Orion shines in night sky

The majestic constellation Orion the Hunter is now well above the eastern horizon after evening twilight.

After the Big Dipper, it’s the most recognizable stellar picture in the sky. Without too much imagination you can see how the ancients saw it as a giant hunter.

At a glance it reminds me of a bow tie or an hourglass in the eastern heavens. That hourglass, according to Greek and Roman mythology, outlines the torso of the mighty nocturnal hermit hunter Orion.

The constellation is best noted by the three bright stars in a row that make up his belt; Alnitak, Alnilam and Mintaka.

Below and to the right of the belt is the famous Great Orion Nebula, visible even to the naked eye. It’s a colossal cloud of hydrogen gas more than 1,500 light years away, where hundreds and hundreds of young stars have and will be born.

With even a small telescope you can easily see four stars in the middle of the nebula, arranged in a trapezoid, that were born from what astronomers call M-42.

In the coming weeks I want to feature the Orion Nebula in more detail in Starwatch.

This week I want to tell you about Orion the Hunters brightest stars, Rigel and Betelgeuse, that are anchored at opposite corners of Orion.

They are the fourth and fifth brightest stars in our Butler skies. Nowhere else in our night sky will you see two stars this bright so close to each other.

Physically, they’re nowhere near each other, but they seem that way because both of these bright shiners are located in nearly the same direction from Earth. That’s why they can both be in the same constellation, Orion.

Rigel is a super blue giant star and Betelgeuse is a super-duper red giant star, and even with the naked eye you can see their color tinges, especially with Betelgeuse.

Rigel is the brightest star in Orion, slightly outshining Betelgeuse even though according to classic star charts Betelgeuse is considered the alpha or brightest star in the great constellation.

Truthfully, there isn’t much difference in their brightness and it’s easy to understand how that mistake could have been made.

Rigel is somewhere between 700 and 800 light years away from Earth. The sun, our closest star, is less than a hundred million miles away by comparison.

Despite being trillions and trillions of miles away, Rigel is so bright in our winter sky because it’s 60 million miles in diameter, making it one hundred times the diameter of our sun and seventeen times the mass of our comparatively diminutive home star.

Most astron-omers believe Rigel kicks out more than 80,000 times more light than our sun, making it the most luminous star in our part of the Milky Way galaxy. Its outer layer has an estimated temperature just under 20,000 degrees Fahrenheit that makes it almost twice as hot as our sun.

Without a doubt, Rigel is one big shiner, but there’s a price to be paid for all that stellar prowess.

Heavier stars like Rigel don’t live nearly as long as smaller stars like our sun. They’re gas guzzlers, going through the hydrogen fuel in their cores at highly prodigious rates.

It’s hard for the best of astronomers to estimate the exact age of a particular star since there are so many factors to consider.

The mass of the star is the main contributor to a stars life span, and the best indications are that Rigel’s total light time is less than one billion years. By comparison, our own sun sips its nuclear fuel and is expected to have a total life expectancy of around 12 billion years.

That being the case, Rigel hasn’t even been around for all that long. When dinosaurs roamed around our world Rigel was not yet in our starry sky, and it will be out of the heavens as we know them before our sun calls it a lifetime.

At the other corner of Orion is without a doubt the biggest single thing you’ve ever seen, Betelgeuse. It’s more than 20 times the mass and more than 1,100 times the diameter or our sun, giving Betelgeuse an estimated girth of about one billion miles across.

It’s so large that if you put it in the place of our sun in our solar system, the planets Mercury, Venus, Earth, Mars and even Jupiter would be living inside Betelgeuse.

Betelgeuse’s diameter and reddish hue are due to the fact that it’s already near the end of its very short life.

Most astronomers estimate that Betelgeuse isn’t much more than a few million years old and it’s already expended its hydrogen and helium fuel to the point where it’s puffed out into the red giant phase of its brief life.

No one really knows for sure but in maybe less than 10,000 years, a thousand years or even next year it could blow itself up in a tremendous supernova explosion, making it brighter than the full moon in our night skies for several weeks.

It’s a good thing that Betelgeuse is more than 400 light years away from Earth, because if it was much closer it could make for a really bad day here on Earth.

In fact, it’s believed by many astronomers that if Betelgeuse exploded within a hundred light years of Earth, the radiation from the blast could change or eliminate life as we know it on our planet.

Keep your distance Betelgeuse!

Mike Lynch is an amateur astronomer and professional broadcast meteorologist and is author of “Pennsylvania Starwatch,” available at bookstores and at his website www.lynchandthestars.com