Orion the Hunter Returns

(Plain Text Version)

A prominent group of stars is now moving into view for evening observers.

This constellation is Orion, the hunter.  Orion is easily recognized by its “belt” of three bright stars.  With a little bit of imagination, one finds stars for the head, a shoulder, a club, two feet, and a sword kept beneath the belt.

Some constellations are visible only from northern latitudes, others only from southern latitudes.  Orion is one can be seen from any place on Earth.  For northerners, Orion stands in the southern part of the sky.  For southerners, Orion is in the northern sky.  For those on the equator, the hunter passes directly overhead.  For the few people who visit the poles, half of Orion is just above the horizon, and the other half is just below the horizon.

In the north, the hunter figure will be “right side up”, with the head higher than the feet.  In the south, our hunter is “upside down”. 

Betelgeuse

Of Orion’s two brightest stars, Betelgeuse (pronounced “Beetle juice”) is the distinctly orange one. It is the “shoulder” of the hunter. Betelgeuse is classified as a “Red Supergiant” star.  Its diameter is about 650 times that of our Sun.  If it was at the center of our solar system, it would engulf Mercury, Venus, Earth, and Mars.

Because it is so huge and so close, images of Betelgeuse have been obtained, showing its outline and a glimpse of its surface features.

“Red supergiant” refers to a phase late in the life of many stars.  Early in life, Betelgeuse was much smaller.  When its supply of hydrogen fuel was used up, the star swelled to its current size. 

The next major event would be a supernova explosion.  This is expected “soon” in astronomical terms, meaning around a hundred thousand years for now.  Since Betelgeuse is only 500 light years from us, a supernova would be quite dramatic.  It would rival the Moon for brightness.  Unfortunately, it’s remnant would be very dim, and the Hunter may no longer look like a hunter.

A year ago, Betelgeuse had an obvious decrease in brightness.  There was speculation that the explosion was imminent.  Later, it returned to its normal brightness.  The current thinking is that an enormous cloud of dust was expelled, blocking part of our view of the star. 

The Orion Nebula

So much for the end of a star’s life cycle.  On the other side of the Hunter’s belt, we find the Orion Nebula, which is full of stars at their beginning stages.  The Orion Nebula is very close to the Hunter’s belt of three stars.  In Northern latitudes, look below the star at the left of the belt.  In Southern latitudes, look above the star on the right.  The Orion nebula appears as a fuzzy mass.  In the city, it may not be visible to the naked eye.

The term nebula means “a cloud of gas or dust in interstellar space”.  Virtually all of the gas in a nebula is hydrogen.  The hydrogen in a nebula pulls together into a compact mass, through gravity.  This process takes millions of years.  If enough  hydrogen is available, the molecules will be forced together tightly enough to start a nuclear fusion reaction.  This is the birth of a star.

The Trapezium is a group of stars in the brightest area of the Orion Nebula.  With a small telescope, four of its stars are visible.  The stars of the Trapezium are the main sources of the intense visible and ultraviolet energy which lights up the entire nebula.

Explore Orion

Orion has many more nebulae and double stars to enjoy.  Orion is a favorite of amateur astronomers, and an important study area for researchers.  It is a constellation which “has something for everyone”.