Elliptic, spiral, irregular galaxies, Milky Way


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The universe is all worked up

Galaxies and the Milky Way
automatic translation
Definition

The Galaxy, it is the name of our galaxy, it is an enormous spiral wheel of stars, a diameter of 100 000 light years. What appears of the Earth, it is a white continuous band of the Milky Way. This galaxy really consists of three spiral arms (The arm Sagittarius, the arm of Orion and the arm Perseus). The mass of our Galaxy is of 2x1041 kg or 1011 solar masses. Numerous indications suggest that the center of numerous galaxies is occupied by a black hole. A galaxy is thus an assembly of stars, interstellar matter and probably big quantities of dark matter, the cohesion of which is assured by the strengths of gravitation, and the mass of which is of an order of height superior to hundred million solar masses. The Big and the Small Cloud of Magellan are nearby galaxies of ours, visible in the southern latitudes. They are with the Milky Way and Andromeda, the only visible galaxies in the bare eye. The Galaxies interact with their neighbors, and these interactions modify their shape. Two galaxies can even merge. The galaxies are three main morphological types: elliptic, spiral, irregular. As stars, which are grouped together in galaxies, most of the galaxies are also bound between them by the strength of gravitation.	A structure containing until about fifty galaxies is a group of galaxies. A structure containing several thousand galaxies grouped in a sector of some mega parsecs is a heap of galaxies. The groups and the heap of galaxies are grouped together in super heap, huge collections themselves containing tens of thousand galaxies. On a very large scale, the distribution of the heap of galaxies is not uniform, but not organized in patches or in strands. The spatial telescope Hubble sends regularly images showing us all the variety of the galaxies. Our Galaxy is of type spiral quite as the galaxy M83 above.

A big spiral galaxy		category : galaxies

The Sun is situated in the arm of Orion of our Galaxy and turns in a speed of km/s 270 around the galactic center, making a tour every 200 million years. A big galaxy spiral as our, can be seen in the bare eye. Situated in the constellation of Andromeda, the Big Nebula of Andromeda ( M31) is identical in our, it is situated in 2,3 million light years. To them two, these galaxies dominate the mass of the local group. We can only be amazed at the beauty of these bricks of the universe. They are some hundreds of billions and their number increases every time our spatial technology makes put off the horizon. The galaxies were born 3 in 4 billion years after Big Bang. It is the gravity which transformed diffuse clouds of hydrogen and helium, in embryos of galaxies.	These embryos collapsed under the influence of their own gravity. This collapse compressed and warmed the gaseous matter, transforming it into hundreds of billion small gaseous balls, of some million degrees, called <stars>. When all the gaseous matter metamorphosed into stars, these galaxies become then elliptic; 30 % of the galaxies are elliptic. They prevail in the heart of the heap. Others succeed in transforming into stars, that 4/5 of the gaseous mass, the fifth remainder flattens in a thin disk, continuing to be converted in stars but much more slowly and rather, along the spiral arms which are outlined there. It is the spiral galaxies which dominate the galactic world, 60 % of the galaxies are spiral. One find them especially, in the peripheral galactic regions of the heap.	Others set much more time to convert the gaseous matter in stars, because they are dwarfs, they contain only some billion stars, having no special shape, they are baptized by <irregular galaxies>. 10 % of the galaxies are irregular.

Density of the galaxies		category : galaxies

The galaxies live in the middle of the other galaxies and interact with their environment, especially there where the density of galaxies is very high, in the heart of the heap we can find 1000 in 10000 galaxies in a cube of some million light years aside. In our local group, there are only 10 galaxies in a cube of the same size. The galaxies move in the heap in a speed of the order of 1000km/. In such a traffic, the risks of collision are raised enough (one every 100 millions in 1 billion years).	These collisions can be only collisions, where scratches limit themselves to a loss of outside stars, torn away from their galaxy, they form then a sea of intergalactic stars. This heap, 1 billion years later will take the shape of an elliptic galaxy. From time to time, the collision takes place quite hard, the galaxies merge and the new more massive galaxy becomes more brilliant. If the collision takes place between two spiral galaxies, the disk of one of her can drill, becoming then a galaxy in the form of ring.	This hole will not last, the stars of the border will eventually fill it within a billion years and the galaxy will become elliptic. There are some huge elliptic galaxies in the heart of the heap, they are 10 times as big and more brilliant than their neighbors. Their mass exercises such a gravitational strength, as the galaxies passing near are gobbled up. The huge galaxy becomes then, even more massive and more attractive. A huge galaxy swallows a galaxy all the billion years approximately.

The center of the Milky Way		category : galaxies

The Milky Way is the central region of our galaxy. On the infrared image against this we see the exact center of our galaxy, known as the Central Molecular Zone and purple, the arch radio galactic center. A number of emission nebulae are visible through the massive young stars that illuminate from within. Like nearly all galaxies, our home galaxy at its center, a black hole. This black hole is called Sgr A. The galactic center is also home to the region of star formation, the most active of the galaxy.	This image, in addition to its scientific interest, won the first prize of the photographic UAI / NRAO of 2008. Credit: A. Ginsburg (U. Colorado - Boulder), and al. BGPS team, team GLIMPSE II.

The small cloud of Magellan		category : galaxies

This irregular galaxy which seems to orbit around the Milky Way is since observed time prehistoric by the inhabitants of the southern hemisphere, but it is the route around Ferdinand Magellan's world which will give his name. The Portuguese sailor Ferdinand Magellan and his equipage had all the time to study the southern sky during their navigation around the planet, at the beginning of the 16th century. These cosmic clouds are really irregular dwarfish galaxies, satellites of our own Galaxy. The Small Cloud of Magellan, Cover 15 000 light years in its biggest extension and contains several hundreds of million stars.	Situated in about 210 000 light years of us in the constellation of the Toucan. It is a part of the most close galaxies, the Milky Way, with the dwarfish galaxies of the Big Dog (approximately 25 000 light years), of the Sagittarius (approximately 3,5 million light years) and of the Big Cloud of Magellan (approximately 179 000 light years). With a visible magnitude of 2,7, it is also one of the most remote objects which can be seen in the bare eye. With a declension about 72 °, it is visible easily only since the southern hemisphere. It forms a couple with the Big Cloud of Magellan, situated 20 ° more in the East. As he, it is apparently an former blocked spiral galaxy which was deformed by the strengths of tide of the Milky Way. The Small Cloud of Magellan is a member of the local Group, our galactic heap. The Small Cloud of Magellan is connected with the Big Cloud by a bridge of gas and stars. These two clouds undergo the strengths of tide of the Milky Way. Magnificent sight of the small cloud of Magellan (credit NASA)	This sight of the small cloud of Magellan, includes also two heap spherical leading, NGC 362, the luminous point at the bottom of the image and 47 Toucan to the left of the Small Cloud of Magellan. The heap 47 Toucan is hardly 13 000 light years of us.

The spiral galaxy M33 or NGC 598		category : galaxies

The galaxy of the Triangle, also known under the name of M33, is a spiral galaxy of type Sc, situated in the constellation of the Triangle. The galaxy M33 NGC 598 the third of the local Group in ascending order, after the Milky Way and Andromeda. This galaxy is small compared with its neighbor, the galaxy of Andromeda M31, and with our Milky Way, but in the average of the spiral galaxies of the universe. M33 approaches us in 182 km/sec according to R. Brent Tully, or in 179 +/-3 km/sec according to the Ned. It is situated in 3 million years light. This galaxy was probably discovered before 1654 by Hodierna, follower of Galilee, who maybe grouped it with the opened heap NGC 752.	It was independently rediscovered on August 25th, 1764 by Charles Messier who cataloged it as M33. Classified by William Herschel September 11th, 1784 under the name H V.17, the galaxy of the Triangle was one of the first spiral nebulas identified as some by William Parsons. The galaxy M33 ou NGC 598, the third galaxy of the Local Group.

The spiral galaxy NGC1232		category : galaxies

The galaxy NGC 1232 is in the constellation Eridanus (the river). Distant about 100 million light years. At this distance, the size of the image corresponds to approximately 200 000 light years, is twice the size of our Milky Way. We can notice below to the left, the small galaxy was deformed by the enormous galaxy NGC on 1232.	We notice the difference of color enter the reddish nucleus (old stars) and the arms populated with young stars, thus blue stars. To note the small galaxy companion below to the left. credit photo: European Southern Observatory ESO/VLT

The spiral galaxy M104 or NGC 4594		category : galaxies

Galaxy of the Sombrero M 104 NGC 4594 in the heap Virgo. This brilliant galaxy owes this name of Sombrero to its appearance. According De Vaucouleurs, we see it since just 6 degrees in the South of the equatorial plan, realized by a thick dark band of opaque dust. This characteristic was probably the William Herschel's first discovery with its big telescope.	Opposite, the dissimilar image of 3 photos taken by the camera FORS1 of the VLT Antu (European telescope of 8,2 m of the ESO based in Chile). It was obtained after an exposure of 6:20 am on January 30th, 2000.

The spiral galaxy M101 or NGC 5457		category : galaxies

Galaxy " Pinwheel " M101 or NGC 5457, called also the Galaxy of the Mill, is a spiral galaxy among the most brilliant of the sky. M101 belongs to a group of at least 9 galaxies, the most striking members of which are NGC 5474 and NGC 5585. Other likely members of the group NGC 5204, NGC 5238, NGC 5477, UGC 8508, UGC 8837, and UGC 9405. The distance of M101: 24 (+/-2) million light years. With a diameter of 170 000 light years it is situated among the biggest galaxies. M 101, is a striking example of spiral galaxy, the relative nearness of which about 22 million light years allows to study it in detail. It seems that gravitational interactions with a nearby galaxy create waves of high mass and condense the gas which continues to turn around the center of the galaxy. These waves compress the incited gas and provoke the formation of stars.	The result is that M 101, has numerous regions of formation of extremely brilliant stars (called regions HII) spread over the spiral arms. M 101 is so big as its immense gravity deforms the smallest close galaxies.

The spiral galaxy M81 or NGC 3031		category : galaxies

The beautiful and lavish spiral galaxy M81 is in the constellation of the Great Bear. It was discovered by Johann Elert Bode in 1774. M81 or NGC 3031, is a spectacular, easily detectable galaxy with binoculars. This galaxy forms a remarkable couple with M82, member of the called group, groups of M81. Both galaxies are rather close because the distance of their centers is only about 150 000 light years. It is one of the most brilliant galaxies of the ground heavens, M 81 is also the foyer of second most brilliant supernova. This sight magnificently detailed reveals a brilliant yellow nucleus, bluish spiral arms and vast trails of dust, any characteristics rather similar to those of the Milky Way. A particularly remarkable trail of dusts pierces the galactic disk, down and to the right of the nucleus, unlike the other major spiral structures of M81.	This vein of dusts roaming is can be the persevering track of a contact between M81 and its small satellite galaxy, M82. The examination of the variable stars of M81 allowed to obtain one of the most reliable determinations of distance for an external galaxy, with 11,8 million light years.

The spiral galaxy M74		category : galaxies

With a striking nucleus and spiral arms developed possessions, M74 is a spiral galaxy, distant from 30 million light years, seen by the top situated in the Whale. It was discovered by Pierre Méchain in 1780 then observed by Charles Messier who integrated it into the catalog, some weeks later. Its mass is only 1/5 of that of our Galaxy but its diameter is 80 000 light years. The spiral arms contain many young stars or still in formation.	M74 is the most brilliant constituent of a heap of galaxies which includes besides: NGC 660, UGC on 1171, UGC on 1175, UGC on 1176, UGC on 1195 and UGC on 1200.

The galaxy NGC1672		category : galaxies

Numerous spiral galaxies present a bar in their center, but it certainly has nothing to do with prominent bar of the spiral galaxy NGC on visible 1672 opposite. We distinguish, veins of dusts represented by dark strands, of young people heap of blue stars, nebulas to the characteristic red brightness of the hydrogen, the long and brilliant one bar of stars there overlapping in the center, and to finish a brilliant active nucleus which accommodates probably a super massive black hole. The light puts not less than 60 million years to reach us from NGC on 1672, which measures about 75 000 light years of diameter. NGC 1672 is visible in the constellation of the Sea bream and makes the object of studies to discover how the bar can contribute to the formation of stars in the central regions of the galaxy. NGC 1672 shows here its region of formation of stars which is in a central galactic bar.	Arms in spiral do not twist themselves completely since the center as we are in the habit of seeing it on the spiral galaxies but are attached to both ends of a straight bar of stars including the nucleus. The question which settles is: they develop systematically in the center of the spiral galaxies to disappear then. The visible galaxies behind NGC 1672 give the illusion to be incorporated into the leading galaxy, while they are much more taken away. This remarkable image supplies a sight high definition of the big bar of the galaxy NGC on visible 1672 in the southern hemisphere, in the constellation of the Sea bream. Credit NASA: image of the spatial telescope Hubble

The galaxy Cartwheel or ESO 350-40		category : galaxies

The Galaxy of the wheel of the cart (so known under the name of ESO 350-40) is a lenticular or annular galaxy situated in approximately 500 million years light of distance in the constellation of the sculptor in the southern hemisphere. It is surrounded with a ring of 150 000 light years of diameter, consisted of young and brilliant stars. This galaxy was a galaxy identical to the Milky Way before it undergoes a head-on collision with a nearby galaxy. When the nearby galaxy crossed the Galaxy Cartwheel, the strength of the collision caused a powerful shock wave on the galaxy, as a stone thrown in one has a good laugh. By moving at high speed, this shock wave swept the gas and the dust, so creating a halo around the central part of the galaxy remained unhurt. It explains the bluish cloud around the center, the more brilliant part.		Galaxy CartWheel seen by the telescope Hubble.

The spiral galaxy NGC2683		category : galaxies

NGC 2683 is a spiral galaxy of magnitude 10, situated on the border of the Cancer. NGC2683 is situated between the constellation of the Lynx and that of the Cancer. Its peculiarity is that it appears at us of profile. Indeed, it is almost completely tilted, it does not allow us to distinguish the spiral arms and the central bulb of the galaxy. The fact of seeing the galaxy by the slice allows easily to measure the curve of rotation of the galaxy by using the Doppler effect. By estimating the rotation speed according to the distance in the center of the galaxy, we can determine the mass of the galaxy, it is this technique which shows the presence of dark matter in the Universe.	NGC 2683 is a spiral galaxy of magnitude 10

Fusion of NGC4038 and NGC4039		category : galaxies

There is approximately 500 million years, both galaxies NGC4038 and 4039 began to collide. They form one of the most known galactic couples today: Antennas. In 2004 and 2005, the telescope Hubble, with its new camera in high resolution ACS During the last visit of the telescope Hubble in 2002, the European camera for weakly brilliant objects (FORESAIL) was replaced by a camera of advanced technology for panoramic observations (ACS, Advanced Camera for Surveys). photographed this cosmic shock which takes place in 68 million light years. The cliché shows with an unprecedented neatness the numerous regions of formation of stars (in pink and in blue) appeared further to the compression of the interstellar gas engendered by the meeting. Already, in 1997, the spatial telescope had photographed the central part of Antennas. But this time, the astronomers succeed in detailing heap stellar huge, of which hundred of them only should survive in the form of heap spherical.	both galaxies NGC4038 and 4039 began to collide.

The galaxy NGC4465, heavenly masterpiece		category : galaxies

The galaxy NGC 4565 is a beautiful spiral galaxy, similar to ours. The beautiful spiral galaxy NGC 4565 is seen from Earth. Also known as the Needle Galaxy for its narrow profile. The brilliant NGC 4565 is a show for spring telescopes of the northern hemisphere because it is in the region of the Coma Berenices at a distance of 31 million light-years. This color image shows the disk bulging of the galaxy and its central heart dominated by the lights of a population of yellow stars. The heart is obscured by clouds of dust remarkably cut the central galactic nucleus. This large island universe similar to our Galaxy has a diameter of 100 000 light-years. Some consider NGC 4565 as a masterpiece in heaven.	The spiral galaxy NGC 4565 order by the slice, in the region of the Coma Berenices. We note the important band of dust that hides part of the bulb. It belongs to the cluster of the Virgin. Shot from Earth, it presents its disk of gas and dust profile. It took 2h30 posed for this picture with the Ritchey-Chrétien telescope of 32 centimeters. Robert Gendler, Connecticut, CCD.

The galaxy NGC3370		category : galaxies

The spiral galaxy NGC 3370 is located about 100 million light-years from Earth in the direction of the constellation Leo. It closely resembles our own Milky Way, by its shape and size. In this beautiful image can be seen far into the orange color of many other galaxies scattered across deep space. The data collected from the image sufficiently precise, were used to determine precisely the distance to this galaxy by studying individual stars such as Cepheids. NGC 3370, in 1994 the spiral galaxy hosted a stellar explosion strong studied at the time.	The spiral galaxy NGC 3370 seen by the Advanced Camera for Surveys of the Hubble Space Telescope, Credit: NASA, ESA, Hubble Heritage (STScI / AURA).

The galaxy NGC7331		category : galaxies

NGC 7331, with a diameter of 100 000 al, is the main galaxy of a group of galaxies known as Deer Lick group in the constellation of the northern hemisphere, Pegasus. This group is not a mass as small galaxies visible on the image here against are much more remote than NGC 7331. The heart of the galaxy is composed of old stars that give reddish brown this aspect. As against its spiral arms are home to more young stars, which give them the color blue. It is about 46 million light-years from Earth in the constellation Pegasus Boreal. In a same size as our Milky Way galaxy, NGC 7331 is often seen as the apparent collection of galaxies that we see in the background, like a galactic clusters. But they are not in the same cluster because they are located too far (several hundred million light years) of the galaxy NGC 7331.	The image of the universe Islands, an impressive depth of field, was obtained from data collected at the Calar Alto Observatory in southern Spain. NGC 7331 offers us here, the characteristic richness of its environment. Credit & Copyright: Vicent Peris (OAUV / PTeam), Gilles Bergond, Calar Alto Observatory.

The galaxy NGC 918		category : galaxies

The spiral galaxy NGC 918 is at the center of this beautiful celestial landscape. The galaxy is about 50 000 light years in diameter and is about 60 million light years from us in the constellation Aries. In the foreground of the picture you see the glistening stars in our galaxy, the Milky Way, they are bathed in clouds of cosmic dust reflecting weak starlight. Beyond its beauty, astrophysicists see this particular image, the light of a supernova, SN 2009js, they had no image. Pictured is the supernova to the marked locatiosn of the 2 strokes, just below and left of the center of the galaxy. This supernova is the explosion of a massive star in the plane of NGC 918.	It has been observed for the first time in October 2009 by teams from Japan and the United States specializing in the research of a supernova. The galaxy NGC 918, a beautiful spiral galaxy in the center of the image. Credit & Copyright: Joseph Brimacombe

The polar ring galaxy NGC 660		category : galaxies

The spiral galaxy NGC 660 polar ring is the center of a galaxy in the constellation Pisces. NGC 660 is a distance of more than 20 million light years from our solar system. Particularly rare form earned him the title of polar ring galaxy. It may be noted in this photo, a rotating ring, nearly perpendicular to the plane of the galaxy, as if the ring came from another galaxy captured. The polar ring of NGC 660 has a diameter of about 40 000 light years, it is larger than the disk of the galaxy. The few polar ring galaxies are of particular interest to scientists studying the gravitational influence of dark matter on the rotation of the disk and the polar ring.	Located 20 million light years from our solar system, the galaxy NGC 660, polar ring, seems to have been formed from the collision of two galaxies. Credit & Copyright: Immo Gerber & Dietmar Hager (TAO)

Related subjects

Galaxy groups	Star cluster
Nebulas	Constellations


	\| biographies	\| dwarf planets	\| galaxies	\| multiverse	\| rings	\| sun	\|
articles	\| citations	\| exoplanets	\| galaxy groups	\| nebulas	\| solar system	\| telescopes	\|
asteroids	\| comets	\| elements	\| glossary	\| planets	\| space probes	\|	\|
big bang	\| constellations	\| faq	\| links	\| quasars	\| stars	\|	\|

The universe is all worked up

© copyright : Astronoo		Astronomy - october 15th 2007

Galaxies and the Milky Way