Star date: 02:08:99

Orion, the Mighty Hunter

There is a beauty to the night sky which attracts nearly everyone, sometime in their lives, to gaze to the stars and wonder. But what is it which fascinates the human mind to such a degree?

I believe it is a sense of order which seems to envelop the entire sky. Many of our ancestors believed that they saw pictures in the sky, and many of those imaginary pictures in the sky, passed down through time, became the basis for what we today call the constellations. Legends soon developed about these characters, and some of these stories became todays mythic legends.

One of the easiest constellations to recognize in the winter sky is Orion the Hunter. The three stars which comprise his belt are the only three bright stars which are so close to each other, in so straight a line. If you go outside at about 8 p.m. this week, Orion will be found due south and 45 degrees above the horizon. Look for these three bright stars to guide your way.

Orion holds some special astronomical treats. One of these is the star Betelgeuse (pronounced "Beetle-juice", like the Michael Keaton character). This star is a red giant. This means that this star has already burnt its hydrogen fuel, has collapsed, and started burning helium. This causes the star to swell, destroying any nearby planets. This situation cannot last nearly as long as the hydrogen burning phase, and the star once again collapses. It is at this helium burning phase that Betelgeuse is currently at in its life.

Now we have shown that this star will be a swollen giant, yet we called it a red giant. Why is it red? This is because of a law of physics known as Weins Law. This, simply stated, says that any object (including stars) will have a dominant wavelength of electromagnetic radiation which depends on it's temperature. This is why stars are different colors.

Now, most objects around us do not seem to have a color which depends on their temperature; why? The answer to this is that most objects in everyday life are cool, at least as far as astronomical objects are concerned. For an object at room teperature, Weins Law can determine that the dominant wavelength of radiation received off that object will be somewhere in the infrared range. The human eye cannot see this, and the wavelengths which we perceive as color are determined by the sizes and shapes of the individual molecules. Thus, the star is red. It is also roughly the same temperature as a piece of "red hot" iron.

Another type of giant are the blue giants. These are not just swollen parodies of star going through their death throes, these are actual massive stars, some of them 25 to 50 times as massive as our own Sun. These stars also live for very short periods of time, with an average life expectancy of around a few million years.

One of these blue giants is the star Rigel. Rigel is also in the constellation of Orion, and can be seen as the westernmost foot of the great hunter. It is these blue giants which produce two of the most exotic objects in the universe, neutron stars and black holes. Neutron stars are stars whose interiors consist of nothing but neutrons. These objects are so dense that a single thumbleful of a neutron star would weigh the same as mount Everest.

Black holes are also collapsed dead stars, yet they are so dense that even light cannot escape from their gravitational pull. Rigel, being a blue giant will likely, one day, collapse into one of these types of objects.

Another treat in Orion is M42, the Great Nebula in Orion. This can be seen as the middle "star" in the belt of Orion. It is an easy and beautiful object to view with binoculars or a telescope, and you can, in fact, make out some degree of nebulosity (cloudlike structure) with the naked eye.

Clear skies and good viewing.

"Understanding is joyous" - Carl Sagan

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