HD 18742 is a white to yellow subgiant star that can be located in the constellation of Eridanus. It is calculated at being 2.000 Billion Years old. This information comes from ExoPlanet. HIP13993 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD18742. HD 18742 has at least 1 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 18742, the location is 03h 00m 10.67 and -20d48`09.2 .
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 -023.37 ± 000.41 towards the north and -019.81 ± 000.78 east if we saw them in the horizon.
HD 18742 has a spectral type of G8/K0IV. This means the star is a white to yellow subgiant star. The star has a B-V Colour Index of 0.93 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 4,989 Kelvin.
HD 18742 has been calculated as 4.37 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 3,043,255.66.km. 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 -0.040000, 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 star is believed to be about 2.00 Billion years old. To put in context, the Sun is believed to be about five billion years old and the Universe is about 13.8 billion years old.
HD 18742 has an apparent magnitude of 7.81 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 2.28 If you used the 2007 Parallax value, you would get an absolute magnitude of 2.15. 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 7.82 which gave the calculated distance to HD 18742 as 417.09 light years away from Earth or 127.88 parsecs. It would take a spaceship travelling at the speed of light, 417.09 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 7.39 which put HD 18742 at a distance of 441.36 light years or 135.32 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 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 Stellar Age, Metallicity or Mass is from the E.U. Exoplanets. The information was obtained as of 12th Feb 2017.
|Traditional Name||HD 18742|
|Hipparcos Library I.D.||13993|
|Bonner Durchmusterung||BD-21 533|
|Henry Draper Designation||18742|
|Star Type||subgiant star|
|Age||2.000 Billions of Years|
|Absolute Magnitude||2.28 / 2.15|
|Right Ascension (R.A.)||03h 00m 10.67|
|1997 Distance from Earth||7.82 Parallax (milliarcseconds)|
|417.09 Light Years|
|2007 Revised Distance from Earth||7.39 Parallax (milliarcseconds)|
|441.36 Light Years|
|Proper Motion Dec.||-23.37 ± 0.41 milliarcseconds/year|
|Proper Motion RA.||-19.81 ± 0.78 milliarcseconds/year|
|Colour||(G) White to Yellow|
|Radius (x the Sun)||4.37|
|Calculated Effective Temperature||4,989 Kelvin|
|Mass Compared to the Sun||2.00|
|Name||Status||Mass (Jupiters)||Orbital Period (Days)||Eccentricity||Discovered||Semi-Major Axis||Periastron|
|Hd 18742 B||Confirmed||2.7||772.000||0.23||2011||1.92||102.000|