Mu Draconis

{{Short description|Star in the constellation Draco}}

{{Starbox begin

| name=μ Draconis

}}

{{Starbox image

| image=

{{Location mark

|image=Draco constellation map.svg|alt=|float=center|width=240

|label=|position=right

|mark=Red circle.svg|mark_width=10|mark_link=μ Dra

|x=383|y=935

}}

|caption=Location of μ Draconis (circled)

}}

{{Starbox observe

| epoch=J2000

| ra={{RA|17|05|20.12403}}{{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|+54|28|12.0994}}

| appmag_v=4.92{{cite simbad|title=* mu Dra|access-date=16 May 2017}}
(5.66 / 5.69)

| constell=Draco

}}

{{Starbox character

| class=F7V

| b-v=+0.47{{cite journal|author1=Mermilliod, J.-C.|title=Compilation of Eggen's UBV data, transformed to UBV (unpublished)|journal=Catalogue of Eggen's UBV Data|pages=0|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=−0.01

| variable=

}}

{{Starbox astrometry

| radial_v={{val|−17.30|0.5}}{{cite journal|bibcode=2007A&A...475..519H|doi=10.1051/0004-6361:20077221|arxiv=0707.1891|title=The Geneva-Copenhagen survey of the Solar neighbourhood II|journal=Astronomy and Astrophysics|volume=475|issue=2|pages=519|year=2007|last1=Holmberg|first1=J.|last2=Nordström|first2=B.|last3=Andersen|first3=J.|s2cid=119054949}}

| prop_mo_ra=−58.16

| prop_mo_dec=+67.87

| parallax=36.45

| p_error=0.46

| parallax_footnote=

| absmag_v = +2.73{{cite journal|bibcode=2009A&A...501..941H|title=The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics|journal=Astronomy and Astrophysics|volume=501|issue=3|pages=941|last1=Holmberg|first1=J.|last2=Nordström|first2=B.|last3=Andersen|first3=J.|year=2009|doi=10.1051/0004-6361/200811191|arxiv = 0811.3982 |s2cid=118577511}}

}}

{{Starbox orbit

| reference={{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=16 May 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}}

| primary=μ Dra A

| name=μ Dra B

| period={{val|812.0|70.5}}

| axis={{val|4.48|0.03}}

| eccentricity={{val|0.5139|0.029}}

| inclination={{val|142.2|1.3}}

| node={{val|282.85|0.80}}

| periastron={{val|1946.19|0.72}}

| periarg={{val|193.31|0.083}}

}}

{{Starbox detail

| component1 = μ Dra A

| mass = 1.35{{cite journal|bibcode=2014AJ....147...87T|title=From Binaries to Multiples. II. Hierarchical Multiplicity of F and G Dwarfs|journal=The Astronomical Journal|volume=147|issue=4|pages=87|last1=Tokovinin|first1=Andrei|year=2014|doi=10.1088/0004-6256/147/4/87|arxiv = 1401.6827 |s2cid=56066740}}

| metal_fe = −0.01

| component2 = μ Dra B

| mass2 = 1.30

| age_gyr2 = 2.2

}}

{{Starbox catalog

| names=21 Draconis, GJ 9584, BD+54°1857, SAO 30239, HIP 83608

| component1=A

| names1=Alrakis, HR 6370, HD 154906

| component2=B

| names2=HR 6369, HD 154905

}}

{{Starbox reference

| Simbad = mu+Draconis|sn=μ Dra

| Simbad2 = HD+154906|sn2=μ Dra A

| Simbad3 = HD+154905|sn3=μ Dra B

}}

{{Starbox end}}

Mu Draconis (μ Draconis, abbreviated Mu Dra, μ Dra) is a multiple star system near the head of the constellation of Draco. With a combined magnitude of 4.92, it is visible to the naked eye. Based on parallax estimates by the Hipparcos spacecraft, it is located approximately 89 light-years from the Sun.

The system consists of a single primary star (designated Mu Draconis A, officially named Alrakis {{IPAc-en|æ|l|'|r|ei|k|I|s}} from the traditional name of the system),{{cite book

|last1=Kunitzsch |first1=Paul

|last2=Smart |first2=Tim

|date = 2006 |edition = 2nd rev.

|title = A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations

|publisher = Sky Pub |location = Cambridge, Massachusetts

|isbn = 978-1-931559-44-7

}}{{cite web | url=https://www.iau.org/public/themes/naming_stars/ | title=Naming Stars |publisher=IAU.org |access-date=16 December 2017}} a secondary binary pair (Mu Draconis B) and a further single star (C). B's two components are designated Mu Draconis Ba and Bb.

Mu Draconis A and Ba are nearly identical F-type main-sequence stars, with masses of {{solar mass|1.35}} and {{solar mass|1.30}}, respectively. Both have the spectral class of F5V, and have similar apparent magnitude, at 5.66 and 5.69, respectively. The secondary, Mu Draconis B, has a drifting radial velocity, and is itself a spectroscopic binary with an orbital period of 2,270 days.{{cite journal|title=S_B⁹: The ninth catalogue of spectroscopic binary orbits|display-authors=1|author1=Pourbaix, D.|author2=Tokovinin, A. A.|author3=Batten, A. H.|author4=Fekel, F. C.|author5=Hartkopf, W. I.|author6=Levato, H.|author7=Morrell, N. I.|author8=Torres, G.|author9=Udry, S.|journal=Astronomy and Astrophysics|volume=424|issue=2|pages=727–732|year=2004|doi=10.1051/0004-6361:20041213|arxiv=astro-ph/0406573|bibcode=2004A&A...424..727P|s2cid=119387088}} ([http://sb9.astro.ulb.ac.be/ProcessMainform.cgi?Catalog=HD&Id=154905&Coord=&Epoch=2000&radius=10&unit=arc+min SB9 catalog entry]) The distance between both stars is 2 arcseconds, so a telescope with a diameter of at least 6 centimetres is necessary to see them separate. The smaller component, Mu Draconis Bb, has a mass of {{solar mass|0.2}}. Mu Draconis C is a 14th magnitude common-proper-motion companion 13.2" away from the bright pair, with a mass of {{solar mass|0.29}}.