Universe Guide


Y Lacertae, HD235739, HIP109340

Y Lacertae is a blue to white pulsating star that can be located in the constellation of Lacerta. Y Lacertae is the brightest star in Lacerta based on the Hipparcos 2007 apparent magnitude. The star can not be seen by the naked eye, you need a telescope to see it.

HIP109340 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD235739.

Y Lacertae has alternative name(s), Y Lac.

Location of Y Lacertae

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 Y Lacertae, the location is 22h 09m 02.90 and +51 d 02`45.1 .

Physical Properties (Colour, Temperature, Radius) of Y Lacertae

Y Lacertae has a spectral type of F7. This means the star is a blue to white star. The star has a B-V Colour Index of 0.71 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 5,626 Kelvin. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

Y Lacertae Apparent and Absolute Magnitudes

Y Lacertae has an apparent magnitude of 9.12 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 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 Y Lacertae

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as -2.00 which gave the calculated distance to Y Lacertae as -1630.82 light years away from Earth or -500 parsecs. It would take a spaceship travelling at the speed of light, -1630.82 years to get there. We don't have the technology or spaceship that can carry people over that distance yet.

Variable Type of Y Lacertae

The star is a pulsating Delta Cepheid 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. Y Lacertae brightness ranges from a magnitude of 9.613 to a magnitude of 8.883 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 4.3 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.

Y Lacertae Facts

Alternative Names

Traditional/Proper NameY Lacertae
Short NameY Lac
Hipparcos Library I.D.109340
Bonner DurchmusterungBD+50 3581
Henry Draper Designation235739

Visual Facts

Star Type star
Visual / Apparent Magnitude9.12
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)22h 09m 02.90
Declination (Dec.)+51 d 02`45.1
Galactic Latitude-4.03 degrees
Galactic Longitude98.72 degrees
1997 Distance from Earth-2.00 Parallax (milliarcseconds)
 -1630.82 Light Years
 -500 Parsecs
B-V Index0.71
Radial Velocity-22.90 ± 0.30 km/s
Spectral TypeF7
Colour (F) blue to white

Variable Star Details

Variable Star ClassPulsating
Variable Star TypeDelta Cepheid
Mean Variability Period in Days4.324
Variable Magnitude Range (Brighter - Dimmer)8.883 - 9.613

Estimated Facts

Calculated Effective Temperature5,626 Kelvin

Sources and Links

SIMBAD SourceLink

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