Universe Guide

HD 155806

HD 155806 Facts

  • HD 155806 is a pulsating variable star that can be located in the constellation of Scorpius. The description is based on the spectral class.
  • HD 155806 is not part of the constellation outline but is within the borders of the constellation.
  • Based on the spectral type (O9) of the star, the star's colour is blue - white.
  • 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, the star is 3664.76 light years away from us. Distance

HD 155806's Alternative Names

HIP84401 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD155806.

HD 155806 has alternative name(s) :- , V1075 Sco.

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

Location of HD 155806

The location of the variable 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 HD 155806, the location is 17h 15m 19.25 and -33° 32` 54.3 .

Radial Velocity and Proper Motion of HD 155806

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 -3.05 ± 0.18 milliarcseconds/year towards the north and 0.92 ± 0.40 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 11.60 km/s with an error of about 2.80 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 HD 155806

HD 155806 Temperature and Colour

Based on the star's spectral type of O9 , HD 155806's colour and type is blue - white variable star. The star has a B-V Colour Index of -0.05 which means the star's temperature is about 11,775 Kelvin. The temperature was calculated using information from Morgans @ Uni.edu.

HD 155806 Radius

HD 155806 estimated radius has been calculated as being 23.28 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 16,200,031.97.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 19.10. 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.

HD 155806 Apparent and Absolute Magnitudes

HD 155806 has an apparent magnitude of 5.60 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 -5.08 If you used the 2007 Parallax value, you would get an absolute magnitude of -4.65. 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 HD 155806

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 0.73 which gave the calculated distance to HD 155806 as 4467.99 light years away from Earth or 1369.86 parsecs. If you want that in miles, it is about 26,265,639,381,130,637.64, based on 1 Ly = 5,878,625,373,183.61 miles.

In 2007, Hipparcos data was revised with a new parallax of 0.89 which put HD 155806 at a distance of 3664.76 light years or 1123.60 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 231,757,521.39 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.

Travel Time to HD 155806

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 A3807363,339,197,007.19
Speed of Sound (Mach 1)767.2693,203,112,594.53
Concorde (Mach 2)1,534.541,601,554,209.92
New Horizons Probe33,00074,474,212.04
Speed of Light670,616,629.003,664.76

Variable Type of HD 155806

The star is a pulsating Slow Irregular variable type which means that its size changes over time. The Variable Type is usually named after the first star of that type to be spotted. HD 155806 brightness ranges from a magnitude of 5.645 to a magnitude of 5.572 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 0.1 days (variability).

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 HD 155806 Facts and Figures

Visual Facts

Primary / Proper / Traditional NameHD 155806
Alternative NamesHD 155806, HIP 84401, V1075 Sco
Spectral TypeO9
Constellation's Main StarNo
Multiple Star SystemNo / Unknown
Star TypeVariable Star
GalaxyMilky Way
Absolute Magnitude -5.08 / -4.65
Visual / Apparent Magnitude5.60
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)17h 15m 19.25
Declination (Dec.)-33° 32` 54.3
Galactic Latitude2.87 degrees
Galactic Longitude352.59 degrees
1997 Distance from Earth0.73 Parallax (milliarcseconds)
 4467.99 Light Years
 1369.86 Parsecs
2007 Distance from Earth0.89 Parallax (milliarcseconds)
 3664.76 Light Years
 1123.60 Parsecs
 231,757,521.39 Astronomical Units
Proper Motion Dec.-3.05 ± 0.18 milliarcseconds/year
Proper Motion RA.0.92 ± 0.40 milliarcseconds/year
B-V Index-0.05
Radial Velocity11.60 ± 2.80 km/s

Companions (Multi-Star and Exoplanets) Facts

Exoplanet CountNone/Unaware

Variable Star Details

Variable Star ClassPulsating
Variable Star TypeSlow Irregular
Mean Variability Period in Days0.074
Variable Magnitude Range (Brighter - Dimmer)5.572 - 5.645

Estimated Calculated Facts

Radius (x the Sun)19.10
Effective Temperature11,775 Kelvin

Sources and Links

SIMBAD SourceLink

Related Stars

Comments and Questions

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