Galaxies

The Milky Way (a translation of the Latin Via Lactea, in turn derived from the Greek Galaxia Kuklos) is the galaxy in which the Earth is found. When viewed from the Earth and its environs, it appears in the night sky as a hazy band of white light (hence "milky") across the celestial sphere, formed by stars within the disc of its namesake galaxy. It is also simply known as the Galaxy, as the Earth's solar system is a part of it. The Milky Way appears brightest in the direction of Sagittarius, where the galactic center lies.

Relative to the celestial equator, the Milky Way passes as far north as the constellation of Cassiopeia and as far south as the constellation of Crux. This reflects the fact that the Earth's equatorial plane is highly inclined to the galactic plane, as is the ecliptic (the plane in which the Earth and the other significant planets orbit the Sun). The fact that the Milky Way divides the night sky into two roughly equal hemispheres reflects the fact that the solar system lies close to the galactic plane.

To put the Milky Way into perspective, if you made it 130 km (80 mi) in diameter, our solar system would only be 2 mm (0.08 in) in diameter. Also, if a beam of light were to be shot around the Milky Way, it would take almost 250,000 years to complete its journey.

Age

In 2004, a team of astronomers estimated the age of the Galaxy. The team consisted of Luca Pasquini, Piercarlo Bonifacio, Sofia Randich, Daniele Galli, and Raffaele G. Gratton. They used the UV-Visual Echelle Spectrograph of the Very Large Telescope to measure, for the first time, the beryllium content of two stars in globular cluster NGC 6397. This allowed them to deduce the time elapsed between the rise of the first generation of stars in the entire Galaxy and the first generation of stars in the cluster, at 200 million to 300 million years.

Structure

Observed structure of the Milky Way's spiral arms

The stars in the Galaxy's disk rotate around the Galaxy's center, which is suspected to harbour a supermassive black hole. Sagittarius A* is thought to be the most plausible candidate for the location of this supermassive black hole. It takes the solar system about 226 million years to complete one orbit ("galactic year"), and so has completed about 25 orbits during its lifetime. The orbital speed is 217 km/s, i.e. 1 light-year in ca. 1400 years, and 1 AU in 8 days. The orbital speed of stars in the Milky Way does not depend much on the distance to the center: it is always between 200 and 250 km/s for the Sun's neighbours. Hence the orbital period is approximately proportional to the distance from the star to the Galaxy's center (without the power 1.5 which applies in the case of a central mass). The disk has a bulge at the center.

Observed and extrapolated structure of the spiral arms

Each spiral arm describes a logarithmic spiral (as do the arms of all spiral galaxies) with a pitch of approximately 12 degrees. There are believed to be four major spiral arms and which all start at the Galaxy's center. These are named as follows, according to the image above.

The Earth's solar system may be found close to the inner rim of this Arm, in the Local Fluff, 8.0±0.5 kpc from the galactic center. The distance between the local arm and the next arm out, the Perseus Arm, is about 6,500 light-years.

Outside of these is the Outer Ring or Monoceros Ring, a proposed ring of stars around the Milky Way by astronomers Brian Yanny and Heidi Jo Newberg. This ring consists of gas and stars torn from other galaxies as they merged with our own billions of years ago.

The disk is surrounded by a spheroid halo of old stars and globular clusters. While the disk contains gas and dust obscuring the view in some wavelengths, the halo does not. Active star formation takes place in the disk (especially in the spiral arms, which represent areas of high density), but not in the halo. Open clusters also occur primarily in the disk.

X-ray image of Milky Way taken by Chandra X-ray Observatory

The Galactic Neighborhood

The Milky Way, the Andromeda Galaxy and the Triangulum Galaxy are the major members of the Local Group, a group of some 35 closely bound galaxies; The Local Group is part of the Virgo Supercluster.

The Milky Way is orbited by a number of dwarf galaxies in the Local Group. The largest of these is the Large Magellanic Cloud with a diameter of 20,000 light years. The smallest, Carina Dwarf, Draco Dwarf, and Leo II are only 500 light years in diameter. The other dwarfs orbiting our galaxy are the Small Magellanic Cloud; Canis Major Dwarf, the closest; Sagittarius Dwarf Elliptical Galaxy, previously thought to be the closest; Ursa Minor Dwarf; Sculptor Dwarf, Sextans Dwarf, Fornax Dwarf, and Leo I.

Mythology

There are numerous legends in many traditions around the world regarding the creation of the Milky Way. In particular there are two similar ancient Greek stories that explain the etymology of the name 'Galaxias' and its association with milk. One legend describes the Milky Way as a smear of milk created when the baby Herakles suckled from the Goddess Hera. When Hera realized that the suckling infant was not her own but the illegitimate son of Zeus and another woman, she pushed it away and the spurting milk became the Milky Way Galaxy.

Another story tells that the milk came from the goddess Rhea, the wife of Cronus, and the suckling infant was Zeus himself. Cronus swallowed his children to ensure his position as head of the Pantheon and sky god, and so Rhea conceived a plan to save her newborn son Zeus: She wrapped a stone in infant's clothes and gave it to Cronus to swallow. Cronus asked her to nurse the child once more before he swallowed it, and the milk that spurted when she pressed her nipple against the rock eventually became the Milky Way.

Older mythology associates the constellation with a herd of dairy cows/cattle, whose milk gives the blue glow, and where each cow is a star. As such, it is intimately associated with legends concerning the constellation of Gemini, which it is in contact with. Firstly, with Gemini, it may form the origin of the myth of Castor and Polydeuces, concerning cattle raiding. Secondly, again with Gemini, but also with other features of the Zodiac sign of Gemini (i.e. Canis Major, Orion, Auriga, and the deserted area now regarded as Camelopardalis), it may form the origin of the myth of the Cattle of Geryon, one of The Twelve Labours of Herakles.

Peoples in Eastern Asia believed that the hazy band of stars were "Silvery River" of the Heaven. Also, Altair and Vega were thought to be lovers, who were bound not to meet each other but on the seventh day of the seventh month, Qi Xi (Tanabata in Japan and Chilseok in Korea), when the magpies form the bridge over the galactic river.

References & Links Wikipedia

Blue Galaxies

The Big Bang theory of the creation of the universe is supported by the announcement of the discovery of new celestial bodies know as blue galaxies. The small, distant galaxies, observed by space telescopes, are so far away that the light from them has been traveling for billions of years. We are therefore seeing them as they were when both they and the universe were quite young.

You might think that, because the galaxies are so far away, their light would be so strongly redshifted as to make the galaxies look red. This isn't the case because we see the galaxies when they were so young that they had many hot, young stars, and were actively forming new stars. As a result, most of their light was emitted in the blue and ultraviolet regions of the spectrum. The redshift only serves to shift the ultraviolet light into the blue. This makes it easier for us to see the ultraviolet emission from the galaxies, while still making them look very blue to us.

Lonely Galaxies Appear Blue

Space.com - June 13, 2005

There are galaxies that inhabit the nearly empty deserts of space. Unexpectedly, these "void galaxies" are still forming hot, blue stars even more than the average galaxy in the more populated regions of the universe.

Fiona Hoyle of Widener University presented the discovery of a thousand galaxies in the lonely wilds of the cosmic voids at the 206th Meeting of the American Astronomical Society last month in Minneapolis.

The voids are typically 100 million light-years across, and yet they contain only a few galaxies each. Taken together, the voids fill 40 percent of the volume of the universe, but their galaxies account for less than 5 percent of all galaxies.

"Void galaxies had been observed previously, but this is the first statistical sample," Hoyle told space.com. She and her collaborators were able to identify a large population of galactic oases in the huge map provided by the Sloan Digital Sky Survey.

The researchers found that these galaxies tend to form near the edges, as opposed to the centers, of the voids like hermits that want to remain within earshot of civilization.

But the most remarkable finding is how blue the void galaxies appear. No, this is not because they are lonely. Instead, the blue color indicates that they are still busy making stars.Young massive stars burn hotter and therefore bluer.

Over time, these bright blue stars use up their fuel and disappear, leaving only the less massive red stars to light up an old galaxy.

The implied star formation rate in the voids is higher than what is found in the average dense environment. This was not expected, since the gas supply for making stars is thought to be gravitationally swept up by higher density regions.

Most theories, therefore, assume that voids would need to form galaxies early on before the gas went away.

If this is correct, then the void galaxies may be what Hoyle calls "steady Eddies" - old galaxies that have been very conservative with how many stars they made over their lifetime.

"In this case void galaxies are like people that wisely saved for retirement so that they had funds at an old age, rather than spending all their money during their youth," Hoyle said.

[Metaphors: Blue is the color linked to higher/future frequencies of consciousness. It also connects to electricity, prophecy, indigo children, the blue alien lady, Isis, the Pleiades, Sirius, blue chakra, blue ray and ascended master, and much more.]

Milky Way Center

Sagittarius - The Archer is in the heart of the summer Milky Way.

The center of our Milky Way Galaxy in the constellation Sagittarius.

The Eye of a Galaxy

Serpent, Dragon, DNA

Center of the Milky Way Galaxy or the Heart

The Road Home NASA - June 13, 2009

Suntelia Aion

The Milky Way Galaxy is the inspiration for the symbol of the Ouroboros. In mythology the Milky Way Galaxy keeps a 'great time cycle' that ends in catastrophic change. This refers to a serpent of light (Milky Way) residing in the heavens, who, when viewed at the galactic central point near Sagittarius, eats its own tail. Suntelia Aion refers to the sun (light) rising out of the mouth of the ouroboros (aion) on the winter solstice December 21, 2012. Ancient historians, and especially Plato, referred to a cycle of catastrophe at the End of that Age.

Milky Way Galaxy in the News ....

Sagittarius and the Central Milky Way NASA - May 19, 2009

The Milky Way Over Ontario
NASA - July 29, 2008

New spiral arm in the Milky Way - 3kpc Arm
NASA - July 11, 2008

Two-Armed Spiral Milky Way (Animated) NASA - June 6, 2008

New Milky Way Map Created; Shows Two Fewer Main Arms
National Geographic - June 3, 2008

The Bird is the Word
Thunderbolts - June 10, 2008

Stars and Dust through Baade's Window NASA - December 19, 2007

Sky Over the Grand Tetons, Wyoming NASA - August 13, 2007

Old Faithful Below a Yellowstone Sky NASA - August 7, 2007

A Laser Strike at the Galactic Center NASA - July 31, 2007

Stars of the Galactic Center NASA - February 10, 2007

Origin Of Enigmatic Galactic-center Filaments Revealed
Science Daily - June 4, 2004

Puzzling Filaments in Milky Way Explained
Space.com - June 7, 2004

Andromeda Galaxy

The Andromeda galaxy also called Andromeda Nevula (catalog numbers NGC 224 and M31), great spiral galaxy in the constellation Andromeda, the nearest external galaxy (except for the Magellanic Clouds, which are companions of the Milky Way Galaxy, in which the Earth is located).

The Andromeda Galaxy is one of the few visible to the unaided eye, appearing as a milky blur. It is located about 2,000,000 light-years from the Earth; its diameter is approximately 200,000 light-years; and it shares various characteristics with the Milky Way system. It was mentioned as early as AD 965, in the Book of the Fixed Stars, by the Islamic astronomer as-Sufi, and rediscovered in 1612, shortly after the invention of the telescope, by the German astronomer Simon Marius, who said it resembled the light of a candle seen through a horn.

For centuries astronomers regarded the Andromeda as a component of the Milky Way Galaxy--i.e., as a so-called spiral nebula much like other glowing masses of gas within the local galactic system (hence the misnomer Andromeda Nebula). Only in the 1920s did the American astronomer Edwin Powell Hubble determine conclusively that the Andromeda was in fact a separate galaxy beyond the Milky Way.

Spiral Galaxies

Spiral Galaxies usually consist of two major components: A flat, large disk which often contains a lot of interstellar matter (visible sometimes as reddish emission nebulae, or as dark dust clouds) and young (open) star clusters and associations which have emerged from them, often arranged in conspicuous and striking spiral patterns and/or bar structures, and an ellipsoidally formed bulge component, consisting of an old stellar population without interstellar matter, and often associated with globular clusters.

The young stars in the disk are classified as stellar population I, the old bulge stars as population II. The luminosity and mass relation of these components seem to vary in a wide range, giving rise to a classification scheme. The pattern structures in the disk are most probably transient phenomena only, caused by gravitational interaction with neighboring galaxies. Our sun is one of several 100 billion stars in a spiral galaxy, the Milky Way.

Lenticular Galaxies

These are, in short, "spiral galaxies without spiral structure", i.e. smooth disk galaxies, where stellar formation has stopped long ago, because the interstellar matter was used up. Therefore, they consist of old population II stars only, or at least chiefly. From their appearance and stellar contents, they can often hardly be distinguished from ellipticals observationally.

Elliptical Galaxies

Elliptical galaxies are actually of ellipsoidal shape, and it is now quite safe from observation that they are usually triaxial 'cosmic footballs', as Paul Murdin, David Allen, and David Malin put it. They have little or no global angular momentum, i.e. do not rotate as a whole (of course, the stars still orbit the centers of these galaxies, but the orbits are statistically oriented so that only little net orbital angular momentum sums up). Normally, elliptical galaxies contain very little or no interstellar matter, and consist of old population II stars only: They appear like luminous bulges of spirals, without a disk component.

However, for some ellipticals, small disk components have been discovered, so that they may be representatives of one end of a common scheme of galaxy forms which includes the disk galaxies.

Irregular Galaxies

Often due to distortion by the gravitation of their intergalactic neighbors, these galaxies do not fit well into the scheme of disks and ellipsoids, but exhibit peculiar shapes. A subclass of distorted disks is however frequently occuring.