Scheduled air date: 2003 Jul 21-27
The Summer Triangle—comprised of the bright stars Vega, Altair and Deneb—is prominent in the night sky throughout the Summer. For the next couple of weeks, it appears high in the eastern sky at dusk, reaches the meridian at about 1:00 AM, and then is high in the western sky at dawn.
The three stars which make up the Summer Triangle are dramatically different in size and brightness, as well as distance from us. This shows a comparison of the sizes of these stars with our own Sun. Note the flattened shape of Altair (due to rapid rotation) and the giant size of Deneb!
Vega—the brightest star in the Summer Triangle—will be the "North Star" in about 12,000 years, instead of present-day Polaris.
This change in pole stars is caused by precession, the very slow (26,000-year cycle) wobble of the Earth's rotational axis. The illustration above shows the apparent path of the pole with corresponding years labeled for the present cycle.
If you wish to view illustrations for other episodes, please see our Star Gazer Illustrated directory.
|Illustrations on this page were created using
Software, an advanced desktop planetarium program designed for Windows.|
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