Saturday, April 28, 2012
Lauds -- a Saturday reprise
This is one of the two times each year when my morning walk along the Path takes me straight into the sunrise. That big yellow star seems to be lurking just behind the trees. (Click to enlarge.)
Within 20 light-years of Earth there are about 100 known stars. Of these, nearly 70 are tiny red dwarf stars, much less bright than the Sun, barely hot enough to ignite the fires of nuclear fusion that blaze at a star's core. These stars are so faint that they are not visible to the naked eye, even though they are among our closest neighbors.
The 20-light-year neighborhood includes about 15 orange stars, hotter and bigger than the red dwarfs but not as hot or bright as the Sun.
There are six yellow stars, including the Sun, with surface temperatures of about 6,000 degrees Celsius.
Only three stars in the solar neighborhood are brighter than the Sun: Procyon in Canis Minor, Altair in Aquila the Eagle, and Sirius in Canis Major. Sirius, a white-hot star, is the big boy on the block.
The star population is a pyramid: A few hot giants at the top, a crowd of cool dwarfs at the bottom.
The capstone stars burn fast and furiously and die violently, forging heavy elements like carbon and oxygen and spewing them into space to become part of new generations of stars and planets. The red dwarfs burn their hydrogen fuel so slowly they live for hundreds of billions of years. Because the universe is only about 14 billion years old, every red dwarf star that was ever born is still with us.
The Sun is less than 5 billion years old -- young enough to have heavy-element planets, but old enough for conscious life to have evolved on one of those planets.
I think of all of this as I walk each morning into that doorway of radiance, that nuclear furnace in the trees beyond the pool of mist. Like the eye of a jungle cat shining in darkness. The world's animal soul.
(This post originally appeared in November 2006.)