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.

Pedro Castle, April 24th, 7.00 p.m.

The planet Mars is almost overhead as darkness falls on the
viewing date, very close to one of the brightest stars in our night sky
Regulus, in the constellation of Leo.

Regulus is a multiple star system composed of four stars that are organized into two pairs.
The spectroscopic binary Regulus A consists of a blue-white main-sequence star
and its companion, which has not yet been directly observed, but is probably a
white dwarf star. Located farther away is the pair Regulus B and Regulus C,
which are dim main-sequence stars.
A spectroscopic binary star system is one in which the two components are so close together, or
so far from the Sun, that they cannot be resolved simply by looking at them,
even through a powerful telescope. Their binary nature can, however, be
established because of the Doppler shift of their spectral lines.

The first spectroscopic system to be discovered was Mizar (Zeta Ursae Majoris) in 1889.

Planum Boreum, Mar’s north polar cap, clearly shown in the Hubble image above, contains water
ice “of a very high degree of purity,” according to an international study.
Using radar data from the SHARAD (SHAllow RADar) instrument on board the Mars
Reconnaissance Orbiter (MRO), French researchers say the data point to 95
percent purity in the polar ice cap. The north polar cap is a dome of layered,
icy materials, similar to the large ice caps in Greenland and Antarctica,
consisting of layered deposits, with mostly ice and a small amount of dust.
Combined, the north and south polar ice caps are believed to hold the equivalent
of two to three million cubic kilometers (0.47-0.72 million cu. miles) of ice,
making it roughly 100 times more than the total volume of North America’s Great Lakes, which is 22,684 cu. kms (5,439 miles).

Venus will be sinking in the west, close to the crescent moon and the bright star Aldebaran,
which is part of the star cluster of the Hyades, which forms the head of the
Bull, Taurus.

Saturn in the east, and Crux, the Southern Cross in the south are both rising, and next month will
be visible as it gets dark.

March 2012

Unfortunetly for non-members there was no Public Meeting at Pedros.

There were however special members evenings arranged - one of which was a fund raising event for our new Coronado/Meade H Alpha Scope - the other was a special meeting to observe at the new UCCI Observatory

The next Pedros meeting is planned for around 23rd April - usually 3 days after the new moon.

Local TV viewers were also "treated" to the Society having a few minutes on DayBreak (Cayman 27)

Sunday, 26th February, 7.00 p.m. at Pedro Castle

At viewing time, Venus (pictured above), will be close to Jupiter and the crescent Moon, a brilliant conjunction in our early evening sky.

In the 1940's and 50's, the popular image of the surface of the planet was very different to the harsh reality of the image above.

Venus is high and bright in our evening sky, and on the
afternoon of June 5^th, will give us, quite literally, the chance of
a lifetime, the opportunity to observe the last transit of the planet across
the face of the Sun for 105 years.

The society is
planning to observe this event, hopefully with a solar telescope, the purchase
of which we are fund raising for at the moment. Any donations welcome. We are
planning a BBQ two days after the March meeting. The meeting is scheduled for
Thursday 22^nd March, and the BBQ on Saturday 24^th at
Georgetown Villas on 7 mile beach. Details and ticket purchase availability
will be sent later.

Venus rises
especially high and bright in the evening sky every 8 years, this year
included. For every 8 orbits Earth completes around the Sun, Venus completes
13.004.

Late in March,
Venus reaches its greatest elongation, the farthest distance it will be
from the Sun in the sky as seen from Earth. This year the angular distance will
be 46°, or about four-and-a-half fist widths.
The planets orbit the Sun in roughly
the same plane, which means that, if you were to look at the solar system from
the side, the planets’ paths aren’t tilted much compared to each other. Every
year around this time the line drawn in the Northern Hemisphere’s evening sky
by Earth’s orbital plane, called the ecliptic, makes its widest angle with the
horizon, tracing a curve high on the sky. And since the ecliptic is basically
what Venus follows, too, it'll be moving up and down the sky the same way. So,
not only is Venus at its largest angular distance from the Sun, that separation
points nearly straight up.

Venus (named
after the Goddess of Love) is the planet second closest to the Sun, and the
hottest planet in the Solar System. From looking at most of the facts, Venus
initially appears to be very similar to Earth. The reality is, however, very
different. It might be just 652 km thinner, have similar composition, mass and
position, but for a start, Venus' surface temperature is a scorching 484°C,
secondly it is thought to be completely lifeless, and thirdly its surface
pressure is akin to that of an ocean bed (92 times that of Earth at sea level)
- a pressure high enough to pulverize and crush Venus' surface rocks.

All of these major
features stem from one key difference to the Earth - Venus has no water. This
explain Venus' very dense (mainly Carbon Dioxide) atmosphere - here on Earth
the water of the oceans removes CO² from our atmosphere and keeps
our planet in a state such that we can live on it (in fact the same quantity of
Carbon Dioxide has come out of the Earth's interior as is in Venus'
atmosphere!). In Venus however there is no water to absorb the CO²
and so the atmosphere thickens and produces a runaway greenhouse effect, so the
rays (and heat) of the Sun shine onto the planet and are then trapped there by
the dense atmosphere. In fact, it is very likely that at one point Venus did
have water on it, but because Venus is about 50 million km closer to the Sun
than the Earth is (two thirds of the way between the Sun and Earth) any
remnants of this water have long since evaporated.

Venus' thick
atmosphere makes it very hard for us to see the actual surface of the planet.
The first ideas of what the planet may look like came in the 1960s when we were
able to see through the clouds, albeit in quite a primitive fashion, with radar
imaging from ground-based telescopes. However, global scale radar mapping of Venus'
surface did not start until the Pioneer space probe arrived at Venus in
1978-80, and mapped many of its basic surface features. These were followed by
the Soviet Veneras 15 and 16 but it wasn't really until the Magellan Orbiter
arrived in 1992 that we really got a good idea of what Venus was like.

When the data from
the Magellan mission did come through though, it surprised many scientists, as
there were only a tenth the amount of craters that would be expected had Venus
been as old as we thought it was, and the ones which were there were all found
to be relatively fresh. There are now two theories for this - one is that
volcanic eruptions destroy craters as fast as they are made so there will
always be a constant number of craters on Venus, and the other is that 500
million years or so ago, volcanic eruptions resurfaced the planet, destroying
all previous craters. Another thing these space probes found was that at least
85% of Venus is covered by volcanic rock. These are mostly from lava flows and
form the planet's vast plains.

Venus is
unmistakable in the evening sky, so look up and enjoy.