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Helvetios (51 Pegasi) Star Facts

Helvetios Facts

Information on Helvetios

Extrasolar Planet Discover

The star was an obscure planet that people probably never heard of before 1995. It was the first star discovered to have an exoplanet in orbit round it by Swiss astronomers Michel Mayor and Didier Queloz. They nicknamed the planet, Bellerophon which stuck with it but the planet was later renamed Dimidum. Dimidum is latin for half and refers to the fact that the planet is half the mass of Jupiter. Bellerophon was an ancinet greek hero famed for slaying Chimera, a winged creature.

In the same competition, the star 51 Pegasi obtained the name Helvetios. The name Helvetios comes from the tribe that lived in Switzerland during the middle ages. It was meant to honour the fact that the discoverers were Swiss. ref:I.A.U.

Helvetios's Alternative Names

The Id of the star in the Yale Bright Star Catalogue is HR8729. HIP113357 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD217014. The Gliese ID of the star is GL 882. The star was part of the original catalogue devised by German Astronomer Wilheim Gliese of stars located within 20 parsecs of Earth. Star Names

Flamsteed designations are named after the creator, Sir John Flamsteed. Sir John named the stars in the constellation with a number and its latin name, this star's Flamsteed designation is 51 Pegasi. The Flamsteed name can be shortened to 51 Peg.

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+19 5036.

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

Location of Helvetios

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 Helvetios, the location is 22h 57m 27.85 and +20° 46` 07.3 .

Radial Velocity and Proper Motion of Helvetios

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 60.34 ± 0.16 milliarcseconds/year towards the north and 207.25 ± 0.38 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 -33.02 km/s with an error of about 0.09 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.

Helvetios 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 1.51 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, Metallicity, Age, Mass) of Helvetios

Helvetios Colour and Temperature

Helvetios has a spectral type of G5V. This means the star is a yellow main sequence star.

The star's effective temperature is 5,787 Kelvin which is hotter than our own Sun's effective Temperature which is 5,777 Kelvin.

Helvetios Radius

Radius has been calculated as being 1.20 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 834,202.69.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 1.22. 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 1.11 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 0.200000, 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 6.00 Billion years old but could be between 4.00 and 8.10 Billion years old. In comparison, the Sun's age is about 4.6 Billion Years Old.

Helvetios Apparent and Absolute Magnitudes

Helvetios has an apparent magnitude of 5.45 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 4.52 If you used the 2007 Parallax value, you would get an absolute magnitude of 4.48. 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 Helvetios

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 65.10 which gave the calculated distance to Helvetios as 50.10 light years away from Earth or 15.36 parsecs. If you want that in miles, it is 33,597,893,113.

In 2007, Hipparcos data was revised with a new parallax of 64.07 which put Helvetios at a distance of 50.91 light years or 15.61 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 3,219,771.19 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 7,400.00 Parsecs or 24,136.09 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 Helvetios

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)
Walking48,535,273,145.60
Car120284,509,104.85
Airbus A38073646,387,354.05
Speed of Sound (Mach 1)767.26944,496,900.80
Concorde (Mach 2)1,534.5422,248,421.40
New Horizons Probe33,0001,034,578.56
Speed of Light670,616,629.0050.91

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 Helvetios Facts and Figures

Visual Facts


Primary / Proper / Traditional NameHelvetios
Alternative NamesHD 217014, HIP 113357, HR 8729, 51 Pegasi, 51 Peg, BD+19 5036, Gliese 882
Spectral TypeG5V
Constellation's Main StarNo
Multiple Star SystemNo / Unknown
Star Type Main Sequence Dwarf Star
ColourYellow
GalaxyMilky Way
ConstellationPegasus
Age6.00 Billion Years Old
Age Range4.00 - 8.10 Billion Years Old
Metalicity0.2000
Absolute Magnitude 4.52 / 4.48
Visual / Apparent Magnitude5.45
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)22h 57m 27.85
Declination (Dec.)+20° 46` 07.3
Galactic Latitude-34.73 degrees
Galactic Longitude90.06 degrees
1997 Distance from Earth65.10 Parallax (milliarcseconds)
 50.10 Light Years
 15.36 Parsecs
2007 Distance from Earth64.07 Parallax (milliarcseconds)
 50.91 Light Years
 15.61 Parsecs
 3,219,771.19 Astronomical Units
Galacto-Centric Distance24,136.09 Light Years / 7,400.00 Parsecs
Proper Motion Dec.60.34 ± 0.16 milliarcseconds/year
Proper Motion RA.207.25 ± 0.38 milliarcseconds/year
B-V Index0.66
Radial Velocity-33.02 ± 0.09 km/s
Iron Abundance0.17 ± 9.99 Fe/H
Eccentricity0.13
Semi-Major Axis6524.00
Stellar Luminosity (Lsun)1.51

Companions (Multi-Star and Exoplanets) Facts


Exoplanet Count1

Estimated Calculated Facts


Radius (x the Sun)1.22
Effective Temperature5,689 Kelvin
Mass Compared to the Sun1.11

Sources and Links


SIMBAD SourceLink

Location of Helvetios in Pegasus


Helvetios Location in Pegasus

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


List of Extrasolar Planets orbiting Helvetios


NameStatusMass (Jupiters)Orbital Period (Days)EccentricityDiscoveredSemi-Major AxisPeriastronInclination
51 Peg bConfirmed0.074.2310.006919950.05254.10080.000

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