Special Sub-Topic: The Constellations & Their History
|To the serious astronomer, amateur or professional, what would the definition of a "constellation" be?|
A section of the celestial sphere. In 1928, the International Astronomical Union (IAU) divided the celestial sphere, upon which all objects in the sky can be thought to lie, into 88 constellations with fixed boundaries. These 88 constellations were, however, based on the "traditional" constellations, which were merely groups of stars that formed patterns, such as Orion (the hunter) and Scorpius (the scorpion). To a novice who is just getting acquainted with the celestial sphere, however, using the patterns formed by the stars is the best way to make himself/herself familiar with the sky at night.
|The Greek geographer, astronomer and astrologer, Claudius Ptolemaeus a.k.a. Ptolemy (ca.85-ca.165), in his work "Almagest" introduced 48 constellations, most of which are still recognised today. Which of the following WAS one of the constellations introduced by him?|
Perseus. Many of Ptolemy's constellations, including Perseus, were drawn from ancient mythology (actually, it wasn't all that "ancient" in his times), such as Andromeda, Cepheus, Cassiopeia, Hercules, Draco, Hydra and many others. The telescope and sextant weren't even invented in Ptolemy's times; they were respectively invented by Galileo in 1609 and by a mathematician and inventor (independently) around 1730. The constellation Mensa (the table), is way too far south for Ptolemy to have contrived from his Alexandria location (31 degrees north).
|Out of which Ptolemaic constellation was Crux, the Southern Cross, carved out by the German astronomer Johann Bayer in his 1603 text, "Uranometria"?|
Centaurus. Uranometria, published in Augsburg, Germany in 1603, was the first atlas that covered the entire celestial sphere. It contained 51 charts in all- 48 for each of the Ptolemaic constellations, one for the previously unknown southern skies, and 2 planispheres. Uranometria contained the famous Bayer designations for stars, which are still used today.
|Which two relatively large constellations, one far northern and the other equatorial, did Jacob Bartsch introduce in 1624?|
Camelopardalis (the giraffe) and Monoceros (the unicorn). Camelopardalis and the Monoceros are two of the most barren regions of the sky to the naked eye, and I assure you, bear no resemblance whatsoever to either giraffes or unicorns. The only solace for Monoceros is that the Milky Way passes through it, even though it's at its faintest here. Both of these constellations were named in 1613 by Petrus Plancius, an employee of the Dutch East India Company; they were merely charted by Bartsch in 1624.
|In which hemisphere do the majority (5 out of 7) of the constellations introduced by Johannes Hevelius in his 1690 text "Firmament urn Sobiescianum" lie?|
Northern. Johannes Hevelius made observations of sunspots and the Moon with his 150 ft. focal length telescope and is called the father of lunar topography. He also discovered 4 comets and suggested that these objects orbit the Sun in parabolic orbits. Hevelius introduced the constellations Canes Venatici, Lacerta, Leo Minor, Lynx, Vulpecula (in the northern hemisphere), Scutum and Sextans (in the southern hemisphere).
In September 1679, his instruments, books and observatory were maliciously destroyed by fire. He managed to repair the damage, and even observed the comet of December 1680. However, as a result of the shock, his health suffered and he died in January 1687.
|Among the 48 constellations introduced by Ptolemy was the large and unwieldy Argo Navis, the ship of Jason and the Argonauts. In 1763, Argo was broken up into 3 separate constellations by the French monk Nicolas-Louis de Lacaille: which of the following was NOT one of these?|
Pons Pontis, the deck. Besides Carina, Puppis and Vela, Lacaille also introduced the constellation Pyxis (the compass) under the name "Pyxis Nautica", supposedly to represent the compass carried by the crew of Argo Navis. However, Argo could not have had a compass on board; compasses are not known to have been used by the ancient Greeks for navigation. Besides these, Lacaille is credited with introducing more than 10 other constellations, primarily in the southern hemisphere. He also catalogued nearly 10,000 stars from the Cape of Good Hope (now in South Africa).
|After Lacaille, there was a period when every celestial cartographer felt obliged to introduce new constellations, all of which were rejected by the IAU when it gave a firm footing to 88 constellations in 1922. Among these, Quadrans Muralis, introduced by the Frenchman J. J. Lalande, continues to be remembered, because of a certain periodic event. Which is this?|
A meteor shower. The period that followed Lacaille saw the creation of a number of constellations that had no justification for their existence, with cumbersome names like "Globus Aerostaticus" (the hot-air balloon), "Machina Electrica" (the electric machine) and "Officina Typographica" (the printing shop)- one can clearly tell the Industrial Revolution was well under way!
Quadrans Muralis is, however, remembered for an annual meteor shower, the Quadrantids, which appear to radiate from where Quadrans used to be, hence the name. Quadrans Muralis is now a part of the constellation Bo÷tes. The Quadrantids are seen from the 1st through 5th of January, peaking on the 3rd. The parent body of the Quadrantids is now believed to be an asteroid 2003 EH1, which may be the same object as the comet C/1490 Y1 that was observed by the Chinese, Japanese and Koreans 500 years ago.
|Besides the 88 IAU-recognised constellations, there a few other widely known groups of stars that make easily recognisable patterns, such as the sickle in Leo, the Summer Triangle, the Great Square of Pegasus, and Orion's belt. What are these "unofficial" groups of stars called?|
Asterisms. Astronomical asterisms serve the purpose of merely helping one find one's way around the sky; they are all easy to identify, unlike numerous constellations, and some of them (actually!) bear a striking resemblance to what they are supposed to represent, the teapot of Sagittarius being an excellent example. The first pattern many beginners learn to recognise is the famous Orion's belt, which can be seen from almost the entire world.
|The constellation Ursa Major is the same thing as the "Big Dipper" or the "Plough".|
f. The "Big Dipper" (as it is called in the US) or the "Plough" (UK) is merely an astronomical asterism comprising seven bright stars in the constellation Ursa Major- alpha, beta, gamma, delta, epsilon, zeta and eta Ursae Majoris. Besides these stars, there is much more to Ursa Major, which is ranked third in terms of area covered.
|What is sometimes referred to as "the sea of the sky"?|
A region containing a number of constellations with water-related themes. Some of the constellations that are considered "watery" are Aquarius (the watter-carrier), Cetus (the whale), Pisces (the fish), Piscis Austrinus (the southern fish), Delphinus (the dolphin) and Eridanus (the river). All of these constellations are located in the same region of the celestial sphere, which is hence called the "sea" of the sky.
|The 88 constellations may be ranked according to their "size", or area covered on the celestial sphere. Which of the constellations, only 68 square degrees in area, is the smallest?|
Crux. Crux, or the Southern Cross, may be small, but it is by no means insignificant. It has two first magnitude stars, and contains one of the brightest regions of the Milky Way. It also contains the Jewel Box, an open cluster with stars of a variety of colours, as well as the Coal Sack (around 5 degrees across), dark nebulosity that obscures parts of the Milky Way.
|Among the modern constellations, which is unique in being split into two pieces- Caput (the head) and Cauda (the tail)?|
Serpens. Serpens (the snake) was one of Ptolemy's original 48 constellations, and is split into two parts, Serpens Caput and Serpens Cauda. The constellation Ophiuchus, representing the serpent-bearer, is located between these two parts, with Serpens Caput to its west and Serpens Cauda to its east. Only one star in Serpens- Unukalhai- is brighter than the third magnitude, as a result of which this constellation isn't very conspicuous from light-polluted areas. Part of the Milky Way band runs through Serpens Cauda (the tail).
|Our galaxy, the Milky Way, appears as a faint, hazy band of white light that stretches across the sky. Through which constellations does it pass?|
Cygnus, Vulpecula, Sagitta, Aquila, Scutum, Serpens, Ophiuchus, Sagittarius, Scorpius, Lupus, Ara, Norma, Circinus, Crux, Carina, Vela, Puppis, Canis Major, Monoceros, Gemini, Orion, Auriga, Perseus, Cassiopeia, Andromeda, Lacerta, Cepheus. The word "galaxy" literally means "milk"; the term was coined because the Milky Way, our galaxy, appears (with a little bit of imagination) like a river of milk running across the sky. The Milky Way band is formed by numerous stars in the galactic plane that collectively give it its white appearance. We can imagine our galaxy to be a disk, in which we are somewhere around half-way between the centre and the edge. This is why the Milky Way appears as a complete band around us- generally brighter in the south (in which direction the galactic centre is) and dimmer in the north. The galactic plane is inclined by a significant amount to both the ecliptic and the Earth's equator.
|Quite surprisingly, there are only three constellations that have more than one first-magnitude star (i.e. with magnitudes less than 1.50). Which of the following is NOT one of these?|
Eridanus. Orion, Centaurus and Crux are the only ones of the 88 modern constellations that contain two stars above the first magnitude: Orion contains Rigel (0.18) and Betelgeuse (0.45), Centaurus contains Alpha (-0.28) an Beta (0.61) Centauri, and Crux contains Alpha (0.77) and Beta (1.25) Crucis. Note that Rigel, Betelgeuse, Beta Centauri and Beta Crucis are slightly variable, and the magnitudes of Alpha Centauri and Alpha Crucis refer two the combined magnitude of a double star. Eridanus has only one first-magnitude star- Achernar (0.45).
|The zodiac is a band that extends approximately 8 degrees on either side of the ecliptic, and is a region both astronomers and astrologers are crazy about. While there are actually 13 constellations that lie on the ecliptic, the astrologer community recognises the existence of only 12 of them. Which is this so-called "13th constellation of the zodiac"?|
Ophiuchus. The serpent-bearer intrudes into the zodiac between Scorpius and Sagittarius, much to the ire of astrologers, who fervently wish Ophiuchus did not exist! The excuse given by them is that Ophiuchus was recognised as a part of the zodiac by the IAU only in 1930; however, the fact is that Ophiuchus was recognised as a zodiacal constellation at least 1700 years before the IAU even came into existence. Even Ptolemy's "Almagest", written in the 2nd century A.D., recognised Ophiuchus as a part of the zodiac. Why he eventually decided to remove Ophiuchus from his list of zodiacal constellations remains a mystery; one suspects it was just to make the math easier- 12 is a lot easier to divide than 13!
|The constellation names "Scorpio" (the scorpion) and "Capricorn" (the sea goat) are recognised by the IAU.|
f. The names "Scorpio" and "Capricorn" are used only in western astrology; astronomers use the names "Scorpius" and "Capricornus" respectively for these. Capricornus is the dimmest of all the zodiacal constellations with the exception of Cancer; on the contrary, Scorpius is the most magnificent.
|In the direction of which constellation does the galactic centre lie?|
Sagittarius. The galactic centre is located at a distance of roughly 26,000 light years in the direction of the constellation Sagittarius. Cool clouds of interstellar dust prevent direct observations at optical wavelengths of the galactic centre, though partial clearings like the famous Baade's Window are present. As such, most of our knowledge of the galactic centre comes from observations at gamma ray, X-ray, infrared and radio wavelengths. Exactly at the galactic centre, there is a complex source of radio emissions, Sagittarius A* (pronounced "Sagittarius A-star"), which many astronomers believe is a super-massive black hole.
|Which is the only constellation of the zodiac that represents an inanimate (non-living) object?|
Libra. Surprisingly, all the other zodiacal constellations represent living creatures or people: Aquarius, the water-carrier; Pisces, the fish; Aries, the ram; Taurus, the bull; Gemini, the twins; Cancer, the crab; Leo, the lion; Virgo, the maiden; Scorpius, the scorpion; Ophiuchus, the serpent-bearer; Sagittarius, the archer; and Capricornus, the sea-goat. Libra, which represents the scales, is hence the only exception.
|The two Magellanic Clouds, dwarf galaxies orbiting the Milky Way, are conspicuous objects in the southern hemisphere, where they appear like detached parts of the Milky Way band. The Large Magellanic Cloud (LMC) is located on the border between Dorado and Mensa; in which constellation does the Small Magellanic Cloud (SMC) lie?|
Tucana. The Magellanic clouds, also called Nubecula Major and Minor, are the most distant objects visible to the naked eye, with the exception of the Andromeda Galaxy, M31. Ferdinand Magellan, in his voyage around the world in 1519, was the first to bring the knowledge of the existence of these two objects to the western world. However, the first preserved mention of the LMC is that of the Persian astronomer, Al Sufi, who in the year 964, referred to it as "Al Bakr" or the "White Ox".
|What is the distance (in light years) to Orion?|
The question makes no sense.. Unlike what our ancestors thought, the stars in a constellation are in no way physically related! Constellations are completely arbitrary groupings of stars, and bear little significance in astronomical studies. All that is meant is that the stars of that constellation are in roughly the same direction from us: they may be several hundreds of light years, or more, apart, e.g. in the constellation Orion, the star Betelgeuse is 427 light years away, while Rigel is 773 light years away. Thus, the phrase "distance to a constellation" makes no sense at all. One can however, meaningfully calculate the average distance to a star-cluster or a galaxy, where the stars are all physically related.
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