There are few bright stars in the sky this time of year, which makes it difficult to easily make out many of the constellations.
However, one of the most distinctive constellations in the northern hemisphere, Cassiopeia, the vain Queen, is in the north when it is dark.
Cassiopeia, the wife of King Cepheus, ruler of Aethiopia, was beautiful, arrogant and vain, and it was these latter two characteristics which were to lead to her downfall. Her continual boast that both she and her daughter Andromeda were more beautiful than the sea nymphs, daughters of Nereus, the sea god, brought the wrath of Poseidon, ruling god of the sea, upon the kingdom of Aethiopia. Trying to avert such a fate, Cepheus and Cassiopeia consulted a wise oracle, who told them that the only way to appease the sea gods was to sacrifice their daughter. Accordingly, Andromeda was chained to a rock at the sea's edge, and left there to helplessly await her fate at the mercy of the sea monster. But Perseus arrived in time and saved Andromeda. Poseidon considered that Cassiopeia should not escape punishment entirely, and placed her in the heavens in such a position that she circles the celestial pole in an upside-down position for half the time.
Cassiopeia contains two stars visible to the naked eye that rank among the brightest in the galaxy, ρ (Rho) Cassiopeiae and V509 Cassiopeiae.
Rho Cassiopeiae (also Rho Cas) is a yellow hypergiant in the Cassiopeia constellation. It is about 8-10,000 light years away, yet can still be seen by the naked eye (in the Northern Hemisphere only), as it is 550,000 times brighter than the Sun. The surface diameter is 738 times larger than our sun's. Astronomers think Rho Cas may go supernova in the not too distant future, because it will have consumed most of the nuclear fuel in its core.
If we were to observe Earth's Sun from Alpha Centauri, it would appear to be in Cassiopeia.
The planets this month are late night objects. Mars rises shortly before midnight at the beginning of November, and will be visible just above the horizon by 10.30 on the night of the viewing.
Venus and Saturn are visible in the early morning sky.
Sunday 14th October 7.00 p.m. Pedros Castle
Directly overhead as darkness falls can be seen the distinctive shape known as the Summer Triangle, which consists of the stars Vega, Deneb and Altair. This noticeable pattern is known as an astronomical asterism, a group of stars seen in Earth's sky which is not an official constellation. The triangle connects the constellations of Aquila, Cygnus, and Lyra.
The largest of these three constellations is Cygnus, the Swan, also known as the Northern Cross. Cygnus contains several bright stars.
Deneb, α Cygni, is an extremely brilliant star, very prominent despite its distance (3230 light years). The blue supergiant forms the swan's tail, the upper end of the Northern Cross. It’s also the 18th brightest star in the sky.
Albireo, β Cygni, is at the swan's beak. It is one of the most beautiful double stars of the sky, a golden star easily distinguishable in a small telescope from its blue companion.
Lyra, dominated by its bright star Vega, is a much smaller constellation than Cygnus.
Vega is the second brightest star of the northern hemisphere (after Arcturus) and the fifth brightest star in all. It lies at a distance of only 25.3 ly. It was the first star to be photographed.
Aquila is a much harder pattern to distinguish, although Altair is easy to spot. Altair is located 17 light years away from Earth (about 159 trillion kilometers) and is one of the closest stars visible to the naked eye.
The largest of these three constellations is Cygnus, the Swan, also known as the Northern Cross. Cygnus contains several bright stars.
Deneb, α Cygni, is an extremely brilliant star, very prominent despite its distance (3230 light years). The blue supergiant forms the swan's tail, the upper end of the Northern Cross. It’s also the 18th brightest star in the sky.
Albireo, β Cygni, is at the swan's beak. It is one of the most beautiful double stars of the sky, a golden star easily distinguishable in a small telescope from its blue companion.
Lyra, dominated by its bright star Vega, is a much smaller constellation than Cygnus.
Vega is the second brightest star of the northern hemisphere (after Arcturus) and the fifth brightest star in all. It lies at a distance of only 25.3 ly. It was the first star to be photographed.
Aquila is a much harder pattern to distinguish, although Altair is easy to spot. Altair is located 17 light years away from Earth (about 159 trillion kilometers) and is one of the closest stars visible to the naked eye.
Behind the Summer Triangle lies some of the vast star fields of our Milky Way Galaxy, containing literally billions of stars. The dark band across the middle that seems to divide the stars is actually interstellar dust, which absorbs more visible light than it emits and so appears dark.
Jupiter is the only visible planet in the evening sky this month, shining bright in the south west.
Friday 14th September Pedros Castle 7:00 PM
Friday, 14th September is our viewing date this month, 7.00 p.m. at Pedro Castle.
Sagittarius, the archer — whose brightest stars form the shape of a teapot — is now prominent in the southern sky.
Sagittarius has drawn his bow, and his arrow is pointing at Antares, the bright red heart of Scorpius, the scorpion. The archer is avenging Orion, who was slain by the scorpion's sting.
The constellation Sagittarius is one of the most interesting regions of the sky. The center of our Milky Way galaxy lies inside Sagittarius, about 26,000 light-years away. The constellation also contains several globular clusters — tightly packed collections of hundreds of thousands of stars.
The Milky Way is the galaxy where the Solar System (and Earth) is located. It is a barred spiral galaxy of a Local Group of galaxies within the Virgo Supercluster. The main disk of the galaxy is about 80,000 to 100,000 light-years in diameter, about 250,000 to 300,000 light-years in circumference, and outside the Galactic core, about 2,300–2,600 light-years in thickness. The galaxy is estimated to contain 200 billion stars but this number may be as high as 400 billion if small-mass stars predominate.
As a guide to the relative physical scale of the Milky Way, if the galaxy were reduced to 130 km (80 mi) in diameter, the solar system would be a mere 2 mm (0.08 inches) in width.
The Lagoon Nebula (also known as Messier Object 8 (M8) and NGC 6523) and the Trifid Nebula (also known as Messier 20 and NGC 6514) are giant interstellar clouds and H II regions.
An H II region is a cloud of glowing gas and plasma, sometimes several hundred light-years across, in which star formation is taking place. Young, hot, blue stars which have formed from the gas emit copious amounts of ultraviolet light, ionising the nebula surrounding them.
Nunki, 224 light years away from us, is the second brightest star in the constellation Sagittarius; its Babylonian name is of unknown origin. Blue-white Nunki is a B star and one of the hotter of the bright stars, radiating much of its light in the ultraviolet. Typical of its breed, it is a fast spinner, rotating with a speed of over 200 km/s – 100 times that of our Sun. Although still on the main sequence, Nunki is much more massive than the Sun and will exhaust its internal fusion reserves in another 50 million years or so.
Jupiter is the only planet visible in the evening sky, brilliant and unmistakable in Scorpius, above Antares. Early risers will be able to see Mars overhead before the dawn, and Venus and Saturn in the east.
Wednesday 15th August :730 PM Pedros Castle
CAYMAN ISLANDS ASTRONOMICAL SOCIETY
NEWSLETTER AUGUST 2007
We will aim to meet this month on Wednesday, 15th August, 7.30.p.m. at Pedro Castle, weather permitting.
The Perseid Meteor Shower occurs on August 12-13th. This year the new moon will leave the sky dark. Look to the eastern sky in the constellation Perseus. Between 2 a.m. and dawn on August 13, if you get away from city lights, you could see hundreds of meteors.
This is one of the best showers of the year. The Perseids are a result of debris in space left by comet Swift-Tuttle. Although the comet is nowhere near Earth, the comet's wide tail does intersect Earth's orbit. We glide through it every year in July and August. Tiny bits of comet dust hit Earth's atmosphere traveling 132,000 mph. At that speed, even a tiny smidgen of dust makes a vivid streak of light--a meteor--when it disintegrates. The shower is most intense when Earth is in the dustiest part of the tail.
The mythological illustration that I used last month included the constellation Scorpius, more schematically shown above.
Jupiter, the fourth brightest object to light up the heavens, after the sun, moon, and Venus, shines unmistakably in the southern part of the sky, and serves as a guide to the Scorpion.
This is a distinctive constellation with its wide head and body curving to its tail. Glowing with a reddish hue at the heart of this asterism is the bright star Antares, the sixteenth brightest in the sky, although out shone this month by close Jupiter.
Antares is in the middle of the scorpion's curving body and rivals Mars in its reddish tint. This brilliant red star is one of the behemoths of our stellar neighborhood. If you placed it at the center of our own solar system, it would swallow Mercury, Venus, Earth, and Mars, and almost reach Jupiter.
The Scorpion was sent by Gaia to kill Orion when Orion boasted he would slay all the animals of the Earth; now Orion and Scorpius circle each other on opposite sides of the sky.
The Chinese included these stars in the Azure Dragon, a powerful but benevolent creature whose rising heralded spring, and in Maori mythology, this constellation can be Maui's magic jawbone used to fish up the North Island of New Zealand.
Tuesday 17th July 7:30 PM at Pedros Castle
CAYMAN ISLANDS ASTRONOMICAL SOCIETY
NEWSLETTER JULY 2007
The viewing session this month will be on Tuesday 17th, 7.30 p.m. at Pedro Castle.
Last months illustration showed, as well as the featured constellation Crux, Centaurus (Latin for centaur). One of the 48 constellations listed by Ptolemy, it counts also among the 88 modern constellations. This southern constellation is one of the largest in the sky. This half man, half horse marked the southernmost constellation visible to astronomers of classical times.
The constellation, as depicted above, represents the death of Lupus, the wolf, on the spear of a heavenly centaur. Early representations of the two constellations actually reveal the figure of a centaur holding a staff called the thyrsus and a wolf. The thyrsus is covered with ivy and grape vines and tipped with a pine cone. These are the ingredients of the godly drink called nectar. The she-wolf is Selene, the moon, who helps in the preparation of the drink.
Centaurus contains the closest star to the Sun, Alpha Centauri, 4.4 light years away. Alpha Centauri is also known as Rigil Kentaurus, from the Arabic meaning ‘centaur’s foot’. To the naked eye it appears as the third-brightest star in the sky, but a small telescope reveals it to be double, consisting of two yellow stars like the Sun. A third, much fainter companion star is called Proxima Centauri because it is slightly closer to us than the other two. Beta Centauri is called Hadar, from an Arabic name signifying one member of a pair of stars. Alpha and Beta Centauri mark the front legs of the centaur, and they act as pointers to Crux, the Southern Cross, which lies under the centaur’s rear quarters. Centaurus also contains the largest and brightest globular star cluster visible from Earth, Omega Centauri.
Gamma Centauri, Muhlifain, is a double star approximately 130 light years from Earth, which consists of two spectral type A0 stars each of apparent magnitude +2.9. For the resolution of the double star system a telescope of at least 15 centimeters in aperture is necessary. They have an orbital period of 83 years.
The star forms the hip or backside of the Centaur and is found directly north of the Southern Cross.
Saturn and Venus will be low in the west on viewing night, close to the crescent moon. Both will disappear from the night sky at months end, leaving brilliant Jupiter to shine alone.
Monday 18th June 7:30 PM Pedros Castle
CAYMAN ISLANDS ASTRONOMICAL SOCIETY
NEWSLETTER JUNE 2007
We will aim to meet this month on Monday, 18th June, 7.30.p.m. at Pedro Castle, weather permitting.
Crux, the Southern Cross will be visible for the rest of this month. On the night of the 18th, the constellation will be more upright than in the diagram above, hanging above the southern horizon.
Crux is the smallest constellation in the sky, but one of the most celebrated. The early Portuguese navigators saw it as a symbol of their faith, and the mystery of the unknown lent it an additional charm in the minds of those from whom the southern skies were hidden. There are other cross patterns formed by stars, but the distinguishing feature of the two bright pointers alpha and beta Centauri make Crux unmistakable.
Crux lies in a dense and brilliant part of the Milky Way, which makes the famous dark nebula known as the Coalsack striking in silhouette against the star background.
This is the head of the Emu to the native aborigines of Australia. The rest of the Emu is made from the dark lanes in the Milky Way.
Alpha Crucis was too far south to have been given an ancient name so Acrux is simply a combination of the A in alpha and Crux. Being of first magnitude (0.83), it is the 12th brightest star in the sky and 321 light years distant from us. Under high power, a telescope reveals it to be a binary system with two very similar B type stars having magnitudes of 1.33 and 1.73 separated by 4 arc seconds. With surface temperatures of around 27,000K they are highly luminous, the brightest 25,000 time more luminous than our Sun. In fact, the brighter star is itself a double, the two component stars orbit each other every 76 days but are too close to split with a telescope. So Acrux is a triple star system. A further, type B4, star lies 90 arc seconds away and may belong to the system as well. It has a similar proper motion - that is, its direction of motion through space - but is probably a more distant star that just happens to lie in the same direction.
NGC 4755 (k, kappa Crucis) is an open cluster of stars, that contains about 100 stars and is about 10 million years old. It lies some 7500 light years away and spans a 10 arc minutes field of view so filling a volume of space about 20 light years across. Lying close to Beta Crucis, it is easy to find and best seen with binoculars or a telescope at low power. It contains many highly luminous blue-white stars along with a central red supergiant that makes a beautiful colour contrast. It was named the Jewel box by Sir John Herschel who called it a "casket of variously coloured precious stones". It can easily be seen by the unaided eye as a star, and indeed was originally catalogued as such in pre-telescope times.
The three day crescent Moon will be very close to Venus and Saturn on viewing night, with Jupiter risen in the east.
NEWSLETTER JUNE 2007
We will aim to meet this month on Monday, 18th June, 7.30.p.m. at Pedro Castle, weather permitting.
Crux, the Southern Cross will be visible for the rest of this month. On the night of the 18th, the constellation will be more upright than in the diagram above, hanging above the southern horizon.
Crux is the smallest constellation in the sky, but one of the most celebrated. The early Portuguese navigators saw it as a symbol of their faith, and the mystery of the unknown lent it an additional charm in the minds of those from whom the southern skies were hidden. There are other cross patterns formed by stars, but the distinguishing feature of the two bright pointers alpha and beta Centauri make Crux unmistakable.
Crux lies in a dense and brilliant part of the Milky Way, which makes the famous dark nebula known as the Coalsack striking in silhouette against the star background.
This is the head of the Emu to the native aborigines of Australia. The rest of the Emu is made from the dark lanes in the Milky Way.
Alpha Crucis was too far south to have been given an ancient name so Acrux is simply a combination of the A in alpha and Crux. Being of first magnitude (0.83), it is the 12th brightest star in the sky and 321 light years distant from us. Under high power, a telescope reveals it to be a binary system with two very similar B type stars having magnitudes of 1.33 and 1.73 separated by 4 arc seconds. With surface temperatures of around 27,000K they are highly luminous, the brightest 25,000 time more luminous than our Sun. In fact, the brighter star is itself a double, the two component stars orbit each other every 76 days but are too close to split with a telescope. So Acrux is a triple star system. A further, type B4, star lies 90 arc seconds away and may belong to the system as well. It has a similar proper motion - that is, its direction of motion through space - but is probably a more distant star that just happens to lie in the same direction.
NGC 4755 (k, kappa Crucis) is an open cluster of stars, that contains about 100 stars and is about 10 million years old. It lies some 7500 light years away and spans a 10 arc minutes field of view so filling a volume of space about 20 light years across. Lying close to Beta Crucis, it is easy to find and best seen with binoculars or a telescope at low power. It contains many highly luminous blue-white stars along with a central red supergiant that makes a beautiful colour contrast. It was named the Jewel box by Sir John Herschel who called it a "casket of variously coloured precious stones". It can easily be seen by the unaided eye as a star, and indeed was originally catalogued as such in pre-telescope times.
The three day crescent Moon will be very close to Venus and Saturn on viewing night, with Jupiter risen in the east.
Sunday, 20th May, 7.30 at Pedro Castle.
CAYMAN ISLANDS ASTRONOMICAL SOCIETYNEWSLETTER MAY 2007
The next viewing session will be on Sunday, 20th May, 7.30 at Pedro Castle.
Checkout our website: http://caymanastronews.blogspot.com/.
Saturday, the night before our viewing, look out for the moon and Venus, which will be very near each other, with the moon in a waxing crescent phase.
Jupiter – the king of the planets – will be rising in the east at meeting time. Jupiter is the fourth brightest object to light up the heavens, after the sun, moon, and Venus.
Saturn remains in Leo during May and will continue to form a small quadrilateral with Regulus and two other stars of the constellation.
The constellation illustrated above is Corvus, the Crow or Raven, a very noticeable skewed box that crosses the sky just to the west of first magnitude Spica in Virgo. It has only 11 stars visible to the naked eye (brighter than magnitude 5.5), and can easily be seen in our southern sky. It was one of the 48 constellations listed by Ptolemy, and also counts among the 88 modern constellations.
Although Corvus contains no Messier objects, you can see two objects labeled “NGC” on the picture.
The New General Catalogue (NGC) is the best-known catalogue of deep sky objects in amateur astronomy. It contains nearly 8,000 objects, known as the NGC objects. The NGC is one of the largest comprehensive catalogues, as it includes all types of deep sky objects (not specialised to just galaxies for instance).
The catalogue was compiled in the 1880s by J. L. E. Dreyer using observations mostly from William Herschel, and then subsequently expanded with two Index Catalogues (IC I & IC II), adding nearly 5,000 objects.
NGC 4361 is a Planetary nebula. The nebula itself resembles a small elliptical galaxy, but the magnitude 13 center star gives away its true nature.
A planetary nebula is an astronomical object consisting of a glowing shell of gas and plasma formed by certain types of stars at the end of their lives.
They are in fact unrelated to planets; the name originates from a supposed similarity in appearance to giant planets. 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. About 1,500 are known to exist in the Milky Way Galaxy.
NGC 4038/NGC 4039 are known as the Antennae Galaxies) are a pair of interacting galaxies. They were both discovered by Friedrich Wilhelm Herschel in 1785.
As the two galaxies interact, billions of stars are born, mostly in groups and clusters of stars. The brightest and most compact of these are called super star clusters.
Recent observations show that only about 10% of the newly formed super star clusters in the Antennae will live to see their ten millionth birthday. The vast majority of the super star clusters formed during this interaction will disperse, with the individual stars becoming part of the smooth background of the galaxy. It is however believed that about a hundred of the most massive clusters will survive to form regular globular clusters, similar to the globular clusters found in our own Milky Way galaxy.
The two spiral galaxies started to merge together about 500 million years ago making the Antennae galaxies the nearest (at 63 million light years) and youngest example of a pair of colliding galaxies.
Within 400 million years, the Antennae's nuclei will collide and become a single core with stars, gas, and dust around it. Observations and simulations of colliding galaxies suggest that the Antennae Galaxies will eventually form an elliptical galaxy.
The Antennae galaxies take their name from the long antenna-like arms extending far out from the nuclei of the two galaxies, best seen by ground-based telescopes. These tidal tails were formed during the initial encounter of the galaxies some 500 million years ago. They give us a preview of what may happen when our Milky Way galaxy collides with the neighbouring Andromeda Galaxy about 6 billion years from now.
Clear skies
Nick (9256576, 9473065, 9492557)
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