Lambda Ursae Minoris

λ Ursae Minoris

A light curve for Lambda Ursae Minoris, plotted from Hipparcos data[1]
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Ursa Minor
Right ascension 17h 16m 56.4107s[2]
Declination +89° 02′ 15.734″[2]
Apparent magnitude (V) +6.38[3]
Characteristics
Spectral type M3+ IIIa[4]
U−B color index +1.79[5]
B−V color index +1.57[5]
Variable type SRb[6]
Astrometry
Radial velocity (Rv)+0.19[2] km/s
Proper motion (μ) RA: −23.989[2] mas/yr
Dec.: 3.463[2] mas/yr
Parallax (π)3.7084 ± 0.1329 mas[2]
Distance880 ± 30 ly
(270 ± 10 pc)
Absolute magnitude (MV)−0.85[7]
Details
Radius64[2] R☉
Luminosity741[2] L☉
Temperature3,772[2] K
Other designations
HR 7394, HD 183030, BD+88°112, FK5 914, HIP 84535, SAO 3020
Database references
SIMBADdata

Lambda Ursae Minoris (λ UMi, λ Ursae Minoris) is a star in the constellation Ursa Minor. It is an M-type red giant with an apparent magnitude of +6.38 and is approximately 880 light years from Earth.

Lambda Ursae Minoris is an asymptotic giant branch (AGB) star, a star that has exhausted its core hydrogen and helium and is now fusing material in shells outside its core.[8] AGB stars are often unstable and tend to pulsate, and Lambda Ursae Minoris is classified as a semiregular variable star and its brightness varies by about 0.1 magnitudes.[6] Its variability was discovered from Hipparcos astrometry and it was entered into the General Catalogue of Variable Stars in 1999.[9]

This star was used from 1882 as a reference to measure the magnitudes of stars in the northern hemisphere for the 1908 Revised Harvard Photometry catalogue. Sigma Octantis was used for the southern hemisphere. It was then noted that "Neither of these stars appears to vary perceptibly" but that, due to the procedures used "if they did, the variation would have no effect on the final measures."[10]

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