Characteristics of Stars - Weeblyleannortiz.weebly.com/.../characteristics_of_stars.pdf · Characteristics of Stars The Sun is an average star: it’s not hot or cool it’s not large

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

• Galaxy 4414 - An image from the 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

• Jewel Box open star cluster - 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 TemperatureColor: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 TemperatureColor Temp. Range (oC) ExamplesBlue 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.

SpectrumSpectroscope: 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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