Universe Guide

Mira (Omicron Ceti, 68 Ceti) Star Facts

Mira Facts

Mira's Alternative Names

Omicron Ceti (Omi Cet) is the Bayer Classification for the star. The Bayer Classification was created by Johann Bayer in the early nineteenth century. The brightest star in the constellation is normally given the Alpha designation although there are exceptions such as Pollux which is Beta Geminorum.

The Id of the star in the Yale Bright Star Catalogue is HR681. HIP10826 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD14386.

Mira has alternative name(s) :- , omi Cet.

Flamsteed designations are named after the creator, Sir John Flamsteed. Sir John numbered the stars in the constellation with a number and the latin name, this star's Flamsteed designation is 68 Ceti with it shortened to 68 Cet.

The Gould star designation is one that was designed by American astronomer, Benjamin Apthorp Gould. Gould stars are predominantly in the Southern and Equatorial constellations but do appear in northern constellations such as Bootes and Orion. The star has the designation 233 G. Ceti. There are no stars with a Gould designation in Ursa Major for example.

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-03 353.

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

Location of Mira

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 Mira, the location is 02h 19m 20.79 and -02° 58` 37.4 .

Radial Velocity and Proper Motion of Mira

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 -237.36 ± 1.31 milliarcseconds/year towards the north and 9.33 ± 1.22 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 63.50 km/s with an error of about 0.60 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.

Mira 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 47.05 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

Physical Properties (Colour, Temperature, Radius) of Mira

Mira Colour and Temperature

Mira has a spectral type of M5e-M9e. This means the star is a red variable star. The star has a B-V Colour Index of 0.96 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 5,060 Kelvin.

Mira Radius

Mira has been calculated as 332.00 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 231,005,600.00.km. If you need the diameter of the star, you just need to multiple the radius by 2.

Mira Apparent and Absolute Magnitudes

Mira has an apparent magnitude of 6.47 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 0.93 If you used the 2007 Parallax value, you would get an absolute magnitude of 1.66. 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 Mira

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 7.79 which gave the calculated distance to Mira as 418.69 light years away from Earth or 128.37 parsecs. It would take a spaceship travelling at the speed of light, 418.69 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 10.91 which put Mira at a distance of 298.96 light years or 91.66 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 18,906,100.40 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 7,466.00 Parsecs or 24,351.36 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 Mira

The star is a pulsating Omicron Ceti 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. Mira brightness ranges from a magnitude of 7.321 to a magnitude of 2.935 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 333.8 days (variability).

Meteor Showers Radiating from near Mira

The August omicron Cetids Meteor Shower radiants from a point near this star. The meteor shower runs typically between with a peak date of 10th August. The speed of a meteor in the shower is 66 Km/s.

The Omicron Cetids Meteor Shower radiants from a point near this star. The meteor shower runs typically between May 7-June 9 with a peak date of May 14-25.

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 Mira Facts and Figures

Visual Facts

Primary / Proper / Traditional NameMira
Alternative NamesOmicron Ceti, Omi Cet, HD 14386, HIP 10826, HR 681, 233 G. Ceti, 68 Ceti, 68 Cet, BD-03 353, omi Cet
Spectral TypeM5e-M9e
Constellation's Main StarYes
Multiple Star SystemYes
Star TypeVariable Star
GalaxyMilky Way
Absolute Magnitude 0.93 / 1.66
Visual / Apparent Magnitude6.47
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)02h 19m 20.79
Declination (Dec.)-02° 58` 37.4
Galactic Latitude-57.98 degrees
Galactic Longitude167.75 degrees
1997 Distance from Earth7.79 Parallax (milliarcseconds)
 418.69 Light Years
 128.37 Parsecs
2007 Distance from Earth10.91 Parallax (milliarcseconds)
 298.96 Light Years
 91.66 Parsecs
 18,906,100.40 Astronomical Units
Galacto-Centric Distance24,351.36 Light Years / 7,466.00 Parsecs
Proper Motion Dec.-237.36 ± 1.31 milliarcseconds/year
Proper Motion RA.9.33 ± 1.22 milliarcseconds/year
B-V Index0.96
Radial Velocity63.50 ± 0.60 km/s
Semi-Major Axis5037.00
Stellar Luminosity (Lsun)47.05

Companions (Multi-Star and Exoplanets) Facts

Exoplanet CountNone/Unaware

Variable Star Details

Variable Star ClassPulsating
Variable Star TypeOmicron Ceti
Mean Variability Period in Days333.800
Variable Magnitude Range (Brighter - Dimmer)2.935 - 7.321

Estimated Calculated Facts

Radius (x the Sun)332.00 (332.00 - 402.00)
Effective Temperature5,060 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
14386-03 353.0A-13.00000-233.00000M4Red
14411-03 355.0C9.30000-6.00000-17.00000M1Red1925

Location of Mira in Cetus

Mira Location in Cetus

The map was generated using Night Vision, an awesome free application by Brian Simpson.

Cetus Main Stars

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