55 Ursae Majoris

{{short description|Star in the constellation Ursa Major}}

{{Starbox begin

|name= 55 Ursae Majoris

}}

{{Starbox observe

|epoch=J2000

|constell=Ursa Major

|ra= {{RA|11|19|07.89965}}{{cite journal|title=Validation of the new Hipparcos reduction|url=http://www.aanda.org/index.php?option=com_article&access=bibcode&Itemid=129&bibcode=2007A%2526A...474..653VFUL|author=van Leeuwen, F.|display-authors=etal|journal=Astronomy and Astrophysics|volume=474|issue=2|pages=653–664|date=2007|arxiv=0708.1752|bibcode=2007A&A...474..653V|doi=10.1051/0004-6361:20078357|s2cid = 18759600}}

|dec= {{DEC|+38|11|08.0285}}

|appmag_v=4.80 (4.78 / 5.3){{cite web|url=http://www.usno.navy.mil/USNO/astrometry/optical-IR-prod/wds/orb6|title=Sixth Catalog of Orbits of Visual Binary Stars|work=United States Naval Observatory|access-date=24 June 2017|archive-date=1 August 2017|archive-url=https://web.archive.org/web/20170801102553/http://www.usno.navy.mil/USNO/astrometry/optical-IR-prod/wds/orb6|url-status=dead}}

}}

{{Starbox character

|class=A2V{{cite simbad|title=* 55 UMa|access-date=23 February 2013}}
(A1V + A2V + A1V)

|b-v=+0.09{{cite journal|author1=Mermilliod, J.-C.|title=Compilation of Eggen's UBV data, transformed to UBV (unpublished)|journal=Catalogue of Eggen's UBV Data|url=http://cdsads.u-strasbg.fr/cgi-bin/nph-bib_query?1986EgUBV........0M&db_key=AST&nosetcookie=1|date=1986|bibcode= 1986EgUBV........0M}}

|u-b=+0.04

}}

{{Starbox astrometry

|radial_v=-3.0 ± 2{{cite journal|title=General catalogue of stellar radial velocities|journal=Washington|author=Wilson, Ralph Elmer|date=1953|bibcode=1953GCRV..C......0W}}

|prop_mo_ra=-58.80

|prop_mo_dec=-65.33

|parallax=17.00

|p_error=0.34

|parallax_footnote=

|absmag_v=-0.09 ± 0.20

}}

{{Starbox orbit

|reference={{cite journal|bibcode=1997ApJ...485..350L|doi=10.1086/304418|title=Tomographic Separation of Composite Spectra. V. The Triple Star System 55 Ursae Majoris|journal=The Astrophysical Journal|volume=485|pages=350–358|year=1997|last1=Liu|first1=Ning|last2=Gies|first2=Douglas R.|last3=Xiong|first3=Ying|last4=Riddle|first4=Reed L.|last5=Bagnuolo, Jr.|first5=William G.|last6=Barry|first6=Donald J.|last7=Ferrara|first7=Elizabeth C.|last8=Hartkopf|first8=William I.|last9=Hooda|first9=Jagbir S.|last10=Mason|first10=Brian D.|last11=McAlister|first11=Harold A.|last12=Roberts, Jr.|first12=Lewis C.|last13=Sowers|first13=Jon W.|issue=1|doi-access=free}}

|primary=55 UMa Aa

|name=55 UMa Ab

|period_unitless=2.5537985 d

|periastron=2449602.368

|k1=79.1

|k2=89.1

|eccentricity=0.323

|periarg=116.8

}}

{{Starbox orbit

|reference=

|primary=55 UMa A

|name=55 UMa B

|period_unitless=1872.7 ± 7.4 d

|periastron=2448805 ± 18

|axis=0.0913 ± 0.0009

|inclination=64.8 ± 0.8

|node=130.0 ± 0.8

|eccentricity=0.126 ± 0.008

|periarg=223.9 ± 3.7

|k1=8.4 ± 1.3

|k2=20.2 ± 6.9

}}

{{Starbox detail

|source=

|component1=55 UMa Aa

|gravity=4.25

|rotational_velocity=30 ± 4

|temperature=9230 ± 230

|mass=2.0

|component2=55 UMa Ab

|gravity2=4.25

|rotational_velocity2=45 ± 5

|temperature2=8810 ± 250

|mass2=1.8

}}

{{Starbox detail|no_heading=y

|component1=55 UMa B

|gravity=4.25

|rotational_velocity=55 ± 5

|temperature=9290 ± 190

|mass=2.1

}}

{{Starbox catalog

|names={{odlist|BD=+38 2225|FK5=1293|HD=98353|HIP=55266|HR=4380|SAO=62491}}

}}

{{Starbox reference

|Simbad=55+UMa

}}

{{Starbox end}}

55 Ursae Majoris (55 UMa) is a triple star system in the constellation Ursa Major. Its apparent magnitude is 4.80. Two stars form a close spectroscopic binary with an orbital period of 2.55 days. The third star orbits the central pair every 1873 days. All three stars are A-type main-sequence stars.