Transcript Characteristics of stars

CHARACTERISTICS OF STARS
COULTER
CLASSIFYING STARS
• Characteristics used to classify stars include color, temperature, size, composition, and brightness
COLOR AND TEMPERATURE
• A star’s color reveals it temperature.
• Cooler stars with a surface temperature of 3,200 C appear red.
• Stars with a surface temperature of 5,800 appear yellow.
• The hottest starts over 20,000 C appear bluish.
SIZE
• Many stars are about the size of the sun, which is a medium sized star.
• White dwarfs are about the size of Earth.
• Neutron stars are about 20KM (smallest)
• Giant stars and super giant stars. If our sun were a super giant star it would fill our solar system as far
out as Jupiter.
COMPOSITION
• Stars vary in chemical composition. Most are about 73% hydrogen, 25% helium, 2% other elements.
• Spectrograph is a device that breaks light into colors and produces an iage of the resulting spectrum.
(most large telescopes have these)
• Each chemical element absorbs light at particular wavelengths.
BRIGHTNESS OF STARS
• The brightness of a star depends upon both its size and temperature.
• How bright a star looks from Earth depends on both its distance from Earth and how bright the star
truly is.
• Star can be described as apparent brightness and absolute brightness.
•
Apparent brightness- its brightness as seen from Earth.
•
Absolute brightness- is the brightness the star would have if it were at a standard distance from Earth. (need to
calculate its apparent brightness and distance to get the absolute brightness of a star)
MEASURING DISTANCES TO STARS
• The light-year is a unit astronomers use to measure distances between the stars.
• Light-year is the distance light travels in one year (about 9.5 million km)
•
Light-year is distance not time: example if it took 1 hour to ride a bike 10 km, you could say it took you 1 bikeyear to get to the mall.
• Parallax: is the apparent change in position of an object when you look at it from different places.
Movie theater example: