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Betelgeuse - A neighbor star near its explosive death [Astronomy]
posted October 21 2012 12:50.40 by Giorgos Lazaridis

It is not long since i've learned about this star, and since then i was fascinated from its size and its position in the night sky. Betelgeuse (AKA Alpha Orionis, Orionis, Ori) is a red supergiant located in the constellation of Orion, one of the most well-known constellations (probably the most known one). During the winter time, the Orion constellation is visible from the Northern hemisphere. These days, is is visible in the eastern night sky from my house (i live in Greece - Athens). Here is how the constellations looks like:

Photo: Wikipedia

The most visible stars are the 4 stars on the 4 corners and the three stars in the middle. These stars are called "the Orion's belt". When the ancients looked up to the sky, they saw drawings, symbols, animals and human forms. When they saw this constellation, they saw a Hunter, holding a club on one hand. The three stars in the middle belong to the hunter's belt:

I tried to get a photo from the constellation but my old Canon is... just an old Canon. Nevertheless, after heavy retouch, the basic stars are visible, among them Sirius, the brightest star in the night sky:

As a side-note, during this month, another spectacular celestial object is close to Orion, one of the gas giants, the biggest planet in our solar system, Jupiter. You just can't miss Jupiter! Take a look in the night sky, and you will see a glazing star, brighter and bigger than anything else! You've just found Jupiter!

Betelgeuse - The Red Titan
Titan is a humble adjective to describe the size of Betelgeuse. In astronomical terms, its size is 950-1200 R.. This means that it has 950 to 1200 times bigger diameter of our sun, or 11.7 Astronomical Units! If we place Betelgeuse in the place of our sun, it would completely swallow anything up to Jupiter, and maybe even further. If Betelgeuse had the size of a football stadium (120 meters), then our Sun would have the diameter of a CD (110mm). In that case, our Earth would have a diameter of 1mm!

This super giant is 640 light-years away from Earth. In terms of kilometer, it is 6.054x1015 kilometers, which may sound extremely far, but in astronomical terms we are somewhat neighbors.

In the final countdown
It is known that bigger start have shorter life expectancy than bigger stars. Our sun for example is expected to live some 10 billion years, currently being a middle-aged star around 4.7 billion years old.

Photo: Space Fellowship

Super giants like Betelgeuse have much sorter life expectancy, at around 10 million years. One might think that, being a star bigger should live longer due to its bigger mass - but a big star burns its fuel (primarily hydrogen) much faster than a smaller star (like our sun). Therefore, a big star runs out of fuel much faster.

Betelgeuse is already old, about 10 million years old. So it is reaching the end of it's life. Due to its massive size, it will die in a spectacular way - a Type II Supernova! When all of its fuel has been fused to heavier elements, the star will explode in a colossal explosion. This is how Professor J. Craig Wheeler of The University of Texas at Austin predicts Betelgeuse's end:

Betelgeuse's demise will emit 1046 joules of neutrinos, which will pass through the star's hydrogen envelope in around an hour, then travel at light speed to reach the Solar System centuries later 14providing the first evidence of the cataclysm. The supernova could brighten over a two-week period to an apparent magnitude of "1212, outshining the Moon in the night sky and becoming easily visible in broad daylight. It would remain at that intensity for two to three months before rapidly dimming. Since its rotational axis is not pointed toward the Earth, Betelgeuse's supernova is unlikely to send a gamma ray burst in the direction of Earth large enough to damage ecosystems. The flash of ultraviolet radiation from the explosion will likely be weaker than the ultraviolet output of the Sun. The year following the explosion, radioactive decay of cobalt to iron will dominate emission from the supernova remnant, and the resulting gamma rays will be blocked by the expanding envelope of hydrogen. If the neutron star remnant becomes a pulsar, it could produce gamma rays for thousands of years

Let me share some links that i've found on the net. First of all, the excellent sky-map org. It is one of the best on-line interactive sky-maps I've managed to find, with a huge database of photographs and other documents:


And then, it is the AstroViewer. If you wanna find something in your night-sky, AstroViewer is what you need. Choose your location and date/time and start exploring your sky:


I used AstroViewer to identify this brilliant object near by Aldebaran, which eventually turned to be Jupiter...

Looking at the night sky is nice, but knowing what you're looking at is awesome!


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