Eta Centauri

Eta Centauri Star Facts

• Eta Centauri is a Main Sequence Star.

• Eta Centauri can be located in the Milky Way galaxy, this is the galaxy that you reside in.

• Eta Centauri is not located within the Solar System, there is only one star in the Solar System and that is the Sun.

• When you look at Eta Centauri, you are in fact looking back in time, you are seeing how it looks years ago. Roughly, change the distance from light years to years will tell you how long ago we are looking at the star.

• There are no Exoplanets recorded on the site for the star and is most likely the case. If an exoplanet had been spotted or confirmed, it will probably be recorded in Exoplanet EU database.

• No one has visited Eta Centauri and we have no probes on a rendezvous with the star.

• Eta Centauri is a main star in the constellation Centaurus and makes up the constellation outline.

• Based on the spectral type (B1Vn + A) of the star, the Eta Centauri colour is blue .

• The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.

• Using the most recent figures given by the 2007 Hipparcos data, Eta Centauri distance from Earth is 305.68 light years.

Eta Centauri Location

The location of the main sequence 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 Eta Centauri, the location is 14h 35m 30.45 and -42° 09` 27.9 .

Eta Centauri Radial Velocity and Proper Motion

Eta Centauri 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 -32.72 ± 0.11 milliarcseconds/year towards the north and -34.73 ± 0.21 milliarcseconds/year east if we saw them in the horizon.

Eta Centauri Radial Velocity

The Radial Velocity, that is the speed at which the star is moving away/towards the Sun is 0.00000 km/s with an error of about 1.60 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.

Eta Centauri Physical Properties

Eta Centauri Colour

Based on the star's spectral type of B1Vn + A , Eta Centauri's colour and type is blue main sequence star.

Eta Centauri Surface Temperature

Based on the spectral type as we don't have the exact temperature', we can deduce that the surface temperature of the star is in the order of 10,000 and 25,000K based on the notes from Harvard University. To put this in context, the temperature of our Sun is about 5,778 Kelvin as said by Google.

• Blue (O) > 25,000K

• Blue/White (B) = 10,000 - 25,000K

• Blue/White (A) = 7,500 - 10,000K

• Yellow/White (F) = 6,000 - 7,500K

• Yellow (G) = 5,000 - 6,000K

• Orange/Red (K) = 3,500 - 5000K

• Red (M) = < 3,500K

• Red (C) = < 3,500K

There is a relationship between colour and temperature, stars that are closer to red in the rainbow spectrum are cooler whereas those closer to blue are hotter. Those that are blue stars are normally identified as being young stars whereas redder stars are usually older stars, ones that are at the end of their life. An example of when its a Blue Straggler, the star has stolen matter from a nearby star and grown to appear youthful when its not. These stars are found mainly in Star Clusters.

There is no relationship between colour and size, a red star can be both the largest and the smallest stars in the Universe. Small stars are more energy efficient than larger stars and live longer.

Eta Centauri 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 2,432.97 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

Eta Centauri Radius

Eta Centauri estimated radius has been calculated as being 5.38 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 3,746,465.29.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 5.34. 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.

Eta Centauri Apparent (Brightness) and Absolute Magnitudes

Absolute Magnitude is the apparent magnitude of the star from a distance of 10 parsecs or 32.6 light years. This assumes that there is nothing in between the object and the viewer such as dust clouds. To really compare the brightness of the star, it is best to use Absolute rather than Apparent Magnitude.

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.

Eta Centauri apparent magnitude is 2.33, this is a measure of the brightness of the star as seen from Earth. Apparent Magnitude is also known as Visual Magnitude. If you used the 1997 Parallax value, Eta Centauri absolute magnitude is -2.55 If you used the 2007 Parallax value, Eta Centauri absolute magnitude is -2.53.

Visible from Earth

Eta Centauri is visible from Earth. The lower the Apparent Magnitude of a star or other object is, the easier it is to see in the night sky. An object with a magnitude greater than 6.5 can not be seen without the aid of a telescope or other device.

Eta Centauri Distance from Earth

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 10.57000 which means Eta Centauri distance from Earth is 308.57 light years away from Earth or 94.61 parsecs. If you want that in miles, it is about 1,813,967,431,403,266.54, based on 1 Ly = 5,878,625,373,183.61 miles.

In 2007, Hipparcos data was revised with a new parallax of 10.67000 which puts Eta Centauri distance from Earth as 305.68 light years or 93.72 parsecs. It should not be taken as though the star is moving closer or further away from Earth. It is purely that the distance was recalculated.

Using the 2007 distance, the star is roughly 19,331,002.94 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 7,329.00 Parsecs or 23,904.51 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

Alternative Names and Meanings

• Eta Centauri (Eta Cen) is the Bayer Classification for the star. The Bayer Classification was created by Johann Bayer in 1603. The brightest star in the constellation is normally given the Alpha designation, there are exceptions such as Pollux which is Beta Geminorum.

• The Id of the star in the Yale Bright Star Catalogue is HR5440.

• HIP71352 is the reference name for the star in the Hipparcos Star Catalogue.

• The Id of the star in the Henry Draper catalogue is HD127972. The catalogue was started by the American doctor and has been expanded on over the years.

• The star is catalogued in the Tycho-2 star catalogue as TYC-7814-3706-1. The catalogue lists 2 millions stars and its homepage is E.S.A.

• 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. There are no stars with a Gould designation in Ursa Major for example.