Whirlpool Galaxy

The Whirlpool Galaxy (also known as Whirlpool galaxy, Messier 51 or NGC 5194/5195 refers ) is a large spiral galaxy in the constellation Canes Venatici. She is from the Hubble type Sc, that is, with more pronounced spiral structure. M51 has an apparent magnitude of 8.4 mag and an angular extent of 11.2 '× 6.9 '. The distance from our solar system is probably about 28 million light-years, but there are also different results 15-37 million light years.

M 51 has a close interacting companion. In NGC catalog it bears the number NGC 5195 (M 51 itself has the number NGC 5194 ). The companion galaxy is of irregular type, and has an angular extent of 5.8 ' x 4.6 ' and a brightness of 9.6 mag.

In M 51 is currently an exceptionally active star formation takes place, which is probably caused by the tidal interaction with NGC 5195. Therefore, the galaxy has a high proportion of young and massive stars, but these are only to be comparatively short-lived with a few million years. In M51 three supernovae have been observed within 17 years: SN 1994I in April 1994, SN 2005cs in June 2005 and SN 2011dh in May / June 2011 Two supernovae marked the end of such massive stars as explosions of type Ic and type II.

M 51 is also interesting because it is one of the nearest galaxies with an active galactic nucleus, a Seyfert galaxy of type II At its center a supermassive black hole disappears.

Discovery

The galaxy was discovered on 13 October 1773 by the French astronomer Charles Messier and recorded with the number 51 in his catalog of diffuse objects. 1845 saw the Irish astronomer William Parsons with his recently put into operation first giant telescope, the spiral structure of the object.

The galaxy in different spectral

The galaxy has been extensively studied because of their brightness and variety of interesting phenomena with a variety of methods. In the X-ray range you can clearly see the companion galaxy, while M 51 is only the core itself is as bright. For this, different mechanisms are responsible. The core of M 51 is light, because in him as an active galactic nucleus numerous collisions between gases take place, ie stellar winds, expanding supernova remnants, and the accretion of matter in the central black hole. The X-ray radiation of the companion, however, probably dates from the coronae of many stars of spectral type of the sun and later spectral types. The ultraviolet spectral region is, however, dominated by the spiral arms of M 51. The reason is that there are active regions of star formation and thus many young stars earlier types, ie particularly hot stars that exist that radiate strongly in the ultraviolet. The star-forming region in the spiral arm between M 51 and the companion is seen particularly clearly. The stars of the companion galaxy are in this spectral region, however, as good as invisible.

In visible light, the contributions of the various stars are balanced, but can also be seen here on the more reddish color of the companion, that there exist hardly any early spectral types. The gaseous nebulae, usually H II regions, which are dominated by the pink light of the hydrogen lines Hα to Hδ are clearly enhanced in contrast, they were not so striking to the eye. This fog agree very well with the brighter ultraviolet regions, which is because that the hydrogen lines of the Balmer series shine because the fog are excited by the ultraviolet light of young stars to shine. In the near infrared, however, the distribution of stars of later spectral types can be seen that only a few 1000 Kelvin hot. They are individually not as bright as the stars of earlier types, but much more numerous. In the mid-infrared can be seen at various temperatures of a few hundred Kelvin, finally, the distribution of interstellar dust in the Galactic disk. To appear as the dust lane in the spiral arm on the bottom left, which absorbs visible light, dark against the spiral while lights in the middle infrared themselves. The base situated therein, small star-forming region, clearly visible in the Ultaviolett and the visual at the fog, also excels in the dust as slightly warmer than the environment.

In the radio range, which is not shown here, then again determine gas clouds the picture, but those with neutral gas and molecules, the radiation of different emission lines is also distributed very differently, and thus allows conclusions on the temperature and density of the gas. In addition, there the active core is well marked. The companion is in the radio band, in turn, significantly darker than M 51 itself, since radio emission hardly, except for the late -type stars found there by the wind of individual AGB stars, or the emitted dust.

Ultraviolet light ( GALEX )

Near Infrared ( Hubble Space Telescope)

Mid- infrared ( Spitzer Space Telescope)

Far-infrared ( Herschel Space Telescope )

The active core

The bright region surrounding the active nucleus of the galaxy. In the picture the galaxy above, this region is only a few pixels tall in the center of the spiral. At a distance of 30 million light-years, this region has a diameter of about 120 light years. The to be seen in the picture dark band is a torus of dust, we look almost exactly from the side. Upon getting better pictures finally a bright core immediately adjacent to the dark band was visible. It was suspected the core originally behind the torus, but is now thought to have located this point the actual core. This point, which has a diameter of less than 5 light years, has about one million solar luminosities, the entire center about 100 million. A few hundred light years away from the core, out of the picture, there is a star-forming region, which is unusual in such proximity to the core and is attributed to the influence of the companion.

Observation

M 51 is an interesting object for amateur astronomers. For observing the Galaxy a telescope is necessary in any case, at least one or binocular with an oversized hole. An observation in the city is virtually impossible, best to search for one location with no light pollution. If the aperture of the telescope is less than 10 cm, is merely an elongated stain reveals. Only with openings of 20 cm and more the spiral arms can be observed. With the help of astrophotography, it is possible to scan even the H II regions and to see dark dust clouds.