as a major center for processing zircons, where everything from heat treatment, cutting and marketing is carried out. Another important source is Sri Lanka, well known for a colorless variety of zircon called the ‘Matura diamond’. The gemstones are also found in Burma, France, Norway, Australia and Canada.

Its name is probably derived from the Arabic words “zar” and “gun”, meaning “gold” and “color”. The gemstone is found in a wide range of colors, and possess great brilliance, fire and clarity.

The hyacinth and jacinth, reddish-brown and orange-red varieties of zircon, were a favorite stone of ancient Arabs and was even mentioned in the famed book, ‘Arabian Nights’.

Green zircon was among the stones of the ‘Kalpa Tree’ of the Hindu religion, where it represented the tree’s foliage. This tree was a symbolic offering to the gods. Hindu poets of the 19th century described it as a glowing ensemble of precious stones that also included sapphires, diamonds and topaz.

Zircon was regarded as the amulet for travelers in the Eleventh century, protecting them from disease, injury, and insomnia, as well as assuring a cordial welcome wherever their travels would take them. The gem was also believed to hold magic powers to fight evil spirits. During the Fourteenth century, zircon was popular as a safeguard against the Black Death, the great plague that wiped out one quarter of the population of Europe. The stone was believed to possess healing powers. It was prescribed to insomniacs to induce sleep, used as an antidote against poison, and as an aid to digestion.

December’s birthstones are turquoise and zircon. Find out about the birthstones for all the months of the year:

January birthstone

February birthstone

March birthstone

April birthstone

May birthstone

June birthstone

July birthstone

August birthstone

September birthstone

October birthstone

November birthstone

December birthstone

from EarthSky http://ift.tt/1i0E2Cp

December has two birthstones, turquoise and zircon.

Turquoise

Turquoise is considered by some to be a symbol of good fortune and success, believed to bring prosperity to its wearer.

In the language of chemists and geologists, turquoise is known as “copper aluminum phosphate.” Turquoise is often found in weathered igneous rock that contains copper minerals, where it crystallizes in veins and nodules. The gemstone usually develops in rock near water tables, located in semiarid and arid environments. The chemicals in turquoise come from adjacent rock, leached out by rain and groundwater.

Turquoise is a relatively soft gemstone, and can be easily scratched and broken. This porous opaque stone is easily discolored by oil and pigments, and changes color when it loses some of its water content. A sky blue shade in turquoise is due to the presence of copper, while iron gives it a greener tone. Ochre and brown-black veins in the stone occur during the formation of turquoise, caused by inclusions from nearby rock fragments or from oxide staining. The most valued variety of turquoise is an intense sky blue color, like the color of a robin’s egg. Hard, relatively non-porous compact stones have the best appearance because the stone can be finely polished. Pale and chalky varieties however are sometimes impregnated with oil, paraffin, liquid plastic and glycerin to give it a good polish.

This stone can be found in Armenia, Kazakhstan, China, Australia, Tibet, China, Mexico, Brazil, and Egypt. In Iran, where some of the best stones are found, turquoise is the national gem. The American southwest-Nevada, Arizona, Colorado, New Mexico and California-are primary producers of turquoise. Much of the specimens have a light color, and are porous and chalky-only about 10% is of gem quality.

Its name is believed to originate from the French phrase “pierre turquoise” meaning “Turkish stone” because turquoise was brought to Europe by Venetian merchants who first acquired it in Turkish bazaars. It is also considered by some as a love charm. When received as a gift, the turquoise symbolizes a pledge of affection. Shakespeare used this lore in “The Merchant of Venice’. In it, Leah gave a turquoise ring to Shylock when he was a bachelor, hoping it would win his affections so he would ask her to marry him. In Russia, the turquoise is popularly used in wedding rings.

Turquoise is one of the earliest known stones to be used in jewelry. Pharaohs of Early Egypt wore them. A tomb excavated in 1900 contained the mummified remains of Queen Zer, who ruled in 5500 B.C.; found on her arm were four magnificent turquoise bracelets. Beads dating back to 5000 B.C. have been found in Mesopotamia (now Iraq). In Iran, turquoise was the national gemstone, adorning thrones, daggers, sword hilts, horse trappings, bowls, cups, and ornamental objects. Senior officials wore turquoise seals decorated with pearls and rubies. In the 7th century A.D., turquoise pieces inscribed with passages from the Koran and Persian proverbs were valued amulets. It was used as jewelry in ancient Siberia, around the Fifth and Sixth century B.C. During the Middle Ages, they were popularly used as decoration of vessels and covers for manuscripts. And it was again popular as jewelry during the Renaissance. It has also been found in ancient burial sites in Argentina, Bolivia, Chile, Peru, Mexico and Central America. The Incas crafted beads and figurines out of it, and the Aztecs made pendants and ritual masks.

Turquoise has a rich history in the American southwest. Native Americans have been using this gemstone to create magnificent jewelry and ornamental pieces for the past several thousand years. It was called “Chal-cui-hui-tal”, meaning “the highest and most valued thing in the world”. The Zuni, Hopi, Pueblo and Navajo Indians made magnificent necklaces, ear pendants and rings. The blue in turquoise symbolized the Heavens, and green symbolized the Earth. The stones were used by medicine men to work charms. The Navajo believed that turquoise pieces, thrown into a river while offering a prayer to the rain god, would bring much needed rain. Apache lore held that a turquoise attached to a bow or gun would ensure accurate aim.

There are many superstitions associated with the turquoise. In the Third century, it was believed to protect its owner from falling off a horse. A change in color revealed the infidelity of a wife. Twelfth century Arabian writings said “The turquoise shines when the air is pure and becomes pale when it is dim.” They also believed that its color changed with the weather. Persians said that the reflection of the new moon on a turquoise stone brought good luck, and guarded against evil. It was said to have a healing effect on the eye-merely looking at it strengthened the eye, while placing it on an inflamed eye brought a cure. A 15th century philosopher attributed its change of color to its ability to attract poisons. It was a barometer of its user’s health, turning pale in illness and losing color in death, yet regaining its original beauty in the hands of a new and healthy owner.

Photo credit: Rob Lavinsky

Zircon

The alternate birthstone for December is the zircon.

Zircon, in its unchanged natural form appears colorless to pale yellow, or green. These colors are caused by minute quantities of thorium and uranium that replaces zircon in the crystal structure. But over the vast spans of geologic time, other forces work within the zirconium silicate crystals. The uranium and thorium inclusions emit radiation that alters the original crystal structure. A glass-like material is formed, with colors of red to brown, orange and yellow.

The mineral zircon, known as zirconium silicate, is commonly found as a minor constituent in igneous rock such as granites and some kinds of metamorphic rock. Gem quality zircon stones are usually rare. These gemstones are formed mainly in pegmatites (coarse-grained igneous rock) and in fissures. But due to weathering of the gem-bearing rocks, most zircons are found in alluvial and beach deposits.

A new blue color for zircon, called “starlight blue,” was created by heating golden brown or yellow zircon in the 1920s. From Gems and Crystals by Anna S. Sofianides and George E. Harlow:

In the 1920s, a new blue gemstone suddenly appeared in the market. Endowed with spectacular brilliance, it was an immediate hit.

The gems were zircons, normally brown to green – but not blue. George F. Kunz, the legendary Tiffany gemologist, immediately suspected trickery; not only were there extraordinary stones available in abundance but available all over the world! Upon Kunz’s behest, a colleague made inquiries during a trip to Siam (Thailand) and learned that a large deposit of unattractive brown zircon had stimulated color- improvement experimentation by local entrepreneurs. Heating in an oxygen-free environment had turned the drab material into “new” blue stones, which were sent to outlets worldwide. When the deception was revealed, the market simply accepted the information, and the demand for the new gems continued unabated.

The most prized zircon is the red gemstone, which is rare. The pure intense blue and sky blue varieties are also highly valued, while the colorless, orange, brown and yellow stones are less expensive. Many zircons on the market are heat treated, and sold as blue, golden brown or colorless stones. Colorless zircons are the best imitators of diamonds, in appearance only, with a brilliant fire that is almost as dazzling as the real thing. However, the resemblance is superficial. Zircon is a brittle stone, easily broken with a well-placed knock, due to internal stresses in the crystal caused by radiation damage and heat treatment. But despite its frail disposition, the stone is still highly valued because of its stunning beauty.

Major sources of zircon are the Chanthaburi area of Thailand, the Palin area of Cambodia and the southern part of Vietnam near the Cambodian border, where gemstones are found in alluvial deposits. Bangkok is well-known as a major center for processing zircons, where everything from heat treatment, cutting and marketing is carried out. Another important source is Sri Lanka, well known for a colorless variety of zircon called the ‘Matura diamond’. The gemstones are also found in Burma, France, Norway, Australia and Canada.

Its name is probably derived from the Arabic words “zar” and “gun”, meaning “gold” and “color”. The gemstone is found in a wide range of colors, and possess great brilliance, fire and clarity.

The hyacinth and jacinth, reddish-brown and orange-red varieties of zircon, were a favorite stone of ancient Arabs and was even mentioned in the famed book, ‘Arabian Nights’.

Green zircon was among the stones of the ‘Kalpa Tree’ of the Hindu religion, where it represented the tree’s foliage. This tree was a symbolic offering to the gods. Hindu poets of the 19th century described it as a glowing ensemble of precious stones that also included sapphires, diamonds and topaz.

Zircon was regarded as the amulet for travelers in the Eleventh century, protecting them from disease, injury, and insomnia, as well as assuring a cordial welcome wherever their travels would take them. The gem was also believed to hold magic powers to fight evil spirits. During the Fourteenth century, zircon was popular as a safeguard against the Black Death, the great plague that wiped out one quarter of the population of Europe. The stone was believed to possess healing powers. It was prescribed to insomniacs to induce sleep, used as an antidote against poison, and as an aid to digestion.

December’s birthstones are turquoise and zircon. Find out about the birthstones for all the months of the year:

January birthstone

February birthstone

March birthstone

April birthstone

May birthstone

June birthstone

July birthstone

August birthstone

September birthstone

October birthstone

November birthstone

December birthstone

from EarthSky http://ift.tt/1i0E2Cp

Night-shining cloud season begins in Antarctica

Noctilucent clouds over Antarctica as seen in November, 2014 by NASA’s AIM spacecraft.

We spotted this cool image at the great website Spaceweather.com on Thanksgiving weekend (November 27-30, 2014). The photo shows that NASA’s AIM spacecraft detected noctilucent clouds – sometimes called night-shining clouds – over Antarctica this November. That’s right on schedule. It’s summertime in the Southern Hemisphere now, and these clouds are typically seen at high latitudes in the summer. Their apparition marks the beginning of the 2014-2015 season in Earth’s Southern Hemisphere for these silver-blue clouds.

The secrets of night-shining clouds

from EarthSky http://ift.tt/1rL4jjS

Noctilucent clouds over Antarctica as seen in November, 2014 by NASA’s AIM spacecraft.

We spotted this cool image at the great website Spaceweather.com on Thanksgiving weekend (November 27-30, 2014). The photo shows that NASA’s AIM spacecraft detected noctilucent clouds – sometimes called night-shining clouds – over Antarctica this November. That’s right on schedule. It’s summertime in the Southern Hemisphere now, and these clouds are typically seen at high latitudes in the summer. Their apparition marks the beginning of the 2014-2015 season in Earth’s Southern Hemisphere for these silver-blue clouds.

The secrets of night-shining clouds

from EarthSky http://ift.tt/1rL4jjS

Cassiopeia high up in northern sky on December evenings

Tonight, let’s turn toward the northern sky and its famous constellation Cassiopeia the Queen. On December evenings, this constellation appears high in the northeast at nightfall as seen from latitudes in the Northern Hemisphere. Cassiopeia can also be seen from tropical and subtropical latitudes in the Southern Hemisphere, appearing low in the north at nightfall and early evening.

This constellation won’t look all that mighty in lunar glare on December 1, 2014. The waxing moon will wash the skies over the coming week. But starting on December 10, 2014 or so, moonless evenings will showcase Cassiopeia the Queen in all her starry splendor.

In early December, Cassiopeia swings directly over Polaris, the North Star, at around 8 p.m. local clock time. (You can’t see Polaris from temperate latitudes in the Southern Hemisphere because it’s below the horizon in that part of the world.) Cassiopeia – sometimes called The Lady of the Chair – is famous for having the shape of a telltale W or M. You will find this configuration of stars as a starlit M whenever she reigns highest in the sky, hovering over Polaris.

Because Cassiopeia returns to the same spot in the sky about four minutes earlier with each passing day, look for Cassiopeia to be at her high point over Polaris, the North Star, at about 7 p.m. local time in mid-December and 6 p.m. local time by the month’s end.

EarthSky’s lunar calendar: the perfect gift for any sky lover! On sale 50% off on Cyber Monday

The constellation Cassiopeia has the distinct shape of a W, or M, depending on the time of night you see it. This nice photo from EarthSky Facebook friend Mike O’Neal. Thank you, Mike! Click here to expand image.

From a dark country sky, you’ll see that Cassiopeia sits atop the luminous band of stars known as the Milky Way. Arching from horizon to horizon, this soft-glowing boulevard of stars represents an edgewise view into the flat disk of our own Milky Way galaxy. When Cassiopeia climbs above Polaris, the North Star, on these dark winter evenings, note that this hazy belt of stars that we call the Milky Way extends through the Northern Cross in the western sky and past Orion the Hunter in your eastern sky.

This Milky Way is fainter than the glorious broad band of the Milky Way we see in a Northern Hemisphere summer or Southern Hemisphere winter. That’s because in we are looking toward the star-rich center of the galaxy at the opposite side of the year. On these December nights, we are looking toward the galaxy’s outer edge, not the center.

The famous Double Cluster in the constellation Perseus is not far from Cassiopeia on the sky’s dome. This chart shows how to use the W or M shape of Cassiopeia to find the Double Cluster. To appreciate them fully, look with your binoculars in a dark sky! More about the Double Cluster here.

As the night marches onward, Cassiopeia – like the hour hand of a clock – circles around the North Star, though in a counter-clockwise direction.

By dawn, you will find Cassiopeia has swept down in the northwest – to a point below the North Star. At that time, if you’re at a southerly latitude, you might not be able to see Cassiopeia. The constellation might be below your horizon. But if you’re located at a latitude like those in the northern U.S., you will still see Cassiopeia sitting on or near your northern horizon.

Look northward on these cold December evenings to see the Queen Cassiopeia sitting proudly on her throne, atop the northern terminus of the Milky Way!

Bottom line: Watch for the constellation Cassiopeia the Queen on these December evenings. It is shaped like an M or W. You’ll find Cassiopeia in the northeast at nightfall, sweeping higher in the north as evening progresses.

A planisphere is virtually indispensable for beginning stargazers. Order your EarthSky Planisphere today!

from EarthSky http://ift.tt/1wa3Itg

Tonight, let’s turn toward the northern sky and its famous constellation Cassiopeia the Queen. On December evenings, this constellation appears high in the northeast at nightfall as seen from latitudes in the Northern Hemisphere. Cassiopeia can also be seen from tropical and subtropical latitudes in the Southern Hemisphere, appearing low in the north at nightfall and early evening.

This constellation won’t look all that mighty in lunar glare on December 1, 2014. The waxing moon will wash the skies over the coming week. But starting on December 10, 2014 or so, moonless evenings will showcase Cassiopeia the Queen in all her starry splendor.

In early December, Cassiopeia swings directly over Polaris, the North Star, at around 8 p.m. local clock time. (You can’t see Polaris from temperate latitudes in the Southern Hemisphere because it’s below the horizon in that part of the world.) Cassiopeia – sometimes called The Lady of the Chair – is famous for having the shape of a telltale W or M. You will find this configuration of stars as a starlit M whenever she reigns highest in the sky, hovering over Polaris.

Because Cassiopeia returns to the same spot in the sky about four minutes earlier with each passing day, look for Cassiopeia to be at her high point over Polaris, the North Star, at about 7 p.m. local time in mid-December and 6 p.m. local time by the month’s end.

EarthSky’s lunar calendar: the perfect gift for any sky lover! On sale 50% off on Cyber Monday

The constellation Cassiopeia has the distinct shape of a W, or M, depending on the time of night you see it. This nice photo from EarthSky Facebook friend Mike O’Neal. Thank you, Mike! Click here to expand image.

From a dark country sky, you’ll see that Cassiopeia sits atop the luminous band of stars known as the Milky Way. Arching from horizon to horizon, this soft-glowing boulevard of stars represents an edgewise view into the flat disk of our own Milky Way galaxy. When Cassiopeia climbs above Polaris, the North Star, on these dark winter evenings, note that this hazy belt of stars that we call the Milky Way extends through the Northern Cross in the western sky and past Orion the Hunter in your eastern sky.

This Milky Way is fainter than the glorious broad band of the Milky Way we see in a Northern Hemisphere summer or Southern Hemisphere winter. That’s because in we are looking toward the star-rich center of the galaxy at the opposite side of the year. On these December nights, we are looking toward the galaxy’s outer edge, not the center.

The famous Double Cluster in the constellation Perseus is not far from Cassiopeia on the sky’s dome. This chart shows how to use the W or M shape of Cassiopeia to find the Double Cluster. To appreciate them fully, look with your binoculars in a dark sky! More about the Double Cluster here.

As the night marches onward, Cassiopeia – like the hour hand of a clock – circles around the North Star, though in a counter-clockwise direction.

By dawn, you will find Cassiopeia has swept down in the northwest – to a point below the North Star. At that time, if you’re at a southerly latitude, you might not be able to see Cassiopeia. The constellation might be below your horizon. But if you’re located at a latitude like those in the northern U.S., you will still see Cassiopeia sitting on or near your northern horizon.

Look northward on these cold December evenings to see the Queen Cassiopeia sitting proudly on her throne, atop the northern terminus of the Milky Way!

Bottom line: Watch for the constellation Cassiopeia the Queen on these December evenings. It is shaped like an M or W. You’ll find Cassiopeia in the northeast at nightfall, sweeping higher in the north as evening progresses.

A planisphere is virtually indispensable for beginning stargazers. Order your EarthSky Planisphere today!

from EarthSky http://ift.tt/1wa3Itg

Bar-headed geese in India

Photo Credit: Abhinav Singhai. Visit his Flickr page

EarthSky Facebook friend Abhinav Singhai in India captured this evocative shot of bar-headed geese over Basai Wetlands, a well-known destination for birders near Delhi, India. He said there were hundreds of geese over the wetlands that day.

Thank you, Abhihav!

The bar-headed goose is a fascinating bird, by the way, and one of the world’s highest-flying birds. It’s been heard flying across Mount Makalu – the fifth highest mountain on Earth at 8,481 meters (27,825 ft). The British explorer George Lowe is said to have reported seeing bar-headed geese flying over Mount Everest – 8,848 meters (29,029 ft)! You’ll find mention of Lowe’s tale about the geese here.

According to Wikipedia, the bar-headed goose is:

… a goose that breeds in Central Asia in colonies of thousands near mountain lakes and winters in South Asia, as far south as peninsular India …

The bird is pale grey and is easily distinguished from any of the other grey geese of the genus Anser by the black bars on its head.

A Bar-headed Goose in St James’s Park, London, England. Photo by DAVID ILIFF. License: CC-BY-SA 3.0 via Wikipedia.

Bottom line: A beautiful shot of bar-headed geese flying over a wetlands in India in November 2014. Photo by Abhinav Singhai.

from EarthSky http://earthsky.org/todays-image/bar-headed-geese-in-india

Photo Credit: Abhinav Singhai. Visit his Flickr page

EarthSky Facebook friend Abhinav Singhai in India captured this evocative shot of bar-headed geese over Basai Wetlands, a well-known destination for birders near Delhi, India. He said there were hundreds of geese over the wetlands that day.

Thank you, Abhihav!

The bar-headed goose is a fascinating bird, by the way, and one of the world’s highest-flying birds. It’s been heard flying across Mount Makalu – the fifth highest mountain on Earth at 8,481 meters (27,825 ft). The British explorer George Lowe is said to have reported seeing bar-headed geese flying over Mount Everest – 8,848 meters (29,029 ft)! You’ll find mention of Lowe’s tale about the geese here.

According to Wikipedia, the bar-headed goose is:

… a goose that breeds in Central Asia in colonies of thousands near mountain lakes and winters in South Asia, as far south as peninsular India …

The bird is pale grey and is easily distinguished from any of the other grey geese of the genus Anser by the black bars on its head.

A Bar-headed Goose in St James’s Park, London, England. Photo by DAVID ILIFF. License: CC-BY-SA 3.0 via Wikipedia.

Bottom line: A beautiful shot of bar-headed geese flying over a wetlands in India in November 2014. Photo by Abhinav Singhai.

from EarthSky http://earthsky.org/todays-image/bar-headed-geese-in-india

Sun in constellation Ophiuchus November 30 to December 18

If you could see the stars during the daytime, you’d see the sun shining in front of the border of the constellations Ophiuchus and Scorpius today. At about this time each year, the sun passes out of Scorpius to enter Ophiuchus. Like Scorpius, Ophiuchus is a constellation of the Zodiac, and every year the sun passes in front of Ophiuchus from about November 29 until December 18.

This year, in 2014, the sun enters the constellation Ophiuchus on November 30, at 1:00 a.m. CST in the central U.S. By Universal Time, that’s 7:00 on November 30.

How do I translate Universal Time into my time?

You can’t see the constellation Ophiuchus when the sun lies in front of it. But, each Northern Hemisphere summer, you’ll find this constellation to the north of the bright star Antares in the constellation Scorpius.

Need the perfect gift? Check out these 2015 moon calendars.

The ecliptic – which translates on our sky’s dome as the sun’s annual path in front of the background stars – actually passes through 13 constellations, although this is not commonly known. After all, when you read the horoscope in the daily newspaper or a monthly magazine, you see only 12 constellations, or signs, mentioned. No one ever claims to be an Ophiuchus. There are the 12 traditional zodiacal constellations. But the sun passes through Ophiuchus as surely as it does the others.

Today’s constellation boundaries were drawn out by the International Astronomical Union in the 1930s.

Look at the chart carefully, and you’ll see that the border between Ophiuchus and the constellation Scorpius for the most part lies just south of, or below, the ecliptic. In ancient times, the Ophuichus-Scorpius border was likely placed to the north of, or above, the ecliptic. Had the International Astronomical Union placed its constellation boundary where the ancients might have, the sun’s annual passing in front of Scorpius would be from about November 23 till December 18, not November 23 to November 30.

Bottom line: As seen from Earth, the sun passes in front of the constellation Ophiuchus each year from about November 30 to December 18.

Birthday late November to middle December? Here’s your constellation

from EarthSky http://earthsky.org/tonight/sun-in-ophiuchus-november-30-to-december-18

If you could see the stars during the daytime, you’d see the sun shining in front of the border of the constellations Ophiuchus and Scorpius today. At about this time each year, the sun passes out of Scorpius to enter Ophiuchus. Like Scorpius, Ophiuchus is a constellation of the Zodiac, and every year the sun passes in front of Ophiuchus from about November 29 until December 18.

This year, in 2014, the sun enters the constellation Ophiuchus on November 30, at 1:00 a.m. CST in the central U.S. By Universal Time, that’s 7:00 on November 30.

How do I translate Universal Time into my time?

You can’t see the constellation Ophiuchus when the sun lies in front of it. But, each Northern Hemisphere summer, you’ll find this constellation to the north of the bright star Antares in the constellation Scorpius.

Need the perfect gift? Check out these 2015 moon calendars.

The ecliptic – which translates on our sky’s dome as the sun’s annual path in front of the background stars – actually passes through 13 constellations, although this is not commonly known. After all, when you read the horoscope in the daily newspaper or a monthly magazine, you see only 12 constellations, or signs, mentioned. No one ever claims to be an Ophiuchus. There are the 12 traditional zodiacal constellations. But the sun passes through Ophiuchus as surely as it does the others.

Today’s constellation boundaries were drawn out by the International Astronomical Union in the 1930s.

Look at the chart carefully, and you’ll see that the border between Ophiuchus and the constellation Scorpius for the most part lies just south of, or below, the ecliptic. In ancient times, the Ophuichus-Scorpius border was likely placed to the north of, or above, the ecliptic. Had the International Astronomical Union placed its constellation boundary where the ancients might have, the sun’s annual passing in front of Scorpius would be from about November 23 till December 18, not November 23 to November 30.

Bottom line: As seen from Earth, the sun passes in front of the constellation Ophiuchus each year from about November 30 to December 18.

Birthday late November to middle December? Here’s your constellation

from EarthSky http://earthsky.org/tonight/sun-in-ophiuchus-november-30-to-december-18

M33: Triangulum Galaxy

How to find it

Although long-exposure photographs show the Triangulum galaxy (Messier 33) as a pinwheel of swarming suns, this face-on spiral galaxy looks rather lackluster in binoculars or even the telescope. The Triangulum galaxy has a low surface brightness that makes this faint object a major challenge, with or without optics.

Have you ever seen the Great Andromeda Galaxy (Messier 31)? If not, try finding the Andromeda galaxy before you take on the Triangulum galaxy. Shining 8 to 9 times more brightly than the Triangulum galaxy, the Andromeda galaxy is the most distant object that you can easily see with the unaided eye. Fortunately, the Triangulum and Andromeda galaxies are a relatively close 15 degrees apart. (For reference, a fist-width at an arm length approximates 10 degrees.)

Star-hop to the Andromeda galaxy to orient yourself to the Triangulum galaxy. As seen on the sky chart, the star Mirach stands about midway between the two galaxies. Our Andromeda galaxy sky chart shows you how to star-hop to the Andromeda galaxy. Once you’ve found it, the Andromeda galaxy and Mirach point in the general direction of the Triangulum galaxy.

The constellation Triangulum

Learn the constellation Triangulum, the small triangle made of three rather faint yet visible stars. Look eastward on some autumn evening, placing the star Alpha Triangulum at about the “7 o’clock” position in your binoculars. The Triangulum galaxy appears at the opposite side of the binouclar field, somewhere around 1 or 2 o’clock.

Now for a word of warning: even if you’re staring right at the Triangulum galaxy, it’s still possible to miss it. You won’t see the galaxy’s stars at all. Sometimes, this galaxy looks almost transparent, like a water spot on a window. The small blob in your binocular field might resemble an unwashed spot on an otherwide clean window. If you’ve never seen this deep-sky object before, it’s hard to know what to look for. Once you finally spot the Triangulum galaxy, you may wonder how you overlooked it so easily so many times before.

Science

At a distance of about 2.7 million light-years, the Triangulum galaxy might be a satellite galaxy of the Andromeda galaxy. The diameter of the Triangulum galaxy is about 50,000 light-years, or about one-half that of our Milky Way. After the Milky Way and Andromeda galaxies, the Triangulum galaxy ranks as the third largest of the few dozen galaxies inhabiting our Local Group of Galaxies.

from EarthSky http://earthsky.org/clusters-nebulae-galaxies/triangulum-galaxy-m33-a-binocular-challenge

How to find it

Although long-exposure photographs show the Triangulum galaxy (Messier 33) as a pinwheel of swarming suns, this face-on spiral galaxy looks rather lackluster in binoculars or even the telescope. The Triangulum galaxy has a low surface brightness that makes this faint object a major challenge, with or without optics.

Have you ever seen the Great Andromeda Galaxy (Messier 31)? If not, try finding the Andromeda galaxy before you take on the Triangulum galaxy. Shining 8 to 9 times more brightly than the Triangulum galaxy, the Andromeda galaxy is the most distant object that you can easily see with the unaided eye. Fortunately, the Triangulum and Andromeda galaxies are a relatively close 15 degrees apart. (For reference, a fist-width at an arm length approximates 10 degrees.)

Star-hop to the Andromeda galaxy to orient yourself to the Triangulum galaxy. As seen on the sky chart, the star Mirach stands about midway between the two galaxies. Our Andromeda galaxy sky chart shows you how to star-hop to the Andromeda galaxy. Once you’ve found it, the Andromeda galaxy and Mirach point in the general direction of the Triangulum galaxy.

The constellation Triangulum

Learn the constellation Triangulum, the small triangle made of three rather faint yet visible stars. Look eastward on some autumn evening, placing the star Alpha Triangulum at about the “7 o’clock” position in your binoculars. The Triangulum galaxy appears at the opposite side of the binouclar field, somewhere around 1 or 2 o’clock.

Now for a word of warning: even if you’re staring right at the Triangulum galaxy, it’s still possible to miss it. You won’t see the galaxy’s stars at all. Sometimes, this galaxy looks almost transparent, like a water spot on a window. The small blob in your binocular field might resemble an unwashed spot on an otherwide clean window. If you’ve never seen this deep-sky object before, it’s hard to know what to look for. Once you finally spot the Triangulum galaxy, you may wonder how you overlooked it so easily so many times before.

Science

At a distance of about 2.7 million light-years, the Triangulum galaxy might be a satellite galaxy of the Andromeda galaxy. The diameter of the Triangulum galaxy is about 50,000 light-years, or about one-half that of our Milky Way. After the Milky Way and Andromeda galaxies, the Triangulum galaxy ranks as the third largest of the few dozen galaxies inhabiting our Local Group of Galaxies.

from EarthSky http://earthsky.org/clusters-nebulae-galaxies/triangulum-galaxy-m33-a-binocular-challenge