Universe Guide

84 Ursae Majoris

84 Ursae Majoris Facts

  • 84 Ursae Majoris is a rotating variable star that can be located in the constellation of Ursa Major. The description is based on the spectral class.
  • 84 Ursae Majoris is not part of the constellation outline but is within the borders of the constellation.
  • Based on the spectral type (B9p EuCr) of the star, the star's colour is blue .
  • 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 4.604 Billion Years old. This information comes from ExoPlanet.
  • Using the most recent figures given by the 2007 Hipparcos data, the star is 290.44 light years away from us. Distance

84 Ursae Majoris's Alternative Names

The Id of the star in the Yale Bright Star Catalogue is HR5187. HIP67231 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD120198.

84 Ursae Majoris has alternative name(s) :- CR UMa, CR UMa.

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 84 Ursae Majoris. The Flamsteed name can be shortened to 84 Uma.

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+55 1634.

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

Location of 84 Ursae Majoris

The location of the variable 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 84 Ursae Majoris, the location is 13h 46m 35.68 and +54° 25` 57.7 .

Radial Velocity and Proper Motion of 84 Ursae Majoris

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 -5.09 ± 0.20 milliarcseconds/year towards the north and -18.69 ± 0.23 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 -2.40000 km/s with an error of about 1.60 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 84 Ursae Majoris

84 Ursae Majoris Temperature and Colour

Based on the star's spectral type of B9p EuCr , 84 Ursae Majoris's colour and type is blue variable star. The star has a B-V Colour Index of -0.03 which means the star's temperature is about 11,122 Kelvin. The temperature was calculated using information from Morgans @ Uni.edu.

84 Ursae Majoris 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 47.29 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

84 Ursae Majoris Radius

84 Ursae Majoris estimated radius has been calculated as being 1.59 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 1,104,109.71.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 1.6388095799038534960264292597. 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.

84 Ursae Majoris Mass

The 84 Ursae Majoris's solar mass is 1.23 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.

84 Ursae Majoris Metalicity

The star's metallicity is -0.250000, 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.

84 Ursae Majoris Estimated Age

The star is believed to be about 4.60 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.

84 Ursae Majoris Apparent and Absolute Magnitudes

84 Ursae Majoris has an apparent magnitude of 5.68 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 1.00 If you used the 2007 Parallax value, you would get an absolute magnitude of 0.93. 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 84 Ursae Majoris

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 11.58000 which gave the calculated distance to 84 Ursae Majoris as 281.66 light years away from Earth or 86.36 parsecs. If you want that in miles, it is about 1,655,773,622,610,895.59, based on 1 Ly = 5,878,625,373,183.61 miles.

In 2007, Hipparcos data was revised with a new parallax of 11.23000 which put 84 Ursae Majoris at a distance of 290.44 light years or 89.05 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 18,367,753.01 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 7,413.00 Parsecs or 24,178.49 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 84 Ursae Majoris

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 A380736264,638,442.56
Speed of Sound (Mach 1)767.269253,853,464.33
Concorde (Mach 2)1,534.54126,926,566.74
New Horizons Probe33,0005,902,239.20
Speed of Light670,616,629.00290.44

Variable Type of 84 Ursae Majoris

The star is a rotating Alpha2 Canum Venatic variable type which means that its size changes over time. The Variable Type is usually named after the first star of that type to be spotted. 84 Ursae Majoris brightness ranges from a magnitude of 5.684 to a magnitude of 5.668 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 1.4 days (variability).

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 84 Ursae Majoris Facts and Figures

Visual Facts

Primary / Proper / Traditional Name84 Ursae Majoris
Alternative NamesCR UMa, HD 120198, HIP 67231, HR 5187, 84 Uma, BD+55 1634, CR UMa
Spectral TypeB9p EuCr
Constellation's Main StarNo
Multiple Star SystemYes
Star TypeVariable Star
GalaxyMilky Way
ConstellationUrsa Major
Age4.60 Billion Years Old
Absolute Magnitude 1.00 / 0.93
Visual / Apparent Magnitude5.68
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)13h 46m 35.68
Declination (Dec.)+54° 25` 57.7
Galactic Latitude60.88703118 degrees
Galactic Longitude106.37597387 degrees
1997 Distance from Earth11.58000 Parallax (milliarcseconds)
 281.66 Light Years
 86.36 Parsecs
2007 Distance from Earth11.23000 Parallax (milliarcseconds)
 290.44 Light Years
 89.05 Parsecs
 18,367,753.01 Astronomical Units
Galacto-Centric Distance24,178.49 Light Years / 7,413.00 Parsecs
Proper Motion Dec.-5.09000 ± 0.20000 milliarcseconds/year
Proper Motion RA.-18.69000 ± 0.23000 milliarcseconds/year
B-V Index-0.03
Radial Velocity-2.40000 ± 1.60 km/s
Semi-Major Axis8127.0000000
Stellar Luminosity (Lsun)47.2900000

Companions (Multi-Star and Exoplanets) Facts

Exoplanet CountNone/Unaware

Variable Star Details

Variable Star ClassRotating
Variable Star TypeAlpha2 Canum Venatic
Mean Variability Period in Days1.386
Variable Magnitude Range (Brighter - Dimmer)5.668 - 5.684

Estimated Calculated Facts

Radius (x the Sun)1.64
Effective Temperature11,122 Kelvin
Mass Compared to the Sun1.23

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
120198+55 1634.0A5.50000-25.000001.00000A0White

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