ثانیه شمالی یا قفزةالثانیه (جَست دوم) یا لاندا خرس بزرگ یک ستاره است که در صورت فلکی خرس بزرگ قرار دارد.
نام قفزةالثانیه به معنی جهش دوم است که به جهش دوم آهویی اشاره دارد که در نگارههای قدیمی این صورت فلکی ترسیم میشد.
Lambda Ursae Majoris
Location of λ Ursae Majoris (circled)
Epoch J2000 Equinox J2000
Right ascension 10 h 17 m 05.78287 s
+42° 54′ 51.6808″
Apparent magnitude (V) +3.45
 Astrometry Radial velocity (R v) +18.1 km/s  Proper motion (μ) RA: –180.65  mas/ yr Dec.: –46.07  mas/ yr Parallax (π) 23.72 ± 0.78  mas Distance 138 ± 5 ly (42 ± 1 pc) Absolute magnitude (M V) +0.10 
Details Mass 2.11  M ☉ Radius 2.3  R ☉ Luminosity 37  L ☉ Surface gravity (log g) 3.76 ±0.14  cgs Temperature 9,247 ±314  K [Fe/H] Metallicity +0.20  dex Rotational velocity ( v sin i) 50 km/s  Age 380  Myr
Tania Borealis, λ Ursae Majoris, λ UMa, Lambda UMa, 33 Ursae Majoris,
 Database references
Lambda Ursae Majoris ( λ Ursae Majoris, abbreviated Lambda UMa, λ UMa), also named Tania Borealis, is a  star in the northern circumpolar constellation of Ursa Major.
This star has an
apparent visual magnitude of +3.45, making it one of the  brighter members of the constellation. The distance to this star has been measured directly using the parallax technique, which yields a value of roughly 138 light-years (42 parsecs) with a 4% margin of error. The stellar classification of Lambda Ursae Majoris is A2 IV, with the  luminosity class of 'IV' indicating that, after 410 million years on the  main sequence, this star is in the process of evolving into a giant star as the supply of hydrogen at its core becomes exhausted. Compared to the Sun it has 240% of the mass and 230% of the Sun's radius, but is radiating 37 times as much luminosity. This energy is being emitted from the star's  outer atmosphere at an effective temperature of 9,280 K, giving it the characteristic white-hot glow of an  A-type star.
Nomenclature λ Ursae Majoris ( Latinised to Lambda Ursae Majoris) is the star's Bayer designation.
It bore the traditional names
Tania (shared with Mu Ursae Majoris) and Tania Borealis. Tania comes from the Arabic phrase 'the Second Spring (of the Gazelle)'. Al Fiḳrah al Thānia and  Borealis (originally borealis ) is  Latin for 'the north side'. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016  included a table of the first two batches of names approved by the WGSN; which included  Tania Borealis for this star.
Chinese, 三台 ( Sān Tái), meaning , refers to an asterism consisting of Lambda Ursae Majoris, Three Steps Iota Ursae Majoris, Kappa Ursae Majoris, Mu Ursae Majoris, Nu Ursae Majoris and Xi Ursae Majoris. Consequently, the Chinese name for Lambda Ursae Majoris itself is 中台一 ( Zhōng Tái yī, English: Star of First Middle Step).
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(in Chinese) (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 6 月 21 日