Steele Planetarium

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We are located at:
STEELE SCHOOL
320 So. Marion Parkway
Denver, CO 80209

Ralph Sodano
Director
303.744.1717

WELCOME TO THE PLANETARIUM!

Greetings!

We are now in the midst of fall. Yet when the sun goes down our attention is brought to three bright stars shining above and slightly to the west called the Summer Triangle. Unlike many titles given to stellar patterns, the "Summer Triangle" is fairly modern in origin. Also, the title does not describe the stars' present position but where they were making their first appearance in June on the eastern horizon at sunset, announcing the coming of summer.

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I know for a fact there are more than a few teachers and students ready for the Summer Triangle to disappear in the west and retake its June position in the sky once again, but you may still want to pause to appreciate these stars where they currently reside.

The dimmest of the three stars is Deneb which means "tail" and occupies that very position in the figure of the constellation Cygnus the Swan. It is also the brightest of five stars in Cygnus which together make an asterism called the "Northern Cross." Although Deneb is the dimmest appearing star of the Summer Triangle, it is actually the brightest of the three. But at a distance of 1,800 light years from Earth, (one light year being roughly six trillion miles) this brilliant blue-white giant star does not get to show off all its stuff to us.

The second brightest star in the Summer Triangle is Altair in the constellation Aquila the Eagle. Altair is a white star and at only 16 light years away, it's one of our sun's closest neighbors. If we could switch Deneb and Altair's positions in space, Altair would be barely visible on the clearest of nights and Deneb would bedazzle us as the brightest appearing star in the sky after the sun. Altair also has a speeding problem. Our sun rotates about once every 25 days at its equator. Altair spins at a dizzying speed of one rotation every 6.5 hours! Because of its rotational speed, Altair bulges prominently at its equator and is flattened at its poles.

The third and brightest star of the trio is Vega in the constellation Lyra the Harp. Vega is about 26.1 light years from our Earth and is the fifth brightest star in the entire night sky. Vega is notable as it is among the few stars that has a telescopically discernible ring of debris left over from its formation. Our own sun once has such a disc of dust, gas and debris about it. What happened to it? It became Pluto, Neptune, Uranus Saturn, Jupiter, Mars, Mercury, Venus the Earth and the moon plus you and me! Will the disc around Vega ever become a system of planets? Will there be a future species of beings on a planet orbiting Vega looking to their skies and upon seeing a dwarf yellow star we call our sun wonder if there's life down here? We just don't know, but we can imagine.

Vega has an important future date with our Earth. Right now our north pole points to the star called Polaris. But Polaris has not always been our "North Star" nor will it remain as such. Our Earth's poles have a slow circular "wobble" called, "precession." How slow? Very slow. It takes 26 thousand years for our Earth to complete a single wobble! Back almost 3,000 years ago during the time of the ancient Egyptian pharaohs, our north pole was pointing toward a star called Thuban in the constellation Draco the Dragon. However, after 2,800 years of precession not only has the north star job been taken away from Thuban by Polaris, but modern light pollution has made Thuban and Draco almost invisible in most urban skies.

Now fast forward some 12,000 years into the future and precession (our wobble) will make Vega the new north star. If you miss having Polaris as the north star, just wait around for another 14,000 years while the north pole completes its 26,000 year precession cycle and we find ourselves once again in our present position.

So wait for a clear night and brave the cold to observe the three stars of the Summer Triangle. Find Deneb and see if you can locate the Northern Cross or trace from its tail feather position all the stars that gracefully outline a swan in flight. Locate Altair and imagine its huge flaming mass spinning at such an outrageous rate. Finally, look to bright Vega, our future north star. After several hours it will disappear below the western horizon, but 12,000 years in the future our descendants will observe it unmoving in the northern sky from sundown to sun up.

Then like myself, you can look forward to the evening when the Summer Triangle once again makes its appearance on the eastern horizon, announcing the coming of the warmer days (and nights) of summer.