Universe Guide
Search

Theta Hydrae (22 Hydrae) Star Facts

Theta Hydrae Facts

  • Theta Hydrae is a main sequence star that can be located in the constellation of Hydra. The description is based on the spectral class.
  • Theta Hydrae is a main star of the constellation outline.
  • Based on the spectral type (B9.5V) of the star, the star's colour is blue .
  • 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 113.49 light years away from us. Distance

Theta Hydrae's Alternative Names

Theta Hydrae (The Hya) 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 HR3665. HIP45336 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD79469.

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 22 Hydrae. The Flamsteed name can be shortened to 22 Hya.

The Gould star designation is one that was designed by American astronomer, Benjamin Apthorp Gould. Gould stars are predominantly in the Southern and Equatorial constellations but do appear in northern constellations such as Bootes and Orion. The star has the designation 108 G. Hydrae. There are no stars with a Gould designation in Ursa Major for example.

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+02 2167.

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

Location of Theta Hydrae

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 Theta Hydrae, the location is 09h 14m 21.79 and +02° 18` 54.1 .

Radial Velocity and Proper Motion of Theta Hydrae

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 -313.94 ± 1.10 milliarcseconds/year towards the north and 114.64 ± 1.55 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 -10.70000 km/s with an error of about 0.30 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 Theta Hydrae

Theta Hydrae Temperature and Colour

Based on the star's spectral type of B9.5V , Theta Hydrae's colour and type is blue main sequence star. The star has a B-V Colour Index of -0.06 which means the star's temperature is about 10,611 Kelvin. The temperature was calculated using information from Morgans @ Uni.edu.

Theta Hydrae 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 52.11 that I have given is based on the value in the Simbad Hipparcos Extended Catalogue at the University of Strasbourg from 2012.

Theta Hydrae Radius

Theta Hydrae estimated radius has been calculated as being 1.82 times bigger than the Sun. The Sun's radius is 695,800km, therefore the star's radius is an estimated 1,264,346.96.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 1.6046458307427292491572608465. 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.

Theta Hydrae Iron Abundance

Theta Hydrae Iron Abundance is -0.42 with an error value of 0.04 Fe/H with the Sun has a value of 1 to put it into context. The value comes from the Hipparcos Extended Catalog.

Theta Hydrae Apparent and Absolute Magnitudes

Theta Hydrae has an apparent magnitude of 3.89 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 0.91 If you used the 2007 Parallax value, you would get an absolute magnitude of 1.18. 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 Theta Hydrae

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 25.34000 which gave the calculated distance to Theta Hydrae as 128.71 light years away from Earth or 39.46 parsecs. If you want that in miles, it is about 756,637,871,782,462.44, based on 1 Ly = 5,878,625,373,183.61 miles.

In 2007, Hipparcos data was revised with a new parallax of 28.74000 which put Theta Hydrae at a distance of 113.49 light years or 34.79 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 7,175,902.61 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 7,422.00 Parsecs or 24,207.84 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 Theta Hydrae

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)
Walking419,027,070,306.30
Car120634,235,676.88
Airbus A380736103,407,990.80
Speed of Sound (Mach 1)767.26999,193,739.39
Concorde (Mach 2)1,534.5449,596,805.05
New Horizons Probe33,0002,306,311.55
Speed of Light670,616,629.00113.49

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.

Hide Explanations
Show GridLines

Additional Theta Hydrae Facts and Figures

Visual Facts


Primary / Proper / Traditional NameTheta Hydrae
Alternative NamesThe Hya, HD 79469, HIP 45336, HR 3665, 108 G. Hydrae, 22 Hydrae, 22 Hya, BD+02 2167
Spectral TypeB9.5V
Constellation's Main StarYes
Multiple Star SystemYes
Star Type Main Sequence Dwarf Star
ColourBlue
GalaxyMilky Way
ConstellationHydra
Absolute Magnitude 0.91 / 1.18
Visual / Apparent Magnitude3.89
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)09h 14m 21.79
Declination (Dec.)+02° 18` 54.1
Galactic Latitude32.52955064 degrees
Galactic Longitude228.77126610 degrees
1997 Distance from Earth25.34000 Parallax (milliarcseconds)
 128.71 Light Years
 39.46 Parsecs
2007 Distance from Earth28.74000 Parallax (milliarcseconds)
 113.49 Light Years
 34.79 Parsecs
 7,175,902.61 Astronomical Units
Galacto-Centric Distance24,207.84 Light Years / 7,422.00 Parsecs
Proper Motion Dec.-313.94000 ± 1.10000 milliarcseconds/year
Proper Motion RA.114.64000 ± 1.55000 milliarcseconds/year
B-V Index-0.06
Radial Velocity-10.70000 ± 0.30 km/s
Iron Abundance-0.4200 ± 0.04 Fe/H
Eccentricity0.33930
Semi-Major Axis6268.0000000
Stellar Luminosity (Lsun)52.1100000

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Estimated Calculated Facts


Radius (x the Sun)1.60
Effective Temperature10,611 Kelvin

Sources and Links


SIMBAD SourceLink

Multi-Star System

The star has been identified as being a multi-star system, one in which there is at least one star in close orbit to another star or two or more stars orbiting a central point. The stars may be of equal mass, unequal mass where one star is stronger than the other or be in groups orbiting a central point which doesn't necessarily have to be a star. More information can be found on my dedicated multiple star systems page. The source of the info is Simbad. The file is dated 2000 so any differences between this and any other source will be down to the actual source from where the information came from.


Proper Motion mas/yr
H.D. IdB.D. IdStar CodeMagnitudeR.A.Dec.SpectrumColourYear
79469+02 2167.0A3.80000129.00000-313.00000A0White
B9.80000-33.0000026.000001953
C1924
D12.400001962

Hydra Main Stars


Comments and Questions

There's no register feature and no need to give an email address if you don't need to. All messages will be reviewed before being displayed. Comments may be merged or altered slightly such as if an email address is given in the main body of the comment.

You can decline to give a name which if that is the case, the comment will be attributed to a random star. A name is preferred even if its a random made up one by yourself.

   
x
This website is using cookies. More info. That's Fine