Beyond OurSolar System

Ch. 25

•star: a body of gases that gives off a tremendous amount of radiant energy in the form of light and heat

Star Groups

• constellations: a group of stars that form a pattern in the sky (88 different ones)

Orion

Ursa Major

Ursa Minor

Composition and Temperature

• stars differ in size, density, mass, and composition

• color of a star depends on its surface temperature–hot stars are blue (average surface temperature 35,000 K)

–cool stars are red (average surface temperature 3,000 K)

–our sun is yellow (average surface temperature 5,500 K)

Parallax

• the nearest stars have the largest parallax angles, while those of distant stars are too small to measure.

• the slight shifting of the apparent position of a star due to the orbital motion of Earth.

Original Photo

Photo taken 6 months later

Distance to Stars

• light-year: the distance light can travel in one year (9.5 trillion km)

• it takes 8 minutes for the sun’s light to reach Earth

• closest other star- Alpha Centauri (4.3 l.y.a)

Motion•actual motion: must

be measured only with a telescope

•apparent motion: motion due to the Earth’s movement

Stellar Magnitudes

• apparent magnitude: how bright a star appears from Earth- the lower the number, the brighter the object

• absolute magnitude: how bright a star really is

Distance, Apparent Magnitude, and Absolute Magnitude of Some Stars

Electromagnetic Radiation

The Study of Light

Electromagnetic radiation includes gamma rays, X-rays, ultraviolet light, visible light, infrared radiation, microwaves, and radio waves.

The electromagnetic spectrum is the arrangement of electromagnetic radiation according to wavelength.

Electromagnetic Spectrum

• a spectroscope is used to measure different compositions and temperatures–separates light into different colors

–Hydrogen and Helium are most abundant elements in stars

• spectrum of a star tells astronomers about its motion

Sun Spectrum

• Doppler effect: apparent shift in the wavelength of light emitted by a light source moving toward or away from the observer

In astronomy, the Doppler effect is used to determine whether a star or other body in space is moving away from or toward Earth.

The Doppler Effect

• blue shift: light waves appear to have shorter wavelengths as the star moves toward the Earth (spectrum shifted toward blue end)

• red shift: light waves appear to have longer wavelengths as the star moves away from the Earth (spectrum shifted toward red end)

A refracting telescope is a telescope that uses a lens to bend or refract light.

Simple Refracting Telescope

Keck Telescope

A reflecting telescope is a telescope that reflects light off a concave mirror, focusing the image in front of the mirror.

Detecting Invisible Radiation

Tools for Studying Space

Radio Telescopes• A radio telescope is a telescope designed to

make observations in radio wavelengths. • A radio telescope focuses the incoming radio

waves on an antenna, which, just like a radio antenna, absorbs and transmits these waves to an amplifier.

Radio Telescopes

Space Telescopes

24.2 Tools for Studying Space

Space telescopes orbit above Earth’s atmosphere and thus produce clearer images than Earth-based telescopes.

• The first space telescope, built by NASA, was the Hubble Space Telescope. Hubble was put into orbit around Earth in April 1990.

Hubble Space Telescope

Hubble Space Telescope

Space Telescopes

24.2 Tools for Studying Space

Other Space Telescopes• To study X-rays, NASA uses the Chandra X-Ray

Observatory. This space telescope was launched in 1999.

• Another space telescope, the Compton Gamma-Ray Observatory, was used to study both visible light and gamma rays.

• In 2011, NASA plans to launch the James Webb Space Telescope to study infrared radiation.

•nebula: a cloud of gas and dust

• protostar: shrinking, spinning, glowing nebula (temperature rises)

Nuclear fusion begins- a star forms!

• main sequence star: longest stage of life cycle- nuclear fusion releases energy

• red giant: very large, cool bright stars- starts when hydrogen is used up- star cools and outer layers expand- size is 10x’s bigger than our sun- this is next stage of our sun!

• white dwarf: small, hot, dim star- outer gases are lost and only core remains

• supergiant: extremely large, cool giant stars- very bright- 100 x’s larger than the sun

• supernova: star that blows apart with a tremendous explosion- occurs in very massive stars

• neutron star: collapsed core of a supernova- dense ball of neutrons

• black hole: hole in space with gravity so great that not even light escapes- formed from collapsed supernova

Classification of Stars

H-R Diagram: graph plotting surface temperature and absolute magnitude of each star

•galaxies: large scale groups of stars held together by gravity

• there are 50 billion-1 trillion galaxies

• we are in the Milky Way galaxy

Images of the Milky Way Galaxy

Types of Galaxies•spiral:

bright center of stars with arms spiraling out

• Milky Way is a spiral

Andromeda Galaxy

Structure of the Milky Way

• barred spiral: have a group of stars making a bar through the center

• elliptical: shape ranges from spherical to oblong–no arms

• irregular: small, faint stars spread out unevenly with no pattern

Large Magellanic

Cloud

Small Magellanic Cloud

Galaxy Cluster

The big bang theory states that at one time, the entire universe was confined to a dense, hot, supermassive ball. Then, about 13.7 billion years ago, a violent explosion occurred, hurling this material in all directions.

The Big Bang

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