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.

Pedros Castle Friday 27th JAN 2011 6:30 PM

Hi all,
there was no meeting in December for two reasons.

1) it fell on a ridiculous date, 26th or 27th December.

2)there was no-one to run it. It was barely a week after I had back surgery, and Chris had to go to the UK for urgent family business.

We're back now, though I'm still rather delicate.

FYI, we have been involved with the observatory at UCCI, and will be having a meeting there at some time

regards

Nick

Pedro Castle, 28th November 2011, 6.30

Prominent in the night sky this month is the planet Jupiter, the brightest “star” in the sky visible through the end of the year and into the next.
Easily visible even through modest binoculars are the four Galilean moons, discovered by Galileo Galilei in January 1610. They are the largest of the many moons of Jupiter and derive their names from the lovers of Zeus: Io, Europa, Ganymede and Callisto. They are among the most massive objects in the Solar System outside the Sun and the eight planets, with radii larger than any of the dwarf planets.
Io is the innermost of the four Galilean moons and is the most geologically active object in the Solar System, with over 400 active volcanoes. This extreme geologic activity is the result of tidal heating from friction generated within Io's interior as it is pulled between Jupiter and the other Galilean satellites.
Ganymede is the largest moon in the Solar System, 8% larger than that of the planet Mercury, 2% larger than that of Titan, and nearly 50% larger than our own Moon. Its surface is composed of two main types of terrain. Dark regions, saturated with impact craters and dated to four billion years ago, cover about a third of the satellite. Lighter regions, crosscut by extensive grooves and ridges and only slightly less ancient, cover the remainder. The cause of the light terrain's disrupted geology is not fully known, but was likely the result of tectonic activity brought about by tidal heating.
Callisto is the fourth Galilean moon of Jupiter by distance, with an orbital radius of about 1,880,000 km. It does not form part of the orbital resonance that affects three inner Galilean satellites—Io, Europa and Ganymede—and thus does not experience appreciable tidal heating.
Europa is the smallest of its four Galilean satellites, but still one of the largest bodies in the Solar system, slightly smaller than the Moon.

A model of Europa's interior, including a global ocean. If a 100 kilometer-deep ocean existed below the Europan ice shell, it would be 10 times deeper than any ocean on Earth and would contain twice as much water as Earth's oceans and rivers
New research suggests that there may be plenty of oxygen available in that ocean to support life, a hundred times more oxygen than previously estimated.
The chances for life there have been uncertain, because Europa’s ocean lies beneath several miles of ice, which separates it from the production of oxygen at the surface by energetic charged particles (similar to cosmic rays). Without oxygen, life could conceivably exist at hot springs in the ocean floor using exotic metabolic chemistries, based on sulfur or the production of methane. However, it is not certain whether the ocean floor actually would provide the conditions for such life.
Therefore a key question has been whether enough oxygen reaches the ocean to support the oxygen-based metabolic process that is most familiar to us. An answer comes from considering the young age of Europa’s surface. Its geology and the paucity of impact craters suggests that the top of the ice is continually reformed such that the current surface is only about 50 million years old, roughly 1% of the age of the solar system.
Richard Greenberg of the University of Arizona has considered three generic resurfacing processes: gradually laying fresh material on the surface; opening cracks which fill with fresh ice from below; and disrupting patches of surface in place and replacing them with fresh material. Using estimates for the production of oxidizers at the surface, he finds that the delivery rate into the ocean is so fast that the oxygen concentration could exceed that of the Earth’s oceans in only a few million years.
Greenberg says that the concentrations of oxygen would be great enough to support not only microorganisms, but also “macrofauna”, that is, more complex animal-like organisms which have greater oxygen demands. The continual supply of oxygen could support roughly 3 billion kilograms of macrofauna, assuming similar oxygen demands to terrestrial fish.
The good news for the question of the origin of life is that there would be a delay of a couple of billion years before the first surface oxygen reached the ocean. Without that delay, the first pre-biotic chemistry and the first primitive organic structures would be disrupted by oxidation. Oxidation is a hazard unless organisms have evolved protection from its damaging effects. A similar delay in the production of oxygen on Earth was probably essential for allowing life to get started here.

Pedro Castle, Saturday 29th October 6.30, 2011

The illustration above is of Lyra, a small constellation, quite easily identified as it appears to consist of an equilateral triangle attached to a parallelogram. The brightest star, Vega, is one of the three stars, along with Deneb and Altair that form the asterism of the Summer Triangle, which is still visible in our night sky as darkness falls
Vega is the fifth brightest star in the sky and the second brightest star in the northern celestial hemisphere, after Arcturus. It is a relatively close star at only 25 light-years from Earth, and, together with Arcturus and Sirius, one of the most luminous stars in the Sun's neighborhood.
Vega is only about a tenth of the age of the Sun, but since it is 2.1 times as massive its expected lifetime is also one tenth of that of the Sun; both stars are at present approaching the midpoint of their life expectancies.
Vega has been extensively studied by astronomers, leading it to be termed "arguably the next most important star in the sky after the Sun." Vega was the northern pole star around 12,000 BC and will be so again around AD 13,727. Vega was the first star other than the Sun to be photographed and the first to have its spectrum recorded. It was one of the first stars whose distance was estimated through parallax measurements. Vega has served as the baseline for calibrating the photometric brightness scale, and was one of the stars used to define the mean values for the UBV photometric system.
Epsilon Lyrae shown in the diagram above as the Double Double is a multiple star system .The widest two components of the system are easily separated when viewed through binoculars, or even with the naked eye under excellent conditions. The northern star is called ε1 and the southern one is called ε2; they both lie around 162 light years from Earth and orbit each other. When viewed at higher magnifications, both stars of the binary can be further split into binaries; that is, the system contains two binary stars orbiting each other.
A number of other nearby stars may also be part of the system, bringing the system to a total of ten stars. Also shown on the diagram above is the famously named "Ring Nebula" catalogued as Messier 57. It is one of the most prominent examples of a planetary nebula, the gaseous remains of red giant star that has ended its life by expelling its material into the interstellar medium.

This nebula was discovered by Antoine Darquier de Pellepoix in January, 1779, who reported that it was "...as large as Jupiter and resembles a planet which is fading." Later the same month, Charles Messier independently found the same nebula while searching for comets. It was then entered into his catalogue as the 57th object. Messier and William Herschel also speculated that the nebula was formed by multiple faint stars that were unable to resolve with his telescope.
In 1800, Count Friedrich von Hahn discovered the faint central star in the heart of the nebula. In 1864, William Huggins examined the spectra of multiple nebulae, discovering that some of these objects, including M57, displayed the spectra of bright emission lines characteristic of fluorescing glowing gases. Huggins concluded that most planetary nebulae were not composed of unresolved stars, as had been previously suspected, but were nebulosities.
A planetary nebula is an emission nebula consisting of an expanding glowing shell of ionized gas ejected during the asymptotic giant branch phase of certain types of stars late in their life. This name originated with their first discovery in the 18th century because of their similarity in appearance to giant planets when viewed through small optical telescopes, and is otherwise unrelated to the planets of the solar system. They are a relatively short-lived phenomenon, lasting a few tens of thousands of years, compared to a typical stellar lifetime of several billion years.
At the end of the star's life, during the red giant phase, the outer layers of the star are expelled via pulsations and strong stellar winds. Without these opaque layers, the hot, luminous core emits ultraviolet radiation that ionizes the ejected outer layers of the star. This energized shell radiates as a planetary nebula.
Planetary nebulae play a crucial role in the chemical evolution of the galaxy, returning material to the interstellar medium that has been enriched in heavy elements and other products of nucleosynthesis (such as carbon, nitrogen, oxygen and calcium). In more distant galaxies, planetary nebulae may be the only objects that can be resolved to yield useful information about chemical abundances.
In recent years, Hubble Space Telescope images, (including the image above of M57) have revealed many planetary nebulae to have extremely complex and varied morphologies. About a fifth are roughly spherical, but the majorities are not spherically symmetric. The mechanisms which produce such a wide variety of shapes and features are not yet well understood, but binary central stars, stellar winds and magnetic fields may all play a role.

Pedro Castle, Friday September 30th 2011 7.00 pm

The constellation Sagittarius is clearly visible high in the south in the early evening, but will getting lower on the western horizon as October progress’.
It is one of the 12 original constellations of the zodiac, the band of constellations that lies along the ecliptic, the apparent yearly path of the sun across the sky. The modern asterism of the Teapot, formed from the constellation’s brightest stars, is illustrated above. It is much easier to discern than the classical depiction of Sagittarius, below, a centaur, half man, half beast, with a raised bow and arrow. It has been visualised this way, at least since the times of the ancient Greeks. It probably originated with the Sumerian civilisation around the Euphrates, who saw the constellation as Nergal, their archer god of war. The archer is aiming his arrow at the heart of Scorpius, the bright star Antares.The Milky Way is at its densest near Sagittarius, as this is where the Galactic Center lies.
The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky. The term "Milky Way" is a translation of the Latin for "milky road", Via Lactea, in turn derived from the Greek kyklos galaktikos or "milky circle", "milk" also being the root for the Greek word for Galaxy, Γαλαξίας (Galaxias).
The galaxy has this appearance because of the Earth's position within the galactic plane around two thirds of the way out from the center, on the inner edge of the Orion–Cygnus Arm, with the majority of the galaxy being seen edge on. The concept of this faint band of light being made up of stars was proven in 1610 when Galileo Galilei used his telescope to resolve it into individual stars. In the 1920s observations by astronomer Edwin Hubble showed that the Milky Way was just one of around 200 billion galaxies in the observable universe.
The Galactic Center is the rotational center of the Milky Way galaxy, in which we live. It is located at a distance of 27,000±1,000 ly from the Earth.
The complex astronomical radio source Sagittarius A, near the border of the constellations Sagittarius and Scorpius, appears to be located almost exactly at the Galactic Center and contains an intense compact radio source, Sagittarius A*, which coincides with a supermassive black hole at the center of our Galaxy.
Accretion of gas onto the black hole, probably involving a disk around it, would release energy to power the radio source, itself much larger than the black hole. The latter is too small to see with present instruments. Because of interstellar dust along the line of sight, the Galactic Center cannot be studied at visible, ultraviolet or soft X-ray wavelengths.
The available information about the Galactic Center comes from observations at gamma ray, hard X-ray, infrared, sub-millimetre and radio wavelengths.
Easily visible to the naked eye, however, are the bright stars of the Teapot, which appear to be pouring tea onto the equally bright tail of the Scorpion.

Pedro Castle, 2nd September 2011, 7.30

The illustration above shows the three day old Moon in the faint constellation of Libra.
The stars forming the triangle which the moon appears to be exiting are, from the “top”, Zubeneschamali, Zubenelgenubi, a visual binary, and Brachium, an eclipsing variable.
A much fainter star in the constellation of the Scales is Gliese 581, a red dwarf star with spectral type M3V, located 20.3 light years away from Earth. Its estimated mass is about a third of that of the Sun, and it is the 89th closest known star system to the Sun. Observations suggest that the star has at least four, and possibly six, planets: Gliese 581 e, b, c, g (unconfirmed), d and f (unconfirmed).
Gliese 581 has been the subject of a "huge amount of attention" in the quest to discover the first habitable planet; in 2010, attention focused on unconfirmed planet g, which would have been close to the middle of the star's habitable zone, but more recently, in a study published in The Astrophysical Journal Letters, planet d "can be considered the first confirmed exoplanet that could support Earth-like life."
The star system first gained attention after Gliese 581 c, the first low-mass extrasolar planet found to be near its star's habitable zone, was discovered in April 2007. It has since been shown that under known terrestrial planet climate models, Gliese 581 c is likely to have a runaway greenhouse effect, and hence is probably too hot to be habitable, analogous to Venus. A subsequently discovered planet Gliese 581 d, may be just inside or just outside the outer boundary of the habitable zone (depending in part on the greenhouse properties of its atmosphere), analogous to Mars The discovery of exoplanet Gliese 581 e the least-massive planet known around a normal star, was announced in April 2009.
Excitement spiked again in September 2010 with the claimed discovery of Gliese 581 g, orbiting between c and d, believed to be the planet with the greatest likelihood of having conditions suitable for liquid water at its surface found to date because it is within the middle of the habitable zone. However, its existence was later put in "serious doubts" following further analysis.
The much more distinctive, and much larger, constellation of Scorpius follows Libra in the sky. Scorpius occupies an area of 497 square degrees and contains ten stars with known planets.
The brightest star in the constellation is alpha Scorpii, or Antares ("like Mars"), named for its reddish-orange colour, which resembles that of the planet Mars. Antares is a red supergiant with a radius about 800 times that of the Sun. It is classified as a variable star; its apparent magnitude varies between 0.9 and 1.8. It has a hot blue companion star about 2.9 arcseconds away. Antares is the 16th brightest star in the sky. It is approximately 600 light-years distant from Earth. It is also of the brightest stars near the ecliptic, the Sun’s apparent path in the sky.
The only planets in the night sky are Saturn, which is setting at viewing time, and Jupiter which does not rise until past 10 o’clock.