galactic center

(redirected from Galactic Centre)

galactic center

The innermost region of our Galaxy, or its exact center. Interstellar extinction obscures this region by up to 30 magnitudes at optical wavelengths and information on the very complex phenomena in the galactic center has been derived mainly from radio, infrared, and X-ray observations. The central region (with radius around 200 parsecs) is bright in radio and infrared continuum emission, particularly in lines of molecular CO and atomic C. This central molecular zone accounts for about 10% of the Galaxy's total molecular mass and has a high density and temperatures (30–200K). Star formation at rates of 0.5 solar masses a year is occurring at many places within this central molecular zone, probably triggered by external events, such as shocks. In particular the central parsec shows evidence for recent massive star formation, with many emission-line stars centered on the core of the central stellar cluster. The peak of this infrared emission and the stellar density coincide with the radio emission from an H II region in Sagittarius A (West). This is generally considered to be the dynamic center of the galaxy. There is also extended X-ray line emission centered on the Galactic nucleus, with a size roughly half that of the central molecular zone, indicating that some of the gas not consumed by star formation is present as a hot plasma. The X-rays also reveal a point source at the position of Sgr A West.

The density of dust at the center is very low but probably increases beyond a radius of 1 parsec to give rise to a double-lobed structure, with a 100 μm luminosity of about 107 L O. This may be heated by ultraviolet radiation from a central object located at the position of Sgr A West. The source of this heating radiation is thought to be emission from a massive black hole.

Farther away from the center, radio observations indicate that there is a thin rapidly rotating disk of hydrogen extending out to a radius of about 750 parsecs and also gas moving rapidly away from the center. In particular there are two expanding arms of gas both roughly at a radius of 3 kiloparsecs. The arm on the sunward side of the center is approaching us with a speed of 50 km s–1 and the one on the other side is receding at 135 km s–1.

Galactic Center

(religion, spiritualism, and occult)

Earth is located in a spiral-shaped galaxy approximately 100,000 light-years in diameter. Our solar system lies on the outskirts of the galaxy, about 30,000 light-years away from the galactic center (GC). From Earth’s perspective, the GC is located in the latter degrees of the sign Sagittarius. (Owing to the tropical or moving zodiac that most Western astrologers use, the exact position of the GC appears to be is gradually shifting.) The GC is such an intense source of infrared emissions and microwaves that astrophysicists have speculated that an explosion took place there 10 million years ago. Because our solar system is actually rotating around the GC, the GC can be thought of as a bit like the sun of our solar system. The 250 million years that it takes for our solar system to complete one rotation is called a cosmic year.

Astrologers who have studied the effects of the galactic center in horoscopes have found that it exerts a powerful influence within a narrow orb of 2°, with some effect out to 4°. Individuals with inner planets or one of the angles conjunct the GC have, as noted in Philip Sedgwick’ book The Astrology of Deep Space, a potential link “with whatever it is behind all this.” When this transpersonal link is ignored, the individual can experience stress and confusion; when it is consciously appropriated, information can be grasped that the individual may seem to have no outward way of knowing. The GC is not significant in such natural events as earthquakes, but it does appear to be prominent in important events involving technology. It also seems to play a major role in human inventiveness, especially technological inventiveness.

Given the many points occupying contemporary astrological space—heliocentric planets, multiple midpoints, thousands of asteroids, and so forth—everyone surely has some such point in the latter degrees of Sagittarius. On this basis, some astrologers find it useful to examine the position of the galactic center in every chart, and, by its house placement, determine to which area of the native’s life the cosmos is “speaking.” The GC was located at 26°09’ Sagittarius in 1950, at 26°34’ in 1980, and at 26°51’ in 2000.

Sources:

Brau, Jean-Louis, Helen Weaver, and Allan Edmands. Larousse Encyclopedia of Astrology. New York: New American Library, 1980.
Sedgwick, Philip. The Astrology of Deep Space. Birmingham, MI: Seek-It Publications, 1984.

galactic center

[gə′lak·tik ′sen·tər]
(astronomy)
The gravitational center of the Milky Way Galaxy; the sun and other stars of the Galaxy revolve about this center.
References in periodicals archive ?
The Sun, just one of billions of other stars, is found on the outer edges of the galaxy - about two-thirds of the way - out from the galactic centre.
To put things in perspective, our solar system lives on the edge of the galaxy, about two-thirds away from the galactic centre.
In this study, RAVE stars were used to examine the kinematics (velocities) of stars in a large, 3D region around the Sun - the region surveys 6500 light years above and below the Sun's position as well as inwards and outwards from the Galactic centre, reaching a quarter of the way to the centre.
It's been long suspected that our Galactic Centre might have sporadically flared up in the past.
Gary will also be posting astrophotography from Chile, including his long-hoped-for shot of the galactic centre, at flickr account www.
When looking towards Cetus we are looking in completely the opposite direction to the galactic centre, towards the South Galactic Pole (which is actually in nearby Sculptor).
The detection of the galactic centre haze and the serendipitous mapping of cold gas are good examples of this.
Surveys are the principal product of the IRSF and excellent results have been achieved on the Magellanic Clouds, the Galactic Centre and the population of dwarf galaxies.
And anyway, the Sun and the galactic centre will not exactly coincide even in 2012.
Just as swirling leaves caught in a gust of wind can provide clues about air currents, so the stars' movements reveal information about forces at work at the galactic centre.
The Gemini image clearly suggests that the gas cloud through which the star is travelling is falling towards the galactic centre.
While some of the heating is down to the fierce ultraviolet radiation pouring from a cluster of massive stars that live very close to the Galactic Centre, they are not enough to explain the high temperatures alone.