Universe Guide

HD 198357

HD 198357 Facts

  • HD 198357 is a giant star that can be located in the constellation of Microscopium. The description is based on the spectral class.
  • HD 198357 is not part of the constellation outline but is within the borders of the constellation.
  • Based on the spectral type (K3III) of the star, the star's colour is orange to red .
  • 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 587.68 light years away from us. Distance

HD 198357's Alternative Names

HIP102916 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD198357.

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

Location of HD 198357

The location of the giant 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 198357, the location is 20h 51m 00.76 and -37° 54` 47.8 .

Radial Velocity and Proper Motion of HD 198357

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 -17.35 ± 0.18 milliarcseconds/year towards the north and -7.85 ± 0.33 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 16.50000 km/s with an error of about 2.90 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 198357

HD 198357 Temperature and Colour

Based on the star's spectral type of K3III , HD 198357's colour and type is orange to red giant star. The star has a B-V Colour Index of 1.38 which means the star's temperature is about 4,192 Kelvin. The temperature was calculated using information from Morgans @ Uni.edu.

HD 198357 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 384.54 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

HD 198357 Radius

HD 198357 estimated radius has been calculated as being 26.80 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 18,644,644.97.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 25.12281609277913217037658026. 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 198357 Apparent and Absolute Magnitudes

HD 198357 has an apparent magnitude of 5.52 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 -0.90 If you used the 2007 Parallax value, you would get an absolute magnitude of -0.76. 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 198357

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 5.20000 which gave the calculated distance to HD 198357 as 627.24 light years away from Earth or 192.31 parsecs. If you want that in miles, it is about 3,687,308,979,075,687.54, based on 1 Ly = 5,878,625,373,183.61 miles.

In 2007, Hipparcos data was revised with a new parallax of 5.55000 which put HD 198357 at a distance of 587.68 light years or 180.18 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 37,164,533.82 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 7,262.00 Parsecs or 23,685.98 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 HD 198357

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 A380736535,472,799.63
Speed of Sound (Mach 1)767.269513,650,337.14
Concorde (Mach 2)1,534.54256,824,833.85
New Horizons Probe33,00011,942,666.08
Speed of Light670,616,629.00587.68

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 198357 Facts and Figures

Visual Facts

Primary / Proper / Traditional NameHD 198357
Alternative NamesHD 198357, HIP 102916
Spectral TypeK3III
Constellation's Main StarNo
Multiple Star SystemNo / Unknown
Star TypeGiant Star
ColourOrange to Red
GalaxyMilky Way
Absolute Magnitude -0.90 / -0.76
Visual / Apparent Magnitude5.52
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)20h 51m 00.76
Declination (Dec.)-37° 54` 47.8
Galactic Latitude-39.05994156 degrees
Galactic Longitude4.67783310 degrees
1997 Distance from Earth5.20000 Parallax (milliarcseconds)
 627.24 Light Years
 192.31 Parsecs
2007 Distance from Earth5.55000 Parallax (milliarcseconds)
 587.68 Light Years
 180.18 Parsecs
 37,164,533.82 Astronomical Units
Galacto-Centric Distance23,685.98 Light Years / 7,262.00 Parsecs
Proper Motion Dec.-17.35000 ± 0.18000 milliarcseconds/year
Proper Motion RA.-7.85000 ± 0.33000 milliarcseconds/year
B-V Index1.38
Radial Velocity16.50000 ± 2.90 km/s
Semi-Major Axis7244.0000000
Stellar Luminosity (Lsun)384.5400000

Companions (Multi-Star and Exoplanets) Facts

Exoplanet CountNone/Unaware

Estimated Calculated Facts

Radius (x the Sun)25.12
Effective Temperature4,192 Kelvin

Sources and Links

SIMBAD SourceLink

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Comments and Questions

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