Orionid Meteor Shower This Weekend

The Orionids

This weekend, from Saturday night into Sunday morning (10/21-10/22), you may observe the annual Orionid meteor showers streaking across the sky. Dozens of meteors will scorch the sky every hour.(Of course, the sky must be clear and dark, which, unfortunately, is not for me.) Fortunately, the moon is only in its crescent phase, so its light does not interfere with observing the meteor shower. The Orionid meteor shower happens every year in late October when Earth cross through debris left by Halley’s comet. Halley’s comet last passed through our solar system in 1986, and will not come back until 2061. When Halley’s comet neared the Sun, the heat melted the comet to form gas and dust. Though the comet leaves the solar system, that gas and debris continues to orbit the Sun. Most of the particles that form meteors are only the size of a few grains of sand, but comets have high kinetic energy as they hit Earth’s atmosphere— over 50,000 miles per hour! As the grains, or debris meteoroids, contact Earth’s atmosphere, they ionize molecules in the atmosphere, forming a bright trail across the sky known as a meteor or shooting star. Small meteoroids burn up in Earth’s atmosphere. A meteoroid must be bigger than the size of your fist to survive and hit Earth’s surface. Meteorites are usually found in deserts or Antarctica, where their black coloration stick out easily against the ground. Most meteorites land in the ocean, so no harm done there! In fact, 800 meteorites heavier than 100 grams strike the Earth every day; during meteor showers the frequency is higher.

Orionids Crossing Betelgeuse

Blazin’ Facts

  • Why “Orionid”? The meteors seem to intersect at Betelgeuse in the Orion constellation (but it’s just an optical illusion).
  • The Orionids historically have only produced 20 meteors at its peak, but in the last decade, scientists have observed more than 60 meteors per hour!
  • Meteors travel in space; meteoroids fall though the atmosphere; meteorites strike the surface
  • Did you know Halley never saw Halley’s comet? Halley suggested that the comet spotted in 1682 was the same one in 1531 and 1607. Halley’s observations led to the conclusion that comets orbit the sun. In 1705, he predicted the comet would appear in 1758, but died before he actually saw the comet.
  • Aside from Orionids, the other annual meteor shower is the Eta Aquarids that peaks early May.

References

Pereira, Pablo. “Meteor Shower Created by Halley’s Comet Peaks Tonight.” FOX News. FOX News, 20 Oct 2012. Web. 21 Oct 2012.

Meteors, Meteorites, and Meteoroids

Meteors

Meteors, Meteorites, and Meteoroids

Meteoroids are debris in space from comets or asteroids; meteors are shooting stars or fire balls in air; meteorites are meteoroids that invade Earth’s atmosphere and impact the ground; micrometeorites are perfect shiny spheres microscopic in size and the major cause of small-scale erosion on the moon. The three major types of meteoroids are stony, stony iron, and iron.

  • Several meteors can be seen per hour on any given night; when this number increases dramatically, these events are called “meteor showers” that occur annually or at regular intervals as the Earth passes through the trail of dusty debris left by a comet
  • The Perseids peak around August 12 every year; each Perseid meteor part of the comet Swift-Tuttle that swings around the Sun every 135 years
  • Other meteor showers and their associated comets: Leonids (Tempe-Tuttle), the Aquarids and Orionids (Halley), and the Taurids (Encke)
  • Comet dust in meteor showers burns up in the atmosphere before reaching the ground
  • Most meteorites no bigger than an average Earth rock
  • Large meteorites can cause extensive destruction: Barringer Meteor Crater in Arizona (1,000 meters, 50,000 years old), asteroid impact which created the 300 km Chicxulub crater on Yucatan Peninsula (65 million years ago)
  • Ann Hodges of Sylacauga, Alabama was severely bruised by a 3.6 kilogram stony meteorite that crashed through her roof in November, 1954
  • Meteorites have a “burned” exterior, formed as the meteorite is melted by friction as it passes through the atmosphere
  • Three types of meteorites: “irons,” “stones,” “stony-irons”
  • More than 30,000 meteorites found on Earth, 99.8% came from asteroids
  • Evidence for an asteroid origin includes: orbits calculated from photographic observations of meteorite falls project back to the asteroid belt, spectra of several classes of meteorites match those of some asteroid classes
  • All but rare lunar and Martian meteorites are very old, 4.5-4.6 million years
  • Only one group of meteorites can be traced to a specific asteroid; eucrite, diogenite, and howardite igneous meteorites traced to third largest asteroid Vesta
  • Meteorites and asteroids that fall on Earth are of the original diverse materials from which planets formed; tells the conditions and processes during the formation and earliest history of the solar system
  • Remaining 0.2% of meteorites split equally between meteorites from the Moon and Mars
  • 35 known Martian meteorites blasted off Mars by meteoroid impacts; all igneous rocks crystallized by magma
  • Controversy of whether structures in meteorite ALH84001 might be evidence of fossil Martian bacteria
  • 36 lunar meteorites similar in mineralogy and composition to Apollo Moon rocks, but come from other parts of the Moon

TIMELINE

4.55 billion years ago: Formation age of most meteorites, age of the solar system

65 million years ago: Chicxulub impact leads to the extinction of dinosaurs and 75 percent of animals on Earth

50,000 years ago: Age of Barringer Meteor Crater in Arizona

1478 BC: First recorded observation of meteors

1794 AD: Ernst Friedrick Chladni publishes first book on meteorites

1908 (Tunguska), 1947 (Sikote Alin), 1969 (Allende and Muchison), 1976 (Jilin): Important 20th century meteor falls

1969: Discovery of meteorites in a small area of Antarctica leads to annual expeditions by US and Japanese teams

1982-1983: Meteorites from the Moon and Mars are identified in Antarctic collections

1996: A team of NASA scientists suggests that Martian meteorite ALH 84001 may contain evidence of microfossils from Mars

2005: NASA’s Mars Exploration Rover Opportunity finds an iron meteorite on Mars

References: NASA <www.nasa.gov>