| | Betelgeuse | |
Looking at the sky, stars look like a lot of bright dots, different for intensity, colour and dimensions, that are printed on one area to draw the most varied forms. Since the old times, we could always group the nearest and the brightest ones to form some figures, called Constellations. In the reality they occupy these different parts of the sky because there is a perspective effect; in fact they are thousand of light years far...
Classification of the stars for bright and colour.
A typical view of the distance from the space.
...I think that after this introduction you're ready to learn more about one of the most beautiful stars in the Universe : Betelgeuse.
Betelgeuse
Other Names
Betelguex, Betelgeuze, Beteiguex, Al Mankib.
Alpha Orionis , HR 2061 , HD 39801
Data
Ra 05 55 10.3
Dec +07 24 25
V 0.50
B-V +1.85
Spectral Type M1-2Ia-Iab
Betelgeuse is the 7th brightest star in the northern hemisphere. It's also called Alpha Orionis and it is a variable star.
" Alpha Orionis "
Betelgeuse is one of the names of Alpha Orionis; it's situated in the constellation of Orion and it's the brightest star in the northern hemisphere...This name maybe comes from an Arabic expression: "vad al-giawza" that means "the shoulder of the giant". The “original” meaning of this word designates a black sheep with a white spot in the center of its body; it could also have the same meaning of the Arabic word, "jauz", which means “the center of anything” or “the central one”. A lot of changes in Arabic languages and the change of a d to a t evolved the current name, "Betelgeuse". It's a red supergiant, 520 light years far from the Earth; it has a diameter 400 times more than the Sun's and its diameter can vary by about 60% during the whole cycle, very different from the radius of the Earth's orbit...! It has also a brilliance 10.000 times higher! Its own annual cycle is of 0'',32, whereas its radial component of the actual speed is of 21Km/s on removal. It's so bright that it sometimes could became a competitor of Rigel...
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| Atmosphere of Betelgeuse |
Betelgeuse at its first "scene"...
In the end of the last century the American physical Albert A. Michelson devised a system that, exploited the interference of the light. This new type of instrument, extremely sensitive, from him planned and built is known like interferometer .The idea that interferometer might be applied to measure the size of stars was first proposed by a French astronomer, Armand Fizeau, in 1868. But the first real achievement of interferometer theory was made by Dr. Albert A. Michelson that began in April 1887. Michelson devised a system using mirrors and semitransparent mirrors for merging separated beams of light coming from the same object. The optical elements in the system were arranged in such a way that the beams "interfered" with each other; that is, the directions and distances of their light paths were so closely meshed that the beams could interact. Using this instrument, Albert A. Michelson was the first man to try to measure the diameter of Betelgeuse. In 1920, using a 6-metre interferometer attached to a 254-centimetre telescope, he succeeded in measuring the diameter of the star Betelgeuse as 386,160,000 km (300 times the diameter of the Sun!!!). This was the first substantially accurate determination of the size of a star. Betelgeuse was selected as the first test object since theoretical calculations had suggested that the star was unusually great in size. The experiment was a great success.
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| Albert A. Michel | Interferometer theory | Interferometer |
Using this theory there were some other news thanks to the interferometer. In fact in 1975 it reveled that there were some brightness variations on the surface of the star. They could discover it, using another new invention : the speckle interferometer.
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| The "twinkle" |
I'd like to end this page, writing a phrase, so you can think about the importance of the Universe:..." Man is a god who remembers the sky"...
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