Pedro Castle, March 29th, 7.00 p.m.

The Pleiades, known as the Seven Sisters, will be close to the crescent Moon on the 29th March . This is a nearby, fairly loose open cluster of about 500 stars in the constellation Taurus. Although it is also known as the Seven Sisters, most people can see only six stars, all of them bright blue-white B or Be stars: Alcyone, Atlas, Electra, Maia, Merope, and Taygeta (Pleione is the seventh brightest).
Dust that forms a faint reflection nebulosity around the brightest stars was thought at first to be left over from the formation of the cluster (hence the alternate name Maia Nebula after the star Maia), but is now known to be an unrelated dust cloud in the interstellar medium that the stars are currently passing through. Astronomers estimate that the cluster will survive for about another 250 million years, after which it will disperse due to gravitational interactions with its galactic neighborhood.
They have long been known to be a physically related group of stars rather than any chance alignment. The Reverend John Michell calculated in 1767 that the probability of a chance alignment of so many bright stars was only 1 in 500,000, and so correctly surmised that the Pleiades and many other clusters of stars must be physically related. When studies were first made of the stars' proper motions, it was found that they are all moving in the same direction across the sky, at the same rate, further demonstrating that they were related.
The distance to the Pleiades is an important first step in the so-called cosmic distance ladder, a sequence of distance scales for the whole universe. The size of this first step calibrates the whole ladder, and the scale of this first step has been estimated by many methods. As the cluster is so close to the Earth, its distance is relatively easy to measure. Accurate knowledge of the distance allows astronomers to plot a Hertzsprung-Russell diagram for the cluster which, when compared to those plotted for clusters whose distance is not known, allows their distances to be estimated. Other methods can then extend the distance scale from open clusters to galaxies and clusters of galaxies, and a cosmic distance ladder can be constructed. Ultimately astronomers' understanding of the age and future evolution of the universe is influenced by their knowledge of the distance to the Pleiades.
The nine brightest stars of the Pleiades are named for the Seven Sisters of Greek mythology: Sterope, Merope, Electra, Maia, Taygete, Celaeno, and Alcyone, along with their parents Atlas and Pleione.
The Pleiades are a prominent sight in winter in the Northern Hemisphere and in summer in the Southern Hemisphere, and have been known since antiquity to cultures all around the world, including the Māori and Australian Aborigines, the Persians (who called them Parveen/parvin), the Chinese, the Maya (who called them Tzab-ek), the Aztec (Tianquiztli), and the Sioux of North America. Some Greek astronomers considered them to be a distinct constellation, and they are mentioned by Hesiod, and in Homer's Iliad and Odyssey. They are also mentioned three times in the Bible (Job 9:9 and 38:31, as well as Amos 5:8). The Pleiades (Krittika) are particularly revered in Hindu mythology as the six mothers of the war god Skanda, who developed six faces, one for each of them. Some scholars of Islam suggested that the Pleiades (At-thuraiya) are the Star in Najm which is mentioned in the Quran.
Saturn is risen in the east (magnitude +0.5, near the hind foot of Leo) and is just past opposition. The planet is well up in the southeast by midevening, and highest in the south around midnight. Don't confuse Saturn with slightly fainter Regulus 18° (nearly two fist-widths at arm's length) to its upper right in early evening, and more directly to Saturn's right late at night.
Saturn's rings are 3½° from edge on. The rings will open to 4° by late May, then will close to exactly edge-on next September 4th — when, unfortunately, Saturn will be out of sight practically in conjunction with the Sun.

March 2nd 2009

The revolution of the Moon around the Earth makes the Moon appear as if it is changing shape in the sky. This is caused by the different angles from which we see the bright part of the Moon's surface. These are called "phases" of the Moon. Of course, the Moon doesn't generate any light itself; it just reflects the light of the Sun. The Moon passes through four major shapes during a cycle that repeats itself every 29.5 days. The phases always follow one another in the same order.
Although this cycle is a continuous process, there are eight distinct, traditionally recognized stages, called phases. The phases designate both the degree to which the Moon is illuminated and the geometric appearance of the illuminated part. These phases of the Moon, in the sequence of their occurrence (starting from New Moon), are listed below.
(1) New Moon - When the Moon is roughly in the same direction as the Sun, its illuminated half is facing away from the Earth, and therefore the part that faces us is all dark: we have the new moon. When in this phase, the Moon and the Sun rise and set at about the same time. (2) Waxing Crescent Moon - As the Moon moves around the Earth, we get to see more and more of the illuminated half, and we say the Moon is waxing. At first we get a sliver of it, which grows as days go by. This phase is called the crescent moon. (3) Quarter Moon - A week after the new moon, when the Moon has completed about a quarter of its turn around the Earth, we can see half of the illuminated part; that is, a quarter of the Moon. This is the first quarter phase. (4) Waxing Gibbous Moon - During the next week, we keep seeing more and more of the illuminated part of the Moon, and it is now called waxing gibbous (gibbous means "humped"). (5) Full Moon - Two weeks after the new moon, the moon is now halfway through its revolution, and now the illuminated half coincides with the one facing the Earth, so that we can see a full disk: we have a full moon. As mentioned above, at this time the Moon rises at the time the Sun sets, and it sets when the Sun rises. If the Moon happens to align exactly with the Earth and Sun, then we get a lunar eclipse. (6) Waning Gibbous Moon - From now on, until it becomes new again, the illuminated part of the Moon that we can see decreases, and we say it's waning. The first week after full, it is called waning gibbous. (7) Last Quarter Moon - Three weeks after new, we again can see half of the illuminated part. This is usually called last quarter. (8) Waning Crescent Moon - Finally, during the fourth week, the Moon is reduced to a thin sliver from us, sometimes called waning crescent. A while after four weeks (29.5 days, more precisely) the illuminated half of the Moon again faces away from us, and we come back to the beginning of the cycle: a new moon. Sometimes, when the Moon is almost new, it is possible to dimly see its darkened disk. The light from the Sun cannot reach this part of the Moon directly; but at this time the Earth (as viewed from the Moon) is at its full and very bright, and what we see is light reflected from the Earth, that then bounces back at us from the Moon. It's a long trip for this light: from the Sun to the Earth, to the Moon, and back to the Earth, about 480,000 miles in total.
Venus (visible in the west) is the next closest visible heavenly body, but it is never closer than 25,000,000 miles from the earth. The moon appears to be as large as it is because of its closeness, but it is comparatively small since it is only a quarter of the diameter of the earth.
The sun is a hundred times the diameter of the earth, but it is also about 93,000,000 miles away. It just happens that size and distance cancel each other and both the sun and the moon appear to be the same size. Although the moon is moving from west to east, the earth's spin overtakes it and makes it seem to move from east to west. It appears to "rise" in the east, moves westward, and "sets" in the west.

January 2009, Pedro Castle 7.00 pm

The extremely bright object high in the western sky is the planet Venus.
Venus is the second-closest planet to the Sun, orbiting it every 224.7 Earth days.
The planet is named after Venus, the Roman goddess of love. It is the brightest natural object in the night sky, except for the Moon, reaching an apparent magnitude of −4.6. Because Venus is an inferior planet from Earth, it never appears to venture far from the Sun: its elongation reaches a maximum of 47.8°. Venus reaches its maximum brightness shortly before sunrise or shortly after sunset, for which reason it is often called the Morning Star or the Evening Star.
Classified as a terrestrial planet, it is sometimes called Earth's "sister planet," because they are similar in size, gravity, and bulk composition. Venus is covered with an opaque layer of highly reflective clouds of sulfuric acid, preventing its surface from being seen from space in visible light; this was a subject of great speculation until some of its secrets were revealed by planetary science in the twentieth century. Venus has the densest atmosphere of all the terrestrial planets, consisting mostly of carbon dioxide, as it has no carbon cycle to lock carbon back into rocks and surface features, nor organic life to absorb it in biomass. It has become so hot that the earth-like oceans that the young Venus is believed to have possessed have totally evaporated, leaving a dusty dry desertscape with many slab-like rocks. The best hypothesis is that the evaporated water has dissociated, and with the lack of a planetary magnetic field, the hydrogen has been swept into interplanetary space by the solar wind. The atmospheric pressure at the planet's surface is 92 times that of the Earth.
Venus rotates once every 243 days—by far the slowest rotation period of any of the major planets. To an observer on the surface of Venus the time from one sunrise to the next would be 116.75 days.
As the brightest point-like object in the sky, Venus is a commonly misreported 'unidentified flying object'. U.S. President Jimmy Carter reported having seen a UFO in 1969, which later analysis suggested was probably the planet, and countless other people have mistaken Venus for something more exotic.
As it moves around its orbit, Venus displays phases in a telescopic view like those of the Moon: In the phases of Venus the planet presents a small "full" image when it is on the opposite side of the Sun. It shows a larger "quarter phase" when it is at its maximum elongations from the Sun. Venus is at its brightest in the night sky and presents a much larger "thin crescent" in telescopic views as it comes around to the near side between the Earth and the Sun. Venus is at its largest and presents its "new passes" when it is between the Earth and the Sun. Since it has an atmosphere it can be seen in a telescope by the halo of light refracted around the planet.
Venus was known in the Hindu Jyotisha since early times as the planet Shukra.
In the West, before the advent of the telescope, Venus was known as a 'wandering star'.
Several cultures historically held its appearances as a morning and evening star to be those of two separate bodies. Pythagoras is usually credited with recognizing in the sixth century BC that the morning and evening stars were a single body, though he thought that Venus orbited the Earth. When Galileo first observed the planet in the early 17th century, he found that it showed phases like the Moon's, varying from crescent to gibbous to full and vice versa. This could be possible only if Venus orbited the Sun, and this was among the first observations to clearly contradict the Ptolemaic geocentric model that the solar system was concentric and centered on the Earth.
There is a spacecraft operating in orbit around the planet now. Venus Express probe was designed and built by the European Space Agency. Launched on November 9, 2005 by a Russian Soyuz-Fregat rocket it successfully assumed a polar orbit around Venus on April 11, 2006. The probe is undertaking a detailed study of the Venusian atmosphere and clouds, and is also mapping the planet's plasma environment and surface characteristics, particularly temperatures.
As one of the brightest objects in the sky, Venus has been known since prehistoric times and as such has gained an entrenched position in human culture. It is described in Babylonian cuneiform texts such as the Venus tablet of Ammisaduqa, which relates observations that possibly date from 1600 BC. The Babylonians named the planet Ishtar , the personification of womanhood, and goddess of love.
The Ancient Egyptians believed Venus to be two separate bodies and knew the morning star as Tioumoutiri and the evening star as Ouaiti.
Likewise believing Venus to be two bodies, the Ancient Greeks called the morning star, Phosphoro, the "Bringer of Light". The evening star they called Hesperos, the "star of the evening", but by Hellenistic times, they realized the two were the same planet. Hesperos would be translated into Latin as Vesper and Phosphoros as Lucifer ("Light Bearer"), a poetic term later used to refer to the fallen angel cast out of heaven.
The Romans would later name the planet in honor of their goddess of love, Venus, whereas the Greeks used the name of her Greek counterpart, Aphrodite (Phoenician Astarte).
Venus was important to the Maya civilization, who developed a religious calendar based in part upon its motions, and held the motions of Venus to determine the propitious time for events such as war. They named it Noh Ek', the Great Star, and Xux Ek', the Wasp Star. The Maya were aware of the planet's synodic period, and could compute it to within a hundredth part of a day.
The Maasai people named the planet Kileken, and have an oral tradition about it called The Orphan Boy.
Venus is important in many Australian aboriginal cultures, such as that of the Yolngu people in Northern Australia. The Yolngu gather after sunset to await the rising of Venus, which they call Barnumbirr. As she approaches, in the early hours before dawn, she draws behind her a rope of light attached to the Earth, and along this rope, with the aid of a richly decorated "Morning Star Pole", the people are able to communicate with their dead loved ones, showing that they still love and remember them. Barnumbirr is also an important creator-spirit in the Dreaming, and "sang" much of the country into life.

December 30th 2008

The prominent constellations of winter are now rising in the early part of the evening, Taurus, the Bull, illustrated above, being among the first.
Taurus is marked by a V-shaped pattern of stars that outlines the bull's face. Bright red Aldebaran, the "eye" of the bull, stands at one point of the V. This pattern is part of a cluster of stars called the Hyades — the second-closest star cluster to Earth. It consists of several hundred stars that lie about 130 light-years away.
Aldebaran outshines all the other stars that outline the bull's face. But Aldebaran isn't a member of the Hyades cluster — it just lies in the same direction. It's about 70 light-years away, half as far as the stars of the Hyades. Aldebaran is a red-giant — an old, bloated star that's used up most of its nuclear fuel. It's much larger and much brighter than our own middle-aged Sun.
On the other side of the sky, Venus is shining bright in the west.

November 30th, 2008, Pedro Castle 6.30 p.m.

I don’t know about you, but I have seen very little in the media about India’s successful mission to the Moon.
“In a historic event, the Indian space programme achieved a unique feat today (November 14, 2008) with the placing of Indian tricolour on the Moon's surface on Pandit Jawaharlal Nehru's birthday. The Indian flag was painted on the sides of Moon Impact Probe (MIP), one of the 11 payloads of Chandrayaan-1 spacecraft, that successfully hit the lunar surface today at 20:31 hrs (8:31 pm) IST. This is the first Indian built object to reach the surface of the moon. The point of MIP's impact was near the Moon's South Polar Region. It may be recalled that the modern Indian space programme was initiated in 1962 when Pandit Jawaharlal Nehru was the Prime Minister of India.”
As of writing this, everything is going as planned; the instruments have been activated and are operating correctly. And Mumbai is suffering.

Venus and Jupiter have been getting closer to each other and on viewing night will be joined by the crescent moon. Look to the west after dusk and watch the planets approach each other.
Dec. 1st is the best night of all. The now-15% crescent Moon moves in closer to form an isosceles triangle with Venus and Jupiter as opposing vertices. The three brightest objects in the night sky will be gathered so tightly together, you can hide them all behind your thumb held at arm's length.

Pedro Castle, October 30th 6.30 p.m.

This is what the sky will look like at 7.00 on viewing night.
I am going to continue with the theme of the Summer Triangle while it is still high in the early evening sky.
The alpha star of Aquila, Altair, is a vertex of the Summer Triangle asterism.
Aquila (Latin: eagle; sometimes named the Vulture), is one of the 48 constellations listed by Ptolemy, also mentioned by Eudoxus (4th century BC) and Aratus (3rd century BC) and now also part of the list of 88 constellations acknowledged by the IAU. It lies roughly at the celestial equator.
NASA's Pioneer 11 mission, which flew by Jupiter and Saturn (in 1974 and 1979 respectively) will pass near one of the stars in the constellation in about four million years.

The constellation resembles a wide winged, soaring, short necked, bird, which the ancients identified as an eagle. In classical Greek mythology, it was identified as the eagle which carried the thunderbolts of Zeus and was sent by him to carry the shepherd boy Ganymede who he desired, represented by the neighbouring Aquarius, to Mount Olympus where he became the wine-pourer for all the gods. This explains why the largest moon of Jupiter was called Ganymede, Jupiter being the Roman name of Zeus. The eagle was used to carry or retrieve the lightning bolts that were thrown by Zeus.
In the Chinese love story of Qi Xi, Niu Lang (Altair) and his two children (β and γ Aquilae) are separated forever from their wife and mother Zhi Nu (Vega in Lyra, another vertex of the Summer Triangle) who is on the far side of the river, the Milky Way.
In Hinduism, the constellation Aquila is identified with the half eagle, half human deity, Garuda.
Altair (α Alpha Aquilae) is the brightest star in the constellation Aquila and the twelfth brightest star in the nighttime sky, at visual magnitude 0.77. It is an "A" type or white star located 17 light-years (5.2 pc) away from Earth, one of the closest stars visible to the naked eye.
The name "Altaïr" is Arabic for "the bird". The spelling "Atair" is also used frequently. The name was given by Arabic astronomers and adopted by Western astronomers.

Pedro Castle,Thursday, 2nd October, 7.00 p.m.

As darkness falls on viewing night, the constellation of Cygnus, the Swan, is overhead, in the orientation that is shown above, up being north.
Because of the pattern of its main stars, it is sometimes known as the Northern Cross (in contrast to the Southern Cross).
One of the most recognizable constellations of the northern summer and autumn, it resembles a swan flying south along the Milky Way. Albireo, a double star with blue and yellow components is at the "head". Deneb, its brightest star, is at the tail and is one star of the summer triangle.
The Summer Triangle is an astronomical asterism involving an imaginary triangle drawn on the northern hemisphere's celestial sphere, with its defining vertices at Altair, Deneb, and Vega. This triangle connects the constellations of Aquila, Cygnus, and Lyra.
Looking toward the south, Jupiter, the fourth brightest object in the sky, is in the constellation of Sagittarius. Venus is setting in the west.