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absolute zero: the temperature at which there is no longer any atomic or molecular vibrational motion: -459.67° Fahrenheit, -273.15° Centigrade, and 0° Kelvin. Deep outer space is 3° above absolute zero everywhere due to heat left over from the Big Bang 13.7 billion years ago. This 3° Kelvin background radiation (see "COBE") is the strongest evidence we have that the Big Bang actually took place. In late 2003 physicists at MIT were able to get within ½ of one billionth of 1 degree of absolute zero. Since temperature is a measure of atomic speed, cooling slows atoms down. At room temperature atoms move at the speed of a jet plane. At this new temperature it takes atoms half a minute to move just one inch, allowing physicists to study important tiny atomic movements that are otherwise drowned out in the fast vibrational motion of atoms and molecules at higher temperatures.

accidental (house) ruler: a planet ruling a house by virtue of its ruling the sign on the cusp of that house (see "ruler" below).

accidentally dignified: said of a planet conjunct an angle. Such a planet is most projected, manifest or noticeable; if the orb is relatively small the planet is often the most influential planet in the chart.

accretion: there are two meanings in astrophysics for this term: 1) the growth of an already massive object by gravitationally attracting more matter to itself, usually gaseous (see accretion disk below); and 2) in solar nebular theory, the collision and subsequent electrostatic adhesion of cooled, microscopic ice and dust particles in protoplanetary discs, eventually leading to planetesimals and perhaps to planets. If the central body is a black hole or some other massive body, the accretion disc often exhibits jets emerging from the disc’s axis of rotation. No one yet knows what causes these jets, but they are spectacular in their energy and extent.

accretion disk: a disk-like structure caused by matter falling into a gravitational source, such as a protosun in a solar nebula, a galactic nucleus, a black hole or a gamma-ray burster. As a large cloud of material collapses, the conservation of angular momentum requires that any small rotation it might have must increase. Since it is statistically unlikely that a large, dynamic cloud will have absolutely no rotation, all such clouds end up spinning as they contract inward. Centripetal force then causes the rotating cloud to form a disc, and tidal effects tend to align the disc’s rotation with that of the central gravitational source. It is probable that Jupiter-sized planets have accretion discs of their own, similar to the solar system as a whole of which they are a part.

adaptive optics (AO): A primary issue confronting large, modern telescopes is the turbulence of the Earth's atmosphere through which their images must necessarily pass before reaching the telescope. The larger the telescope, the more extreme this problem becomes. This is why nowadays all large telescopes are put on the tops of mountains particularly selected for the lack of turbulence in the atmosphere above them, as well as far from light pollution. It is also why the Hubble Telescope (and its planned successors) is in outer space.

Another way to address this problem, however, is referred to by some as the most revolutionary advance in astronomy since Galileo's 1609 introduction of the telescope itself. Known as adaptive optics, it is a procedure of measuring the atmospheric distortion in a celestial object's light beam, and then sending signals to deform a multitude of mirrors in the light path to exactly compensate for the atmospheric turbulence. This is accomplished by dividing the light reflected from the telescope mirror into hundreds of smaller beams, each of which is examined for deviation from a standard due to turbulence. The system's electronic circuitry computes the shape of many small mirrors, so that when each is altered their individual distorted beams realign in the same direction. Then these deformable mirrors are sent a signal that in fact does change their shapes, producing a composite, undistorted beam.

In order to know how to deform the deformable mirror, the shape of both the distorted and undistorted image need to be known. The undistorted shape for stars is usually just a point without detail. In fact, since stars are so far away, anything more than just a geometrical point must be an artifact (imperfection) of the optical system. To determine the final distorted shape of an ideal point source once it reaches the Earth’s surface, adaptive optics systems initially used a bright star near the telescope’s target as a comparison source for the distorted wavefront. This, however, required that the object being observed was close to a relatively bright star, which is usually not the case.

Subsequent AO techniques use a laser beam instead of a guide star. There's a naturally occurring layer of sodium atoms 60 miles above the Earth's surface (in the mesospheric layer) whose atoms fluoresce when excited by a laser beam. A laser directed into the sky very close to the direction of a celestial object will cause the mesosphere's sodium atoms to fluoresce, and that directional location becomes a "guide star" for the celestial object of interest. This allows any object to be observed even with no bright stars nearby.

aegis: the shield of Pallas Athena and Zeus, fashioned by Hephaestus with Medusa’s head in the center and ornamented with golden tassels; or, the skin of the giant Pallas slain by Athena (or of the goat Amalthea which suckled Zeus) used as a cuirass or thrown over the shoulders. Originally the agent of protection of these gods, it has come to mean any protection, shield or sponsorship.

afflicted: said of a planet in a sign contrary to its nature, as Moon in Capricorn or Scorpio; Mars in Libra, Taurus or Cancer; Venus in Aries, Virgo or Scorpio; OR with a hard aspect from Mars, Saturn, Uranus, Neptune or Pluto. Jupiter afflictions are not as severe, and denote excesses or poor judgment.

air: one of the four elements (earth, air, fire and water) by which the signs and houses are categorized. Air represents thought, relationship, and the breath. For its application in the signs and houses, see below. In matter, if a liquid is continuously heated there comes a point at which the average vibrational energy of the constituent atoms or molecules so exceeds their bonding energy that they repel each other. At this point the liquid boils and becomes a gas, the physical manifestation of the astrological element air. Continued heating turns the gas into plasma, of which stars are made. See "plasma" for an explanation of temperature, absolute zero, and the four states of matter.

air house: the third, seventh and eleventh houses; houses with the same ordinal numbers as the three air signs.

air sign: The element of thought, knowledge, relationship, and all aspects of the mind, as exemplified by the air signs Gemini, Libra and Aquarius.

albedo: the extent to which an object diffusely reflects light, defined as the ratio of diffusely reflected to incident electromagnetic radiation. Albedos range from 0 (least reflective) to 1 (most reflective). Charcoal has an albedo of 0.04; fresh snow an albedo of 0.9. Enceladus (see pages 164, 165) has an astounding albedo of 0.99, whereas the average albedo of the Earth is about 30% (0.30).

angle(s): the first, fourth, seventh and tenth house cusps, formed from the intersection of the local horizon and meridian circles with the ecliptic.

angular: the first, fourth, seventh or tenth houses, or said of a planet therein; a planet in these houses is very strong, and if conjunct an angle (orb about 3-6°) its energy is probably the most projected or noticeable in the chart; the closer to the angle, the stronger this effect is.

angular momentum: the amount of energy in a body rotating about a point or an axis, defined as the product of that body’s radial displacement from its point or axis of rotation times the bodies linear momentum (momentum = mass times velocity). This relationship is expressed as L = r x mv. Therefore a body’s angular momentum increases in direct proportion to its mass, its velocity, and its distance from its point or axis of rotation. Angular momentum is a conserved quantity, which means that unless a body is acted upon by an outside force, its angular momentum remains constant. This is what causes a planet’s or a gyroscope’s axis to tend to stay pointed in the same direction, which gives us compasses and a north polar star by which to navigate.

anomalistic (month): The Moon’s orbit is an ellipse with extreme distances from Earth called apsides: the closest point to Earth being perigee, the furthest apogee. The line of apsides joining perigee to apogee is not fixed in space, but makes a full circle (lunar precession) every 9 years. The average period for the Moon to return to the same precessing apsis is the anomalistic month, averaging 27.554551 days (27d 13h 18m 33.2s). Since the Moon’s distance from Earth and hence its apparent diameter varies over the anomalistic month, it therefore has relevance in predicting eclipses.

Antikythera mechanism: an ancient mechanical computer designed to calculate the positions of the Sun, Moon and the 5 visible planets, built about 100 BC perhaps by Archimedes or Hipparchos. The oldest known complex scientific calculator, it had at least 37 gears and could predict eclipses using the saros and exeligmos cycles.

aperture: the diameter of the mirror on a reflecting/compound telescope or the lens on a refractor; the aperture of a telescope determines the its light gathering power.

aphelion: the point in its orbit where an object is furthest from the Sun (opposite of perihelion); the term apogee is used for objects orbiting the Earth; "apoapsis" is used to refer to the furthest point in an orbit around bodies other than the Sun.

APOD: "Astronomy Picture of the Day;" an archive of popular astronomical photographs (Hubble, space missions, etc., updated daily: on the internet and maintained since June 16, 1995 by Robert Nemiroff and Jerry Bonnell of NASA. Many—if not most— of the astronomical photographs in this book are APODs.

apogee: the point in its orbit where an object is furthest from the Earth (opposite of perigee).

applying: said of aspects that become closer or more exact with time; stronger than a separating aspect.

apsides: plural of apsis (see next)

apsis: that point in the orbit of a planet or moon nearest to (lower apsis) or farthest from (higher apsis) the center of attraction; the "line of apsides" is the major (or long) axis of an elliptical orbit.

Archimedes of Syracuse (c. 287-c. 212 BCE): Greek astronomer, physicist, inventor: the greatest mathematician of antiquity and perhaps of all time. He invented siege engines, the screw pump, explained the principal of the lever, approximated pi accurately, and may have invented machines to lift ships out of the water and set them on fire with mirrors. He was killed during the siege of Syracuse.

Aristarchus of Samos (c. 310-c. 230 BCE): a Greek astronomer and mathematician who first promulgated the idea that the earth and all the planets known at the time revolved around the sun. He also placed the planets in their correct order of distance from the sun and the fixed stars much more distant still; but Aristotle's and Ptolemy's geocentric model was favored over Aristarchus' heliocentric one.

arcsecond (''): a unit of angular measure equal to 1/60 of 1 minute of arc, or the apparent diameter of a dime 2.3 miles away. With 60 angular minutes (') in 1° (one degree), and 60 angular seconds (") in one angular minute, there are 3600" in 1°. Seen from Earth, Saturn and Uranus have respective angular diameters of 20" and 3". The closest star to us, Alpha Centauri, and the brightest star in the sky, Sirius, both have angular diameters of 0.007".

Arp, Halton: an American astronomer known for his 1966 Atlas of Peculiar Galaxies, the galaxies in which are often referred to by their Arp number.

ascendant (Asc): the intersection of the local eastern horizon and the ecliptic; where planets rise or ascend in the east; the beginning/cusp of the first house; that part of self with which we most identify in our ego, and where we project our personality.

Asclepius: the ancient Greek god of medicine and healing. Killed by Zeus for raising Hippolytus from the dead, his snake-entwined staff the rod of Asclepius, is still the symbol of the medical profession.

aspect: The angle in the ecliptic plane between two planets with the Earth at its apex is the "aspect" between those two planets. Planets are said to be "in aspect" when the angle between them is close to 360° divided by 1, 2, 3, 4, 6, 8 or 12. These divisors are the "harmonic number" of that aspect. This division results in aspects of 360°=0° (the conjunction-first harmonic), 180° (opposition-second harmonic), 120° or 240° (trine-third harmonic), 90° or 270° (square-fourth harmonic), 60° or 300° (sextile-sixth harmonic), 45° or 135° (semisquare and sesquiquadrate - eighth harmonics), and 30° or 150° (semisextile and quincunx - 12th harmonics). Aspects from 360° divided by 5, 7, 9, 10, 11, or integers >12 are less common, but the fifth (quintile) and seventh (septile) harmonics are calculated and displayed in your chart on page three.

Planets in aspect combine energies and work in harmony, in discord, or in a more esoteric fashion. Two planets 122° apart, for example, are said to be in an harmonious "trine" aspect, because they’re close to one third of the circle (120°) apart.

Although the faster of two planets in aspect is the active force making the aspect, the faster one is always learning lessons from and being shaped by the slower planet, never vice-versa. In the case of Venus opposed Neptune for example, since Venus is closer to the Sun and therefore faster in its orbit than Neptune, Venus is the one learning lessons from and being shaped by Neptune. The planets from slowest to fastest—from teacher to student—are Pluto, Neptune, Uranus, Saturn, Jupiter, Mars, Sun, Venus, Mercury and the Moon.

asteroid: one of millions of small bodies orbiting primarily between Mars and Jupiter. Their total mass is about ¼ the Moon’s; the largest four are Ceres, Pallas, Vesta and Hygiea (see pages 71, 143-148).

AU ("astronomical unit"): the distance of the Earth to the Sun: 92,956,000 miles. The AU is a unit of astronomical distance, usually between objects in or near the solar system. For example, the asteroids range from 2.5 AU to 3.3 AU from the Sun, Jupiter’s orbit has a mean radius of 5.2 AU, Chiron is 8.4 to 19 AU from the Sun, Pluto is 29.6 to 49.6 AU from the Sun, and Eris’ greatest distance from the Sun is 96.7 AU. The boundary between the Sun’s influence and interstellar space where the Sun’s solar wind runs into the solar winds of the stars (the heliopause) is estimated to be 100 AU from the Sun. Comets in highly elliptical orbits can travel as far as 50,000 AU from the Sun. For larger distances, light years or parsecs are used. There are 63,240 AU in 1 light year.

Augustus, Gaius Julius Caesar: aka Octavius, first emperor of the Roman Empire, 27 BC-14 AD. Posthumously adopted by his great-uncle Julius Caesar, he came into his inheritance on Caesar’s assassination in 44 BC. In 293 AD when the Roman Empire was divided into the Tetrarchy of 4 prefectures, Augustus became the title of the senior emperor of each prefecture, and Caesar the title of his second, junior emperor and successor.


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