Universe Guide


V721 Monocerotis, HD44816, HIP30407

V721 Monocerotis is a orange to red pulsating star that can be located in the constellation of Monoceros. V721 Monocerotis is the brightest star in Monoceros 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.

HIP30407 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD44816.

V721 Monocerotis has alternative name(s), V721 Mon.

Location of V721 Monocerotis

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 V721 Monocerotis, the location is 06h 23m 35.92 and -09d52`29.1 .

Proper Motion of V721 Monocerotis

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 4.11 ± 0.26 miliarcseconds/year towards the north and -2.00 ± 0.46 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of V721 Monocerotis

V721 Monocerotis has a spectral type of K5. This means the star is a orange to red star. The star has a B-V Colour Index of 1.84 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 2,817 Kelvin.

V721 Monocerotis Radius has been calculated as being 147.69 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 102,764,333.71.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 105.04. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

V721 Monocerotis Apparent and Absolute Magnitudes

V721 Monocerotis has an apparent magnitude of 6.11 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 -2.88 If you used the 2007 Parallax value, you would get an absolute magnitude of -2.14. 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 V721 Monocerotis

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 1.59 which gave the calculated distance to V721 Monocerotis as 2051.34 light years away from Earth or 628.93 parsecs. It would take a spaceship travelling at the speed of light, 2051.34 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 2.24 which put V721 Monocerotis at a distance of 1456.09 light years or 446.43 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 V721 Monocerotis

The star is a pulsating Slow Irregular 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. V721 Monocerotis brightness ranges from a magnitude of 6.261 to a magnitude of 6.177 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.

V721 Monocerotis Facts

Alternative Names

Traditional/Proper NameV721 Monocerotis
Short NameV721 Mon
Hipparcos Library I.D.30407
Bonner DurchmusterungBD-09 1444
Henry Draper Designation44816

Visual Facts

Star Type star
Absolute Magnitude-2.88 / -2.14
Visual / Apparent Magnitude6.11
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)06h 23m 35.92
Declination (Dec.)-09d52`29.1
Galactic Latitude-10.63 degrees
Galactic Longitude218.67 degrees
1997 Distance from Earth1.59 Parallax (milliarcseconds)
 2051.34 Light Years
 628.93 Parsecs
2007 Revised Distance from Earth2.24 Parallax (milliarcseconds)
 1456.09 Light Years
 446.43 Parsecs
Proper Motion Dec.4.11 ± 0.26 milliarcseconds/year
Proper Motion RA.-2.00 ± 0.46 milliarcseconds/year
B-V Index1.84
Radial Velocity30.10 ± 0.70 km/s
Spectral TypeK5
Colour(K) Orange to Red

Variable Star Details

Variable Star ClassPulsating
Variable Star TypeSlow Irregular
Mean Variability Period in Days0.077
Variable Magnitude Range (Brighter - Dimmer)6.177 - 6.261

Estimated Facts

Calculated Effective Temperature2,817 Kelvin

Sources and Links

SIMBAD SourceLink

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