1 / 23

The Solar System:

The Solar System:. A3: Characteristics of Stars. Characteristics of Stars. Like our sun, all stars are huge spheres of glowing gas. They are made up of mostly hydrogen. They produce energy through the process of nuclear fusion.

leandra-boyer
Download Presentation

The Solar System:

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. The Solar System: A3: Characteristics of Stars

  2. Characteristics of Stars • Like our sun, all stars are huge spheres of glowing gas • They are made up of mostly hydrogen • They produce energy through the process of nuclearfusion • Theenergy they produce is what causes them to give off light

  3. Classifying Stars • Stars are classified using their physicalcharacteristics such as color, temperature, size, chemical composition, and brightness • Color and Temperature – looking at the stars, you can see slight differences in their colors • Example • Betelgeuse, the bright star in Orion’s shoulder looks reddish. • While Rigel, the star in Orion’s knee, looks blue-white

  4. Color and Temperature • Like objects on Earth, a star’s color reveals its temperature • Which is hotter: red hot or white hot? • white hot • The coolest stars (about 3,200o C) appear reddish • Our sun (about 5,800o C) appears yellow • The hotteststars (over20,000o C) appear bluish-white

  5. Star Size • Most stars appear to be points of light all about the same size • However, the actual size of stars vary greatly • Some of the smallest stars, such as neutron stars, are only about 20 km in diameter. • Our sun has a diameter of 1,400,000 km • The earth’s diameter is only about 12,700 km • The diameter of a red giant star is around 1,000,000,000km • The diameter of a super giant star is around 2,940,000,000 km

  6. Chemical Composition • Although most stars are about 70% hydrogen, their chemical composition can vary • Spectrographs – Astronomers use spectrographs to determine the elements found in stars • Device that breakslight into colors and produces an image of the resulting spectrum • The gases in a star’s atmosphere absorb certain wavelengths of light • This results in darklines that appear in the spectrum

  7. Chemical Composition • Different chemical elements absorb differentwavelengths in the spectrum • So each chemical produces a unique dark line patter in the spectrum, like a fingerprint • Knowing the dark line pattern for different elements, astronomers can use a spectrograph to determine the chemical composition of different stars

  8. Chemical Composition • These are the dark line patterns for four elements • These are spectrums given off by 3 stars • What is their chemical composition? • Star A: • Hydrogen & Helium • Star B: • Helium & Calcium • Star C: • Hydrogen & Sodium

  9. Wavelengths and Shifts • Wavelengths – wavelengths are measured by calculating the distance from one peak to the adjacent (next) peak λ • Example: • Electromagnetic Spectrum – Since energy travels in waves, the EM spectrum is the range of all possible EM radiation (waves)

  10. Wavelengths and Shifts • Smaller • distance • Bigger • distance • between peaks • between peaks • Purple/blue end • Red/orange end • High energy • Low energy • High frequency • Low frequency • More dangerous • Less dangerous

  11. Wavelengths and Shifts • Doppler Effect – The change in wavelengths as objects move towards or away from the observer • Example 1: A car gets louder as it get closer • This is because the wavelengths of sound become compressed as the car moves towards us • Higher Frequency • Conversely, as the car moves away, the wavelengths get longer so the car seemsquieter • Lower Frequency

  12. Wavelengths and Shifts • Example 2: A stationary sound produces a constant frequency • The sound does not change • However, if the object begins moving, the sound will change because the wavelengths (frequency) changes • For observers on the left, does the sound get louder or quieter? • Quieter • For observers on the right, does the sound get louder or quieter? • Louder

  13. Wavelengths and Shifts • Example 3: Planets, stars, solar system, and galaxies are always in motion • Because of this, as stars get closer or further away, thespectra we see (light) appears to change • Moving towards us • Not Moving • Moving away • Shift toward blue • Shift toward red

  14. Spectra of star 4 G 2Y 3R 4 B 2G 3O Star showing red-shift Wavelengths and Shifts • Red Shift – Visible light from a star that is moving away from us shifts towards the red side of the spectra (the wave is being stretched)

  15. Spectra of star 4 V 2B 3Y 4 B 2G 3O Star showing blue-shift Wavelengths and Shifts • Blue Shift – Visible light from a star that is moving towards us shifts towards the blue side of the spectra (the wave is being compressed)

  16. Brightness of Stars • The brightness of a star depends upon both its size and temperature • Apparent Brightness – the brightness as seen from Earth • Apparent brightness can be measured easily using electronic devices • However, it does not tell the actual amount of light a star gives off • This is because the closer a star is to the Earth, the brighter it will appear • But that does not mean that it actually produces more light than another star that may be furtheraway and appears dimmer

  17. Brightness of Stars • Absolute Brightness – the brightness a star would have if it was a standarddistance from Earth • Find the absolute brightness is more difficult • First, the astronomer must find its apparent brightness • Second, the astronomer must find the star’s distance from Earth • Then they use calculations to determine the star’s absolute brightness

  18. Measuring Distances of Stars • Light Years – Astronomers use a unit called a light-year to measure distances between stars • On Earth, we use measurements like kilometers to measure distance • However, distances in space are so large that kilometers are not a practical unit of measurement • In space, light travels at about 300,000 km per second. • A light-year is the distance that light travels in oneyear • About 9.5 million millionkilometers • No, that is NOT a typo – 9,500,000,000,000

  19. The Hertzsprung-Russel Diagram • About 100 years ago two different scientists made graphs to find out if the temperature and absolute brightness of stars were related • Plotted the surface temperatures on the x-axis • Plotted the absolute brightnesson the y-axis • The points formed a pattern and the graph is still used today • Astronomers use the H-R diagram to classify stars and understand how they change over time

  20. Main Sequence -Most of the stars form a diagonal called the main sequence • Over 90% of all stars including our sun are in the main sequence • As the surface temperature increases, the absolute brightness increases

  21. Where are the hottest stars located on the graph? • On the left • Where are the brightest stars located on the graph? • At the top • Based on the graph, describe super giants • Super giants are very bright but not very hot • Based on the graph, describe white dwarfs • White dwarfs are medium hot and dim

  22. In Closing • What characteristics do we use to classify stars? • Color • Temperature • Size • Chemical Composition • Brightness

  23. In Closing • How can we know when a star is moving closer to us or away from us? • The star’s spectra has a red shift or a blue shift • How do we measure the distance between stars? • In light years • What is the H-R diagram used for? • Classifying stars and understanding how they change over time

More Related