ASTRONOMICAL SOCIETY: OCTOBER 2012
                
       Weather permitting; we will meet on Thursday, 18th October, 6.30 p.m. at Pedro Castle.
If the sky is more than 50% cloud covered, we cancel. This can be, as you will appreciate, a sometimes difficult decision.
    Almost directly overhead at viewing time is the constellation Aquila.  Aquila lies just a few degrees north of the celestial equator and is located along the Milky Way. Because of this location along the line of our galaxy, many clusters and nebulae are found within its borders, but they are dim and there are few galaxies.
    Astronomers observed two major novae in Aquila, the first one being in 389 BC. It was recorded as brighter than the planet Venus. The second one was observed in the year 1918 (Nova Aquilae). It was brighter than Altair. A nova should not be confused with a supernova. A nova is an old star that brightens temporarily, and a supernova (dying star) is a massive star exploding.                                                      NASA’s Pioneer 11 mission will pass near one of constellation Aquila’s stars in about four million years.                                                                                                                                                  Altair (Alpha Aquila), the brightest star of the constellation, is a multiple star system. It is about eight times brighter than the sun and the twelfth brightest star in the night sky. It is an A-type main sequence star with an apparent visual magnitude of 0.77. Class A stars are among the more common naked eye stars, and are white or bluish-white. Other examples include Sirius, Deneb, Vega and Fomalhaut.  Altair is located 16.7 light-years (5.13 parsecs) from Earth and is one of the closest stars visible to the naked eye. Altair is a type-A main sequence star with approximately 1.8 times the mass of the Sun and 11 times its luminosity. Altair possesses an extremely rapid rate of rotation; it has a rotational period of approximately 9 hours. For comparison, the equator of the Sun requires just over 25 days for a complete

                  CAYMAN ISLANDS ASTRONOMICAL SOCIETY
                         NEWSLETTER; OCTOBER 2012
       Weather permitting; we will meet on Thursday, 18th October, 6.30 p.m. at Pedro Castle.
If the sky is more than 50% cloud covered, we cancel. This can be, as you will appreciate, a sometimes difficult decision.
    Almost directly overhead at viewing time is the constellation Aquila.  Aquila lies just a few degrees north of the celestial equator and is located along the Milky Way. Because of this location along the line of our galaxy, many clusters and nebulae are found within its borders, but they are dim and there are few galaxies.
    Astronomers observed two major novae in Aquila, the first one being in 389 BC. It was recorded as brighter than the planet Venus. The second one was observed in the year 1918 (Nova Aquilae). It was brighter than Altair. A nova should not be confused with a supernova. A nova is an old star that brightens temporarily, and a supernova (dying star) is a massive star exploding.                                                     
    NASA’s Pioneer 11 mission will pass near one of constellation Aquila’s stars in about four  million years.
                                                                                                                                                   Altair (Alpha Aquila), the brightest star of the constellation, is a multiple star system. It is about eight times brighter than the sun and the twelfth brightest star in the night sky. It is an A-type main sequence star with an apparent visual magnitude of 0.77. Class A stars are among the more common naked eye stars, and are white or bluish-white. Other examples include Sirius, Deneb, Vega and Fomalhaut.  Altair is located 16.7 light-years (5.13 parsecs) from Earth and is one of the closest stars visible to the naked eye. Altair is a type-A main sequence star with approximately 1.8 times the mass of the Sun and 11 times its luminosity. Altair possesses an extremely rapid rate of rotation; it has a rotational period of approximately 9 hours. For comparison, the equator of the Sun requires just over 25 days for a complete

The name Altair comes from the Arabic al-nasr al-ta’ir, meaning ‘flying eagle’ or ‘vulture’. Ptolemy called this star Aetus, the eagle, the same as the constellation. The German scholar Paul Kunitzsch notes that the Babylonians and Sumerians referred to Altair as the eagle star, testimony to an even more ancient origin of the name. Altair’s neighbouring stars Beta and Gamma Aquilae lie in the eagle’s neck and in its left shoulder respectively, according to Ptolemy’s description. These two stars have their own names, Alshain and Tarazed, which come from a Persian translation of an old Arabic word meaning ‘the balance’.
           In China, Altair and its two flanking stars, Beta and Gamma Aquilae, were known as Hegu, a large battle drum – beating the drum was a signal for the army to attack. The line to the south formed by Theta, 62, 58 and Eta Aquilae was Tianfu, the drumstick. Delta Aquilae and surrounding stars including Mu, Sigma and Iota were Youqi, a banner flying on the right side of the drum, while the stars of Sagitta to the north were a banner on the left of the drum.
    Altair and its attendant stars also had two other identifications. In one they were known as the Three Generals, the commanding officer in the centre flanked by two subordinates.

Aquila represents an eagle, the thunderbird of the Greeks. There are several explanations for the presence of this eagle in the sky. In Greek and Roman mythology, the eagle was the bird of Zeus, carrying (and retrieving) the thunderbolts which the wrathful god hurled at his enemies. But the eagle was involved in love as well as war.
   According to one story, Aquila is the eagle that snatched up the beautiful Trojan boy Ganymede, son of King Tros, to become the cup-bearer of the gods on Olympus. Authorities such as the Roman poet Ovid say that Zeus turned himself into an eagle, whereas others say that the eagle was simply sent by Zeus. Ganymede himself is represented by the neighbouring constellation of Aquarius, and star charts show Aquila swooping down towards Aquarius. Germanicus Caesar says that the eagle is guarding the arrow of Eros (neighbouring Sagitta) which made Zeus love-struck.

Pedro Castle, September 19th, 7.00 p.m. 2012

Mars will be very close to the crescent moon in the faint constellation of Libra on viewing night.  Libra was known in Babylonian astronomy as MUL Zibanu ("the scales"), or alternatively as the Claws of the Scorpion. The scales were held sacred to the sun god Shamash, who was also the patron of truth and justice. It was also seen as the Scorpion's Claws in ancient Greece. Since these times, Libra has been associated with law, fairness and civility. In Arabic zubānā means "scorpion's claws", and likely similarly in other Semitic languages: this resemblance of words may be why the Scorpion's claws became the Scales.

    Alternatively, another source says the Romans made it into a separate constellation in the time of Julius Caesar. Since then the Scales of Libra have become regarded as the symbol of justice, held aloft by the goddess of justice, Astraea. One legend identifies Astraea with the neighbouring figure of Virgo.

     The two brightest stars, the alpha and beta of the constellation, are called Zubenelgenubi and Zubeneschamali respectively. Zubeneschamali, the northern one of the two, comes from an Arabic phrase meaning "the northern claw," that of the Alpha star meaning "the southern claw”.

    The illustration above comes from Alexander Jamieson’s Celestial Atlas which appeared in February 1822, with a second edition following in September that same year. For all the fame that the Atlas achieved, its author remains little known. He evidently had a wide knowledge of science, mathematics and languages, for he wrote a number of educational works on subjects as diverse as cartography, logic, rhetoric, algebra, mechanics and hydrostatics as well as editing a Latin dictionary and running a series of private schools

   Jamieson was born in Rothesay on the Isle of Bute, west Scotland, in 1782, the son of a wheelwright. He obtained MA and LLD degrees from Marischal College, Aberdeen, in 1821 and 1823. In 1825 he became a mature student at St John’s College Cambridge but there is no record that he ever resided there or obtained any degree. In fact, he seems to have spent most of his working life in and around London as a writer, teacher and finally an actuary.

     Venus shines bright in the east before long before dawn, and Jupiter is overhead, close to the red giant star Aldebaran in the constellation Taurus.

Cayman Islands Astronomical Society News Letter

 No observing sessions are planned for the immediate future.
The chart above is for 8.00 p.m. 05th August and applies all month.
Perhaps the most interesting spectacle this month, and a naked eye event, will be the changing pattern formed by Saturn, Mars and the bright star Spica, shown by the white dot beside Mars.
The brightest constellations, and easy ones to make out, at that time of the evening, are Sagittarius and Scorpio in the south, and Cygnus, the Swan, or Northern Cross high in the NE.
Cygnus contains the bright star Deneb, which forms a point of the Summer Triangle, an astronomical asterism involving an imaginary triangle drawn on the northern hemisphere's celestial sphere, with its defining vertices at Altair, Deneb, and Vega, being the brightest stars in the three constellations of Aquila, Cygnus, and Lyra.

The English term was popularized by British astronomer Sir Patrick Moore in the 1950s, although he did not invent it. The Austrian astronomer Oswald Thomas described these stars as "Grosses Dreieck" (Great Triangle) in the late 1920s and "Sommerliches Dreieck" (Summerly Triangle) in 1934. The asterism was remarked upon by J. J. Littrow, who described it as the "conspicuous triangle" in the text of his atlas (1866), and Bode connected the stars in a map in a book in 1816, although without label.
The Perseid meteor shower peaks on the night 11-12 August, conveniently a Saturday night, Sunday morning for those of you who want to stay up late.

Pedro Castle, Friday 22nd June, 2012

The viewing of the Transit of Venus was, if you weren’t there, a huge success. Fortunately, we had seven telescopes for more than a thousand people to look through, and the atmosphere was orderly and convivial.

    Early risers can see Venus and Jupiter before and in the dawn, while Saturn, Mars and Mercury are visible when darkness falls.

      Saturn is close to the 15^th brightest star in the sky, Spica, which lies in the constellation of Virgo. Roughly halfway between this brilliant duo and the star Regulus in Leo, Mars glows distinctly in an area of dim stars. Mercury is visible as the sun sets, a good excuse to go the beach for the waning of the day.

    Further north from this line of the ecliptic, the bright star Arcturus is unmistakable. In the illustration above it is the alpha, α, orange star in the kilt of the Herdsman, Boötes.

    In ancient Babylon the stars of Boötes were known as SHU.PA. They were apparently depicted as the god Enlil, who was the leader of the Babylonian pantheon and special patron of farmers.

    Exactly whom Boötes is supposed to represent in Greek mythology is not clear. According to one version, he was a ploughman who drove the oxen in the constellation Ursa Major using his two dogs Chara and Asterion (from the constellation Canes Venatici). The oxen were tied to the polar axis and so the action of Boötes kept the heavens in constant rotation.

     The Boötes void, or the Great Void is a huge and approximately spherically shaped region of space, containing very few galaxies. It is located in the vicinity of the constellation Boötes, hence its name. At nearly 250 million light-years in diameter (approximately 0.27% of the diameter of the visible universe), the Boötes void is one of the largest known voids in the universe, and is referred to as a supervoid. According to astronomer Greg Aldering, the scale of the void is such that "If the Milky Way had been in the center of the Boötes void, we wouldn't have known there were other galaxies until the 1960s."

   The Boötes Dwarf Galaxy is a faint, satellite galaxy of the Milky Way located in Boötes about 197 000 light-years  away from Earth.

     To the naked eye, orange-yellow Arcturus has a visual magnitude of −0.04, making it the brightest star north of the celestial equator, and the fourth brightest star in the night sky, after −1.46 magnitude Sirius, −0.86 magnitude Canopus, and −0.27 magnitude Alpha Centauri. However, Alpha Centauri is a bright binary star, whose unresolved components to the naked eye are both fainter than Arcturus. This makes Arcturus the third brightest individual star, just ahead of Alpha Centauri A (α Cen A), whose visual magnitude is −0.01.

     The apparent (visual) magnitude (m) of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere. The brighter the object appears, the lower the value of its magnitude.

Transit Of Venus 5th June 5PM Camana Bay

How You Can Learn a Lot from a Dot
Transit of Venus June 5th 2012

If you have heard of the recent Solar Eclipse visible from the Western USA, you may be interested to know that there is another trick the Sun is about to pull off on June 5th.

More importantly this event will be visible from the Cayman Islands, particularly at Sunset.

The planet Venus will appear as a “dot” which crosses the suns surface.  The event, although not technically an eclipse, is called the Transit of Venus, (TOV).


Please also note this picture was taken with a small telescope fitted with a specialist filter.
Remember staring at the sun can cause serious damage to your eyesight.

So where and how can I see the event safely?

The Cayman Islands Astronomical Society, with the support of Dart Enterprises, will be holding a free rooftop event for the general public at 62 Forum Lane, Camana Bay.  Directions on how to find us are available on a separate sheet.

From the rooftop terrace the event can be seen, in safety, using solar viewing glasses provided by Camana Bay, as well as through several telescopes belonging to the members of the Cayman Islands Astronomical Society (CIAS), all of which will be fitted with specialist solar filters.

There will also be a small exhibition and, hopefully, live pictures of the transit from other world-wide locations will be shown if the weather is cloudy. Representatives from other Astronomy Societies in the Caribbean will also be present. This event also marks the 21st anniversary of the Cayman Islands Astronomical Society.

Timing is fairly critical so we cannot use “Cayman-time” for this event, but generally speaking this will be a fairly relaxed affair.  The “show” starts at 5:00PM and some important measurements will need to be made within the first half hour (see more information on this at the end of the article).  Venus will then start a leisurely 6 hour transit across the Sun’s surface, although we will leave it somewhat earlier, as the sun sets, at around 7:00 PM.
If you are thinking of observing the Sun from elsewhere then I recommend waiting until close to sunset, so that sun is very low on the horizon and so safer to observe.  We are all used to visitors taking photos of the setting sun but this time you will probably be staring at the sun for longer so take extra care.

Observing the Sun directly with a telescope or a camera with a telephoto lens will seriously damage your eyesight - and your camera might get damaged too.

You may also have heard that you can use welding glass to look at the Sun- this is true but the older type number 14 is the only safe grade.  If you can see landscape through the glass as well as the sun, it is not good enough. Sunglasses? No way- unless they are the bone-fide solar-viewing glasses, which will be available on the rooftop terrace at Camana Bay.


So why is this an Important Event?

Quite simply Transits of Venus are among the rarest of predictable astronomical events. After a first attempt to predict the event, by Johannes Kepler, it was in fact observed 8 years later by Jeremiah Horrocks in 1639. This enabled, for the first time, accurate measurements in astronomical distances to be made, in particular the distance of the Sun from the Earth. This important “yard stick” is called the “The Astronomical Unit”.  Each successive transit attracted world-wide expeditions including that of James Cook’s first voyage to Hawaii to see the event in 1769.

There is a curious mathematical pattern to the frequency of the transits.  Think of a pair of transits 8 years apart, of which we are about to observe the second of the pair.  Both of these transits occur in June.  We then have to wait a mere 105 ½ years until the next pair. So the next pair of events will be in December 2117 and December 2125.  Follow this by another long wait, but this time 121 ½ years, which brings us back to June but in 2247 and the cycle begins again.

Schools will be interested to know that there is a world–wide experiment to time the two points when Venus starts to cross the Sun’s disk.  These two moments in time are not easy to measure; the second produces the famous “tear drop” effect.


The trick is to time exactly when the “drop” is inside the Sun’s disk. This time there is even a free “app” for your electronic gadgets, so you can practice the timing beforehand.

For more information visit http://www.transitofvenus.org/

Without doubt this is a very rare event and unique in our lifetime, and it is an interesting thought to think how old our children’s children will be in 2117 when the next transit occurs. So please just come with your eyes and enjoy!

PEDRO CASTLE, MAY 20TH 2012 7.00 P.M.

As darkness falls on the moonless night, three planets will be visible.
     Low in the west, Venus this month is sinking rapidly toward the setting Sun. The planet shines at magnitude –4.5 on May 20th, when its crescent is 51 arcseconds long and 8% lit. After that Venus's crescent should be easy to see in binoculars — and might even be visible to sharp naked eyes.       
     On June 5th, the planet will transit the face of the Sun. The event, which will not re-occur for 105 years, will be visible from 5.00 p.m. until sunset. Caymana Bay has graciously allowed us to use the top of the CNB building as an observation site. We will have a number of special telescopes for safe viewing and we also should have some solar glasses. DO NOT LOOK AT THE SUN DIRECTLY. This cannot be emphasized enough.
     Directly overhead on Sunday, Mars (magnitude +0.2) shines fire-orange under the belly of Leo, close to the bright star Regulus, the heart of the Lion.
      Mars has two moons, Phobos and Deimos, which are thought to be captured asteroids. Both satellites were discovered in 1877 by Asaph Hall, and are named after the characters Phobos (panic/fear) and Deimos (terror/dread) who, in Greek mythology, accompanied their father Ares, god of war, into battle. Ares was known as Mars to the Romans.
     If viewed from the surface of Mars near its equator, full Phobos looks about one third as big as the Earth's full moon from Earth. It would look smaller when the observer is further away from the Martian equator, and is completely invisible (always beyond the horizon) from Mars' polar ice caps. Deimos looks more like a bright star or planet for an observer on Mars, only slightly bigger than Venus looks from Earth.
     The motions of Phobos and Deimos would appear very different from that of our own Moon. Speedy Phobos rises in the west, sets in the east, and rises again in just eleven hours, while Deimos, being only just outside synchronous orbit, rises as expected in the east but very slowly. Despite its 30 hour orbit, it takes 2.7 days to set in the west as it slowly falls behind the rotation of Mars, and has long again to rise.
     In contrast the third visible planet has more than 60 moons. The moons of Saturn are numerous and diverse, ranging from tiny moonlets less than 1 kilometre across, to the enormous Titan, which is larger than the planet Mercury. Saturn has 62 moons with confirmed orbits, fifty-three of which have names, and only thirteen of which have diameters larger than 50 kilometres.
    The rings of Saturn are made up of objects ranging in size from microscopic to hundreds of meters, each of which is on its own orbit about the planet. Thus a precise number of Saturnian moons cannot be given, as there is no objective boundary between the countless small anonymous objects that form Saturn's ring system and the larger objects that have been named as moons. At least 150 moonlets embedded in the rings have been detected by the disturbance they create in the surrounding ring material, though this is thought to be only a small sample of the total population of such objects.