Milky+Way+Galaxey

  After the //Big Bang// the universe and it's large number of galaxeys came to life. When that happend our own galaxy the Milky Way was created.The //Milky Way// is the galaxy which is the home of our Solar System together with at least 200 billion other stars (more recent estimates have given numbers around 400 billion) and their planets, and thousands of clusters and nebula, including at least almost all objects of Messier's catalog which are not galaxies on their own (one might consider two globular clusters as possible exceptions, as probably they are just being, or have recently been, incorporated or imported into our Galaxy from dwarf galaxies which are currently in close encounters with the Milky Way. As a galaxy, the Milky Way is actually a giant, as its mass is probably between 750 billion and one trillion solar masses, and its diameter is about 100,000 light years. Radio astronomial investigations of the distribution of hydrogen clouds have revealed that the Milky Way is a [|spiral galaxy] of Hubble type Sb or Sc. Therefore, our galaxy has both a pronounced disk component exhibiting a spiral structure, and a prominent nuclear reagion which is part of a notable bulge/halo component. Decade-long observations have brought up more and more evidence that the Milky Way may also have a bar structure (so that it would be type SB), so that it may look like M61 or M83, and is perhaps best classified as SABbc. [|Recent investigations] have brought up support for the assumption that the Milky Way may even have a pronounced central bar like barred spiral galaxies [|M58], M91 , M95 , or M109 , and thus be of Hubble type SBb or SBc. ·  More on the structure of the Milky Way The Milky Way Galaxy belongs to the Local Group, a smaller group of 3 large and over 30 small galaxies, and is the second largest but perhaps the most massive member of this group. M31, at about 2.9 million light years, is the nearest large galaxy, but a number of faint galaxies are much closer: Many of the dwarf Local Group members are satellites or companions of the Milky Way. The two closest neighbors, both already mentioned, have only recently been discovered: The nearest of all, discovered in 2003, is an already almost disrupted dwarf galaxy, the Canis Major Dwarf, the nucleus of which is about 25,000 light-years away from us and about 45,000 light-years from the Galactic Center. These two dwarfs are currently in close encounters with our Galaxy and in sections of their orbits situated well within the volume ocupied by our Milky Way. They are followed in distance by the more conspicuous Large and Small Magellanic Cloud at 179,000 and 210,000 light years, respectively. The spiral arms of our Milky Way contain interstellar matter, diffuse nebulae and young stars and open star clusters emerging from this matter. On the other hand, the bulge component consists of old stars and contains the globular star clusters ; our galaxy has probably about 200 globulars, of which we know about 150. These globular clusters are strongly concentrated toward the Galactic Center: From their apparent distribution in the sky, Harlow Shapley has concluded that this center of the Milky Way lies at a considerable distance (which he overestimated by factors) in the direction of Sagittarius and not rather close to us, as had been thought previously. Our solar system is thus situated within the outer regions of this galaxy, well within the disk and only about 20 light years "above" the equatorial symmetry plane (to the direction of the Galactic North Pole, see below), but about 28,000 light years from the Galactic Center. Therefore, the Milky Way shows up as luminous band spanning all around the sky along this symmetry plane. The solar system is situated within a smaller spiral arm, called the //Local// or //Orion Arm//, which is merely connection between the inner and outer next more massive arms, the //Sagittarius Arm// and the //Perseus Arm//; see our Milky Way Spiral Structure page. Similar to other galaxies, there occur supernovae in the Milky Way at irregular intervals of time. If they are not too heavily obscurred by interstellar matter, they can be, and have been seen as spectacular events from Earth. Unfortunately, none has yet appeared since the invention of the telescope. In order to obtain a picture of the whole Milky Way as it appears from Earth, one must either compose a mosaic of many photographs In the infrared light, the structure of the Milky Way can be better investigated, as the obscurring dust clouds are of better transparency for long wavelength IR than for the visible light. Our Sun, together with the whole Solar System, is orbiting the Galactic Center at the distance given, on a nearly circular orbit. We are moving at about 250 km/sec, and need about 220 million years to complete one orbit (so the Solar System has orbited the Galactic Center about 20 to 21 times since its formation about 4.6 billion years ago). In addition to the overall Galactic Rotation, the solar system is moving between the neighboring stars (peculiar motion) at a velocity of about 20 km/s, to a direction called "Solar Apex," at the approximate position RA=18:01, Dec=+26 (2000.0); this motion has been discovered by [|William Herschel] in 1783. The Milky Way galaxy has a whopping circumference of roughly 250-300 thousand light years! Within the main body of the Milky Way there are estimated to be between 200 and 400 billion stars. The Earth’s solar system is believed to exist very close to the Galaxy’s galactic plane, due to the fact that the Milky Way essentially divides the night sky into two virtually equal hemispheres. Scientists now estimate that in roughly three billion years, the Milky Way galaxy will actually collide with the Andromeda Galaxy, which is very slowly working its way towards us at a modest speed of about 1,800 kilometers per minute. Our Galaxy is classified as Sb (Sky Catalogue 2000.0) or Sbc by most sources. Newer investigations have brought up more and more evidence that the Milky Way probably has a bar, or barlike structure, in its central region, which would modify its classification to become a barred spiral of type SB, or intermediate type between barred and "normal" spirals, SAB. Recent investigations have brought up evidence that our Galaxy may even have a pronounced bar structure measuring as much as 27,000 light-years in length.
 * Galactic Mass[1] || 7 × 1011 Msolar ||
 * Galactic Center Distance (//R//0)[2] || 7.62±0.32 kpc ||
 * Local Disk Rotation Speed (Ω0) || 208±16 km s-1 ||
 * Solar Peculiar Motion (//V//0) ||
 * Direction of Rotation: || 5.25±0.62 km s-1 ||
 * To Galactic North: || 7.17±0.38 km s-1 ||
 * Galactic Disk Radius[1] || 15 kpc ||
 * Central Black Hole Mass[2] || ( 3.61±0.32 ) × 106 Msolar ||
 * Central Black Hole Position[3] ||
 * Right Ascension (2000.0J): || 17h 45m 40s ||
 * Declination (2000.0J): || −29° 00′ 28″ ||
 * Central Black Hole Proper Motion ||
 * Backer and Sramek[4] ||
 * Galactic Longitude: || −6.18±0.19 mas yr-1 ||
 * Galactic Latitude: || −0.65±0.17 mas yr-1 ||
 * Reid et al.[5] ||
 * Galactic Longitude: || −5.90±0.35 mas yr-1 ||
 * Galactic Latitude: || +0.20±0.30 mas yr-1 ||