Star search (Part 1).
On a clear, dark night far from light pollution, stargazers can spot approximately 2,500 celestial points of light. But that number dwindles as you approach cities. People living in the suburbs of New York City, for example, can only see an estimated 250 stars. Residents of Manhattan are lucky if they can make out 15.
Why are some stars easier to spot than others-despite light pollution? Some stars can outshine artificial light. A star's apparent magnitude, or its brightness as seen from Earth, depends on its temperature, size, and distance from Earth. The brighter a star's apparent magnitude is, the lower its measurement number.
The sun is the brightest celestial object as seen from Earth, with an apparent magnitude of -26. The full moon comes in second, with an apparent magnitude of -11.
Below is a chart showing the apparent magnitudes of the 10 brightest stars (other than the sun) as seen from Earth. The stars are listed in alphabetical order. Study the chart to complete the activities that follow.
ACTIVITY A: Use the chart to answer the following questions in complete sentences.
1. The chart above is in alphabetical order. List the star names in order from brightest to least bright. (Hint: Look at the apparent magnitudes.)
2. In which constellation can you find the fifth-brightest star?
3. Objects with a magnitude of 6 or below can be seen by the naked eye. Would a stargazer need a telescope to see any of the stars on the chart?
4. Which constellation contains the star Rigel?
5. Which constellation contains two of the 10 brightest stars as seen from Earth?
ANSWERS TO SKILLS PAGES
1. Sirius, Canopus, Alpha Centauri system, Arcturus, Vega, Capella system, Rigel, Procyon, Achernar, Betelgeuse
2. The fifth-brightest star is found in the constellation Lyra.
3. No, a stargazer would not need a telescope to see any of the 10 stars featured on the chart.
4. Orion contains the star Rigel.
5. The constellation Orion contains two of the 10 brightest stars as seen from Earth.
ACTIVITY B: Match each star in the left column with a fact about the object in the right column.
2. Alpha Centauri system
6. Capella system
a. It looks very bright because it is just 11.4 light-years away.
b. It is a giant star with a diameter 33 times that of the sun.
c. It is twice as bright as any other star in the night sky.
d. It takes 37 years for its light to reach us.
e. It was the first star to be photographed.
f. It is a star system made up of several stars. Two of its stars are in the process of dying and will eventually become white dwarfs.
g. Of the 10 brightest stars as seen from Earth, it is the hottest star.
h. It is visible at latitudes roughly south of Pittsburgh, Pennsylvania.
i. It is a star system made up of three stars bound together by their gravitational pulls.
j. Its brightness changes over time.
ANSWERS TO SKILLS PAGES
1. g 2. i 3. d 4. j 5. h 6. f 7. a 8. b 9. c 10. e
10 BRIGHTEST STARS AS SEEN FROM EARTH Apparent Star Name Constellation Magnitude Did You Know? Achernar Eridanus 0.45 With a temperature of between 13,726 and 18,726 degrees Celsius (24,740 and 33,740 degrees Fahrenheit), Achernar is the hottest star in this Top-10 list. Alpha Centaurus -0.27 Alpha Centauri is actually a Centauri star system made up of three system stars that are bound together by their gravitational pulls. The stars' names: Alpha Centauri A, Alpha Centauri B, and Alpha Centauri C. Arcturus Bootes -0.04 Arcturus is 37 light-years away. A light-year is the distance that light travels in one year. That means it takes 37 years for the light from Arcturus to reach us. Betelgeuse Orion 0.5 Betelgeuse is a variable star, meaning that its brightness changes over time. If this massive star were to be relocated to where the sun is, it would engulf Mercury, Venus, Earth, and Mars. Canopus Carina -0.72 Canopus is visible only at latitudes below 37 degrees north, or roughly south of Pittsburgh, Pennsylvania. Canopus is approximately 65 times the size of the sun. Capella Auriga 0.08 Capella is a star system made system up of several stars. Two of its stars are in the process of dying and will eventually become white dwarf stars. A white dwarf is what remains of a star after its outer layers have expanded and drifted into space. Procyon Canis Minor 0.34 Procyon is only seven times more luminous than the sun, but it appears as a very bright star because it is so close: just 11.4 light-years away. Rigel Orion 0.12 Rigel is a giant star with a diameter 33 times that of the sun and 40,000 times as luminous. Why doesn't it appear as bright as the sun? Because it is approximately 775 light-years away. Sirius Canis Major -1.42 Sirius comes from the Greek word meaning "scorching." It is aptly named, since it is twice as bright as any other star in the night sky. Vega Lyra 0.03 Vega was the first star to be photographed. J.A. Whipple took the photo on the night of July 16-17,1850.
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|Title Annotation:||CHART-READING SKILLS|
|Date:||Apr 2, 2007|
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