Characteristics of Stars Section 27.1. Definition of a star Its a body of gases that gives off lots...
-
Upload
isaiah-reilly -
Category
Documents
-
view
213 -
download
0
Transcript of Characteristics of Stars Section 27.1. Definition of a star Its a body of gases that gives off lots...
Characteristics of Stars
Section 27.1
Definition of a star
• It’s a body of gases that gives off lots of energy in the form of light and heat
• They vary in size and mass, some are smaller that 20 km in diameter or up to a 1000 times the size of our sun!
Variations in composition and temperature
• Using a spectrometer, scientists can determine what type of gases compose a star
• Every chemical element has a characteristic spectrum
Temperature
• The temperature of a star is indicated by its color
• The red ones are the coolest and the blues are the hottest
• Most Temps range between 2800°C to 24,000°C.
Star Temperatures
Motion
• Actual motion can only be measured by high powered telescopes since stars are so far away
• Apparent motion of stars is what we see and is only due to the motion of the earth
Actual Motion of Stars
• They rotate on an axis, they revolve around other stars, and they move towards or away from earth
• Don’t forget the red shift
Distance to the Stars
• It’s measured in light years- the distance that light travels in one year ( about 9.5 trillion km)
• Light from the sun takes about 8 minutes to reach earth
Parallax
• Scientists can use this to measures stars within 1000 light years of accuracy by measuring the angle between a stars’ apparent position over a period of 6 months
• The closer the star, the larger the angle
Stellar Magnitudes
• The visibility of a star depends on its brightness and distance from earth
• Over 3 billion stars can be seen through a telescope, but only 6000 can be seen with the naked eye
• The 2 scales that scientists use to measure brightness are apparent magnitude and absolute magnitude
Apparent Magnitude
• The brightness of a star as is appears from earth
• The most powerful telescopes can detect stars with an apparent magnitude of about 29
• Those stars are 1.5 billion times fainter than those seem with a naked eye
Apparent magnitude
Absolute Magnitude
• How bright a star would be if it were 32.6 light years away
• Scientists use this distance because it’s equal to one parsec
Classification of stars
• Main-sequence stars- stars that are visible in the night sky, this includes the sun
• Super giants – are bright because they have so much surface area to project light
• White dwarfs- these stars are hot and dim because of their size