Download Characteristics of Stars ppt.

Warm-up questions:
1. List the moon phases in order beginning
with new moon.
2. Illustrate a neap tide and a spring tide
using the sun, moon and Earth.
3. Illustrate the position of the sun, moon
and Earth during a solar eclipse.
4. Illustrate the position of the sun, moon
and Earth during a lunar eclipse.
No talking. When finished, quietly study
for root words test #4. Thank you.
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Characteristics of Stars
Characteristics of Stars
The Sun is an average star:
it’s not hot or cool
it’s not large or small.
We can compare stars by color,
temperature, size, brightness and
spectrum.
Stars
•
Galaxies and Stars - important ideas
about characteristics of galaxies and
stars.
Stars
4414 - An image from the
• Galaxy
Hubble Space Telescope shows great detail of
Galaxy 4414. Astronomers study this particular
galaxy to refine their calculations of the rate of
expansion of the cosmos and the age of the
universe.
Stars
Box open star cluster • Jewel
This is an image of NGC 4755, the Jewel Box
open star cluster. It is located in the
constellation Crux and is 7,600 light-years from
Earth. The cluster was described as a "superb
piece of jewelry" in an early astronomical
catalog, hence the popular name.
Characteristics of Stars
Magnitude
Color
Size
Luminosity
Stars
Characteristics of Stars (5:07;
overview of star characteristics)
• Colors and Temperatures of
Stars (2:56; describes relationship of
star color to temperature;)
Stars
•
The appearance of stars is affected by several different factors, including
magnitude, color, size, and luminosity.
•
Magnitude is the brightness of a star, expressed as either absolute (how
bright the star actually is) or apparent (how bright it seems to be from
Earth).
•
Star color is directly related to star temperature, with red being the
coolest and blue the warmest.
•
Star size helps to indicate how long a star will live, since large stars burn
their fuel quickly.
•
Luminosity is all the energy radiating from a star, as both heat and light.
Some stars that appear as a single star from Earth are actually binary stars,
which are two stars that rotate around a common center of mass.
Color and Temperature
Color:
Stars range in color from red, orange, yellow, white,
to blue.
Red ----------- Yellow (Sun) ----------- > Blue
Temperature:
Stars range in temperature from 2000oC--50 000oC.
2 000oC ---------5 000oC (Sun)--------- > 50 000oC
Color and Temperature
Color and temperature are linked.
The 2000oC stars are red in color.
The 50,000oC stars are blue in color.
Color and Temperature
Color
Temp. Range (oC)
Examples
Blue
25000 – 50 000
Zeta Orionis
Bluish-white
11 000 – 25 000
Rigel, Spica
White
7 500 - 11 000
Vega, Sirius
Yellowish-white
6 000 - 7 500
Polaris, Procyon
Yellow
5 000 - 6 000
Sun, Alpha Centauri
Orange
3 500 - 5 000
Arcturus, Aldebaran
Red
2 000 - 3 500
Betelgeuse, Antares
Stars
•
Although it is not always apparent
from Earth, the distances of stars
from Earth varies greatly, and all of
the stars we see in the night sky are
extremely far from Earth. These
distances are so great that scientists
measure them in light years (the
distance light travels in one year.)
Stars
Essential Questions:
1. What are some important physical
properties of stars?
2.Why do scientists measure a star’s
distance from Earth in light years?
The Sun is larger than 95% of the stars.
Dwarf Star
Sun
Giant Star
Super Giant Star
Brightness
Brightness is related to the distance
from the earth and the age of the
star.
Hipparchus developed the idea of
classifying stars by their brightness.
1st magnitude stars are the brightest
6th magnitude stars are the weakest
Apparent Magnitude – refers to the
brightness of a star as it appears to us.
Absolute Magnitude – refers to the
actual amount of light given off by a
star at a standard distance.
Spectrum
Spectroscope: Used to measure the
chemical composition of the stars. (also
temperature and direction the star is
moving in relation to the Earth.)
How? Set up a spectroscope with
different tubes; each gas has different
spectras – light patterns.
Questions
1. How is the color of a star related to its
temperature?
2. Explain why a cooler star could actually
appear brighter than a hotter star.
#1
The color of a star depends on its
temperature, from red and orange (cool
stars) to yellow and white (hotter stars) to
blue (very hot stars).
#2
A cool star, such as a red giant, could be
either closer to us or much larger than a
hotter star, such as a white dwarf. (Could be
closer and larger)
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