Whirlpool Galaxy (M51A/B or NGC 5194/5). Credit: NASA/ESA
|Observation data (J2000 epoch)|
|Right ascension||13h 29m 52. The National Aeronautics and Space Administration ( NASA, ˈnæsə is an agency of the United States government, responsible for the nation's public space program The European Space Agency ( ESA) established in 1975 is an intergovernmental organisation dedicated to the exploration of space, currently with 17 member In Astronomy, an epoch is a moment in time used as a reference for the Orbital elements of a Celestial body. In Astronomy, an epoch is a moment in time used as a reference for the Orbital elements of a Celestial body. In common usage a constellation is a group of celestial bodies that are connected together in some arrangement typically stars to form a visible figure or picture Canes Venatici ( Hunting dogs) is a small northern Constellation that was introduced by Johannes Hevelius in the 17th century Right ascension (abbrev RA; symbol α) is the Astronomical term for one of the two Coordinates of a point on the Celestial sphere 7s|
|Declination||+47° 11′ 43″|
|Redshift||463 ± 3 km/s|
|Distance||23 ± 4 Mly (7. In Astronomy, declination (abbrev dec or δ) is one of the two coordinates of the Equatorial coordinate system, the other being either In Physics and Astronomy, redshift occurs when Electromagnetic radiation – usually Visible light – emitted or reflected by A light-year or light year (symbol ly) is a unit of Length, equal to just under ten trillion Kilometres As defined by 1 ± 1. 2 Mpc)|
|Apparent dimensions (V)||11′. History The first direct measurements of an object at interstellar distances were undertaken by German Astronomer Friedrich Wilhelm Bessel in 1838 Galaxy morphological classification is a system used by Astronomers to divide galaxies into groups based on their visual appearance The angular diameter of an object as seen from a given position is the "visual diameter" of the object measured as an angle 2 × 6′. 9|
|Apparent magnitude (V)||9. The apparent magnitude ( m) of a celestial body is a measure of its Brightness as seen by an observer on Earth, normalized to the value 0|
|Notable features||Interacting with NGC 5195|
|Question Mark Galaxy, Rosse's Galaxy, M51a, NGC 5194, UGC 8493, PGC 47404, VV 001a, VV 403, Arp 85|
|See also: Galaxy, List of galaxies|
The Whirlpool Galaxy (also known as Messier 51a, M51a, or NGC 5194) is an interacting grand-design spiral galaxy located at a distance of approximately 23 million light-years in the constellation Canes Venatici. NGC 5195 (also known as Messier 51b or M51b) is a Dwarf galaxy that is interacting with the Whirlpool Galaxy (also known as M51a or NGC The Messier objects are a set of Astronomical objects first listed by French astronomer Charles Messier in his "Catalogue des Nébuleuses The New General Catalogue ( NGC) is the best-known catalogue of Deep sky objects in Amateur astronomy. The Uppsala General Catalogue of Galaxies (UGC is a catalogue of 12921 galaxies visible from the northern hemisphere The Catalogue of Principal Galaxies ( PGC) is an Astronomical catalogue published in 1989 that lists B1950 and J2000 Equatorial The Atlas of Peculiar Galaxies is a catalog of Peculiar galaxies produced by Halton Arp. A galaxy is a massive gravitationally bound system consisting of Stars an Interstellar medium of gas and dust, and Dark matter This is a list of notable galaxies. List 4C 3711 Abell 1835 IR1916 AM 0644-741 Interacting galaxies ( Colliding galaxies) are the result of one Galaxy 's Gravity disturbing another galaxy A grand design spiral galaxy is a type of Spiral galaxy with prominent and well-defined spiral arms as opposed to multi-arm and flocculent spirals which have subtler structural A spiral galaxy is a Galaxy belonging to one of the three main classes of galaxy originally described by Edwin Hubble in his 1936 work “The Realm of the A light-year or light year (symbol ly) is a unit of Length, equal to just under ten trillion Kilometres As defined by In common usage a constellation is a group of celestial bodies that are connected together in some arrangement typically stars to form a visible figure or picture Canes Venatici ( Hunting dogs) is a small northern Constellation that was introduced by Johannes Hevelius in the 17th century It is one of the most famous spiral galaxies in the sky. The galaxy and its companion (NGC 5195) are easily observed by amateur astronomers, and the two galaxies may even be seen with binoculars. NGC 5195 (also known as Messier 51b or M51b) is a Dwarf galaxy that is interacting with the Whirlpool Galaxy (also known as M51a or NGC Amateur astronomy, a subset of Astronomy, is a Hobby whose participants enjoy studying and observing celestial objects Binocular telescopes, or binoculars (also known as field glasses are two identical or Mirror - symmetrical telescopes mounted side-by-side and  The Whirlpool Galaxy is also a popular target for professional astronomers, who study it to further understand galaxy structure (particularly structure associated with the spiral arms) and galaxy interactions. A spiral galaxy is a Galaxy belonging to one of the three main classes of galaxy originally described by Edwin Hubble in his 1936 work “The Realm of the
The Whirlpool Galaxy was discovered by Charles Messier on October 13, 1773. Charles Messier ( June 26, 1730 &ndash April 12, 1817) was a French astronomer most notable for publishing an Events 54 - Nero ascends to the Roman throne 409 - Vandals and Alans crossed the Pyrenees Year 1773 ( MDCCLXXIII) was a Common year starting on Friday (link will display the full calendar of the Gregorian calendar (or a Common Its companion galaxy, NGC 5195, was discovered in 1781 by Pierre Méchain. NGC 5195 (also known as Messier 51b or M51b) is a Dwarf galaxy that is interacting with the Whirlpool Galaxy (also known as M51a or NGC Pierre François André Méchain ( August 16, 1744 &ndash September 20, 1804) was a French Astronomer and surveyor It was however not until 1845 that the Whirlpool became the first galaxy to be recognized as a spiral. This was achieved by Lord Rosse employing a 72-inch reflecting telescope which he constructed at Birr Castle, Ireland. William Parsons 3rd Earl of Rosse KP ( June 17, 1800 &ndash October 31, 1867) built the world's largest telescope in 1845 and it A reflecting telescope (also called a reflector) is an Optical telescope which uses a single or combination of Curved mirrors that reflect Light This article is about the castle in Birr the town in Ireland For alternative meanings see Birr (disambiguation. In 2005 a supernova (SN 2005cs) was observed in the Whirlpool Galaxy, peaking at apparent magnitude 14. A supernova (plural supernovae or supernovas) is a stellar Explosion. SN 2005cs was a Supernova in the Whirlpool Galaxy. It was a type II supernova discovered by a German amateur astronomer The apparent magnitude ( m) of a celestial body is a measure of its Brightness as seen by an observer on Earth, normalized to the value  Sometimes M51 is used to refer to the pair of galaxies, in which case the individual galaxies may be referred to as M51A (NGC 5194) and M51B (NGC 5195).
With the recent SN 2005cs derived estimate of 23 Mly distance, and an angular diameter of roughly 11. 2′, we can infer that M51's bright circular disk has a radius of about ~38,000 light-years. Its mass is estimated to be 160 billion solar masses. Mass is a fundamental concept in Physics, roughly corresponding to the Intuitive idea of how much Matter there is in an object Compared to 100 kly diameter of the Milky Way, M51 has about half its size and mass. The Milky Way (a translation of the Latin Via Lactea, in turn derived from the Greek Γαλαξίας (Galaxias sometimes referred to simply
A black hole surrounded by a ring of dust exists at the heart of the spiral. A black hole is a theoretical region of space in which the Gravitational field is so powerful that nothing not even Electromagnetic radiation (e The dust ring stands almost perpendicular to the relatively flat spiral galaxy. A secondary ring crosses the primary ring on a different axis, a phenomenon that is contrary to expectations. A pair of ionization cones extend from the axis of the main dust ring. Ionisation cones are cones of material extending out from spiral galaxies. 
Located within the constellation Canes Venatici, M51 is easy to find by following the easternmost star of the Big Dipper, Eta Ursae Majoris, and going 3. Canes Venatici ( Hunting dogs) is a small northern Constellation that was introduced by Johannes Hevelius in the 17th century This article is about the asterism; for other uses see Big Dipper (disambiguation. Eta Ursae Majoris (η UMa / η Ursae Majoris is a Star in the Constellation Ursa Major. 5° southeast. Its declination is +47°, so it is circumpolar for observers located above 43°N latitude and reaches high altitudes throughout the northern hemisphere making it an accessible object, especially from the very early hours in winter through the end of spring season, after which summer solstice somewhat hinders observations. A circumpolar star is a star that as viewed from a given latitude on Earth never sets (that is never disappears below the horizon due to its proximity to one of the Celestial Solstices occur twice a year when the tilt of the Earth's axis is most oriented toward or away from the Sun, causing the Sun to reach its northernmost and southernmost extremes
M51 is visible through binoculars on a dark night, but with modern amateur telescopes this galaxy is truly a sight to behold. It is very forgiving on the instrument, when seen even through a humble 10 cm telescope the basic outlines of M51 and its companion are visible. Under dark skies and seen with a moderate eyepiece through a 15 cm telescope one can detect M51's intrinsic spiral structure. With larger (>30 cm) instruments M51 is simply breathtaking. The various spiral bands are very obvious and several HII regions appear to be visible, and M51 can be seen to be attached to M51B. An H II region (also known as Emission nebula) is a cloud of glowing Gas and plasma, sometimes several hundred Light-years across The shape of the X-formation in the nucleus has often been compared to the Christian cross. The Christian cross is the best-known Religious symbol of Christianity.
As is usual for galaxies, the true extent of its size can only be gathered from inspecting deep photographs, and very long exposures reveal a large nebula extending beyond the visible circular appearance.
In January 2005 the Hubble Heritage Team constructed a 11477x7965 pixel composite image (shown in the info box above) of M51 using Hubble's ACS instrument, revealing this splendid galaxy and its companion in unprecedented detail. 
The very pronounced spiral structure of the Whirlpool Galaxy is believed to be the result of the close interaction between it and its companion galaxy NGC 5195. NGC 5195 (also known as Messier 51b or M51b) is a Dwarf galaxy that is interacting with the Whirlpool Galaxy (also known as M51a or NGC
Induced spiral structure in the larger galaxy isn't the only effect of the interaction. Significant compression of hydrogen gas occurs that leads to the development of starbirth regions. In pictures of M51 these show up as the bright blue 'knots' throughout the spiral arms.
Generally speaking, hydrogen gas is the most common component of the interstellar medium (the vast space between stars and planetary systems in galaxies). It exists primarily in its atomic and molecular form, and forms huge clouds throughout the entire galaxy. When large sources of gravitational pull pass nearby, such as other galaxies, gravitational interactions produce compression (density) waves that sweep through these hydrogen clouds. This causes some regions of the previously diffuse gas to compress into tight pockets of opaque and dense gas, these are dust lanes one so often sees in the spiral arms. In regions where the concentration and density of gas reaches a critical value, further collapse under its own gravitational pull occurs, and stars are born at the center of the collapse, where the gas is compressed so strongly that fusion initiates. In Physics and Nuclear chemistry, nuclear fusion is the process by which multiple- like charged atomic nuclei join together to form a heavier nucleus
When this happens, these new-born stars gobble up huge amounts of gas causing them to expand, shine even hotter, and finally sweep away the surrounding layers of dust and gas by increasing efflux of the stellar wind. The gigantic proportions of the clouds out of which they are born means stars seldom, if ever, are created in isolation. Thus regions of several hot young stars emit sufficient light energy that they can be seen in the high resolution pictures of M51 across millions of lightyears distance.
For an example of such a formation in our own galaxy, see M16, the Eagle Nebula. For an object in the constellation of Canis Major also called Eagle nebula see Seagull Nebula.
Decades ago, it wasn't known for certain if the companion galaxy NGC 5195 was actually a true companion or rather some other galaxy passing at a distance. The advent of radio astronomy and subsequent radio images of M51 unequivocally demonstrated the reality of the interaction.
Recent simulations bear out that M51's spiral structure was caused by NGC 5195 passing through the main disk of M51 about 500 to 600 million years ago. In this model, NGC 5195 came from behind M51 through the disk towards the observer and made another disk crossing as recently as 50 to 100 Myrs ago until it is where we observe it to be now, slightly behind M51.
The Whirlpool Galaxy is the brightest galaxy in the M51 Group, a small group of galaxies that also includes M63 (the Sunflower Galaxy), NGC 5023, and NGC 5229. The M51 Group is a Group of galaxies located in Canes Venatici. Galaxy groups and clusters are the largest Gravitationally bound objects to have arisen thus far in the process of cosmic structure formation The Sunflower Galaxy (also known as Messier 63, M63, or NGC 5055) is an Unbarred spiral galaxy in the Canes Venatici Constellation  This small group may actually be a subclump at the southeast end of a large, elongated group that includes the M101 Group and the NGC 5866 Group, although most group identification methods and catalogs identify the three groups as separate entities. The M101 Group is a loose Group of galaxies located in Ursa Major. The NGC 5866 Group is a small Group of galaxies located in the Constellation Draco.