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Why Look at Just One Star?

This may seem like an odd idea that we spend very little time looking at individual stars at FDO. Some clubs and groups spend a great deal of time looking at individual stars - particularly members of AAVSO [The American Association of Variable Star Observers]. For the general public however, individual stars have very little interest unless something is happening to them, like a nova or an occultation.

While individual stars simply look like bright points of light, collections of stars can be very beautiful. Anything from a pair of stars to collections in the trillions are among the best the sky has to offer. A bright star next to a dim star that circle each other can be quite a test of the ability to see clearly. In addition the two stars may be noticeably different in color. For example Sirius A (the brightest star in the sky) has an almost invisible companion Sirius B (often called the Pup because Sirius A is the Dog Star). Sirius is interesting to look at simply because it is a pair. Albireo's two components are distinctly colored - turquoise and topaz, truly lovely.

Telescopes cannot resolve stars into disks as we can with the planets. A few huge stars have photographs of a few huge red giants as smudges showing much less detail than a three telescope show of Jupiter. What we see in a big telescope is exactly what we see by eye - a point of light. All the telescope does is make the star image brighter, so we see dim stars well and bright stars as dazzling points of light. Almost nothing of interest can be told by the apparent brightness of a star. Distant bright stars may appear dimmer the close dim stars simply because of the distance factor. Double the distance and you quarter the brightness.

Galaxies are huge collections of stars from hundreds of millions of stars in small galaxies to incredible trillion star collection like M87. Weirdly enough, occasionally a star in one of these galaxies suddenly outshines it millions to trillions of neighbors. For a star to become a trillion times brighter than normal it must burn all its nuclear fuel in a sudden explosive burst called a supernova. Within days this brilliant star fades to invisibility, a dead remnant of a once huge beacon. When such a "new" star shines in a galaxy close to use, many many telescopes turn to view it while its still is bright. No such star has exploded in our galaxy since Kepler's Star almost four centuries ago.

Besides stars and galaxies, other objects shine or seem to shine with their own light. Nebulae, clouds of hydrogen and helium gas with sprinklings of just about every other atom, can be bright enough to see easily with your eye. If you look into Orion's sword, the middle "star" is not another star at all but a wonderful swirl of gas. You'll need a big telescope to see it well although some detail shows up in binoculars and small scopes. Nebulae can be emission ,reflective, absorptive or a combination. Emission nebulae radiate light by converting ultraviolet light from embedded stars into regular light (just as happens in a fluorescent lamp). Reflective nebula acts as brightly lit walls or mirrors for starlight in front of them. Absorbing nebula block light from stars behind them and look like areas where no stars exist. Sometimes absorbing nebulae act like filters changing the colors of stars that just peep though. Orion is an example where all three major type of nebulae combine in a single cloud we call M42.

Clusters are clumps of star groups like the Pleiades or M15. These clumps can be spherical balls like M15 or loosely bound groups like the Pleiades. They are usually some of the prettiest groups available.

Star remnants (old supernovae, planetary nebula and gassy shells) are certainly worth a trip to a big telescope to view. And anyone with a pair of eyes can view the grandest "collection" of stars in the sky the constellations. Come to FDO the next nice Friday night when the Moon is not too close to full and we'll show you a selection of these.

Leslie Coleman
Author:
Leslie Coleman
Entry Date:
Feb 1, 2004
Published Under:
Leslie Coleman's Columns
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