Universe Guide

AC Monocerotis

AC Monocerotis Facts

  • AC Monocerotis is a pulsating variable star that can be located in the constellation of Monoceros. The description is based on the spectral class.
  • AC Monocerotis is not part of the constellation outline but is within the borders of the constellation.
  • Based on the spectral type (F7.5) of the star, the star's colour is yellow to white .
  • The star can not be seen by the naked eye, you need a telescope to see it.
  • Using the most recent figures given by the 2007 Hipparcos data, the star is 2346.50 light years away from us. Distance

AC Monocerotis's Alternative Names

HIP33791 is the reference name for the star in the Hipparcos Star Catalogue.

AC Monocerotis has alternative name(s) :- AC Mon, AC Mon.

More details on objects' alternative names can be found at Star Names .

Location of AC Monocerotis

The location of the variable star in the night sky 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 object is compared to the celestial equator and is expressed in degrees. For AC Monocerotis, the location is 07h 00m 59.82 and -08° 42` 32.4 .

Radial Velocity and Proper Motion of AC Monocerotis

Proper Motion

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 3.37 ± 1.45 milliarcseconds/year towards the north and -1.44 ± 2.15 milliarcseconds/year east if we saw them in the horizon.

Radial Velocity

The Radial Velocity, that is the speed at which the star is moving away/towards the Sun is 40.50000 km/s with an error of about 1.78 km/s . When the value is negative then the star and the Sun are getting closer to one another, likewise, a positive number means that two stars are moving away. Its nothing to fear as the stars are so far apart, they won't collide in our life-time, if ever.

Physical Properties of AC Monocerotis

AC Monocerotis Temperature and Colour

Based on the star's spectral type of F7.5 , AC Monocerotis's colour and type is yellow to white variable star. Based on the star's spectral, the stars temperature is between 6,000.00 and 7,500.00 degrees kelvin.

AC Monocerotis Radius

AC Monocerotis Apparent and Absolute Magnitudes

AC Monocerotis has an apparent magnitude of 10.38 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 0.15 If you used the 2007 Parallax value, you would get an absolute magnitude of 1.10. 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 AC Monocerotis

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 0.90000 which gave the calculated distance to AC Monocerotis as 3624.04 light years away from Earth or 1111.11 parsecs. If you want that in miles, it is about 21,304,373,497,432,329.98, based on 1 Ly = 5,878,625,373,183.61 miles.

In 2007, Hipparcos data was revised with a new parallax of 1.39000 which put AC Monocerotis at a distance of 2346.50 light years or 719.42 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.

Using the 2007 distance, the star is roughly 148,389,992.91 Astronomical Units from the Earth/Sun give or take a few. An Astronomical Unit is the distance between Earth and the Sun. The number of A.U. is the number of times that the star is from the Earth compared to the Sun.

Travel Time to AC Monocerotis

The time it will take to travel to this star is dependent on how fast you are going. U.G. has done some calculations as to how long it will take going at differing speeds. A note about the calculations, when I'm talking about years, I'm talking non-leap years only (365 days).

The New Horizons space probe is the fastest probe that we've sent into space at the time of writing. Its primary mission was to visit Pluto which at the time of launch (2006), Pluto was still a planet.

DescriptionSpeed (m.p.h.)Time (years)
Airbus A3807362,138,046,086.89
Speed of Sound (Mach 1)767.2692,050,912,939.20
Concorde (Mach 2)1,534.541,025,455,133.10
New Horizons Probe33,00047,684,906.67
Speed of Light670,616,629.002,346.50

Variable Type of AC Monocerotis

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. AC Monocerotis brightness ranges from a magnitude of 10.619 to a magnitude of 9.891 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 8.0 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.

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Additional AC Monocerotis Facts and Figures

Visual Facts

Primary / Proper / Traditional NameAC Monocerotis
Alternative NamesAC Mon, HIP 33791, AC Mon
Spectral TypeF7.5
Constellation's Main StarNo
Multiple Star SystemNo / Unknown
Star TypeVariable Star
ColourYellow - White
GalaxyMilky Way
Absolute Magnitude 0.15 / 1.10
Visual / Apparent Magnitude10.38
Naked Eye VisibleRequires a 4.5 - 6 Inch Telescope - Magnitudes
Right Ascension (R.A.)07h 00m 59.82
Declination (Dec.)-08° 42` 32.4
Galactic Latitude-1.85447086 degrees
Galactic Longitude221.76944605 degrees
1997 Distance from Earth0.90000 Parallax (milliarcseconds)
 3624.04 Light Years
 1111.11 Parsecs
2007 Distance from Earth1.39000 Parallax (milliarcseconds)
 2346.50 Light Years
 719.42 Parsecs
 148,389,992.91 Astronomical Units
Proper Motion Dec.3.37000 ± 1.45000 milliarcseconds/year
Proper Motion RA.-1.44000 ± 2.15000 milliarcseconds/year
B-V Index-99
Radial Velocity40.50000 ± 1.78 km/s

Companions (Multi-Star and Exoplanets) Facts

Exoplanet CountNone/Unaware

Variable Star Details

Variable Star ClassPulsating
Variable Star TypeDelta Cepheid
Mean Variability Period in Days8.013
Variable Magnitude Range (Brighter - Dimmer)9.891 - 10.619

Estimated Calculated Facts

Calculated Temperature Range6,000.00 - 7,500.00

Sources and Links

SIMBAD SourceLink

Related Stars

Comments and Questions

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