Wednesday, February 24, 2010

The Constellations

-By Rishi Shah and Suresh Bhattarai

Throughout human history and across many different cultures, extraordinary names from mythical fables have been associated with distinguished star patterns of various shapes and sizes. Known commonly as constellations, they are seen magnificently all over the night sky. The current 88 constellations as recognised by the apex institution, the International Astronomical Union (IAU), are based on what was historically suggested by veteran Greek-Egyptian mathematician-cum-astronomer Claudius Ptolemy (circa 90-168 AD).

He had propounded the geocentric model of the Solar System and eventually of the universe in 150 AD, which was accepted by the society until the heliocentric model was proposed by Polish astronomer Nicolous Copernicus in 1543. In about 500 AD, Indian mathematician and astronomer Aryabhatta had already divulged an ingenious notion of the heliocentric Solar System independently. Among the constellations, the 12 zodiac manifestations bear special significance both in horoscopic astrology and astronomy.

Zodiacus in Latin figuratively describes the quaint circle of animals. The creation of the zodiacal signs has been motivated by classical figures from the Greek zodiac that represents weird animals, people, tools and mythological hybrids. Furthermore, the constellations through which the Sun traverses within one year are called the zodiacal constellations

Fantasy picture

In colloquial usage, any constellation is a group of celestial bodies, usually observable stars which appear to form a unique fantasy picture in the sky. Astronomers today still utilise old expressions, though the new system focuses primarily on constellations as queer grid-like segments of the celestial sphere. However, in Hindu Vedic astronomy, the 12 constellations of the zodiac are called Raashis. These are exclusively divided into 27 Nakshatras or lunar houses.

In 1922 and 1930, Belgian astronomer Eugene Delporte aided the IAU in partitioning the celestial sphere into 88 constellations, clearly devising their final demarcations. These constellations share the names of their renowned Greco-Roman predecessors, like Auriga (charioteer), Andromeda (chained princess), Orion (hunter), Leo (lion) and Scorpius (scorpion). While such formations were originally linked to mystical events, creatures, devices or persons, the categorisation of the night sky into recognisable displays was important on land and for sea navigation prior to the invention of the compass.

The division of the ecliptic into zodiacal representations allocated with particular stars had presumably originated from Babylonians (who inhabited Mesopotamia that is Iraq today) during the first millennium BC. The ecliptic is the apparent path that the Sun takes in the sky as it seemingly travels on an imaginary celestial sphere in one year. Zodiacal postulation was expounded also in the holy Rigveda roughly in 1700-1100 BC. The ecliptic was then cleaved into 12 equal zones of celestial longitude to create the first known celestial coordinate system, which is ostensibly advantageous over the modern equatorial or ecliptic coordinate system.

The Babylonian calendar assigns each month to a constellation that begins with the Sun’s position at the vernal equinox, which had dwelled then in Aries (ram). Consequently, it was dubbed the Age of Aries. For this reason, the first astrological symbol is Aries even after the vernal equinox has drifted away from Aries and lies presently in Pisces (fishes) due to the precession of the earth.

Popularly identified as precession of the equinoxes (because the equinoxes advance westward along the ecliptic relative to the fixed stars, opposite to the solar motion along the ecliptic), precession of the earth denotes a gravity-induced gradual shift in the orientation of the earth’s axis of rotation, mimicking the wobbling top that traces out a cone, which requires approximately 26,000 years to complete one cycle.

Greek astronomer and mathematician Hipparchus (190-120 BC) is credited for its discovery. As the earth revolves around the Sun, it arrives at two opposite points that are designated vernal and autumnal equinox from where the tilt of its axis (generally twenty three and half degrees to the perpendicular) is neither away from nor towards the Sun, and the Sun hovers vertically above the equator. They occur on March 20 and September 23 this year (2010). The duration of the night and day are almost equal worldwide on these days. If visualised from the earth’s perspective, at equinox, the Sun is at one of these two opposite equinoctial points on the celestial sphere where the celestial equator and ecliptic intersect.

In modern astronomy, a zodiac is a spherical celestial coordinate system. It characterises the ecliptic as its fundamental plane and the position of the Sun at vernal equinox peculiarly as its prime meridian. Since there are merely 365 and one fourth days in one year and 360 degrees in a circle, the Sun is allegedly gliding gracefully along the ecliptic plane at a rate of slightly less than one degree per day.

Traditionally, there were 12 zodiac constellations which were being used by astrologers. These zodiac constellations were separated by exotic boundaries that were adopted from antiquity. Now they have been redefined by astronomers in such a way that the Sun journeys quirkily through 13 constellations annually. The controversial 13th zodiac constellation is the famed Ophiuchus (serpent bearer) that is not embraced as one of the conventional zodiac constellations, even though the Sun spends a substantial amount of time from December 1 to December 19 each year comfortably in Ophiuchus.

The sprawling Ophiuchus alias Aesculapius was the legendry first doctor of medicine that encompasses the Serpens Caput (snake’s head) and Serpens Cauda (snake’s tail). Although the principal northern portion stays above the ecliptic, Ophiuchus’ southern part actually crosses it. The enchanting Scorpius stretches curiously below its feet as well as below the ecliptic.

The stellar arrangement that is not classed as a constellation is referred to as asterism, but nonetheless they are widely recognised by the astronomy community. Some obvious examples of asterisms include the exquisite circlet of Pisces, seven bright stars in the Ursa Major (great bear) known as Saptarsi locally or the Big Dipper or Plough elsewhere, and the large alluring summer triangle that is sketched by the resplendent stars Altair (Sravana), Deneb and Vega (Avijit) and could be viewed in the summer night sky fascinatingly in the Northern Hemisphere. These stars belong to the confounding constellations Aquila (eagle), Cygnus (swan) and Lyra (harp).

Whilst a grouping of stars may be officially labelled a constellation by the IAU, this does not unequivocally say that stars located in that constellation are necessarily gathered together in space. Sometimes they are apparently discerned near to each other, like the awe-inspiring Pleiades (Seven Sisters) that resides bewitchingly in the zodiacal constellation Taurus (bull). They are our bewildering interpretation of two dimensional images made up of stars with varying luminosity and differing distances.

Simple planetarium

To understand the Solar System, zodiac and equinoxes with the movements of the earth, moon, planets and other cosmic entities, the human orrey should prove to be one of the best instruments. It could effectively demonstrate astronomical concepts in a precise manner. The key features of the orbits of the heavenly objects are logically elucidated on the ground in great detail. The human orrey could be further considered as a simple planetarium on a modest ground.

Sky-enthusiasts especially school students and younger generation could play the role of the moving planets and comprehend the existence of our universe and the baffling evolution of lives on our blue planet earth through mind-boggling games and educative activities.

Source: The Rising Nepal, National English Daily,February 24,2010

Thursday, February 11, 2010

Photo Report: TWAN in the Land of Himalaya,Nepal

Finally, a report on TWAN activities in collaboation with Nepal Astronomical Society(NASO) is out now. Here are the some glimpses of the collaborative work of TWAN and NASO in Nepal during November 2009.

You can find more news on the follwing links:

We would like to thank Babak tafreshi and Oshin Zakarian to visit Nepal in our invitation to make these successful movements regarding astronomical outreach in Nepal. WE can not forgot the team of Acquainted WIth The Nights from Markham Street Film Company, Canada who have travelled such a long distance to film NASO/TWAN and AWB activities in Nepal as NASO is an affiliate of AWB since the beginning.Keep updated with our upcoming events through our blogs :-)

Observation Programme from the Central department of Physics, Tribhuvan University

An observational programme was held today in the Central department of physics of Tribhuvan University, Nepal by Nepal Astronomical Society. Though the climate was quite disappointing in the previous day, it swaggered the following day. The programme continued for five long hours from 3pm to 8pm. During day time, Sun was shown using solar filter in telescope. There was a long queue of observers for observing the awe-inspiring Sun. They were thrilled to see the Sunspots. Professors and lecturers of Tribhuvan University also participated in observation including the HOD of Physics, Prof. Dr. Lok Narayan Jha.

Followed by the sun observation, a brief introduction to evening celestial bodies and constellation was given including a brief insight to the global astronomy month, GAM2010 to be held in this April globally. As the Sun disappeared in the horizon and night sky slowly began to spread its beauty, the red planet was shown followed by the blue star- Sirius, the Orion nebula and other celestial bodies. Introduction and position of various constellations, stars and other objects were also given to the participants using pointer. Overall, it was a good outreach programme conducted by NASO.

Thursday, February 4, 2010

Night Sky in February 2010!

-By Rishi Shah

The alluring beauty of major planets, enchanting magnificence of arcane galaxies and nebulae along with mysterious entities of the heavens can be relished this month. As it gets dark, the entire sky comes alive with twinkling stars that sketch gorgeous constellations of different sizes and shapes resembling various unique objects. The zodiacal constellations of Pisces (fishes), Aries (ram), Taurus (ram), Gemini (twins), Cancer (crab) and Leo (lion) are unfurling fascinatingly across the sky from western to eastern horizon. Pentagon-alike constellation Auriga (charioteer) is dominating the evening sky with its bright star Capella (Brahma Ridaya) that is roughly fourty three light-years away. Perseus (legendary person) and Andromeda (chained princess) are drifting towards northwestern sky. Ancient constellation Auriga is teeming with fulgent star clusters and exquisite nebulae. It houses remarkable open star clusters M36, M37 and M38, emission nebula IC410 with intriguing Tadpoles, Flaming Star Nebula IC405 as well as the enigmatic pair IC417 and NGC1931 that are popularly recognized as imaginary spider and petite fly. This perplexingly intimidating predator and the cringing prey are barely ten thousand light-years away. They represent young star clusters that have evolved weirdly in interstellar clouds and are embedded bafflingly in glowing hydrogen gas. M38 manifests rich open star cluster, which is spreading out and their stars are slowly escaping over time as they rush around our galactic centre. Though it contains innumerable lurid blue stars, its most lambent star is puzzlingly yellow and it is nine hundred times more luminous than our Sun. M36 and M37 are equally engrossing embodiments of star clusters. All these three clusters are circa four thousand light-years away.

When strange star Epsilon Aurigae fades repeatedly every twenty seven years, it remains dim for two years before becoming lustrous again. It is eclipsed regularly by its dark companion. Starting from August 2009 its obscuration had arrived at its deepest point by December. It is now expected to remain dull and murky throughout 2010, before regaining its normal brightness in 2011. Huge Epsilon Aurigae is supposedly low mass star that is creeping towards its inevitable demise. It is periodically hidden by a single star dwelling in deluding dusty disk, which is estimated to possess a radius of sheer four AU (four times Earth-Sun distance that stretches on average to 150 million kilometers). It is perhaps one half AU thick. (AU is the abbreviation for Astronomical Unit) and is utterly two thousand light-years away. Similarly, eclipsing binary star Zeta Aurigae varies in magnitude with a period of fairly one thousand days. It is modestly eight hundred light-years away. Beguilingly fiery star AE Aurigae is engulfed in enticing emission nebula IC405, which is nicknamed the Flaming Star Nebula.

Unmistakably attractive Orion (hunter) is decorating the eastern sky after sunset. Canis Major (great dog), Canis Minor (small dog), Monoceros (unicorn) and dinky Lepus (hare) are following Orion. Their distinguished stars Betelgeuse (Ardra), Rigel, Procyon (Manda) and Sirius (Lubdhak) are scintillating enthrallingly. If supergiant Betelgeuse would be placed at our Solar System’s center it would extend to planet Jupiter’s orbit. Betelgeuse is about six hundred light-years away. It is reaching the end of its life span. When it would explode (supernova), it would be visible even during the day time. Blue Rigel would pass its supergiant stage soon either collapsing or shedding its outer layers and would transform into white dwarf. It is probably just over seven hundred light-years away. They are practically nine and eleven light-years away. Lengthy watery constellations Hydra (sea serpent), Eridanus (river) and Cetus (whale) are sprawling in southern sky. Tiny constellations Corvus (crow), Crater (cup) and Sextans (sextant) are straddled snugly on Hydra’s back. Bewitchingly giant binary star Mira consists of oscillating variable Mira A and Mira B. It is virtually over two hundred light-years away. Circumpolar constellations Draco (dragon), Cepheus (king), Cassiopeia (queen) and Ursa Major (great bear) are circling Polaris, the Pole Star alias Dhruba Tara, which resides cozily in Ursa Minor (little bear). Our galaxy the Milky Way runs mainly through Lacerta (lizard), Cassiopeia, Auriga and Monoceros from northwest to southeast horizon.

Elusive planet Mercury is hurrying in eastern sky across Sagittarius (archer) and Capricornus (sea goat) before sunup during the beginning of February. Ruddy Mars is blazing in eastern sky in Cancer right after sundown. It is floating above the famed Beehive star cluster (M44).

Minor meteor shower Delta Leonids would peak before dawn in western sky on 24 February with flashes of sporadic shooting stars that would emanate from Leo. Asteroid Vesta-4 would be dashing across the star field of Leo. Comet 81P/Wild is tumbling across Virgo above its resplendent star Spica (Chitra). Comet C/2007Q3 (Sliding Spring) is ploughing towards northeast horizon after crossing constellation Bootes (herdsman). They could be marvelled late at night through good binoculars. New moon falls on 14 February, while full moon (commonly referred to as full snow moon or colourful holi purnima) mystifies us all on 28 February. Venerated Maha Shivaratri is celebrated respectfully on 12 February.

( Note: Er. Rishi Shah, president of Nepal Astronomical Society(NASO) and Academician of Nepal Academy of Science and Technology(NAST) has been writting about astronomy for more than a decade).
Source: The Rising Nepal, National English Daily,Thursday,February 4,2010

"Hello Red Planet" in Nepal 2010!

An observational programme was arranged by Nepal Astronomical Society (NASO) on the premises of H.B. complex, Lalitpur on 29th January, 201o from 6:30pm to 9:00pm. The date was chosen as the opposition of Mars. A part from the beauty of Mars, people also enjoyed the marvelous moon, orion nebula, pleides and other celestial bodies. Overall, "Hello Red Planet" in Nepal was a success.