Universe Guide

Kochab (Beta Ursae Minoris, 7 Ursae Minoris) Star Facts

Kochab Facts

  • Kochab is a giant star that can be located in the constellation of Ursa Minor. The description is based on the spectral class.
  • Kochab is a main star of the constellation outline.
  • Based on the spectral type (K4IIIvar) of the star, the star's colour is orange to red .
  • Kochab is the 57th brightest star in the night sky and the 2nd brightest star in Ursa Minor based on the Hipparcos 2007 apparent magnitude. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.
  • It is calculated at being 2.950 Billion Years old. This information comes from ExoPlanet.
  • Kochab has at least 1 Extrasolar Planets believed to be in orbit around the star.
  • Using the most recent figures given by the 2007 Hipparcos data, the star is 130.94 light years away from us. Distance

Kochab's Alternative Names

Beta Ursae Minoris (Bet Umi) is the Bayer Classification for the star. The Bayer Classification was created by Johann Bayer in 1603. The brightest star in the constellation is normally given the Alpha designation, there are exceptions such as Pollux which is Beta Geminorum.

The Id of the star in the Yale Bright Star Catalogue is HR5563. HIP72607 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD131873.

Kochab has alternative name(s) :- , 7 UMi, Beta Umi.

Flamsteed designations are named after the creator, Sir John Flamsteed. Sir John named the stars in the constellation with a number and its latin name, this star's Flamsteed designation is 7 Ursae Minoris. The Flamsteed name can be shortened to 7 Umi.

BD number is the number that the star was filed under in the Durchmusterung or Bonner Durchmusterung, a star catalogue that was put together by the Bonn Observatory between 1859 to 1903. The star's BD Number is BD+74 595.

More details on objects' alternative names can be found at Star Names .

Location of Kochab

The location of the giant star in the night sky is determined by the Right Ascension (R.A.) and Declination (Dec.), these are equivalent to the Longitude and Latitude on the Earth. The Right Ascension is how far expressed in time (hh:mm:ss) the star is along the celestial equator. If the R.A. is positive then its eastwards. The Declination is how far north or south the object is compared to the celestial equator and is expressed in degrees. For Kochab, the location is 14h 50m 42.40 and +74° 09` 19.7 .

Radial Velocity and Proper Motion of Kochab

Proper Motion

All stars like planets orbit round a central spot, in the case of planets, its the central star such as the Sun. In the case of a star, its the galactic centre. The constellations that we see today will be different than they were 50,000 years ago or 50,000 years from now. Proper Motion details the movements of these stars and are measured in milliarcseconds. The star is moving 11.42 ± 0.11 milliarcseconds/year towards the north and -32.61 ± 0.12 milliarcseconds/year east if we saw them in the horizon.

Radial Velocity

The Radial Velocity, that is the speed at which the star is moving away/towards the Sun is 16.96000 km/s with an error of about 0.19 km/s . When the value is negative then the star and the Sun are getting closer to one another, likewise, a positive number means that two stars are moving away. Its nothing to fear as the stars are so far apart, they won't collide in our life-time, if ever.

Physical Properties of Kochab

Kochab Temperature and Colour

Based on the star's spectral type of K4IIIvar , Kochab's colour and type is orange to red giant star. The star has a B-V Colour Index of 1.46 which means the star's temperature is about 4,059 Kelvin. The temperature was calculated using information from Morgans @ Uni.edu.

Kochab Luminosity

Luminosity is the amount of energy that a star pumps out and its relative to the amount that our star, the Sun gives out. The figure of 537.07 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

Kochab Radius

Kochab estimated radius has been calculated as being 28.19 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 19,613,643.12.km. If you need the diameter of the star, you just need to multiple the radius by 2. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 29.24654911847996194778318703. The figure is derived at by using the formula from SDSS rather than peer reviewed papers. It has been known to produce widely incorrect figures.

Kochab Mass

The Kochab's solar mass is 1.40 times that of our star, the Sun. The Sun's Mass is 1,989,100,000,000,000,000,000 billion kg. which to calculate using this website is too large. To give idea of size, the Sun is 99.86% the mass of the solar system.

Kochab Metalicity

The star's metallicity is -0.270000, this value is the fractional amount of the star that is not Hydrogen (X) or Helium (Y). An older star would have a high metallicity whereas a new star would have a lower one.

Kochab Estimated Age

The star is believed to be about 2.95 Billion years old. To put in context, the Sun is believed to be about five billion years old and the Universe is about 13.8 billion years old.

Kochab Apparent and Absolute Magnitudes

Kochab has an apparent magnitude of 2.07 which is how bright we see the star from Earth. Apparent Magnitude is also known as Visual Magnitude. If you used the 1997 Parallax value, you would get an absolute magnitude of -0.87 If you used the 2007 Parallax value, you would get an absolute magnitude of -0.95. Magnitude, whether it be apparent/visual or absolute magnitude is measured by a number, the smaller the number, the brighter the Star is. Our own Sun is the brightest star and therefore has the lowest of all magnitudes, -26.74. A faint star will have a high number.

Distance to Kochab

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 25.79000 which gave the calculated distance to Kochab as 126.47 light years away from Earth or 38.77 parsecs. If you want that in miles, it is about 743,469,750,946,531.16, based on 1 Ly = 5,878,625,373,183.61 miles.

In 2007, Hipparcos data was revised with a new parallax of 24.91000 which put Kochab at a distance of 130.94 light years or 40.14 parsecs. It should not be taken as though the star is moving closer or further away from us. It is purely that the distance was recalculated.

Using the 2007 distance, the star is roughly 8,279,411.63 Astronomical Units from the Earth/Sun give or take a few. An Astronomical Unit is the distance between Earth and the Sun. The number of A.U. is the number of times that the star is from the Earth compared to the Sun. The star's Galacto-Centric Distance is 7,412.00 Parsecs or 24,175.23 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

Travel Time to Kochab

The time it will take to travel to this star is dependent on how fast you are going. U.G. has done some calculations as to how long it will take going at differing speeds. A note about the calculations, when I'm talking about years, I'm talking non-leap years only (365 days).

The New Horizons space probe is the fastest probe that we've sent into space at the time of writing. Its primary mission was to visit Pluto which at the time of launch (2006), Pluto was still a planet.

DescriptionSpeed (m.p.h.)Time (years)
Airbus A380736119,307,800.82
Speed of Sound (Mach 1)767.269114,445,574.37
Concorde (Mach 2)1,534.5457,222,712.61
New Horizons Probe33,0002,660,925.50
Speed of Light670,616,629.00130.94

Meteor Showers Radiating from near Kochab

The Ursids Meteor Shower radiants from a point near this star. The meteor shower runs typically between December 17-25 with a peak date of Dec. 22. The speed of a meteor in the shower is 33 Km/s. The amount of meteors predicted to be seen per hour (Zenith Hourly Rate) is 33.

Source of Information

The source of the information if it has a Hip I.D. is from Simbad, the Hipparcos data library based at the University at Strasbourg, France. Hipparcos was a E.S.A. satellite operation launched in 1989 for four years. The items in red are values that I've calculated so they could well be wrong. Information regarding Metallicity and/or Mass is from the E.U. Exoplanets. The information was obtained as of 12th Feb 2017.

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Additional Kochab Facts and Figures

Visual Facts

Primary / Proper / Traditional NameKochab
Alternative NamesBeta Ursae Minoris, Bet Umi, HD 131873, HIP 72607, HR 5563, 7 Ursae Minoris, 7 Umi, BD+74 595, 7 UMi, Beta Umi
Spectral TypeK4IIIvar
Constellation's Main StarYes
Multiple Star SystemYes
Star TypeGiant Star
ColourOrange to Red
GalaxyMilky Way
ConstellationUrsa Minor
Age2.95 Billion Years Old
Absolute Magnitude -0.87 / -0.95
Visual / Apparent Magnitude2.07
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)14h 50m 42.40
Declination (Dec.)+74° 09` 19.7
Galactic Latitude40.50260950 degrees
Galactic Longitude112.64710240 degrees
1997 Distance from Earth25.79000 Parallax (milliarcseconds)
 126.47 Light Years
 38.77 Parsecs
2007 Distance from Earth24.91000 Parallax (milliarcseconds)
 130.94 Light Years
 40.14 Parsecs
 8,279,411.63 Astronomical Units
Galacto-Centric Distance24,175.23 Light Years / 7,412.00 Parsecs
Proper Motion Dec.11.42000 ± 0.11000 milliarcseconds/year
Proper Motion RA.-32.61000 ± 0.12000 milliarcseconds/year
B-V Index1.46
Radial Velocity16.96000 ± 0.19 km/s
Iron Abundance-0.1700 ± 9.99 Fe/H
Semi-Major Axis9477.0000000
Stellar Luminosity (Lsun)537.0700000
Brightest in Night Sky57th

Companions (Multi-Star and Exoplanets) Facts

Exoplanet Count1

Estimated Calculated Facts

Radius (x the Sun)29.25
Effective Temperature4,059 Kelvin
Mass Compared to the Sun1.40

Sources and Links

SIMBAD SourceLink

Multi-Star System

The star has been identified as being a multi-star system, one in which there is at least one star in close orbit to another star or two or more stars orbiting a central point. The stars may be of equal mass, unequal mass where one star is stronger than the other or be in groups orbiting a central point which doesn't necessarily have to be a star. More information can be found on my dedicated multiple star systems page. The source of the info is Simbad. The file is dated 2000 so any differences between this and any other source will be down to the actual source from where the information came from.

Proper Motion mas/yr
H.D. IdB.D. IdStar CodeMagnitudeR.A.Dec.SpectrumColourYear
131873+74 595.0A2.20000-34.0000010.00000K5Orange

Location of Kochab in Ursa Minor

Kochab Location in Ursa Minor

The map was generated using Night Vision, an awesome free application by Brian Simpson.

List of Extrasolar Planets orbiting Kochab

NameStatusMass (Jupiters)Orbital Period (Days)EccentricityDiscoveredSemi-Major AxisPeriastron
beta Umi bConfirmed1.0522.3000.1920141.4307.400

Ursa Minor Main Stars

Kochab Solar System

This is a N.A.S.A. impression of what the solar system might look like. If the star is not on display, its because its so small compared to the orbits of the outer planets. The green area denotes the habital zone which if the planet is within that area, life could exist. The habital zone might not appear on the picture because its outside the area for the picture. Our planets show the orbit of the planet if its was in our solar system. For more information about the planet and other exoplanetary stuff, visit N.A.S.A.

Kochab Solar System

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