Universe Guide


HR 7403, HD183362, HIP95673

HR 7403 is a blue eruptive main sequence dwarf star that can be located in the constellation of Lyra. HR 7403 is the brightest star in Lyra 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.

HIP95673 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD183362.

HR 7403 has alternative name(s), V558 Lyr.

Location of HR 7403

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 HR 7403, the location is 19h 27m 36.40 and +37d56`28.3 .

Proper Motion of HR 7403

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 -4.46 ± 0.23 miliarcseconds/year towards the north and -0.13 ± 0.29 miliarcseconds/year east if we saw them in the horizon.

HR 7403 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 1060.0000000 that I have given is based on the Spectral Types page that I have found on the Internet. You might find a different figure, one that may have been calculated rather than generalised that I have done. The figure is always the amount times the luminosity of the Sun. It is an imprecise figure because of a number of factors including but not limited to whether the star is a variable star and distance.

Physical Properties (Colour, Temperature, Radius) of HR 7403

HR 7403 has a spectral type of B3Ve. This means the star is a blue main sequence dwarf star. The star has a B-V Colour Index of -0.12 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 12,367 Kelvin.

HR 7403 Radius has been calculated as being 7.09 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 4,930,440.41.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 8.10. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

HR 7403 Apparent and Absolute Magnitudes

HR 7403 has an apparent magnitude of 6.30 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 -2.71 If you used the 2007 Parallax value, you would get an absolute magnitude of -3.00. 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 HR 7403

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 1.58 which gave the calculated distance to HR 7403 as 2064.32 light years away from Earth or 632.91 parsecs. It would take a spaceship travelling at the speed of light, 2064.32 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 1.38 which put HR 7403 at a distance of 2363.50 light years or 724.64 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 HR 7403

The star is a eruptive Gamma Cassiopeiae 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. HR 7403 brightness ranges from a magnitude of 6.298 to a magnitude of 6.225 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.1 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.

HR 7403 Facts

Alternative Names

Traditional/Proper NameHR 7403
Short NameV558 Lyr
Hipparcos Library I.D.95673
Bonner DurchmusterungBD+37 3465
Henry Draper Designation183362

Visual Facts

Star Typemain sequence dwarf star
Absolute Magnitude-2.71 / -3.00
Visual / Apparent Magnitude6.30
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)19h 27m 36.40
Declination (Dec.)+37d56`28.3
Galactic Latitude9.79 degrees
Galactic Longitude70.71 degrees
1997 Distance from Earth1.58 Parallax (milliarcseconds)
 2064.32 Light Years
 632.91 Parsecs
2007 Revised Distance from Earth1.38 Parallax (milliarcseconds)
 2363.50 Light Years
 724.64 Parsecs
Proper Motion Dec.-4.46 ± 0.23 milliarcseconds/year
Proper Motion RA.-0.13 ± 0.29 milliarcseconds/year
B-V Index-0.12
Radial Velocity-27.70 ± 7.40 km/s
Spectral TypeB3Ve
Colour(B) blue

Variable Star Details

Variable Star ClassEruptive
Variable Star TypeGamma Cassiopeiae
Mean Variability Period in Days0.063
Variable Magnitude Range (Brighter - Dimmer)6.225 - 6.298

Estimated Facts

Luminosity (x the Sun)1,060.0000000
Calculated Effective Temperature12,367 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

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