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Bezek, Eta Aquilae, 55 Aquilae, HD187929, HIP97804, HR7570

Bezek (Eta Aquilae) is a blue to white pulsating star that can be located in the constellation of Aquila. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.

Eta Aquilae is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR7570. HIP97804 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD187929. The Id of the star in the Gould Star Catalogue is 89. Stars in the southern hemisphere are more likely to have a Gould Id than the northern hemisphere. For example, there are no Gould classified stars in Ursa Major.

Bezek has alternative name(s), eta Aql.

Location of Bezek

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 Bezek, the location is 19h 52m 28.36 and +01d 00` 20.4 .

Proper Motion of Bezek

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 -8.21 ± 0.81 miliarcseconds/year towards the north and 6.91 ± 1.04 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 -25.10000 km/s with an error of about 0.20 km/s .

Physical Properties (Colour, Temperature, Radius) of Bezek

Bezek has a spectral type of F6Ibv SB. This means the star is a blue to white star. The star has a B-V Colour Index of 0.63 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 5,807 Kelvin.

Bezek Radius has been calculated as being 55.85 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 38,861,768.89.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 65.92. 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 0.13 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context.

Bezek Apparent and Absolute Magnitudes

Bezek has an apparent magnitude of 3.87 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 -3.91 If you used the 2007 Parallax value, you would get an absolute magnitude of -4.27. 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 Bezek

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 2.78 which gave the calculated distance to Bezek as 1173.25 light years away from Earth or 359.71 parsecs. It would take a spaceship travelling at the speed of light, 1173.25 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 2.36 which put Bezek at a distance of 1382.05 light years or 423.73 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.

Variable Type of Bezek

The star is a pulsating Delta Cepheid 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. Bezek brightness ranges from a magnitude of 4.465 to a magnitude of 3.646 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 7.2 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.

Bezek Facts

Alternative Names

Traditional/Proper NameBezek
Flamsteed Name55 Aquilae
Flamsteed Short Name55 Aql
Short Nameeta Aql
Bayer DesignationEta Aquilae
Hipparcos Library I.D.97804
Yale Bright Star Catalogue (HR) Id7570
Bonner DurchmusterungBD+00 4337
Gould I.D.89
Henry Draper Designation187929

Visual Facts

Star Type star
Absolute Magnitude-3.91 / -4.27
Visual / Apparent Magnitude3.87
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)19h 52m 28.36
Declination (Dec.)+01d 00` 20.4
Galactic Latitude-13.07 degrees
Galactic Longitude40.93 degrees
1997 Distance from Earth2.78 Parallax (milliarcseconds)
 1173.25 Light Years
 359.71 Parsecs
2007 Revised Distance from Earth2.36 Parallax (milliarcseconds)
 1382.05 Light Years
 423.73 Parsecs
Proper Motion Dec.-8.21 ± 0.81 milliarcseconds/year
Proper Motion RA.6.91 ± 1.04 milliarcseconds/year
B-V Index0.63
Radial Velocity-25.10 ± 0.20 km/s
Iron Abundance0.13 ± 9.99 Fe/H
Spectral TypeF6Ibv SB
Colour(F) blue to white

Variable Star Details

Variable Star ClassPulsating
Variable Star TypeDelta Cepheid
Mean Variability Period in Days7.178
Variable Magnitude Range (Brighter - Dimmer)3.646 - 4.465

Estimated Facts

Calculated Effective Temperature5,807 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

Location of Bezek in Aquila

Bezek (Eta Aquilae) Location in Aquila

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

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