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V638 Monocerotis - HD42657 - HIP29401

V638 Monocerotis is a blue star that can be located in the constellation of Monoceros. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.

HIP29401 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD42657.

Location of V638 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 V638 Monocerotis, the location is 06h 11m 43.72 and -04d39`55.6 .

Proper Motion of V638 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 -2.37 ± 0.56 miliarcseconds/year towards the north and -6.95 ± 0.69 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of V638 Monocerotis

V638 Monocerotis has a spectral type of B9MNp.... This means the star is a blue star. The star is 7544.00000000 Parsecs from the Galactic Centre or terms of Light Years is 24605.7626713600000000s. The star has a B-V Colour Index of -0.07 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 12,523 Kelvin.

V638 Monocerotis Radius has been calculated as being 2.09 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 1,452,018.50.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 2.03. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

V638 Monocerotis Apparent and Absolute Magnitudes

V638 Monocerotis has an apparent magnitude of 6.18 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 -0.11 If you used the 2007 Parallax value, you would get an absolute magnitude of -0.05. 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 V638 Monocerotis

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 5.52 which gave the calculated distance to V638 Monocerotis as 590.88 light years away from Earth or 181.16 parsecs. It would take a spaceship travelling at the speed of light, 590.88 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 5.68 which put V638 Monocerotis at a distance of 574.23 light years or 176.06 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 7,544.00 Parsecs or 24,605.76 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

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.

V638 Monocerotis Facts

Alternative Names

Traditional/Proper NameV638 Monocerotis
Hipparcos Library I.D.29401
Bonner DurchmusterungBDD-04 1393
Henry Draper Designation42657

Visual Facts

Star Type star
Absolute Magnitude-0.11 / -0.05
Visual / Apparent Magnitude6.18
Naked Eye VisibleYes - Ref: Wiki
Right Ascension (R.A.)06h 11m 43.72
Declination (Dec.)-04d39`55.6
Galactic Latitude-10.95 degrees
Galactic Longitude212.58 degrees
1997 Distance from Earth5.52 Parallax (milliarcseconds)
 590.88 Light Years
 181.16 Parsecs
2007 Revised Distance from Earth5.68 Parallax (milliarcseconds)
 574.23 Light Years
 176.06 Parsecs
Galacto-Centric Distance24,605.76 Light Years / 7,544.00 Parsecs
Proper Motion Dec.-2.37 ± 0.56 milliarcseconds/year
Proper Motion RA.-6.95 ± 0.69 milliarcseconds/year
B-V Index-0.07
Radial Velocity23.30 ± 3.50 km/s
Spectral TypeB9MNp...
Colour(B) blue

Estimated Facts

Calculated Effective Temperature12,523 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
42657-04 1393.0A6.10000-16.00000-10.00000B9Blue/White
B8.600001958

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