Tuesday October 16, 2012

1. TuesdayOctober 16, 2012 (Comets; Meteoroids, Meteors, and Meteorites)

2. The Launch Pad Tuesday, 10/16/12 Identify this object. • comet

3. The Launch Pad Tuesday, 10/16/12 Identify this object. • comet

4. The Launch Pad Tuesday, 10/16/12 Identify this object. • asteroids

5. The Launch Pad Tuesday, 10/16/12 Identify this object. • Winslow, Arizona meteor crater

6. Announcements Happy Fall!

8. Recent Events in Science NASA Chat: Orionids, Planets, Constellations Brighten October Skies Read All About It! http://www.nasa.gov/connect/chat/orionids2012.html The 2012 Orionid meteor shower peaks on the night of Oct. 20-21, and that night's almost-new moon favors a good show. The moon's absence from the pre-dawn sky during the Orionids' peak also means that bright moonlight won't be a problem. In addition to Orionids, you'll see brilliant Venus, red Mars, the dog star Sirius and bright winter constellations such as Orion, Gemini and Taurus. Even if you don't spy a meteor, the rest of the sky is dynamite! Set your alarm, brew some hot chocolate and plan to enjoy the show with NASA astronomer Bill Cooke and his team from NASA's Marshall Space Flight Center. They'll be answering your questions via live Web chat on Saturday, Oct. 20 from 10 p.m. to 2 a.m. CDT. 

9. Comets The origin of comets is not well known because they form at great distances from the Sun. The most famous short-period comet is Halley’s comet, with a 76-year orbital period and potato-shaped nucleus (10 mi. by 5 mi.) Halley’s Comet

10. Comets Comets are often described as large, dirty snowballs. Comets are composed of frozen gases and rocky, metallic materials. The frozen gases vaporize when near the Sun, which produces a glowing head called the coma. Some comets may develop a tail that points away from Sun due to radiation pressure and the solar wind.

11. Comet Hale-Bopp In 1997, Comet Hale-Bopp's intrinsic brightness exceeded any comet since 1811. Since it peaked on the other side of the Earth's orbit, however, the comet appeared only brighter than any comet in two decades. Visible above are the two tails shed by Comet Hale-Bopp. The blue ion tail is composed of ionized gas molecules, of which carbon monoxide particularly glows blue when reacquiring electrons. This tail is created by the particles from the fast solar wind interacting with gas from the comet's head. The blue ion tail points directly away from the Sun. The white dust tail is created by bits of grit that have come off the comet's nucleus and are being pushed away by the pressure of light from the Sun. This tail points nearly away from the Sun.

12. Comet Halley Halley's Comet or Comet Halley is the best-known of the short-period comets and is visible from Earth every 75–76 years. Halley is the only short-period comet that is clearly visible to the naked eye from Earth, and thus the only naked-eye comet that might appear twice in a human lifetime. Other naked-eye comets may be brighter and more spectacular, but will appear only once in thousands of years.

13. Comet Kohoutek Comet Kohoutek was first sighted on March 7,1973 by Czech astronomer Luboš Kohoutek. It attained perihelion on December 28th that same year. Comet Kohoutek is a long-period comet; its previous apparition was about 150,000 years ago, and its next apparition will be in about 75,000 years. At its apparition in 1973 it had a hyperbolic trajectory due to gravitational perturbations from giant planets. Due to its path, scientists theorized that Kohoutek was an Oort-cloud object. As such, it was believed likely that this was the comet's first visit to the inner Solar System, which would result in a spectacular display of out-gassing. Infrared and visual telescopic study have led many scientists to conclude, in retrospect, that Kohoutek is actually a Kuiper-belt object, which would account for its apparent rocky makeup and lack of out-gassing.

14. Orientation of a Comet’s Tail as it Orbits the Sun Figure 22.27

15. Meteoroids, Meteors, and Meteorites A meteoroid is a sand- to boulder-sized particle of debris roaming through the Solar System.

16. Meteoroids, Meteors, and Meteorites The visible path of a meteoroid that enters Earth's (or another body's) atmosphere is called a meteor (shooting star or falling star.)

17. Meteoroids, Meteors, and Meteorites Many meteors appearing seconds or minutes apart are called a meteor shower. A meteor shower occurs when Earth encounters a swarm of meteoroids associated with a comet’s path.

18. Meteoroids, Meteors, and Meteorites If a meteoroid reaches the ground and survives impact, then it is called a meteorite.

19. Meteoroids, Meteors, and Meteorites Meteoroids are referred to as meteorites when they are found on Earth. Meteorites are classified by their composition: Iron Meteorites Mostly iron 5%–20% nickel Stony Meteorites Silicate minerals with Inclusions of other minerals

20. Meteoroids, Meteors, and Meteorites Stony- Iron Meteorites Mixtures of iron and stone Carbonaceous Chondrites A rare composition of simple amino acids and other organic material. These may give an idea as to the composition of Earth’s core and the age of the solar system

21. Worksheet Comets and Meteoroids • Go to www.irvingisd.net/nimitz • Click on Faculty. • Scroll down and find my name – click on Website. • When on my website, click on Earth and Space Science Class Notes. • Scroll down to today’s date and download today’s PowerPoint. • Use the PowerPoint to complete this Worksheet on Comets and Meteoroids.