![]() Now it's believed that there's a true lack of material north and south of the ecliptic plane (Earth's orbital plane) headed toward our planet at those times of year.įor something as seemingly random as sporadic meteors, you might be surprised to learn that they arise from a variety of radiants, many based upon Earth's motion around the Sun. It used to be thought that the angle of the ecliptic to the horizon played a role in this cyclic variation. In the southern hemisphere, rates peak in late spring and bottom out in September and October. If you live in the northern hemisphere, sporadic rates drop to their lowest in spring and peak in November. Superimposed on the daily rise and fall in the number of random meteors are additional dips and enhancements. Numbers vary from a low of 6 per hour in the spring to 16 per hour in the fall. Mean annual sporadic rates as seen from latitude 45° north under dark skies. Around dawn, the planet plows straight into whatever dribs and drabs of comet lie ahead of us, so meteor rates increase. At dusk, the direction of our orbital motion is opposite that at sunset, forcing meteoroids to catch up to Earth from behind. The number of sporadic meteors visible varies over the course of the night, rising from a minimum of 4–6 per hour around 6 p.m. Red arrow shows the direction of rotation. ![]() Earth scoops up meteoroids on the dawn side of the planet and outruns them on the dusk side. The rate of meteor activity is usually greatest near dawn because Earth's orbital motion is to the east, in the direction of the dawn terminator. A couple thousand years from now, an amateur astronomer, looking up to see a former Perseid meteoroid ionize its signature across the sky, will dismiss it as an unknown. Jupiter can bounce meteoroids right out of the Solar System others get pulled in by the Sun's gravity or blown out by its wind. ![]() Over time, meteoroids that are dribbled out by vaporizing comets and colliding asteroids can spread into streams so broad we no longer know from whence they came. No question about it, some sporadic meteors originate from ancient meteor showers that have long since dispersed. But where do they come from? Are they truly random, or were they once members of long-lost meteor showers witnessed by our distant ancestors? If you were to make a lifelong tally of meteors, the sporadics would easily outnumber those from meteor showers. Those random meteors that flash across the sky on any old clear night. Is this loner a member of a long-lost meteor shower? NASA But have you ever wondered where all the random meteors come from? We explore their origins. Meteor showers like the Perseids get all the press.
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