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Sigma Bootis, 28 Bootis, HD128167, HIP71284, HR5447

Sigma Bootis is a blue to white main sequence dwarf star that can be located in the constellation of Bootes. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it. The star has an estimated age of 1.40 Billion of Years but could be as young as 0.60 to 1.90 according to Hipparcos.

Sigma Bootis's Alternative Names

Sigma Bootis is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR5447. HIP71284 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD128167. The Gliese ID of the star is GL 557. The star was part of the original catalogue devised by German Astronomer Wilheim Gliese of stars located within 20 parsecs of Earth. Ref : Star Names.

Flamsteed designations are named after the creator, Sir John Flamsteed. Sir John numbered the stars in the constellation with a number and the latin name, this star's Flamsteed designation is 28 Bootis with it shortened to 28 Boo.

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+30 2536.

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

Location of Sigma Bootis

The location of the star in the galaxy 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 star is compared to the celestial equator and is expressed in degrees. For Sigma Bootis, the location is 14h 34m 40.69 and +29° 44` 41.3 .

Proper Motion of Sigma Bootis

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 131.77 ± 0.14 miliarcseconds/year towards the north and 188.35 ± 0.25 miliarcseconds/year east if we saw them in the horizon. The Radial Velocity, that is the speed at which the star is moving away/towards us is 0.37000 km/s with an error of about 0.09 km/s .

Sigma Bootis 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 3.4000000 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

Physical Properties (Colour, Temperature, Age) of Sigma Bootis

Sigma Bootis has a spectral type of F3Vwvar. This means the star is a blue to white main sequence dwarf star. The star is 7396.00000000 Parsecs from the Galactic Centre or terms of Light Years is 24123.0409222400000000s. The star has a B-V Colour Index of 0.36 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 6,918 Kelvin.

Sigma Bootis Radius has been calculated as being 1.29 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 894,112.48.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 1.31. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures. The star's Iron Abundance is -0.32 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context.

The stars age according to Hipparcos data files put the star at an age of about 1.40 Billion years old but could be between 0.60 and 1.90 Billion years old. In comparison, the Sun's age is about 4.6 Billion Years Old.

Sigma Bootis Apparent and Absolute Magnitudes

Sigma Bootis has an apparent magnitude of 4.47 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 3.52 If you used the 2007 Parallax value, you would get an absolute magnitude of 3.47. 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 Sigma Bootis

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 64.66 which gave the calculated distance to Sigma Bootis as 50.44 light years away from Earth or 15.47 parsecs. It would take a spaceship travelling at the speed of light, 50.44 years to get there. We don't have the technology or spaceship that can carry people over that distance yet.

In 2007, Hipparcos data was revised with a new parallax of 63.16 which put Sigma Bootis at a distance of 51.64 light years or 15.83 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.

The star's Galacto-Centric Distance is 7,396.00 Parsecs or 24,123.04 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

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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Sigma Bootis Facts

Visual Facts

Alternative NamesHD 128167, HIP 71284, HR 5447, 28 Bootis, 28 Boo, BD+30 2536, Gliese 557
Star Type main sequence Dwarf Star
GalaxyMilky Way
Age1.40 Billion Years Old
Age Range0.60 - 1.90 Billion Years Old
Absolute Magnitude3.52 / 3.47
Visual / Apparent Magnitude4.47
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)14h 34m 40.69
Declination (Dec.)+29° 44` 41.3
Galactic Latitude67.20 degrees
Galactic Longitude45.63 degrees
1997 Distance from Earth64.66 Parallax (milliarcseconds)
 50.44 Light Years
 15.47 Parsecs
2007 Revised Distance from Earth63.16 Parallax (milliarcseconds)
 51.64 Light Years
 15.83 Parsecs
Galacto-Centric Distance24,123.04 Light Years / 7,396.00 Parsecs
Proper Motion Dec.131.77 ± 0.14 milliarcseconds/year
Proper Motion RA.188.35 ± 0.25 milliarcseconds/year
B-V Index0.36
Radial Velocity0.37 ± 0.09 km/s
Iron Abundance-0.32 ± 9.99 Fe/H
Semi-Major Axis10295.00
Stellar Luminosity (Lsun)3.40
Spectral TypeF3Vwvar
Colour(F) blue to white

Estimated Facts

Calculated Effective Temperature6,918 Kelvin

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
128167+30 2536.0A4.50000188.00000129.00000F0Yellow/White

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