Editing Thuban (section)

==Binary system==
[[File:AlphaDraLightCurve.png|thumb|left|A [[light curve]] for Thuban, plotted from ''[[Transiting Exoplanet Survey Satellite|TESS]]'' data.<ref name=MAST>{{cite web |title=MAST: Barbara A. Mikulski Archive for Space Telescopes |url=https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.html |publisher=Space Telescope Science Institute |access-date=16 October 2022}}</ref> The main plot shows the entire light curve, and the inset plots show the primary and secondary minima with an expanded scale.]]
Thuban is a single-lined [[spectroscopic binary]]. For a long time, only the primary star could be detected in the [[stellar spectrum|spectrum]]. The radial velocity variations of the stars can be measured and the pair have a somewhat eccentric orbit of 51.4 days.<ref name=Pavlovski/> The secondary is a [[main-sequence star]] slightly cooler than the primary, with an A1 spectral class.<ref name=Pavlovski/>

The secondary star was detected in high spatial resolution observations using the [[Navy Precision Optical Interferometer]]. The secondary star is 1.8 magnitudes (at 700 [[Nanometre|nm]]) fainter than the primary star and was detected at separations ranging from 6.2 to 2.6 [[milliarcseconds]].<ref>{{Cite journal|last1=Hutter|first1=D. J.|last2=Zavala|first2=R. T.|last3=Tycner|first3=C.|last4=Benson|first4=J. A.|last5=Hummel|first5=C. A.|last6=Sanborn|first6=J.|last7=Franz|first7=O. G.|last8=Johnston|first8=K. J.|date=2016-11-01|title=Surveying the Bright Stars by Optical Interferometry. I. A Search for Multiplicity among Stars of Spectral Types F-K|journal=The Astrophysical Journal Supplement Series|volume=227|issue=1|pages=4|doi=10.3847/0067-0049/227/1/4|issn=0067-0049|bibcode=2016ApJS..227....4H|arxiv = 1609.05254 |s2cid=118803592 |doi-access=free }}</ref> Eclipses were detected using data obtained with the [[Transiting Exoplanet Survey Satellite]] (TESS).<ref>{{Cite journal|last1=Bedding|first1=Timothy R.|last2=Hey|first2=Daniel R.|last3=Murphy|first3=Simon J.|date=2019-10-31|title=A Dance with Dragons: TESS Reveals α Draconis is a Detached Eclipsing Binary|journal=Research Notes of the AAS|language=en|volume=3|issue=10|pages=163|doi=10.3847/2515-5172/ab5112|arxiv=1910.12449|bibcode=2019RNAAS...3..163B|s2cid=213224065 |issn=2515-5172 |doi-access=free }}</ref> The presence of eclipses places Thuban into the class of binaries known as [[eclipsing binaries]].<ref name=Pavlovski/>