Universe Guide

Tau1 Gruis

Tau1 Gruis Facts

  • Tau1 Gruis is a subgiant star that can be located in the constellation of Grus. The description is based on the spectral class.
  • Tau1 Gruis is not part of the constellation outline but is within the borders of the constellation.
  • Based on the spectral type (G3IV) of the star, the star's colour is yellow .
  • The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.
  • The star has an estimated age of 5.30 Billion of Years but could be as young as 5.00 to 5.70 according to Hipparcos.
  • Tau1 Gruis has at least 1 Extrasolar Planets believed to be in orbit around the star.
  • Using the most recent figures given by the 2007 Hipparcos data, the star is 106.38 light years away from us. Distance

Tau1 Gruis's Alternative Names

Tau1 Gruis (Tau01 Gru) 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 HR8700. HIP113044 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD216435.

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

Location of Tau1 Gruis

The location of the subgiant 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 Tau1 Gruis, the location is 22h 53m 37.74 and -48° 35` 53.1 .

Radial Velocity and Proper Motion of Tau1 Gruis

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 -81.76 ± 0.25 milliarcseconds/year towards the north and 217.04 ± 0.39 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 -1.10000 km/s with an error of about 0.62 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.

Physical Properties of Tau1 Gruis

Tau1 Gruis Colour and Temperature

Based on the star's spectral type of G3IV , Tau1 Gruis's colour and type is yellow subgiant star. The star has a B-V Colour Index of 0.62 which means the star's temperature is about 5,824 Kelvin. The temperature was calculated using information from Morgans @ Uni.edu.

Tau1 Gruis 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 3.77 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

Tau1 Gruis Radius

Tau1 Gruis estimated radius has been calculated as being 1.90 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 1,321,026.48.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 1.8639175801182534268360622442. 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.

Tau1 Gruis Mass

The Tau1 Gruis's solar mass is 1.30 times that of our star, the Sun. 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.

Tau1 Gruis Metalicity

The star's metallicity is 0.244000, 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.

Tau1 Gruis Estimated Age

The stars age according to Hipparcos data files put the star at an age of about 5.30 Billion years old but could be between 5.00 and 5.70 Billion years old. In comparison, the Sun's age is about 4.6 Billion Years Old.

Tau1 Gruis Apparent and Absolute Magnitudes

Tau1 Gruis has an apparent magnitude of 6.03 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 3.42 If you used the 2007 Parallax value, you would get an absolute magnitude of 3.46. 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 Tau1 Gruis

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 30.04000 which gave the calculated distance to Tau1 Gruis as 108.58 light years away from Earth or 33.29 parsecs. If you want that in miles, it is about 638,301,143,020,276.37, based on 1 Ly = 5,878,625,373,183.61 miles.

In 2007, Hipparcos data was revised with a new parallax of 30.66000 which put Tau1 Gruis at a distance of 106.38 light years or 32.62 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 6,728,311.10 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 7,384.00 Parsecs or 24,083.90 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 Tau1 Gruis

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)
Airbus A38073696,929,615.48
Speed of Sound (Mach 1)767.26992,979,381.41
Concorde (Mach 2)1,534.5446,489,630.11
New Horizons Probe33,0002,161,824.15
Speed of Light670,616,629.00106.38

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 Tau1 Gruis Facts and Figures

Visual Facts

Primary / Proper / Traditional NameTau1 Gruis
Alternative NamesTau01 Gru, HD 216435, HIP 113044, HR 8700
Spectral TypeG3IV
Constellation's Main StarNo
Multiple Star SystemYes
Star TypeSubgiant Star
GalaxyMilky Way
Age5.30 Billion Years Old
Age Range5.00 - 5.70 Billion Years Old
Absolute Magnitude 3.42 / 3.46
Visual / Apparent Magnitude6.03
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)22h 53m 37.74
Declination (Dec.)-48° 35` 53.1
Galactic Latitude-58.70956545 degrees
Galactic Longitude341.69435950 degrees
1997 Distance from Earth30.04000 Parallax (milliarcseconds)
 108.58 Light Years
 33.29 Parsecs
2007 Distance from Earth 30.66000 Parallax (milliarcseconds)
 106.38 Light Years
 32.62 Parsecs
 6,728,311.10 Astronomical Units
Galacto-Centric Distance24,083.90 Light Years / 7,384.00 Parsecs
Proper Motion Dec.-81.76000 ± 0.25000 milliarcseconds/year
Proper Motion RA.217.04000 ± 0.39000 milliarcseconds/year
B-V Index0.62
Radial Velocity-1.10000 ± 0.62 km/s
Iron Abundance0.1900 ± 0.01 Fe/H
Semi-Major Axis6933.0000000
Stellar Luminosity (Lsun)3.7700000
Associated / Clustered StarsTau2 Gruis
Tau2 Gruis B
Tau3 Gruis

Companions (Multi-Star and Exoplanets) Facts

Exoplanet Count1

Estimated Calculated Facts

Radius (x the Sun)1.86
Effective Temperature5,824 Kelvin
Mass Compared to the Sun1.30

Sources and Links

SIMBAD SourceLink

List of Extrasolar Planets orbiting Tau1 Gruis

NameStatusMass (Jupiters)Orbital Period (Days)EccentricityDiscoveredSemi-Major AxisPeriastron
HD 216435 bConfirmed0.131311.0000.0720022.56100.000

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