stars and galaxies. constellations constellations- certain groups of stars named after animals,...
TRANSCRIPT
Stars and Galaxies
Constellations
• Constellations- Certain groups of stars named after animals, characters in mythology, or familiar objects– From earth constellations look like groups of
stars close together – Brightest star in the winter sky is Sirius– 88 constellations – Star Polaris – North Star
– Appear to move because earth is moving – Stars also appear to change position in the sky
throughout the year • Earth revolves around the sun
• As earth orbits different constellations come into view while other disappear
• Appendix j pg 674-675
Absolute and Apparent Magnitudes
• Absolute Magnitude – Is a measure of the amount of light is actually
given off
• Apparent Magnitude– Amount of light received on earth
• Example: Sirius – 100x closer to earth then Rigel, therefore appears brighter
Determining distances
• Parallax– Apparent shift in the position of an object
when viewed from two different positions – The nearer an object is to the observer, the
greater its parallax– Distance in space are measures in light years
• Light year is the distance light travels in 1 year
• Light travels at 300,000 km/s
• Nearest star other then the sun is Proxima Centuri– 4.2 light years away – It takes 4.2 years for light from that star to
reach you
• Stars temperature is determined by the color of the star
– Very hot stars – blue white color – Cool stars – orange or red– Stars temperature close to the sun – yellow
Evolution of Stars
• H-R Diagram – Graph that shows relationship a stars
temperature to its absolute magnitude – Most stars fit into the main sequence of stars
• Hot blue bright stars (upper left)
• Cool Red dim stars (lower right)
• Sun is a yellow medium temp. star
• 90% of all stars are Main Sequence
– The other 10% are Super Giants, Giants, White Dwarfs
• Evolution of Stars– Stars begin as a large cloud of gas and dust
called a nebula– At high temperature Fusion begins – Main sequence star forms – Begins to use its hydrogen
– When hydrogen fuel runs out, expands and becomes a giant
– Core collapses– Outer portion of the giant blows away forming
a white dwarf– Eventually the white dwarf uses its fuel and
becomes a cold dead star– If a super giant (30 times our sun) collapses it
may turn into a black hole
Black Hole
The Sun
The Sun
• 99% of all matter in our solar system is the sun
• It is the center
• Makes life possible on earth
• Just an average star
• Enormous ball of gas, fusing hydrogen into helium at its core
• Layers of the suns atmosphere– Photosphere –
• lowest layer from which light is given off
• Temp. 6000* C
– Chromosphere-• Upward about 6000 Km
– Corona• Largest layer, extend out millions of km in space
• Temp. 2, 000,000*C
• Charge particle escape causing solar wind
• Sunspots– Dark areas on the suns surface, which are
cooler then their surroundings – Sun rotates
• Rotates faster at its equator than at its poles
• It takes 25 days for a sunspot to go around the sun at the equator
• Prominences and flares – Intense magnetic field associated with sunspots
may cause prominence, huge arching columns of gases
– So eruptive that material from the sun is blasted into space 1000 Km/sec
• Sun is a main sequence star
• Most star are in a system in which two stars orbit each other (Binary system)
• Our sun does not do this
• Some stars move through space as star cluster
Galaxies
Galaxies
• Large group of stars, gas, and dust held together by gravity
• Galaxies are separated by huge distances, often millions of light years
• Three types of galaxies – Elliptical– Spiral – Irregular
Types of Galaxies
• Elliptical is the most common – Vary in size – Football shaped
• Cluster of galaxies that the Milky Galaxy belongs to is called Local Groups
• Spiral Galaxies have spiral arms– Milky Way is a spiral Galaxy
• Irregular Galaxies – Many different shapes – Cloud of Magellan Orbit
Spiral
Irregular
Elliptical
Milky Way Galaxy
• In our galaxy, all stars orbit a central region
• 200 million years for the sun to orbit this central region
• Contains more then 200 billion stars
Expansion of the Universe
• When a Spectrograph is used to study light from galaxies beyond the Local group, there is a red shift in the light
• Because there is a red shift in the light, all galaxies must be moving away from earth
• Doppler Shift • Big Bang Theory states that between 15 and 20
billion years ago, the universe began expanding out of an enormous explosion
• There is evidence that supports the Big Bang Theory – Scientist have discovered radiation in space
that they believe was created by the explosion
• All matter exerts a gravitational force • If there is enough matter, gravity will halt
expansion • A big crunch would result
Meteors
• A meteoroid is matter revolving around the sun or any object in interplanetary space that is too small to be called an asteroid or a comet
• A meteorite is a meteoroid that reaches the surface of the Earth without being completely vaporized
• term meteor describe the streak of light produced as matter in the solar system falls into Earth's atmosphere creating temporary incandescence resulting from atmospheric friction.
