| 词条 | NGC 3921 |
| 释义 |
| name = NGC 3921 | image = Evolution in slow motion.jpg | image_size = 280px | caption = NGC 3921, imaged by the Hubble Space Telescope | epoch = J2000 | constellation name = Ursa Major | ra = {{RA|11|51|06.863}}[1] | dec = {{DEC|+55|04|43.38}}[1] | z = 0.019667[2] | h_radial_v = 5896 km/s[2] | dist_ly = {{cvt|85.19|Mpc|Mly|lk=on|order=flip}}[3] | group_cluster = | type = (R')SA0/a(s) pec[2] | size = {{cvt|55240|pc|ly|lk=on|order=flip}}[2][4] | appmag_v = 12.64[5] | appmag_b = 13.4[5] | absmag_v = −22.09[11] | size_v = 2.1′ × 1.3′ | notes = | names = Arp 224, UGC 6823, MGC+09-20-009, PGC 37063 }}NGC 3921 is a interacting galaxy in the northern constellation of Ursa Major. Estimates using redshift put the galaxy at about 59 million light years (18 megaparsecs) away.[3] It was discovered on 14 April 1789 by William Herschel,[6] and it was described as "pretty faint, small, round" by John Louis Emil Dreyer, the compiler of the New General Catalogue.[7] NGC 3921 is the remnant of a galaxy merger. The two progenitor galaxies are thought to have been disk galaxies that collided about 700 million years ago.[15] The image shows noticeable star formation and structures like loops, indicative of galaxies interacting.[8] Because of this, NGC 3921 was included in Halton Arp's Atlas of Peculiar Galaxies under the designation Arp 224.[5] Being a starburst galaxy, NGC 3921 has important features. One of them is an ultraluminous X-ray source, designated X-2, with an X-ray luminosity of {{val|8e39}} erg/s.[9] Additionally, two candidates globular clusters have been detected within NGC 3921.[11] They are both fairly young, and are about half as massive as Omega Centauri: this demonstrates that mergers of gas-rich galaxies can also create more metal-rich globular clusters.[10] References1. ^1 {{cite journal|title=The Two Micron All Sky Survey (2MASS)|author=Skrutskie, M.|journal=The Astronomical Journal|volume=131|issue=2|pages=1163–1183|year=2006|doi=10.1086/498708|bibcode=2006AJ....131.1163S}} 2. ^1 2 3 {{cite web|url=http://nedwww.ipac.caltech.edu/cgi-bin/nph-objsearch?objname=NGC+3921&extend=no&out_csys=Equatorial&out_equinox=J2000.0&obj_sort=RA+or+Longitude&of=pre_text&zv_breaker=30000.0&list_limit=5&img_stamp=YES|title=NED results for object NGC 3921|publisher=National Aeronautics and Space Administration / Infrared Processing and Analysis Center|accessdate=28 May 2017}} 3. ^1 {{cite journal|bibcode=2007ApJ...655..790C|doi=10.1086/510201|arxiv=astro-ph/0610732|title=Groups of Galaxies in the Two Micron All Sky Redshift Survey|journal=The Astrophysical Journal|volume=655|issue=2|pages=790–813|year=2007|last1=Crook|first1=Aidan C.|last2=Huchra|first2=John P.|last3=Martimbeau|first3=Nathalie|last4=Masters|first4=Karen L.|last5=Jarrett|first5=Tom|last6=Macri|first6=Lucas M.}} 4. ^POSS1 103a-O values used. 5. ^1 2 {{cite simbad|title=NGC 3921|access-date=28 May 2017}} 6. ^{{cite web|url=http://cseligman.com/text/atlas/ngc39.htm#3921|title=New General Catalogue objects: NGC 3900 - 3949|author=Seligman, Courtney|website=cseligman.com|accessdate=28 May 2017}} 7. ^{{cite web|url=http://spider.seds.org/ngc/ngc.cgi?NGC+3921|title=Revised NGC Data for NGC 3921 - Hartmut Frommert - SEDS|website=seds.org|accessdate=28 May 2017}} 8. ^1 {{cite web|url=http://www.spacetelescope.org/images/potw1537a/|title=Evolution in slow motion | ESA/Hubble|website=www.spacetelescope.org|date=2015|accessdate=28 May 2017}} 9. ^{{cite journal|bibcode=2012ApJ...758...28J|doi=10.1088/0004-637X/758/1/28|arxiv=1208.4502|title=The Nature of the Bright Ulx X-2 in Ngc 3921: Achandraposition Andhstcandidate Counterpart|journal=The Astrophysical Journal|volume=758|issue=1|pages=28|year=2012|last1=Jonker|first1=P. G.|last2=Heida|first2=M.|last3=Torres|first3=M. A. P.|last4=Miller-Jones|first4=J. C. A.|last5=Fabian|first5=A. C.|last6=Ratti|first6=E. M.|last7=Miniutti|first7=G.|last8=Walton|first8=D. J.|last9=Roberts|first9=T. P.}} 10. ^1 2 {{cite journal|bibcode=2004AJ....128..202S|doi=10.1086/421851|arxiv=astro-ph/0404424|title=Keck Spectroscopy of Two Young Globular Clusters in the Merger Remnant NGC 3921|journal=The Astronomical Journal|volume=128|issue=1|pages=202–210|year=2004|last1=Schweizer|first1=François|last2=Seitzer|first2=Patrick|last3=Brodie|first3=Jean P.}} Notes{{reflist|group=note}}{{Ngc40}} 7 : Arp objects|NGC objects|UGC objects|Principal Galaxies Catalogue objects|Starburst galaxies|Interacting galaxies|Ursa Major (constellation) |
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