Universe Guide

BM Capricorni

BM Capricorni Facts

  • BM Capricorni is a giant star that can be located in the constellation of Capricornus. The description is based on the spectral class.
  • BM Capricorni is not part of the constellation outline but is within the borders of the constellation.
  • Based on the spectral type (K2III + F/G) of the star, the star's colour is orange to red .
  • 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 254.02 light years away from us. Distance

BM Capricorni's Alternative Names

HIP102723 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD198141.

BM Capricorni has alternative name(s) :- , BM Cap.

BD number is the number that the star was filed under in the Durchmusterung or Bonner Durchmusterung, a star catalogue that was put together by the Bonn Observatory between 1859 to 1903. The star's BD Number is BD-21 5839.

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

Location of BM Capricorni

The location of the giant 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 BM Capricorni, the location is 20h 48m 55.66 and -20° 37` 08.1 .

Radial Velocity and Proper Motion of BM Capricorni

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 -21.62 ± 1.11 milliarcseconds/year towards the north and 70.28 ± 2.38 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 -37.20000 km/s with an error of about 0.30 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 BM Capricorni

BM Capricorni Colour and Temperature

Based on the star's spectral type of K2III + F/G , BM Capricorni's colour and type is orange to red giant star. The star has a B-V Colour Index of 0.74 which means the star's temperature is about 5,446 Kelvin. The temperature was calculated using information from Morgans @ Uni.edu.

BM Capricorni 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 1.31 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

BM Capricorni Radius

BM Capricorni estimated radius has been calculated as being 1.52 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 1,054,851.49.km. If you need the diameter of the star, you just need to multiple the radius by 2. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 1.260964822636598114941277744. The figure is derived at by using the formula from SDSS rather than peer reviewed papers. It has been known to produce widely incorrect figures.

BM Capricorni Iron Abundance

BM Capricorni Iron Abundance is -0.05 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context. The value comes from the Hipparcos Extended Catalog.

BM Capricorni Apparent and Absolute Magnitudes

BM Capricorni has an apparent magnitude of 9.06 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 4.20 If you used the 2007 Parallax value, you would get an absolute magnitude of 4.60. 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 BM Capricorni

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 10.66000 which gave the calculated distance to BM Capricorni as 305.97 light years away from Earth or 93.81 parsecs. If you want that in miles, it is about 1,798,683,005,432,989.15, based on 1 Ly = 5,878,625,373,183.61 miles.

In 2007, Hipparcos data was revised with a new parallax of 12.84000 which put BM Capricorni at a distance of 254.02 light years or 77.88 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 16,063,791.18 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. The star's Galacto-Centric Distance is 7,345.00 Parsecs or 23,956.70 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

Travel Time to BM Capricorni

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 A380736231,453,853.39
Speed of Sound (Mach 1)767.269222,021,267.77
Concorde (Mach 2)1,534.54111,010,489.20
New Horizons Probe33,0005,162,122.31
Speed of Light670,616,629.00254.02
BM Capricorni brightness ranges from a magnitude of 9.420 to a magnitude of 9.160 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.3 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 BM Capricorni Facts and Figures

Visual Facts

Primary / Proper / Traditional NameBM Capricorni
Alternative NamesHD 198141, HIP 102723, BD-21 5839, BM Cap
Spectral TypeK2III + F/G
Constellation's Main StarNo
Multiple Star SystemYes
Star TypeGiant Star
ColourOrange to Red
GalaxyMilky Way
Absolute Magnitude 4.20 / 4.60
Visual / Apparent Magnitude9.06
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)20h 48m 55.66
Declination (Dec.)-20° 37` 08.1
Galactic Latitude-34.69013410 degrees
Galactic Longitude25.65962348 degrees
1997 Distance from Earth10.66000 Parallax (milliarcseconds)
 305.97 Light Years
 93.81 Parsecs
2007 Distance from Earth12.84000 Parallax (milliarcseconds)
 254.02 Light Years
 77.88 Parsecs
 16,063,791.18 Astronomical Units
Galacto-Centric Distance23,956.70 Light Years / 7,345.00 Parsecs
Proper Motion Dec.-21.62000 ± 1.11000 milliarcseconds/year
Proper Motion RA.70.28000 ± 2.38000 milliarcseconds/year
B-V Index0.74
Radial Velocity-37.20000 ± 0.30 km/s
Iron Abundance-0.0500 ± 9.99 Fe/H
Semi-Major Axis7089.0000000
Stellar Luminosity (Lsun)1.3100000

Companions (Multi-Star and Exoplanets) Facts

Exoplanet CountNone/Unaware

Variable Star Details

Mean Variability Period in Days0.314
Variable Magnitude Range (Brighter - Dimmer)9.160 - 9.420

Estimated Calculated Facts

Radius (x the Sun)1.26
Effective Temperature5,446 Kelvin

Sources and Links

SIMBAD SourceLink

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
198141-21 5839.0A9.30000-5.0000041.00000G5Yellow

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