Vildandshopen

Vildandshopen
Messier 11
Öppna stjärnhopen Messier 11. Bild:ESA
Observationsdata
StjärnbildSkölden[1]
Rektascension18t 51m 05,00s[2][3]
Deklination-06° 16′ 12″[2][3]
KlassI,2,r
Avstånd6 120[4] ljusår (1 877 pc) lj
Skenbar storlek22,8[4] bågminuter'
Skenbar magnitud5,8[5]
Fysiska egenskaper
Massa3 700 - 11 000[6] solmassor
Radie95 ljusår[6]
Antal stjärnornärmare 3 000[1]
Uppskattad ålder316 ± 50 miljoner[1][7] år
Upptäckt
Upptäcktsårföre 1681[1]
UpptäckareGottfried Kirch[1]
Andra beteckningar
M11, NGC 6705[1], C 1848-063, Cl Collinder 391, Cl Melotte 213, OCl 76.0, [KPR2004b] 453, [KPS2012] MWSC 3008[2]
Se också: Öppna stjärnhopar, Lista över öppna stjärnhopar

Vildandshopen[1] eller Messier 11 (M11) även känd som NGC 581, är en öppen stjärnhop i stjärnbilden Skölden. Stjärnhopen upptäcktes 1681 av Gottfried Kirch[5] och Charles Messier lade till den i sin katalog över diffusa objekt 1764. Dess populära namn relaterar till de ljusare stjärnorna som bildar en triangel som kan likna en flygande flock änder[5] (eller, från andra vinklar, en badanka). Hopen ligger strax öster om mittpunkten av Sköldens stjärnmoln.[8]

Egenskaper

Vildandshopen är en av de rikaste och mest kompakta av de kända öppna stjärnhoparna.[1] Den är även en av de mest massiva öppna hoparna som är kända, och har studerats i stor utsträckning. Dess ålder har uppskattats till cirka 316 miljoner år.[7] Kärnradien är 1,23 pc medan tidvattenradien är 29 pc. Uppskattningarna av stjärnhopens massa varierar från 3 700[9] till 11 000 solmassor,[6] beroende på vilken metod som tillämpats. Den ljusaste stjärnorna i hopen är av skenbar magnitud 8 och den har 870 medlemmar av minst magnitud 16,5. Den har en integrerad absolut magnitud på –6,5 och en visuell fördunkling på 1,3.[8]

Messier 11 är metallrik med ett järnöverskott av [Fe/H] = 0,17±0,04 dex. Trots dess låga ålder visar den en förstärkning av Alfa-processelementen. Möjligen beror detta på ett tillskott till dess ursprungliga molekylmoln från en närliggande supernovaexplosion av typ II.[7] Minst nio variabla stjärnor har identifierats med stor sannolikhet, plus 29 med lägre sannolikhet. Bland de förstnämnda ingår två förmörkelsevariabler.[10] Stjärnhopen ligger 6 800 pc från Vintergatans centrum, nära det galaktiska planet, och är inte långt från dess födelseplats.[7]

Galleri

  • En del av M11, avbildad av Hubble Space Telescope.[11]
    (c) ESA/Hubble, CC BY 4.0
    En del av M11, avbildad av Hubble Space Telescope.[11]
  • De blå stjärnorna i bildens centrum är de unga heta stjärnorna i stjärnhopen.[12]
    De blå stjärnorna i bildens centrum är de unga heta stjärnorna i stjärnhopen.[12]
  • M11 kan observeras i stjärnbilden Skölden med handkikare.
    M11 kan observeras i stjärnbilden Skölden med handkikare.

Referenser

Den här artikeln är helt eller delvis baserad på material från engelskspråkiga Wikipedia, Wild Duck Cluster, 26 april 2021.

Noter

  1. ^ [a b c d e f g h] Vildänder tar till flykten i öppen stjärnhop, ESO, 1 oktober 2014
  2. ^ [a b c] Messier 103 (u-strasbg.fr). Hämtad 26 april 2021.
  3. ^ [a b] Wu, Zhen-Yu; Zhou, Xu; Ma, Jun; Du, Cui-Hua (November 2009), ”The orbits of open clusters in the Galaxy”, Monthly Notices of the Royal Astronomical Society 399 (4): 2146–2164, doi:10.1111/j.1365-2966.2009.15416.x, Bibcode: 2009MNRAS.399.2146W. 
  4. ^ [a b] Kharchenko, N. V.; Piskunov, A. E.; Röser, S.; Schilbach, E.; Scholz, R.-D. (2005), ”Astrophysical parameters of Galactic open clusters”, Astronomy and Astrophysics 438 (3): 1163–1173, doi:10.1051/0004-6361:20042523, Bibcode: 2005A&A...438.1163K. 
  5. ^ [a b c] O'Meara, Stephen James; Levy, David H. (1998), Deep-Sky Companions: The Messier Objects, Cambridge University Press, s. 65, ISBN 978-0521553322, https://books.google.com/books?id=jis4evHuuzUC&pg=PA65. 
  6. ^ [a b c] Santos, J. F. C., Jr.; Bonatto, C.; Bica, E. (October 2005), ”Structure and stellar content analysis of the open cluster M 11 with 2MASS photometry”, Astronomy and Astrophysics 442 (1): 201–209, doi:10.1051/0004-6361:20053378, Bibcode: 2005A&A...442..201S. 
  7. ^ [a b c d] Casamiquela, L.; Carrera, R.; Balaguer-Núñez, L.; Jordi, C.; Chiappini, C.; Anders, F.; Antoja, T.; Miret-Roig, N.; et al. (March 2018), ”NGC 6705 a young α-enhanced open cluster from OCCASO data”, Astronomy & Astrophysics 610: 10, doi:10.1051/0004-6361/201732024, A66, Bibcode: 2018A&A...610A..66C. 
  8. ^ [a b] Crossen, Craig; Rhemann, Gerald (2012), Sky Vistas: Astronomy for Binoculars and Richest-Field Telescopes, Springer Science & Business Media, s. 56, ISBN 978-3709106266, https://books.google.com/books?id=3vELBwAAQBAJ&pg=PA56. 
  9. ^ Cantat-Gaudin, T.; Vallenari, A.; Zaggia, S.; Bragaglia, A.; Sordo, R.; Drew, J. E.; Eisloeffel, J.; Farnhill, H. J.; et al. (September 2014), ”The Gaia-ESO Survey: Stellar content and elemental abundances in the massive cluster NGC 6705”, Astronomy & Astrophysics 569: 18, doi:10.1051/0004-6361/201423851, A17, Bibcode: 2014A&A...569A..17C. 
  10. ^ Messina, S.; Parihar, P.; Koo, J. -R.; Kim, S. -L.; Rey, S. -C.; Lee, C. -U. (April 2010), ”ACE-OC project: rotation and variability in the open cluster M 11 (NGC 6705)”, Astronomy and Astrophysics 513: 26, doi:10.1051/0004-6361/200912373, A29, Bibcode: 2010A&A...513A..29M. 
  11. ^ ”Wild cosmic ducks” (på engelska). www.spacetelescope.org. https://www.spacetelescope.org/images/potw1912a/. 
  12. ^ ”Wild Ducks Take Flight in Open Cluster”. www.eso.org. European Southern Observatory. http://www.eso.org/public/news/eso1430/. 

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Se även: Klotformig stjärnhop · Stjärnbild · Galax · Nebulosa

Media som används på denna webbplats

Wild cosmic ducks Messier 11.jpg
(c) ESA/Hubble, CC BY 4.0
This star-studded image shows us a portion of Messier 11, an open star cluster in the southern constellation of Scutum (The Shield). Messier 11 is also known as the Wild Duck Cluster, as its brightest stars form a “V” shape that somewhat resembles a flock of ducks in flight.

Messier 11 is one of the richest and most compact open clusters currently known. By investigating the brightest, hottest main sequence stars in the cluster astronomers estimate that it formed roughly 220 million years ago. Open clusters tend to contain fewer and younger stars than their more compact globular cousins, and Messier 11 is no exception: at its centre lie many blue stars, the hottest and youngest of the cluster’s few thousand stellar residents.

The lifespans of open clusters are also relatively short compared to those of globular ones; stars in open clusters are spread further apart and are thus not as strongly bound to each other by gravity, causing them to be more easily and quickly drawn away by stronger gravitational forces. As a result Messier 11 is likely to disperse in a few million years as its members are ejected one by one, pulled away by other celestial objects in the vicinity.
Eso1430a.jpg
Författare/Upphovsman: ESO, Licens: CC BY 4.0
Wild Ducks Take Flight in Open Cluster

The Wide Field Imager on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile has taken this beautiful image, dappled with blue stars, of one of the most star-rich open clusters currently known — Messier 11, also known as NGC 6705 or the Wild Duck Cluster.

Messier 11 is an open cluster, sometimes referred to as a galactic cluster, located around 6000 light-years away in the constellation of Scutum (The Shield). It was first discovered by German astronomer Gottfried Kirch in 1681 at the Berlin Observatory, appearing as nothing more than a fuzzy blob through the telescope. It wasn’t until 1733 that the blob was first resolved into separate stars by the Reverend William Derham in England, and Charles Messier added it to his famous catalogue in 1764.

Messier was a comet hunter and the catalogue came into being as he was frustrated by constantly observing fixed, diffuse objects that looked like comets (for example, objects that we now know to be clusters, galaxies and nebulae). He wanted a record in order to avoid accidentally observing them again and confusing them with possible new comets. This particular stellar cluster was noted down as the eleventh such object — hence the name of Messier 11.

Open clusters are typically found lying in the arms of spiral galaxies or in the denser regions of irregular galaxies, where star formation is still common. Messier 11 is one of the most star-rich and compact of the open clusters, being almost 20 light-years across and home to close to 3000 stars. Open clusters are different to globular clusters, which tend to be very dense, tightly bound by gravity, and contain hundreds of thousands of very old stars — some of which are nearly as old as the Universe itself.

Studying open clusters is great way to test theories of stellar evolution, as the stars form from the same initial cloud of gas and dust and are therefore very similar to one another — they all have roughly the same age, chemical composition, and are all the same distance away from Earth. However, each star in the cluster has a different mass, with the more massive stars evolving much faster than their lower mass counterparts as they use up all of their hydrogen much sooner.

In this way, direct comparisons between the different evolutionary stages can be made within the same cluster: for example, does a 10 million year old star with the same mass as the Sun evolve in a different way to another star that is the same age, but half as massive? In this sense, open clusters are the closest thing astronomers have to “laboratory conditions”.

Because the stars within open clusters are very loosely bound to one another, individuals are very susceptible to being ejected from the main group due to the effect of gravity from neighbouring celestial objects. NGC 6705 is already at least 250 million years old, so in a few more million years it is likely that this Wild Duck formation will disperse, and the cluster will break up and merge into its surroundings [1].

This image was taken by the Wide Field Imager on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in northern Chile. Notes

[1] The alternative and evocative name for NGC 6705, the Wild Duck Cluster, came about in the 19th century. When the cluster was seen through a small telescope it was noticed that the brightest stars formed an open triangle pattern on the sky that resembled ducks flying in formation.

About the Object Name: M 11, Wild Duck Cluster Type: • Milky Way : Star : Grouping : Cluster : Open 

       • X - Star Clusters

Distance: 6000 light years Constellation: Scutum

Coordinates Position (RA): 18 51 3.49 Position (Dec): -6° 15' 33.12" Field of view: 35.59 x 25.70 arcminutes Orientation: North is 0.0° left of vertical

Colours & filters Band Telescope Optical B MPG/ESO 2.2-metre telescope WFI Optical V MPG/ESO 2.2-metre telescope WFI

Infrared I MPG/ESO 2.2-metre telescope WFI