Messier 102
NGC 5866, en av flera möjliga kandidater till M102, fotograferad av Rymdteleskopet Hubble.
Messier 102 är en galax som även kallas Spolgalaxen. M102 heter den eftersom den är det 102:a objektet i Charles Messiers 1700-talskatalog över diffusa objekt på himlen.
Dess bestämning är omtvistad. Upptäckaren Pierre Méchain har senare menat att observationen var en förväxling med Messier 101.[1][2]
Det finns emellertid skäl att tro att det kan vara frågan om NGC 5866, men det finns också flera andra galaxer som föreslagits som den rätta identiteten för M102.
M102 ligger i stjärnbilden Draken, 50 miljoner ljusår från oss, en platt galax, som från oss ter sig som ett tjockt streck.
Andra möjliga objekt
M101 and NGC 5866 anses som de troligaste kandidaterna för M102, men det finns flera andra objekt som också är möjliga.
NGC 5879, NGC 5907 och NGC 5908 är alla galaxer som befinner sig nära NGC 5866s position. Emellertid är ingen av dessa tre objekt lika ljusstarka, varför de är mindre troliga som kandidater.
NGC 5928 är en galax av 14:e magnituden mellan stjärnorna ο Boötis och ι Serpentis.
J. L. E. Dreyer föreslog i sina kommentarer till New General Catalogue, att detta kunde vara den galax som numrerades M102. Det skulle i så fall bero på att ι Serpentis vid observationen förväxlats med ι Draconis.[3]
Referenser
- ^ Smith, William Henry (1844). A Cycle of Celestial Objects
- ^ O'Meara, Stephen James (2005). ”M102: Mystery Solved”. Sky and Telescope 109 (3): sid. 78.
- ^ Dreyer, J L E (1888, 1895, 1908, 1971). New General Catalogue of Nebulæ and Clusters of Stars, Second Index Catalogue. Royal Astronomical Society, London. sid. 283
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Media som används på denna webbplats
Ngc5866 hst big.png
From original NASA press release:
From original NASA press release:
- This is a unique view of the disk galaxy NGC 5866 tilted nearly edge-on to our line-of-sight. Hubble's sharp vision reveals a crisp dust lane dividing the galaxy into two halves. The image highlights the galaxy's structure: a subtle, reddish bulge surrounding a bright nucleus, a blue disk of stars running parallel to the dust lane, and a transparent outer halo. NGC 5866 is a disk galaxy of type "S0" (pronounced s-zero). Viewed face on, it would look like a smooth, flat disk with little spiral structure. It remains in the spiral category because of the flatness of the main disk of stars as opposed to the more spherically rotund (or ellipsoidal) class of galaxies called ellipticals. Such S0 galaxies, with disks like spirals and large bulges like ellipticals, are called lenticular galaxies. NGC 5866 lies in the Northern constellation Draco, at a distance of 44 million light-years. It has a diameter of roughly 60,000 light-years only two-thirds the diameter of the Milky Way, although its mass is similar to our galaxy. This Hubble image of NGC 5866 is a combination of blue, green and red observations taken with the Advanced Camera for Surveys in February 2006.
And from the image's page:
- This is a unique NASA Hubble Space Telescope view of the disk galaxy NGC 5866 tilted nearly edge-on to our line-of-sight.
- Hubble's sharp vision reveals a crisp dust lane dividing the galaxy into two halves. The image highlights the galaxy's structure: a subtle, reddish bulge surrounding a bright nucleus, a blue disk of stars running parallel to the dust lane, and a transparent outer halo.
- Some faint, wispy trails of dust can be seen meandering away from the disk of the galaxy out into the bulge and inner halo of the galaxy. The outer halo is dotted with numerous gravitationally bound clusters of nearly a million stars each, known as globular clusters. Background galaxies that are millions to billions of light-years farther away than NGC 5866 are also seen through the halo.
- NGC 5866 is a disk galaxy of type "S0" (pronounced s-zero). Viewed face on, it would look like a smooth, flat disk with little spiral structure. It remains in the spiral category because of the flatness of the main disk of stars as opposed to the more spherically rotund (or ellipsoidal) class of galaxies called "ellipticals." Such S0 galaxies, with disks like spirals and large bulges like ellipticals, are called 'lenticular' galaxies.
- The dust lane is slightly warped compared to the disk of starlight. This warp indicates that NGC 5866 may have undergone a gravitational tidal disturbance in the distant past, by a close encounter with another galaxy. This is plausible because it is the largest member of a small cluster known as the NGC 5866 group of galaxies. The starlight disk in NGC 5866 extends well beyond the dust disk. This means that dust and gas still in the galaxy and potentially available to form stars does not stretch nearly as far out in the disk as it did when most of these stars in the disk were formed.
- The Hubble image shows that NGC 5866 shares another property with the more gas-rich spiral galaxies. Numerous filaments that reach out perpendicular to the disk punctuate the edges of the dust lane. These are short-lived on an astronomical scale, since clouds of dust and gas will lose energy to collisions among themselves and collapse to a thin, flat disk.
- For spiral galaxies, the incidence of these fingers of dust correlates well with indicators of how many stars have been formed recently, as the input of energy from young massive stars moves gas and dust around to create these structures. The thinness of dust lanes in S0s has been discussed in ground-based galaxy atlases, but it took the resolution of Hubble to show that they can have their own smaller fingers and chimneys of dust.
- NGC 5866 lies in the Northern constellation Draco, at a distance of 44 million light-years (13.5 Megaparsecs). It has a diameter of roughly 60,000 light-years (18,400 parsecs) only two-thirds the diameter of the Milky Way, although its mass is similar to our galaxy. This Hubble image of NGC 5866 is a combination of blue, green and red observations taken with the Advanced Camera for Surveys in November 2005.