HD 154857 is a white to yellow main sequence dwarf star that can be located in the constellation of Ara. The star can not be seen by the naked eye, you need a telescope to see it. The star has an estimated age of 4.90 Billion of Years but could be as young as 4.30 to 5.60 according to Hipparcos.
HIP84069 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD154857. HD 154857 has at least 2 Extrasolar Planets believed to be in orbit around the star.
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 HD 154857, the location is 17h 11m 15.63 and -56d40`50.4 .
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 -55.92 ± 0.43 miliarcseconds/year towards the north and 87.14 ± 0.71 miliarcseconds/year east if we saw them in the horizon.
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 1.0000000 that I have given is based on the Spectral Types page that I have found on the Internet. You might find a different figure, one that may have been calculated rather than generalised that I have done. The figure is always the amount times the luminosity of the Sun. It is an imprecise figure because of a number of factors including but not limited to whether the star is a variable star and distance.
HD 154857 has a spectral type of G5V. This means the star is a white to yellow main sequence dwarf star. The star is 7344.00000000 Parsecs from the Galactic Centre or terms of Light Years is 23953.4359833600000000s. The star has a B-V Colour Index of 0.69 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 5,594 Kelvin.
HD 154857 Radius has been calculated as being 2.43 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 1,690,101.80.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 2.28. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures. The star's solar mass is 2.00 times that of the Sun's. The Sun's Mass is 1,989,100,000,000,000,000,000 billion kg. which to calculate using this website is too large. To give idea of size, the Sun is 99.86% the mass of the solar system.
The star's metallicity is -0.220000, this value is the fractional amount of the star that is not Hydrogen (X) or Helium (Y). An older star would have a high metallicity whereas a new star would have a lower one.
The stars age according to Hipparcos data files put the star at an age of about 4.90 Billion years old but could be between 4.30 and 5.60 Billion years old. In comparison, the Sun's age is about 4.6 Billion Years Old.
HD 154857 has an apparent magnitude of 7.24 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 3.06 If you used the 2007 Parallax value, you would get an absolute magnitude of 3.20. 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.
Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 14.59 which gave the calculated distance to HD 154857 as 223.55 light years away from Earth or 68.54 parsecs. It would take a spaceship travelling at the speed of light, 223.55 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 15.57 which put HD 154857 at a distance of 209.48 light years or 64.23 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 7,344.00 Parsecs or 23,953.44 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.
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.
|Traditional/Proper Name||HD 154857|
|Hipparcos Library I.D.||84069|
|Henry Draper Designation||154857|
|Star Type||main sequence dwarf star|
|Age||4.90 Billion Years Old|
|Age Range||4.30 - 5.60 Billion Years Old|
|Absolute Magnitude||3.06 / 3.20|
|Visual / Apparent Magnitude||7.24|
|Naked Eye Visible||Requires a 7x50 Binoculars - Ref: Wiki|
|Right Ascension (R.A.)||17h 11m 15.63|
|Galactic Latitude||-10.03 degrees|
|Galactic Longitude||333.29 degrees|
|1997 Distance from Earth||14.59 Parallax (milliarcseconds)|
|223.55 Light Years|
|2007 Revised Distance from Earth||15.57 Parallax (milliarcseconds)|
|209.48 Light Years|
|Galacto-Centric Distance||23,953.44 Light Years / 7,344.00 Parsecs|
|Proper Motion Dec.||-55.92 ± 0.43 milliarcseconds/year|
|Proper Motion RA.||87.14 ± 0.71 milliarcseconds/year|
|Radial Velocity||27.90 ± 0.68 km/s|
|Iron Abundance||-0.23 ± 0.03 Fe/H|
|Colour||(G) White to Yellow|
|Luminosity (x the Sun)||1.0000000|
|Calculated Effective Temperature||5,594 Kelvin|
|Mass Compared to the Sun||2.00|
|Name||Status||Mass (Jupiters)||Orbital Period (Days)||Eccentricity||Discovered||Semi-Major Axis||Periastron|
|Hd 154857 B||Confirmed||2.24||408.600||0.46||2004||1.291||57.000|
|Hd 154857 C||Confirmed||2.58||3452.000||0.06||2014||5.36||352.000|