Page 50 - 2009 DT 7 issues

Just an Ordinary Star Although there are “red giants” in planet. Their light is faint and a result
M class as well, these are the cool of convective heat (2,500 °K) rather
stronomers describe our Sun remnants of other stellar types reaching than nuclear fusion. These failed stars
as a modest yellow dwarf star the end of their normal lives. live quiet lives, and because they
Aabout half way through its Most M type stars were born cannot fuse their hydrogen into helium
10-billion-year life cycle. In science- small and dim and are often referred they, too, will live for a very long
speak, it is referred to as an ordinary G to as either red or brown dwarfs. time—they are at least as old as the
type whose surface glows at 5800 °K, Until recently, star surveys paid universe. This neglected class of objects
hardly even noticeable by an observer little attention to them. They start was unknown until 1995 when infrared
in our galactic neighborhood. out on the main sequence (normal detectors revealed their presence.
The stars in our Milky Way sequence of the average star’s life), Spectral scale rankings will never
galaxy are classified on a spectral their interior processes hot enough to place our little G2 star in the celebrity
scale that ranks them by temperature burn hydrogen in their cores (like our section of a Who’s Who in astronomical
and luminosity, with the hottest at the sun), slowly converting it through circles. G stars are also considered
top and coolest at the bottom. These nuclear fusion into helium as they dwarfs because, next to the behemoth
classifications are O, B, A, F, G, K, and age. Because their mass is only 7% to blues and whites, they are quite small
M. (Oh, Be A Fine Girl. Kiss Me!). The 60% of that of our sun, they can live and ordinary, indeed. Even so, our
distribution of a star’s energy radiation (theoretically) for perhaps 20 billion sun is in the top 10% of all the stars
depends upon the mix of elements in our galaxy by mass. For various
within the star. Both the reasons, however, we can
classification and ranking argue that our star is rather
process involve a complex extraordinary, after all.
analysis of emission and The gaseous nebula that
absorption signatures of gave birth to the Sun was
specific atomic elements strewn with debris from
within the star (hydrogen, innumerable collisions
helium, calcium, etc.) in a chaotic free-for-all,
For blue stars (O and B), eventually coalescing into
surface temperatures range planets and numerous other
between approximately bodies that populate space
50,000 °K and 12,000, or at the edges of what would
so. They are short-lived become our solar system.
giants, burning through The eventual result was a
their massive stores of tidy little group of planets
hydrogen gas relatively (nine before poor Pluto
quickly on an astronomical was demoted), some with
scale, perhaps in a few attendant moons, arranged
hundred million years. in a gravitationally stable
White stars (the A’s and F’s) rank just years, longer than the expected carousel around this benevolent and
below the big blues, but they are also life of the universe. Under certain rather quiescent star. Luckily, our solar
very large and very hot. conditions, there is speculation that neighborhood has no lethal real estate
At the opposite end of the scale, even some red dwarfs could meet nearby. Until very recently, ours was
the coolest “red” stars are described the conditions necessary to harbor the only solar system we could point
as having a surface temperature of living planets. to with certainty.
less than 3,500 °K. They represent Brown dwarfs reside in no-man’s Besides the planets, moons and
three-quarters of all stars in our galaxy. land, somewhere between a star and a captured asteroids in our system,

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