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Alterf, Lambda Leonis, 4 Leonis, HD82308, HIP46750, HR3773

Alterf (Lambda Leonis) is a orange to red giant star that can be located in the constellation of Leo. Alterf is the brightest star in Leo based on the Hipparcos 2007 apparent magnitude. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.

Lambda Leonis is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR3773. HIP46750 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD82308. In Arabic, it is known as At-tarf.

Location of Alterf

The location of the star in the galaxy 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 star is compared to the celestial equator and is expressed in degrees. For Alterf, the location is 09h 31m 43.24 and +22d 58` 05.0 .

Proper Motion of Alterf

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 -39.47 ± 0.10 miliarcseconds/year towards the north and -20.17 ± 0.18 miliarcseconds/year east if we saw them in the horizon.

Physical Properties (Colour, Temperature, Radius) of Alterf

Alterf has a spectral type of K5IIIvar. This means the star is a orange to red giant star. The star is 7464.00000000 Parsecs from the Galactic Centre or terms of Light Years is 24344.8319961600000000s. The star has a B-V Colour Index of 1.54 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 3,913 Kelvin.

Alterf Radius has been calculated as being 28.70 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 19,969,881.95.km. However with the 2007 release of updated Hipparcos files, the radius is now calculated at being round 28.05. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures. The star's Iron Abundance is -0.21 with an error value of 9.99 Fe/H with the Sun has a value of 1 to put it into context.

Alterf Apparent and Absolute Magnitudes

Alterf has an apparent magnitude of 4.32 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 -0.75 If you used the 2007 Parallax value, you would get an absolute magnitude of -0.70. 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 Alterf

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 9.69 which gave the calculated distance to Alterf as 336.60 light years away from Earth or 103.20 parsecs. It would take a spaceship travelling at the speed of light, 336.60 years to get there. We don't have the technology or spaceship that can carry people over that distance yet.

In 2007, Hipparcos data was revised with a new parallax of 9.91 which put Alterf at a distance of 329.13 light years or 100.91 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.

The star's Galacto-Centric Distance is 7,464.00 Parsecs or 24,344.83 Light Years. The Galacto-Centric Distance is the distance from the star to the Centre of the Galaxy which is Sagittarius A*.

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.

Alterf Facts

Alternative Names

Traditional/Proper NameAlterf
Flamsteed Name4 Leonis
Flamsteed Short Name4 Leo
Arabic NameAt-tarf
English Meaning'The Glance' of the Lion
Bayer DesignationLambda Leonis
Hipparcos Library I.D.46750
Yale Bright Star Catalogue (HR) Id3773
Bonner DurchmusterungBD+23 2107
Henry Draper Designation82308

Visual Facts

Star Typegiant star
Absolute Magnitude-0.75 / -0.70
Visual / Apparent Magnitude4.32
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)09h 31m 43.24
Declination (Dec.)+22d 58` 05.0
Galactic Latitude44.86 degrees
Galactic Longitude206.69 degrees
1997 Distance from Earth9.69 Parallax (milliarcseconds)
 336.60 Light Years
 103.20 Parsecs
2007 Revised Distance from Earth9.91 Parallax (milliarcseconds)
 329.13 Light Years
 100.91 Parsecs
Galacto-Centric Distance24,344.83 Light Years / 7,464.00 Parsecs
Proper Motion Dec.-39.47 ± 0.10 milliarcseconds/year
Proper Motion RA.-20.17 ± 0.18 milliarcseconds/year
B-V Index1.54
Radial Velocity24.27 ± 0.19 km/s
Iron Abundance-0.21 ± 9.99 Fe/H
Spectral TypeK5IIIvar
Colour(K) Orange to Red

Estimated Facts

Calculated Effective Temperature3,913 Kelvin

Sources and Links

SIMBAD SourceLink

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