Sagittarius Star Cloud

The Sagittarius Star Cloud (also known as Delle Caustiche, Messier 24, IC 4715) is a star cloud in the constellation of Sagittarius, approximately 600 light years wide, which was discovered by Charles Messier in 1764.

The stars, clusters and other objects comprising M24 are part of the Sagittarius or Sagittarius-Carina arms of the Milky Way galaxy. Messier described M24 as a "large nebulosity containing many stars" and gave its dimensions as being some 1.5° across, a description that fits the star cloud rather well. Some sources, improperly, identify M24 as the faint cluster NGC 6603.

M24 fills a space of significant volume to a depth of 10,000 to 16,000 light-years. This is the most dense concentration of individual stars visible using binoculars, with around 1,000 stars visible within a single field of view.

Amazing Milky Way

The Milky Way band

Image extracted from the amazing ALMA planetarium show, produced by ESO and the Association of French Language Planetariums. The emphasis of the show is the incomparable scientific adventure of the ALMA project. A young female astronomer guides the audience through the story that includes unique animations and footage, leading the viewer from the first observations by Galileo, 400 years ago, to the world of modern astronomy, moving from the visible wavelength domain to explore the millimetre-wave view of the Universe, and leaving light-polluted cities for unique settings in some of the highest and driest places on Earth.

Image from Cosmic Origins


Access Road to the ALMA Site

Acces road to the ALMA site in Chajnantor. The image was taken on December 2004.

Dark matter halo

The dark matter halo is the hypothetical gravitational core of a galaxy, consisting of dark matter.

The nature of dark matter in the galactic halo of spiral galaxies is still undetermined, but there are two popular theories: either the halo is composed of weakly-interacting elementary particles known as WIMPs, or it is home to large numbers of small, dark bodies known as MACHOs. It seems unlikely that the halo is composed of large quantities of gas and dust, because both ought to be detectable through observations. Searches for gravitational microlensing events in the halo of the Milky Way show that the number of MACHOs is likely not sufficient to account for the required mass.

The dark matter halo is the single largest part of the Galaxy as it covers the space between 100,000 light-years to 300,000 light-years from the galactic center. It is also the most mysterious part of the Galaxy. It is now believed that about 95% of the Galaxy is composed of dark matter, a type of matter that does not seem to interact with the rest of the Galaxy's matter and energy in any way except through gravity. The dark matter halo is the location of nearly all of the Galaxy's dark matter, which is more than ten times as much mass as all of the visible stars, gas, and dust in the rest of the Galaxy. The luminous matter makes up approximately 90,000,000,000 solar masses. The dark matter halo is likely to include around 600,000,000,000 to 3,000,000,000,000 solar masses of dark matter.

Milky seas effect

Milky seas is a condition on the open ocean where large areas of seawater (up to 6,000 square miles) are filled with bioluminescent bacteria, causing the ocean to uniformly glow an eerie blue at night. The condition has been present in mariner's tales for centuries – notably appearing in chapter 24 of Jules Verne's Twenty Thousand Leagues Under the Sea – but until recently it has not been rigorously documented. There have been 235 documented sightings of milky seas since 1915 - mostly concentrated in the north-western Indian Ocean and near Indonesia.

In 1985 a research vessel in the Arabian Sea took water samples during milky seas. Their conclusions were that the effect was caused by the bacteria Vibrio harveyi.

In 2005, Steven Miller of the Naval Research Laboratory in Monterey, California, was able to match 1995 Satellite images with a first-hand account of a merchant ship. U.S. Defense Meteorological Satellite Program showed the milky area to be approximately 15,400-km² (roughly the size of Connecticut). The luminescent field was observed to glow over three consecutive nights.

While monochromatic photos make this effect appear white, Monterey Bay Aquarium Research Institute scientist Steve Haddock (an author of a milky seas effect study) has commented, "the light produced by the bacteria is actually blue, not white. It is white in the graphic because of the monochromatic sensor we used, and it can appear white to the eye because the rods in our eye (used for night vision) don't discriminate color.

'Wild Rides' Around Ultracool Stars, Outside The Milky Way

Astronomers have found that stars of a recently discovered type, dubbed ultracool subdwarfs, take some pretty wild rides as they orbit around the Milky Way, following paths that are very different from those of typical stars. One of them may actually be a visitor that originated in another galaxy.
Adam Burgasser and John Bochanski of MIT presented the findings on June 9 at the American Astronomical Society's semi-annual meeting in Pasadena, Calif. The result clarifies the origins of these peculiar, faint stars, and may provide new details on the types of stars the Milky Way has acquired from other galaxies.

Ultracool subdwarfs were first recognized as a unique class of stars in 2003, and are distinguished by their low temperatures ("ultracool") and low concentrations of elements other than hydrogen and helium ("subdwarf"). They sit at the bottom end of the size range for stars, and some are so small that they are closer to the planet-like objects called brown dwarfs. Only a few dozen ultracool subdwarfs are known today, as they are both very faint — up to 10,000 times fainter than the Sun — and extremely rare.

Burgasser, associate professor of physics at MIT and lead author of the study, was intrigued by the fast motions of ultracool subdwarfs, which zip past the Sun at astonishing speeds. "Most nearby stars travel more or less in tandem with the Sun tracing circular orbits around the center of the Milky Way once every 250 million years," he explains. The ultracool subdwarfs, on the other hand, appear to pass us by at very high speeds, up to 500 km/s, or over a million miles per hour.

"If there are interstellar cops out there, these stars would surely lose their driver's licenses," says Burgasser.

Burgasser's team of astronomers assembled measurements of the positions, distances and motions of roughly two dozen of these rare stars. Robyn Sanderson, co-author and MIT graduate student, then used these measurements to calculate the orbits of the subdwarfs using a numerical code developed to study galaxy collisions. Despite doing similar calculations for other types of low-mass stars, "these orbits were like nothing I'd ever seen before," says Sanderson.

Sanderson's calculations showed an unexpected diversity in the ultracool subdwarf orbits. Some plunge deep into the center of the Milky Way on eccentric, comet‐like tracks; others make slow, swooping loops far beyond the Sun's orbit. Unlike the majority of nearby stars, most of the ultracool subdwarfs spend a great deal of time thousands of light‐years above or below the disk of the Milky Way.

"Someone living on a planet around one of these subdwarfs would have an incredible nighttime view of a beautiful spiral galaxy — our Milky Way — spread across the sky," Burgasser speculates.

Sanderson's orbit calculations confirm that all of the ultracool subdwarfs are part of the Milky Way's halo, a widely dispersed population of stars that likely formed in the Milky Way's distant past. However, one of the subdwarfs, a star named 2MASS 1227‐0447 in the constellation Virgo, has an orbit indicating that it might have a very different lineage, possibly extragalactic.

"Our calculations show that this subdwarf travels up to 200,000 light years away from the center of the Galaxy, almost 10 times farther than the Sun," says Bochanski, a postdoctoral researcher in Burgasser's group at MIT. This is farther than many of the Milky Way's nearest galactic neighbors, suggesting that this particular subdwarf may have originated somewhere else.

"Based on the size of its one billion‐year orbit and direction of motion, we speculate that 2MASS 1227‐0447 might have come from another, smaller galaxy that at some point got too close to the Milky Way and was ripped apart by gravitational forces," explains Bochanksi.

Astronomers have previously identified streams of stars in the Milky Way originating from neighboring galaxies, but all have been distant, massive, red giant stars. The ultracool subdwarf identified by Burgasser and his team is the first nearby, low‐mass star to be found on such a trajectory. "If we can identify what stream this star is associated with, or which dwarf galaxy it came from, we could learn more about the types of stars that have built up the Milky Way's halo over the past 10 billion years," says Burgasser.

The results presented at the meeting are based in part on two studies recently published in the Astrophysical Journal by Burgasser and coauthor Michael Cushing, a postdoctoral researcher at the University of Hawaii's Institute for Astronomy.

Other authors of this paper are Andrew West of MIT; Dagny Looper of the University of Hawaii, Manoa; and Jacqueline Faherty of the American Museum of Natural History, New York, NY.

Mound Erupts Volcano

Erupts of volcano

Mound of Gravel pieces

The Gravel is rock that is of a particular particle size range. Specifically, it is any loose rock that is bigger than two millimeters (2mm) in its largest measurement (about 1/12 of an inch) and no more than 64 millimeters (about 2.5 inches). The next smaller size class in geology is sand, which is >0.0625 mm to 2 mm in size. The next larger size is cobble, which is >64 millimeters to 256 millimeters (about 2.5 to 10 inches). Gravel can be sub-categorized into granule (>2-4 mm) and pebble (>4-64 mm). One cubic foot (28.32 dm3) of gravel usually weighs about 100 pounds (45 kg).

Gravel is an important commercial product, with a number of applications. Many roadways are surfaced with gravel, especially in rural areas where there is little traffic. Globally, far more roads are surfaced with gravel than with concrete or tarmac; Russia alone has over 400,000 km of gravel-surfaced roads. Both sand and small gravel are also important for the produce of concrete.

Lava -molten rock expelled volcano

Lava is molten rock expelled by a volcano during eruption. When first expelled from a volcanic vent, it is a liquid at temperatures from 700 °C to 1,200 °C (1,300 °F to 2,200 °F). Although lava is quite viscous, with about 100,000 times the viscosity of water, it can flow great distances before cooling and solidifying, because of both its thixotropic and shear thinning properties.

A lava flow is a moving outpouring of lava, which is created during a non-explosive effusive eruption. When it has stopped moving, lava solidifies to form igneous rock. The term lava flow is commonly shortened to lava. Explosive eruptions produce a mixture of volcanic ash and other fragments called tephra, rather than lava flows. The word 'lava' comes from Italian, and is probably derived from the Latin word labes which means a fall or slide. The first use in connection with extruded magma (molten rock below the earth's surface) was apparently in a short account written by Francesco Serao on the eruption of Vesuvius between May 14 and June 4, 1737.

described "a flow of fiery lava" as an analogy to the flow of water and mud down the flanks of the volcano following heavy rain. Felsic lava Felsic lavas such as rhyolite and dacite typically form lava spines, lava domes or 'coulees' (which are thick, short lavas) and are associated with pyroclastic (fragmental) deposits. Most felsic lava flows are extremely viscous, and typically fragment as they extrude, producing blocky autobreccias. The high viscosity and strength are the result of their chemistry, which is high in silica, aluminium, potassium, sodium, and calcium, forming a polymerized liquid rich in feldspar and quartz, which thus has a higher viscosity than other magma types. Felsic magmas can erupt at temperatures as low as 650 to 750 °C. Unusually hot (>950 °C) rhyolite lavas, however, may flow for distances of many tens of kilometres, such as in the Snake River Plain of the northwestern United States.

Mafic lava Mafic or basaltic lavas are typified by their high ferromagnesian content, and generally erupt at temperatures in excess of 950 °C. Basaltic magma is high in iron and magnesium, and has relatively lower aluminium and silica, which taken together reduces the degree of polymerization within the melt. Owing to the higher temperatures, viscosities can be relatively low, although still thousands of times more viscous than water. The low degree of polymerization and high temperature favors chemical diffusion, so it is common to see large, well-formed phenocrysts within mafic lavas. Basalt lavas tend to produce low-profile shield volcanoes or 'flood basalt fields', because the fluidal lava flows for long distances from the vent. The thickness of a basalt lava, particularly on a low slope, may be much greater than the thickness of the moving lava flow at any one time, because basalt lavas may 'inflate' by supply of lava beneath a solidified crust. Most basalt lavas are of a'a or 'pahoehoe' types, rather than block lavas. Underwater they can form 'pillow lavas', which are rather similar to entrail-type pahoehoe lavas on land.

Last Days On Earth

Saturn-moonlets within the rings

Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Saturn, along with Jupiter, Uranus and Neptune, is classified as a gas giant. Together, these four planets are sometimes referred to as the Jovian, meaning "Jupiter-like", planets.

Saturn has a prominent system of rings, consisting mostly of ice particles with a smaller amount of rocky debris and dust. Sixty-one known moons orbit the planet, not counting hundreds of "moonlets" within the rings. Titan, Saturn's largest and the Solar System's second largest moon (after Jupiter's Ganymede), is larger than the planet Mercury and is the only moon in the Solar System to possess a significant atmosphere.

Earth the planet from the Sun

Earth is the third planet from the Sun. Earth is the largest of the terrestrial planets in the Solar System in diameter, mass and density. It is also referred to as the World and Terra.

Earth's outer surface is divided into several rigid segments, or tectonic plates, that gradually migrate across the surface over periods of many millions of years. About 71% of the surface is covered with salt-water oceans, the remainder consisting of continents and islands; liquid water, necessary for all known life, is not known to exist on any other planet's surface.Earth's interior remains active, with a thick layer of relatively solid mantle, a liquid outer core that generates a magnetic field, and a solid iron inner core.

Solar System - creating a bubble

The Solar System consists of the Sun and those celestial objects bound to it by gravity: the eight planets and five dwarf planets, their 173 known moons,and billions of small bodies. The small bodies include asteroids, icy Kuiper belt objects, comets, meteoroids, and interplanetary dust.

The charted regions of the Solar System comprise the Sun, four terrestrial inner planets, the asteroid belt, four gas giant outer planets, and finally the Kuiper belt and the scattered disc. The hypothetical Oort cloud may also exist at a distance roughly a thousand times beyond these regions.

The solar wind, a flow of plasma from the Sun, permeates the Solar System, creating a bubble in the interstellar medium known as the heliosphere, which extends out to the middle of the scattered disc.

The Realm of the Nebulae

An elliptical galaxy is a galaxy having an approximately ellipsoidal shape and a smooth, nearly featureless brightness profile. They range in shape from nearly spherical to highly flattened and in size from hundreds of millions to over one trillion stars.

Elliptical galaxies are one of the three main classes of galaxy originally described by Edwin Hubble in his 1936 work “The Realm of the Nebulae”, along with spiral and lenticular galaxies.

Most elliptical galaxies are composed of older, low-mass stars, with a sparse interstellar medium and minimal star formation activity. They are surrounded by large numbers of globular clusters. Elliptical galaxies are believed to make up approximately 10-15% of galaxies in the local Universe but are the dominant type of galaxy in the universe overall. They are preferentially found close to the centers of galaxy clusters and are less common in the early Universe.

Galactic Center -rotational center of the Milky Way

The Galactic Center is the rotational center of the Milky Way galaxy. It is located about 7.6 kilo parsecs (25,000 ly) away from the Earth in the direction of the constellations Sagittarius, Ophiuchus, and Scorpius where the Milky Way appears brightest. There is a suspected super massive black hole at the Galactic Center of the Milky Way.

Because of interstellar dust along the line of sight, the Galactic Center cannot be studied at visible, ultraviolet or soft X-ray wavelengths. The available information about the Galactic Center comes from observations at gamma ray, hard X-ray, infrared, sub-millimeter and radio wavelengths.

Coordinates of the Galactic Center were first found by Harlow Shipley in his 1918 study of the distribution of the globular clusters. In the Equatorial coordinate system they are: RA 17h45m40.04s, Dec -29° 00' 28.1" (J2000 epoch).

The complex astronomical radio source Sagittarius A appears to be located almost exactly at the Galactic Center, and contains an intense compact radio source, Sagittarius A*, which coincides with a super massive black hole at the center of our Galaxy. Accretion of gas onto the black hole, probably involving a disk around it, would release energy to power the radio source, itself much larger than the black hole. The latter is too small to see with present instruments.

Our bodies receive-Sunlight Healing

The human race evolved under the sun and for thousands of years lived in close harmony with its heat and light.The infrared rays originated from the sun are useful in the treatment of neuralgia, neuritis, arthritis, and sinusitis. In treatment of pains, heat plays an effective role. Warmth keeps our body energetic. It also keeps the skin smooth and protected. Plants get food from the sun in the photosynthesis process. The foods we get from plants stored the solar energy in it. Our bodies receive the solar energy from the food in the form of fats, carbohydrates, and proteins. The ultraviolet rays are antiseptic in nature. It is capable of killing bacteria, viruses, fungi, yeasts, moulds, and mites in air, water and on surfaces. It also kills germs on our skin. For all types of skin diseases, Sunlight is a very useful treatment.

When ultraviolet rays from the sun comes in contact with ergosterol, a fluid found just under the skin, they convert it to vitamin `D`, which is absorbed into the bloodstream. Ten minutes of daily exposure to sunlight will supply us with the entire vitamin `D` that we need. The principal function of vitamin `D` is to promote calcium absorption in the gut and calcium transfer across cell membranes. This contributes to strong bones and a contented nervous system. Ultraviolet light converts cholesterol in the skin to vitamin `D`. This vitamin is essential for the proper handling of calcium in the body and thus in the prevention of rickets and adult osteomalacia. Interestingly, people cant overdose on natural vitamin `D` from the sun, even with day-after-day exposure, whereas synthetic vitamin `D` supplements can easily cause vitamin `D` toxicity.

Sunlight plays an effective role in regulating almost all our bodily processes. Sunlight has been shown to increase our sense of well-being and to improve sleep. Ultraviolet light coming into our eyes stimulate the pineal gland, which helps to regulate our Circadian Rhythm. It has been said, "Dark nights and bright days will help keep the hormones in the body functioning properly.

Sloan Digital Sky Survey

The Sloan Digital Sky Survey or SDSS is a major multi-filter imaging and spectroscopic red shift survey using a dedicated 2.5-m wide-angle optical telescope at Apache Point Observatory in New Mexico. The project was named after the Alfred P. Sloan Foundation.

The surveys were begun in 2000, and aims to map 25% of the sky and obtain observations on around 100 million objects and spectra for 1 million objects. The main galaxy sample has a median redshift of 0.1; there are redshifts for luminous red galaxies as far as z=0.4, for quasars as far as z=5; and the imaging survey has been involved in the detection of quasars beyond a redshift 6.

In the year 2006 the survey entered a new phase, the SDSS-II, by extending the observations to explore the structure and stellar makeup of the Milky Way, the SEGUE and the Sloan Supernova Survey, which watches after supernova Ia events to measure the distances to far objects.

The SDSS telescope uses the drift scanning technique, which lets the telescope fix and makes use of the earth's rotation to record small stripes of the sky. The image of the stars in the focal plane drifts along the CCD chip, instead of staying fixed as in tracked telescopes. This method allows consistent astrometry over the widest possible field and precision remains unaffected by telescope tracking errors. The disadvantages are minor distortion effects and the CCD has to be written and read in the same time.

Moon-largest natural satellite

The Moon is Earth's only natural satellite and the fifth largest natural satellite in the Solar System.

The average center-to-center distance from the Earth to the Moon is 384,403 km, about thirty times the diameter of the Earth. The Moon's diameter is 3,474 km,[6] a little more than a quarter of that of the Earth. Thus, the Moon's volume is about 2 percent that of Earth; the pull of gravity at its surface is about 17 percent that at the Earth's surface. The Moon makes a complete orbit around the Earth every 27.3 days (the orbital period), and the periodic variations in the geometry of the Earth–Moon–Sun system are responsible for the lunar phases that repeat every 29.5 days.

The Moon is the only celestial body to which humans have traveled and upon which humans have performed a manned landing. The first artificial object to pass near the Moon was the Soviet Union's Luna 1, the first artificial object to impact the lunar surface was Luna 2, and the first photographs of the normally occluded far side of the Moon were made by Luna 3, all in 1959. The first spacecraft to perform a successful lunar soft landing was Luna 9, and the first unmanned vehicle to orbit the Moon was Luna 10, both in 1966.[6] The United States (U.S.) Apollo program achieved the only manned missions to date, resulting in six landings between 1969 and 1972. Human exploration of the Moon ceased with the conclusion of the Apollo program, although a few robotic lander and orbiters have been sent to the Moon since that time. Several countries have announced plans to return humans to the surface of the Moon in the 2020s.

Dark matter

In astronomy and cosmology, dark matter is hypothetical matter that is undetectable by its emitted radiation, but whose presence can be inferred from gravitational effects on visible matter. Dark matter is postulated to explain the flat rotation curves of spiral galaxies and other evidence of "missing mass" in the universe. According to present observations of structures larger than galaxies, as well as Big Bang cosmology, dark matter and dark energy account for the vast majority of the mass in the observable universe.

The observed phenomena which imply the presence of dark matter include the rotational speeds of galaxies, orbital velocities of galaxies in clusters, gravitational lensing of background objects by galaxy clusters such as the Bullet Cluster, and the temperature distribution of hot gas in galaxies and clusters of galaxies. Dark matter also plays a central role in structure formation and galaxy evolution, and has measurable effects on the anisotropy of the cosmic microwave background.

All these lines of evidence suggest that galaxies, clusters of galaxies, and the universe as a whole contain far more matter than that which interacts with electromagnetic radiation: the remainder is frequently called the "dark matter component," even though there is a small amount of baryonic dark matter.

Declination

In astronomy, declination (abbrev. dec or δ) is one of the two coordinates of the equatorial coordinate system, the other being either right ascension or hour angle. Dec is comparable to latitude, projected onto the celestial sphere, and is measured in degrees north and south of the celestial equator. Therefore, points north of the celestial equator have positive declinations, while those to the south have negative declinations.

* An object on the celestial equator has a dec of 0°.
* An object at the celestial north pole has a dec of +90°.
* An object at the celestial south pole has a dec of −90°.

The sign is customarily included even if it is positive. Any unit of angle can be used for declination, but it is often expressed in degrees, minutes, and seconds of arc.

A celestial object that passes over zenith, has a declination equal to the observer's latitude, with northern latitudes yielding positive declinations. A pole star therefore has the declination +90° or -90°. Conversely, at northern latitudes φ > 0, celestial objects with a declination greater than 90° - φ, are always visible. Such stars are called circumpolar stars, while the phenomenon of a sun not setting is called midnight sun.

Barred spiral galaxy

A barred spiral galaxy is a spiral galaxy with a central bar-shaped structure composed of stars. Bars are found in approximately half of all spiral galaxies. Bars generally affect both the motions of stars and interstellar gas within spiral galaxies and can affect spiral arms as well.

Edwin Hubble classified these types of spiral galaxies as "SB" ("Spiral", "Barred") in his Hubble sequence, and arranged them into three sub-categories based on how open the arms of the spiral are. SBa types feature tightly bound arms, while SBc types are at the other extreme and have loosely bound arms. SBb type galaxies lie in between. A fourth type, SBm, was subsequently created to describe somewhat irregular barred spirals, such as the Magellan Cloud galaxies, which were once classified as irregular galaxies, but have since been found to contain barred spiral structures.

Sun's location

The Sun (and therefore the Earth and Solar System) may be found close to the inner rim of the Galaxy's Orion Arm, in the Local Fluff or the Gould Belt, at a hypothesized distance of 7.62±0.32 kpc (~25,000±1,000 ly) from the Galactic Center. The distance between the local arm and the next arm out, the Peruses Arm, is about 6,500 light-years. The Sun, and thus the Solar System, is found in what scientists call the galactic habitable zone.

The Apex of the Sun's Way, or the solar apex, is the direction that the Sun travels through space in the Milky Way. The general direction of the Sun's galactic motion is towards the star Vega near the constellation of Hercules, at an angle of roughly 60 sky degrees to the direction of the Galactic Center. The Sun's orbit around the Galaxy is expected to be roughly elliptical with the addition of perturbations due to the galactic spiral arms and non-uniform mass distributions. In addition, the Sun oscillates up and down relative to the galactic plane approximately 2.7 times per orbit. This is very similar to how a simple harmonic oscillator works with no drag force (damping) term. These oscillations often coincide with mass extinction periods on Earth; presumably the higher density of stars close to the galactic plane leads to more impact events.

Elliptical

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 Malian 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 elliptical, 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.

Spiral

Spiral galaxies usually consist of two major components: A flat, large disk which often contains a lot of interstellar matter (visible sometimes as reddish diffuse emission nebulae, or as dark dust clouds) and young (open) star clusters and associations, which have emerged from them (recognizable from the bluish light of their hottest, short-living, most massive stars), often arranged in conspicuous and striking spiral patterns and/or bar structures, and an ellipsoid ally 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.

Melkweg

The Melkweg (English translation: "Milky Way") is a popular music venue and cultural center in Amsterdam, the Netherlands. It is located on the Lijnbaansgracht, near the Leidseplein, a prime nightlife center of Amsterdam. It is housed in a former warehouse and is divided into a number of spaces of varying sizes. Besides a large hall for rock and pop music concerts, there are also spaces for dance/theater, cinema, photography and media-art. The Melkweg is run by a non-profit organization that has existed since 1970.

It is referenced in the Cracker song "Euro-Trash Girl", the Lag wagon song "Infectious" and in title of the Half Man Half Biscuit song "Prag Vec at the Melkweg". The title of The Church's song "Under the Milky Way" is also a reference to the Melkweg.

The website Fabchannel.com streams live and on demand concerts from the Melkweg.