Celestial fireworks are nature’s fingerprints
“Pyrotechnics” are “fire devices.” While the technology has expanded to include such mechanisms as the exploding bolts that release the space shuttle from its launch pad, the term has traditionally referred to fireworks.
Manufacturers of pyrotechnics paint their sky-pictures with glowing atoms.
An atom is composed of a dense nucleus surrounded by a thin cloud of electrons. Pumping heat into an atom “excites” its electrons: They jump outward, away from the nucleus. Later, when the electrons “relax,” they jump back down and release the energy that bumped them up. They release this energy as light.
Just what color of light is released depends on how large a jump the electron makes. A large, high-energy jump might release a bit of blue light; a smaller, lower-energy jump might release a bit of red. Because each jump releases a specific quantity of energy, it is known as a “quantum jump.”
The combination of colors released from each atom is unique; it’s a fingerprint for that atom.
Try this: Table salt is sodium chloride; half of its atoms are sodium. Sprinkled into the flame of the kitchen range, the sodium atoms in salt emit their unique combination of colors, dominated by two very close hues of yellow-orange.
Comets are the icy remains of the matter from which the sun and planets congealed some 41/2 billion years ago. Mixed with the ices are bits of rock dust.
As comets orbit the sun, their ices “sublimate” – they change from solid to gas, without melting. As the ice turns to gas, the rock dust is freed, and forms a torus of dust – a “dusty donut” – orbiting the sun.
Next Monday night, Earth will plow into the dusty torus left by comet Swift-Tuttle. Smashing into our atmosphere at tens of thousands of miles an hour, the dust will shake up atoms of air, exciting the electrons in those atoms. As the electrons relax, they’ll emit the energy it took to excite them. The resulting tube of de-exciting atoms paints the trail of a meteor in the sky. Swift-Tuttle is the parent body of the annual Perseid meteor shower.
Even as they relax and emit their light, the atoms in the meteor’s trail remain hot. Hot atoms of oxygen, especially, readily latch onto atoms in the incoming dust. The reaction pumps energy into the dust atoms, exciting their electrons. As those electrons relax, they emit their colorful fingerprints.
As a result of these upper-air reactions, Perseid meteors often leave “trains” – lingering trails that can be bright white or intensely colored.
Folks who were turned-on to meteor-watching by the Leonid meteor shower last November will find the Perseids a very different show, with fewer but brighter and, with luck, much more colorful meteors.
The peak of this year’s Perseid shower is predicted for early Tuesday morning, before dawn. For best viewing, lay a sleeping bag or blanket in a place that’s quiet and dark, with a good view of as much of the sky a possible.
We should be able to see some Perseids, those toward the outer and inner edges of the comet’s orbit, a few nights before and after the peak.
We’ll look for these outliers during the next Sky Watch, which takes place at Sierra Friends Center on Saturday evening at 8:30 p.m. For more information, call 273-3183.
Alan Stahler trained as a biologist and is an amateur astronomer.
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