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HR 7739, HD192685, HIP99824

HR 7739 is a blue eruptive star that can be located in the constellation of Vulpecula. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.

HIP99824 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD192685.

HR 7739 has alternative name(s), QR Vul.

Location of HR 7739

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 7739, the location is 20h 15m 15.89 and +25d 35` 31.1 .

Proper Motion of HR 7739

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 -3.89 ± 0.29 miliarcseconds/year towards the north and 6.93 ± 0.51 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 -7.00000 km/s with an error of about 1.70 km/s .

HR 7739 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 7739

HR 7739 has a spectral type of B3V. This means the star is a blue star. The star is 7282.00000000 Parsecs from the Galactic Centre or terms of Light Years is 23751.2147100800000000s. The star has a B-V Colour Index of -0.18 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 15,433 Kelvin.

HR 7739 Radius has been calculated as being 5.30 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 3,685,674.37.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 4.37. 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 -0.10 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context.

HR 7739 Apparent and Absolute Magnitudes

HR 7739 has an apparent magnitude of 4.79 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 -3.04 If you used the 2007 Parallax value, you would get an absolute magnitude of -2.62. 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 7739

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 2.72 which gave the calculated distance to HR 7739 as 1199.13 light years away from Earth or 367.65 parsecs. It would take a spaceship travelling at the speed of light, 1199.13 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 3.29 which put HR 7739 at a distance of 991.38 light years or 303.95 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 7,282.00 Parsecs or 23,751.21 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

Variable Type of HR 7739

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 7739 brightness ranges from a magnitude of 4.743 to a magnitude of 4.670 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 7739 Facts

Alternative Names

Traditional/Proper NameHR 7739
Short NameQR Vul
Hipparcos Library I.D.99824
Bonner DurchmusterungBD+25 4165
Henry Draper Designation192685

Visual Facts

Star Type star
Absolute Magnitude-3.04 / -2.62
Visual / Apparent Magnitude4.79
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)20h 15m 15.89
Declination (Dec.)+25d 35` 31.1
Galactic Latitude-5.17 degrees
Galactic Longitude65.19 degrees
1997 Distance from Earth2.72 Parallax (milliarcseconds)
 1199.13 Light Years
 367.65 Parsecs
2007 Revised Distance from Earth3.29 Parallax (milliarcseconds)
 991.38 Light Years
 303.95 Parsecs
Galacto-Centric Distance23,751.21 Light Years / 7,282.00 Parsecs
Proper Motion Dec.-3.89 ± 0.29 milliarcseconds/year
Proper Motion RA.6.93 ± 0.51 milliarcseconds/year
B-V Index-0.18
Radial Velocity-7.00 ± 1.70 km/s
Iron Abundance-0.10 ± 9.99 Fe/H
Spectral TypeB3V
Colour(B) blue

Variable Star Details

Variable Star ClassEruptive
Variable Star TypeGamma Cassiopeiae
Mean Variability Period in Days0.065
Variable Magnitude Range (Brighter - Dimmer)4.670 - 4.743

Estimated Facts

Luminosity (x the Sun)1,060.0000000
Calculated Effective Temperature15,433 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

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
192685+25 4165.0A4.800004.00000-2.00000B3Blue/White

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