Comets, ASTEROIDS, AND mETEORS Chapter 20, section 5

Comets, Asteroids, Meteoroids There are many smaller objects moving through the solar system classified as comets, asteroids, or meteoroids

Comets Comet’s head- the brightest part of the comet Comet- loose collections of ice, dust, and small rocky particles whose orbits are usually very long, narrow ellipses You can think of a comet as a “dirty snowball” about the size of a mountain Comet’s head- the brightest part of the comet Coma- clouds of gas and dust formed around the outer layer of a comet When the comet gets close enough to the sun, energy turns the ice into gas Nucleus- the solid inner core of a comet Comet’s tail- as a comet heats up, some of its gas and dust stream outward forming a tail Most comets have two tails, an ice tail and a dust tail, and usually point away from the sun Comet means “long-haired star” in Greek

Comet

Origin of comets Kuiper Belt- a doughnut shaped region that extends beyond Neptune’s orbit to about 100 times Earth’s distance from the sun Oort Cloud- spherical region of comets that surrounds the solar system out to more than 1,000 times the distance between Pluto and the sun

Asteroids Asteroids- rocky objects that are too small and too numerous to be considered full- fledged planets Asteroid Belt- the region where most asteroids revolve around the sun; between Mars and Jupiter Astronomers have discovered more than 100,000 asteroids and are constantly finding more Scientists believe they are the pieces of the early solar system that never came together to form a planet 65 million years ago one or more large asteroids hit Earth and may have caused extinction

Meteoroid Meteoroid- a chunk of rock or dust in space; come from asteroids or comets On average a meteor strikes overhead every 10 minutes Meteor - When a meteoroid enters Earth’s atmosphere, friction with the air creates heat and produces a streak of light in the sky Meteorites- a meteoroid that passes through Earth’s atmosphere and hit Earth’s surface Craters on the moon were formed by meteoroids

Meteors

Constellations Constellations- a group of stars that forms a pattern in the sky that looks like a familiar object.

Constellations Ancient Greeks and Romans and other early cultures observed patters of stars in the night sky. Were used as navigation tools. No GPS!

Light-Year Light-Year: The distance light travels in one year. Travels 300,000 km/second Or 9.5 Trillion km in one year!

Spectrographs Spectrograph: Breaks the light from an object into colors and photographs the resulting spectrum. Astronomers use spectrographs to get information about stars, including their chemical compositions and temperatures.

Terms Characteristics of Stars Galaxy: Contains hundreds of billions of stars. (Milky Way) Universe: All of space and everything in it. Light-year: Distance that light travels in one year. It is a unit of distance not time. Parallax: The apparent change in position of an object when you look at it from different places.

Classifying Stars Star sizes largest to smallest are: The main characteristics used to classify stars are: Size, Temperature and Brightness. Star sizes largest to smallest are: Super Giant, Giant, Medium, White Dwarf, and Neutron stars.

Color and Temperature of Stars A stars color reveals its temperature. The coolest stars are red and hottest stars are blue, blue-white. The brightness of a star depends upon its size and temperature. How bright a star looks from Earth depends on both how far the star is from Earth and how bright the star actually is.

Colors of Stars Hot Stars- - - Blue-White Cooler Stars- - - Orange-Red

Hertzsprung-Russell Diagram A graph used by astronomers that shows the relationship between surface temperature and brightness of stars. Most stars (90%) fall under the Main Sequence in which surface temperatures increases as brightness increases.

Star Systems and Galaxies

Galaxies 3 Main Galaxies: Spiral Galaxies, Elliptical Galaxies Irregular Galaxies Spiral: A galaxy that has the shape of twin spirals. Elliptical: Look like flatten balls. Irregular: Do not have a regular shape.

Big Bang Theory The initial explosion that resulted in the formation and expansion of the universe. The universe was small, hot, and dense. It exploded about 10 to 15 billion years ago to make our universe.