Universe Guide


BL Telescopii, HD177300, HIP93844

BL Telescopii is a blue to white eclipsing very luminous supergiant star that can be located in the constellation of Telescopium. BL Telescopii is the brightest star in Telescopium based on the Hipparcos 2007 apparent magnitude. The star can not be seen by the naked eye, you need a telescope to see it.

HIP93844 is the reference name for the star in the Hipparcos Star Catalogue. The Id of the star in the Henry Draper catalogue is HD177300.

BL Telescopii has alternative name(s), BL Tel.

Location of BL Telescopii

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 BL Telescopii, the location is 19h 06m 38.11 and -51d25`03.2 .

Physical Properties (Colour, Temperature, Radius) of BL Telescopii

BL Telescopii has a spectral type of F4Ib. This means the star is a blue to white supergiant star. The star has a B-V Colour Index of 0.52 which means the star's temperature has been calculated using information from Morgans @ Uni.edu at being 6,064 Kelvin.

BL Telescopii Radius has been calculated as being 19.20 times bigger than the Sun.The Sun's radius is 695,800km, therefore the star's radius is an estimated 13,362,475.45.km. The figure is derived at by using the formula from SDSS and has been known to produce widely incorrect figures.

BL Telescopii Apparent and Absolute Magnitudes

BL Telescopii has an apparent magnitude of 7.19 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 -1.78 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 BL Telescopii

Using the original Hipparcos data that was released in 1997, the parallax to the star was given as 1.61 which gave the calculated distance to BL Telescopii as 2025.86 light years away from Earth or 621.12 parsecs. It would take a spaceship travelling at the speed of light, 2025.86 years to get there. We don't have the technology or spaceship that can carry people over that distance yet.

Variable Type of BL Telescopii

The star is a eclipsing Beta Persei (Algol)/System with one or both giant or supergiant components 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. BL Telescopii brightness ranges from a magnitude of 8.900 to a magnitude of 7.216 over its variable period. The smaller the magnitude, the brighter the star. Its variable/pulsating period lasts for 779.0 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.

BL Telescopii Facts

Alternative Names

Traditional/Proper NameBL Telescopii
Short NameBL Tel
Hipparcos Library I.D.93844
Henry Draper Designation177300

Visual Facts

Star Typesupergiant star
Visual / Apparent Magnitude7.19
Naked Eye VisibleRequires a 7x50 Binoculars - Magnitudes
Right Ascension (R.A.)19h 06m 38.11
Declination (Dec.)-51d25`03.2
Galactic Latitude-23.16 degrees
Galactic Longitude345.53 degrees
1997 Distance from Earth1.61 Parallax (milliarcseconds)
 2025.86 Light Years
 621.12 Parsecs
B-V Index0.52
Radial Velocity92.30 ± 2.90 km/s
Spectral TypeF4Ib
Colour(F) blue to white

Variable Star Details

Variable Star ClassEclipsing
Variable Star TypeBeta Persei (Algol)/System with one or both giant or supergiant components
Mean Variability Period in Days779.000
Variable Magnitude Range (Brighter - Dimmer)7.216 - 8.900

Estimated Facts

Calculated Effective Temperature6,064 Kelvin

Sources and Links

SIMBAD SourceLink

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