Halley’s Continuing Legacy
Who hasn’t heard of Halley’s Comet, that most famous celestial interloper that passes earth every 76 years? While we’re not due for another visit from the comet until 2062, we’re reminded of it each year around this time.
Week’s end marks the return of the annual Orionid meteor shower, the offspring of Halley’s Comet. Competing light from the waning crescent moon will dampen the shower’s pre-dawn peak Friday and Saturday. Even so, with clear skies you might see six to 10 of these meteors streaking through the sky in a given hour. And keep an eye out for errant meteors over the next several days.
Dubbed shooting stars, meteors aren’t stars at all, but they are made from the same cosmic brew as the sun — and everything else in our solar system. Like the sun and planets, comets were born in the solar system’s infancy from a massive spinning cloud of gas and dust. And like planets, comets continue that spinning in their orbit around the sun.
Unlike the planets, which have enough mass to maintain near-circular orbits around the sun, comets orbit the sun in a sharp elliptic, pulled toward the sun only to be hurled off into the far reaches of the solar system each time they draw too near. Right now, Halley is on it’s way out and doesn’t reach the apex of its orbit until 2024, when it will be farther from the sun than Pluto.
But at the opposite extreme, Halley comes closer to the sun than Venus. The comet itself is no larger than Annapolis, but close to the sun Halley spews so much dust, ice and gas that the head — or coma — is larger than earth. Retreating from the sun, the comet’s tail stretches millions of miles in its wake.
Each year earth crosses through that wake of dust and ice, and as the bits collide against our atmosphere, they burst aflame, with the larger pieces blazing through our skies as meteors.