Melissa Waterman, age 12, of Clearwater, Florida, for her question:
What are some examples 'of the larger star groups?
If the skies are clear tonight, you can see a few real whoppers in the assortment of sparkling summer stars. The easiest to find is in the eye catching constellation Scorpius, the Scorpion that sprawling curve of sparklers near the Milky Way. Its superstar is ruby red Antares, placed cohere the celestial scorpion's heart should be. From a distance of 240 light years, you behold a red supergiant that is 330 times wider than our sun.
The multitudes of stars appear to come in different sizes with magnitudes ranging from brilliant to dim. A sharp eye can detect their delicate color variations. However, each is located at a distance ranging from a few light years to hundreds of lightyears. Distance diminishes their true sizes and dims the brilliance of their true magnitudes. These celestial tricks fool our eyes. But astronomers use skillful techniques to verify a star's real size and magnitude, regardless of distance.
Though probably no two stars are exactly alike, they can be sorted into classes of similar types. This was done by charting them according to their colors and their true magnitudes. Their colors range from dull reds through fiery oranges and yellows. vivid blues and blue whites. The chart revealed that most stars are merely somewhat brighter or dimmer, somewhat larger or smaller than our golden sun. These so called main sequence stars arrange themselves in classes A, F and G with 10 subclasses in each group.
The interesting midgets are outside the main sequence assembly and so are the giants and fabulous supergiants. Some of the Whoppers are white, or rather blue white hot. Others are red hot, which is quite cool for a star. Antares, at the heart of Scorpius, is a red supergiant of Class ii. Its diameter is about 300 million miles and its temperature about 5,500 degrees Fahrenheit, or about half as hot as the sun. Other red supergiants are 2,000 million miles wide and slightly cooler.
Class K includes the reddish orange giants. Their hotter temperatures range up to 7,500 degrees and their diameters up to 1,000 million miles. You can spot a red giant from the Big Dipper. Trace to the end of the handle and continue the arch to the bright star, Arcturus. It is 30 times wider and 30 times brighter than the sun, to see it from 33 light years.
The biggest, brightest and hottest supergiants are the vivid blues and blue whites in classes B and 0. Arch to Arcturus, then spin a straight line to sparkling Spica. This vivid blue white supergiant has a temperature around 36,000 degrees and is brilliant as 2,440 suns.
The biggest, brightest and hottest superstars are the very rare blue white, razzle dazzlers in Class 0. Some have temperatures up to 30 million degrees Fahrenheit and diameters as wide as 30 million miles. Some are more brilliant than a million suns. One of these blue white supergiants is in the winter constellation Orion. But sad to say, because of its enormous distance, it appears as a barely visible dim dot in Orion's sword.