Zeta Ursae Minoris

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Template:Short description

ζ Ursae Minoris
Template:Location mark
Location of ζ Ursae Minoris (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Ursa Minor
Right ascension Template:RA[1]
Declination Template:DEC[1]
Apparent magnitude (V) +4.29[2]
Characteristics
Spectral type A3Vn[3]
U−B Template:Engvar +0.05[4]
B−V Template:Engvar Template:Val[2]
Variable type Suspected δ Sct[5]
Astrometry
Radial velocity (Rv)Template:Val[6] km/s
Proper motion (μ) RA: 19.91[1] mas/yr
Dec.: −1.99[1] mas/yr
Parallax (π)8.84±0.12 mas[1]
DistanceTemplate:Rnd ± Template:Rnd ly
(Template:Rnd ± Template:Rnd pc)
Absolute magnitude (MV)−0.98[2]
Details
Mass~3.4[7] Template:Solar mass
Radius6.15[8] Template:Solar radius
Luminosity227[2] Template:Solar luminosity
Temperature8,720[8] K
Rotational velocity (v sin i)210[9] km/s
Age180[10] Myr
Metallicity [Fe/H]{{{metal_fe2}}} dex
Other designations
Template:Odlist[11]
Database references
SIMBADdata

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Zeta Ursae Minoris, which is Latinized from ζ Ursae Minoris, is a single[12] star in the northern circumpolar constellation of Ursa Minor, forming the northernmost part of the bowl in this "little dipper" asterism.[13] The star has a white hue and is faintly visible to the naked eye with an apparent visual magnitude of +4.28. It is located at a distance of approximately 369 light-years from the Sun based on parallax,[1] but is drifting further closer with a radial velocity of about –13 km/s.[6]

File:ZetaUMiLightCurve.png
A light curve for Zeta Ursae Minoris, plotted from TESS data. The main plot shows the flux as a function of time, and the inset plot shows the same data (excluding the eclipse) folded with the pulsation period.[14]

The stellar classification of Zeta UMi is A3Vn,[3] a notation that indicates this is an A-type main-sequence star with broad "nebulous" absorption lines in its spectrum due to rapid rotation. Based on photometric data, some light variability was suspected by R. A. Baker in 1926, and it may be a Delta Scuti variable.[5] It is a pulsating variable star, with a period of 15.8 hours, and it also undergoes eclipses.[14] The star is spinning with a projected rotational velocity of 210 km/s, which is creating an equatorial bulge that is estimated to be 10% larger than the polar radius.[9]

Zeta Ursae Minoris is about 180[10] million years old with 6.15[8] times the radius of the Sun. It is radiating 227[2] times the luminosity of the Sun from its photosphere at an effective temperature of 8,720 K.[8] This anomalously high temperature and an absolute magnitude of –0.98[2] may indicate it is on the verge of evolving into a giant star.[7] An infrared excess has been detected from an orbiting circumstellar disk.[10] A black body fit to the data yields a mean dust temperature of 160 K and an orbital radius of Template:Val.[8]

In some Arabic star charts it is listed as أخفى الفرقدين ʼakhfā al-farqadayn, meaning "the dimmer of the two calves", and paired with η Ursae Minoris as ʼanwar al-farqadayn, "the brighter of the two calves". The names may originally refer to a pair of Ibexes, and are more properly applied to γ UMi and β UMi, respectively, the brighter two stars in the rectangle of Ursa Minor.[15]

References

Template:Reflist

Template:Stars of Ursa Minor

  1. ↑ a b c d e f Cite error: Invalid <ref> tag; no text was provided for refs named vanLeeuwen2007
  2. ↑ a b c d e f Cite error: Invalid <ref> tag; no text was provided for refs named Anderson2012
  3. ↑ a b Cite error: Invalid <ref> tag; no text was provided for refs named Cowley_et_al_1969
  4. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named clpl99
  5. ↑ a b Cite error: Invalid <ref> tag; no text was provided for refs named Frolov1970
  6. ↑ a b Cite error: Invalid <ref> tag; no text was provided for refs named Gontcharov2006
  7. ↑ a b Cite error: Invalid <ref> tag; no text was provided for refs named kalerzet
  8. ↑ a b c d e Cite error: Invalid <ref> tag; no text was provided for refs named Cotten_Song_2016
  9. ↑ a b Cite error: Invalid <ref> tag; no text was provided for refs named vanBelle2012
  10. ↑ a b c Cite error: Invalid <ref> tag; no text was provided for refs named Su_et_al_2006
  11. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named SIMBAD
  12. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Eggleton_Tokovinin_2008
  13. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Harrington2010
  14. ↑ a b Cite error: Invalid <ref> tag; no text was provided for refs named IVSI
  15. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named allen
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