Universe Guide

EW Boötis

EW Boötis Facts

EW Bootis's Alternative Names

HIP73612 is the reference name for the star in the Hipparcos Star Catalogue.

EW Bootis has alternative name(s) :- EW Boo, EW 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+38 2613.

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

Location of EW Boötis

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 EW Boötis, the location is 15h 02m 46.08 and +37° 54` 36.6 .

Proper Motion of EW Boötis

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 -16.99 ± 1.01 milliarcseconds/year towards the north and 33.17 ± 1.38 milliarcseconds/year east if we saw them in the horizon. . 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 (Colour, Temperature) of EW Boötis

EW Bootis Colour and Temperature

EW Boötis has a spectral type of A0. This means the star is a blue - white variable star. The star has a B-V Colour Index of 0.2 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 7,400 Kelvin.

EW Bootis Radius

Radius has been calculated as being 5.16 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 3,588,577.49.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 2.71. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

EW Boötis Apparent and Absolute Magnitudes

EW Boötis has an apparent magnitude of 10.25 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 0.21 If you used the 2007 Parallax value, you would get an absolute magnitude of 1.61. 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 EW Boötis

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 0.98 which gave the calculated distance to EW Boötis as 3328.20 light years away from Earth or 1020.41 parsecs. It would take a spaceship travelling at the speed of light, 3328.20 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 1.87 which put EW Boötis at a distance of 1744.19 light years or 534.76 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 110,301,399.20 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.

Variable Type of EW Boötis

The star is a eclipsing binary sys Beta Persei (Algol) 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. EW Boötis brightness ranges from a magnitude of 10.693 to a magnitude of 10.312 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.9 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 EW Boötis Facts and Figures

Visual Facts

Primary / Proper / Traditional NameEW Bootis
Alternative NamesEW Boo, HIP 73612, BD+38 2613, EW Boo
Spectral TypeA0
Constellation's Main StarNo
Multiple Star SystemNo / Unknown
Star TypeVariable Star
GalaxyMilky Way
Absolute Magnitude 0.21 / 1.61
Visual / Apparent Magnitude10.25
Naked Eye VisibleRequires a 4.5 - 6 Inch Telescope - Magnitudes
Right Ascension (R.A.)15h 02m 46.08
Declination (Dec.)+37° 54` 36.6
Galactic Latitude60.48 degrees
Galactic Longitude62.69 degrees
1997 Distance from Earth0.98 Parallax (milliarcseconds)
 3328.20 Light Years
 1020.41 Parsecs
2007 Distance from Earth1.87 Parallax (milliarcseconds)
 1744.19 Light Years
 534.76 Parsecs
 110,301,399.20 Astronomical Units
Proper Motion Dec.-16.99 ± 1.01 milliarcseconds/year
Proper Motion RA.33.17 ± 1.38 milliarcseconds/year
B-V Index0.20

Companions (Multi-Star and Exoplanets) Facts

Exoplanet CountNone/Unaware

Variable Star Details

Variable Star ClassEclipsing binary sys
Variable Star TypeBeta Persei (Algol)
Mean Variability Period in Days0.906
Variable Magnitude Range (Brighter - Dimmer)10.312 - 10.693

Estimated Calculated Facts

Radius (x the Sun)2.71
Effective Temperature7,400 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

Comments and Questions

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