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Content Benchmark E.8.B.5
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Earth Science
Atmospheric Process and Water Cycle
Solar System and Universe
  E.8.B.1
  E.8.B.2
  E.8.B.3
  E.8.B.4
  E.8.B.5
  E.8.B.6
  E.8.B.7
Earths Composition and Structure
Content Areas
Nature of Science (NOS)
Life Science
Earth Science
Physical Science

Students know the Sun is many thousands of times closer to Earth than any other star, and billions of times closer than the far end of the Milky Way Galaxy. W/L

“Space is big - really big - you just won't believe how vastly, hugely mind-bogglingly big it is. You may think it's a long way down the road to the chemist, but that's just peanuts to space.” (Douglas Adams from The Hitchhiker’s Guide to the Galaxy).

The Milky Way Galaxy (Figure 1) is home to at least 200 billion stars.  Some estimates suggest that number could be closer to 400 billion stars (http://seds.org/MESSIER/more/mw.html).


Figure 1
. Milky Way Galaxy
(From http://map.gsfc.nasa.gov/media/ContentMedia/dirbe123_2p6dec.jpg)

Out of all those billions, the star closest to Earth is Sol, the lone star of our own solar system.  Sol, more commonly referred to as “the Sun” is centrally located within the solar system.  With such proximity, the Sun is far brighter than any other star twinkling in the sky (Figure 2).


Figure 2. Solar System
(From http://www.solarviews.com/raw/misc/solarsystem.jpg)

The Sun is located an average distance of 149.6 million kilometers (93 million miles) from Earth (http://www.windows.ucar.edu/tour/link=/sun/statistics.html).  Distances in millions of kilometers or millions of miles are comprehendible to most people, but to make the numbers less cumbersome, we typically measure distances within the solar system in astronomical units (AU).  One AU is equivalent to the average distance from Earth to the Sun.  When dealing with interstellar and intergalactic distances, even the AU is too limiting.  Instead, distances are measured with respect to the distance light can travel in a defined time.  Figure 3 depicts how many light minutes the Sun is from the terrestrial planets and how many light hours the Sun is from the Jovian planets.


Figure 3. Distances from the Sun to the Planets.
(From http://www.solarviews.com/eng/solarsys.htm)

Light minutes and light hours work within our solar system, but light years is a unit preferable when referring to distances between stars and galaxies.  The speed of light is 299,792.458 km/sec and a year equals 365.25 days (or 31,557,600 seconds).  Multiplying the speed of light by the number of seconds in a year (299,792.458 km/sec * 31,557,600 sec) lets us compute that light would travel 9.46 x 1012 km in a year (thus, this value equals the distance known as a light year).  To determine, for comparative purposes, how many light years the Sun is from Earth, divide the distance between the two (149,600,000 km) by 9.46 x 1012 km per light year.  This calculation shows the Sun is 1.58 x 10-5 light years (or approximately 8 light minutes) from Earth

When viewing the night sky with our unaided, naked eye, we generally observe stars (other than our Sun) as close as around 4 light years and as far away as a few hundred light years.  A few stars are large enough and bright enough that we detect them with our naked eye to distances as far as 2000 light years (http://www.uwgb.edu/dutchs/CosmosNotes/distance.htm).

Figure 4 is a chart of some of the nearest stars to Earth.  After the Sun, Proxima Centauri is closest to Earth at 4.2 light years.  Dividing this value by the distance between Earth and Sun (4.2 light years / 1.58 x 10-5 light years) reveals Proxima Centauri to be 265,823 times as far from Earth as is the Sun.  So…the nearest star after the Sun is more than one-quarter of a million times further away.  Progressing to the next stars out, the difference in distances increases even more.  For example, Wolf 359 (of Star Trek - The Next Generation fame) is 7.6 light years from Earth, and therefore 481,013 times further from Earth than the Sun (7.6 light years / 1.58 x 10-5 light years). 

The most distant stars we can see with the naked eye, at around 2000 light years, are 126,582,280 times further from Earth than our Sun (2000 light years / 1.58 x 10-5 light years).  To put things into perspective, the distance to those stars are just 0.02 of the diameter of the Milky Way Galaxy.  Our stellar neighbors, even the closest ones, are so far away as to render us unable to readily drop by and borrow a cup of star dust.


Figure 4. Twenty-two Nearest Stars to Earth
(From http://www.essex1.com/people/speer/stars.html)

The Milky Way is a barred-spiral galaxy.  Figure 5 displays the Sun’s location within the Orion Arm of the Milky Way Galaxy.  From this diagram, it is apparent that the Sun is over halfway from the center of the galaxy towards the perimeter of the galactic disk. 


Figure 5. The Sun within the Orion Arm of the Milky Way Galaxy
(From http://www.atlasoftheuniverse.com/milkyway.html)

Figure 6 more specifically depicts the distances involved regarding the Sun’s location in the Milky Way.  From one edge of the galactic disk to the other is between 95,000 – 100,000 light years.  The Sun is approximately 28,000 light years from the center of the Milky Way Galaxy.  This places the Sun a bit less than 22,000 light years to its nearest edge of the galactic disk, and around 78,000 light years to its furthest edge of the galactic disk.

Using the aforementioned distances, the closest edge of the galaxy is 1,392,405,100 times further from Earth than is the Sun (22,000 light years / 1.58 x 10-5 light years), the center of the galaxy is 1,772,151,900 times further from Earth than is the Sun (28,000 light years / 1.58 x 10-5 light years), and the furthest edge of the galaxy is 4,936,708,900 times further from Earth than is the Sun (78,000 light years / 1.58 x 10-5 light years).


Figure 6. The Sun’s location within the Milky Way Galaxy
(From http://boojum.as.arizona.edu/~jill/NS102_2006/Lectures/MilkyWay/milkyway.html)

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Content Benchmark E.8.B.5

Students know the Sun is many thousands of times closer to Earth than any other star, and billions of times closer than the far end of the Milky Way Galaxy. W/L

Common misconceptions associated with this benchmark

1. Students mistakenly believe the Sun is not a star because it doesn’t shine at night.

Since early childhood, students have learned the bright object in the daytime sky is called the Sun and that the small, twinkling dots of light in the nighttime sky are called stars.  They are not taught that the Sun is a star till later in their education, and even then, their own observations conflict with the information that our Sun is simply a star (albeit a star at the center of a solar system) because they do not look and act the same.  Students must also be taught that when they are experiencing nighttime, the Sun (our star) is visible and shining for persons in the daylight on the opposite side of the world.

For information discussing the Sun as a star, refer to http://www.nineplanets.org/sol.html

This misconception as well as numerous others can be found at the following site,
(http://amazing-space.stsci.edu/resources/myths/solar_system.php.p=
Teaching+tools%40%2Ceds%2Ctools%2C%3EMyths+vs.+realities
%40%2Ceds%2Ctools%2Ctype%2Cmyths.php%3EOverview%3A+
Solar+system+myths%40%2Ceds%2Coverviews%2Cmyths%2C
solar_system.php&a=%2Ced



2. Students have a misconception that nighttime visible stars are located within our solar system.

Such a notion has been considered since the times of the ancient Greeks.  Aristotle proposed a geocentric model of the solar system with Earth at the center.  Crystalline spheres surrounded Earth.  Each of those spheres contained the celestial bodies, with the Moon in the first sphere surrounding Earth, followed by spheres containing Mercury, Venus, the Sun, Mars, Jupiter and Saturn.  The last sphere containing celestial objects held the stars (Figure 7).  It simply appears that the stars are close and are therefore members of our solar system.  The planets even resemble the stars, leading to further presumption of association.  It is difficult to discern the actual depth of field of the starry sky by merely looking at it; distances to the stars required the development of mathematical strategies involving parallax, and a knowledge of the diameter of Earth’s orbit about the Sun.

For additional views on early beliefs that the stars are part of our solar system, review the information found at http://www.pas.rochester.edu/~blackman/ast104/aristotle8.html
and at http://astronomy.nmsu.edu/nicole/teaching/
ASTR110/lectures/lecture11/slide01.html
.

This misconception as well as others can be viewed at the following site,
(http://www.huntel.net/rsweetland/science/misconceptions/space.html)


Figure 7. The Celestial Spheres of Aristotle
(From http://www.pas.rochester.edu/~blackman/ast104/aristotle8.html)


3. Students incorrectly believe the closest stars are nearer to Earth than is the Sun.

This mistaken belief stems both from visual misperception (the stars appear to be about as close to Earth as is the Moon and students know the Moon is closer than the Sun) as well as a vague understanding of the relationship between the various measurement units utilized in astronomy.  When students find themselves reading values recorded as millions of kilometers, Astronomical Units (A.U.), and light years, they often have no basis of comparison.  In such circumstances, it may be natural to assume that the smaller number represents a closer distance and the larger number represents a further distance.  For example, when comparing distances of 4 light years, 10 A.U. and 150 million kilometers, students believe these are already arranged in order of closest to furthest distance based on the numerical value of each.

The Astronomical Conversion Calculator will help students understand the relationships between the various units used in astronomical measurement. This site is found at
http://www.sciencelab.com/data/conversion_calculators/
astronomical-conversion.shtml

This misconception was pulled from an extensive list of astronomy misconceptions and can be viewed at the following site.
http://www.physics.umaine.edu/ncomins/stars.htm#distance


4. Students may incorrectly belief that all the stars in the sky are the same distance from Earth.

When students look at the night sky, it appears as though all the stars are painted upon some celestial tapestry.  There are obvious differences in brightness of the stars, but to the casual viewer, the stars appear to be near each other and all the same distance from Earth.  By the same reasoning, students believe the stars in the various constellation are all in the same plane.

For further discussion on this topic, visit the following site
http://www.space.com/spacewatch/070124_ns_far_constellations.html

The above stated misconception came from a list of misconceptions found at http://www.newyorkscienceteacher.com/sci/miscon/common-miscon/astr.php


5. Students have the misconception that there are millions of stars in close proximity to Earth

As students star watch, they observe more stars in the night sky than they can count.  They already have the misconception that all the stars are located the same distance from the Earth, and the stars seem tantalizingly close.  It follows for them that these millions of stars they see must all be quite close to Earth.  In reality, there are just 40 stars located within 16 light years of Earth.  Our solar system is located in a sparsely populated region of the Milky Way GalaxyStars are more densely-packed and closer together nearer the center of the galaxy.

More information on proximity of stars to Earth can be found at
http://hyperphysics.phy-astr.gsu.edu/Hbase/starlog/strclos.html#c0

The above stated misconception came from the following list of misconceptions,
http://www.physics.umaine.edu/ncomins/stars.htm#distance

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Content Benchmark E.8.B.5

Students know the Sun is many thousands of times closer to Earth than any other star, and billions of times closer than the far end of the Milky Way Galaxy. W/L

Sample Test Questions

Depth Of Knowledge Level 1

  1. The closest star to Earth is
    1. Proxima Centauri.
    2. Sigma 2398.
    3. Wolf 359.
    4. the Sun.
  1. A light year is a
    1. name given to a non-leap year since it has fewer days.
    2. period of time with which we define one star year.
    3. metric quantity comprised of 1,000,000 kilometers.
    4. measurement defined as the distance light can travel in a year.
  1. The Sun is 1.58 x 10-5 light years from Earth.  If a star is 1.58 light years from Earth, how many times further is that star from Earth than is the Sun
    1. 1,000 times
    2. 10,000 times
    3. 100,000 times
    4. 1,000,000 times
  1. Use the data table showing the distance from Earth to various stars to answer the question below.


(Condensed from http://www.closeststars.com/)

  1. What star is farthest from Earth?
    1. Kruger 60
    2. Ross 128
    3. Wolf 359
    4. Lacaille 9352
  1. Use the diagram below indicating the location of the Sun in the Milky Way Galaxy to answer the question that follows.


(From http://boojum.as.arizona.edu/~jill/NS102_2006
/Lectures/MilkyWay/milkyway.html
)

  1. Select the answer that BEST describes the location of the Sun compared to the rest of the Milky Way Galaxy.  The Sun is
    1. closer to the furthest edge of the galaxy than to the center of the galaxy.
    2. located within the bulge, so is equally located between the edges of the galaxy.
    3. part of the halo and globular clusters outside the disk of the Milky Way Galaxy.
    4. further from the center of the galaxy than from the nearest edge of the galaxy.


Depth of Knowledge Level 2

  1. The Sun is located 149,600,000 km from Earth.  Proxima Centauri is 4.2 light years from Earth.  Neptune is 29.06 AU from Earth.  Which of the following statements accurately compares the distance of each from Earth?
    1. The Sun is closer to Earth than Neptune and Proxima Centauri.
    2. Proxima Centauri is closer to Earth than Neptune and the Sun.
    3. Neptune is closer to Earth than the Sun but further from Earth than Proxima Centauri.
    4. All three are the same distance from Earth, just expressed in different units
  1. Use the diagram below depicting how Aristotle arranged the celestial objects known in his time to answer the question that follows.

 

(From http://www.pas.rochester.edu/~blackman/ast104/aristotle8.html)

  1. Interpreting the organization of the above graphic suggests that Aristotle believed each of the following EXCEPT
    1. all stars are the located the same distance from Earth.
    2. the Sun is a big star closer to Earth than the other stars.
    3. stars are found a little beyond the orbit of the last planet.
    4. stars orbit the Earth, as do the planets and the Sun.
  1. Which of the following statements most correctly compares the distances between Earth, the Sun, and the other stars in the Milky Way Galaxy?  The Sun is many thousands of times closer to Earth than the next nearest star, and
    1. hundreds of times closer to Earth than stars at the far end of the Milky Way Galaxy.
    2. millions of times closer to Earth than stars at the far end of the Milky Way Galaxy.
    3. billions of times closer to Earth than stars at the far end of the Milky Way Galaxy.
    4. trillions of times closer to Earth than stars at the far end of the Milky Way Galaxy.
  1. Use the picture below indicating the location of the Sun within the Milky Way Galaxy to answer the following question.


(From http://www.atlasoftheuniverse.com/milkyway.html)

  1. Based upon the diagram, which of the following is the BEST conclusion?
    1. Most of the stars in the Milky Way Galaxy are very close to Earth.
    2. Only of few of the stars in the Milky Way Galaxy are close to Earth.
    3. The Earth is located in the center of the Milky Way Galaxy.
    4. The Milky Way Galaxy has the shape of an elliptical galaxy.


Constructed Response E.8.B.5

1.  Use the following diagram and information to answer the question below. Earth’s star, the Sun, is one of a few hundred billion stars in the Milky Way Galaxy. The top part of the diagram shows a drawing of the Milky Way Galaxy as viewed from above.  The bottom part of the diagram is a side view of the galaxy.  This view helps to visualize the size of the Milky Way Galaxy by showing the width and depth of the disk.  The Earth and Sun are located within the Orion arm of the Milky Way Galaxy.  

(From http://boojum.as.arizona.edu/~jill/NS102_2006
/Lectures/MilkyWay/milkyway.html
)

  1. Name the arm, and describe the location within that arm, of the stars which are furthest from Earth.  Determine the approximate distance in light years those stars are from Earth.
  2. Observe the distance between the Earth and Sun to stars within the Orion arm and to stars within the Perseus arm and Sagitattarius arm.  Describe how it is possible that some stars which are not located in the same arm as Earth could be closer to Earth than are some stars which are in the arm containing Earth.

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Content Benchmark E.8.B.5

Students know the Sun is many thousands of times closer to Earth than any other star, and billions of times closer than the far end of the Milky Way Galaxy. W/L

Answers to Sample Test Questions

  1. D, DOK level 1
  2. D, DOK level 1
  3. C, DOK level 1
  4. A, DOK level 1
  5. D, DOK level 1
  6. A, DOK level 2
  7. B, DOK level 2
  8. C, DOK level 2
  9. B, DOK level 2


Constructed Response E.8.B.5 Score Rubric:

3 points

Response addresses all parts of the question clearly and correctly.

  1. The stars furthest from Earth are located at the outer end of the Centaurus arm of the Milky Way Galaxy.  These stars are somewhat over 75,000 light years from Earth
  1. Earth and the Sun are located near the inner end of the Orion arm, and are close the other stars at that end of the arm.  However, stars at the outer end of the Orion arm are quite far away from Earth as compared to stars in the adjacent Sagittarius arm and Perseus arm.  When a line is drawn from the center of the galaxy through the Earth and Sun, it is clear that the distance between Earth and those arms is shorter than the distance between Earth and the outer end of the Orion arm.

2 points

 Response addresses all parts of the question and includes only minor errors.

1 point

 Response does not address all parts of the question. 

0 points

 The response is totally incorrect or no response provided. 

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Content Benchmark E.8.B.5

Students know the Sun is many thousands of times closer to Earth than any other star, and billions of times closer than the far end of the Milky Way Galaxy. W/L

Intervention Strategies and Resources

The following is a list of intervention strategies and resources that will facilitate student understanding of this benchmark.

1. The Milky Way Galaxy

This comprehensive website covers many details of the Milky Way Galaxy.  It provides numerical relationships, describes and provides links for terms.  The site also discusses the structure of the Milky Way Galaxy and has links to many photos and graphics.

To access this site, go to http://seds.org/MESSIER/more/mw.html


2. An Atlas of the Universe

Graphic views of the universe as seen outward from the Earth and Sun are provided through this site.  The URL takes you to a main page with links to nine other pages.  Respectively, graphic, clickable images and information are provided for: 1) 12.5 light years from the Sun, 2) 250 light years from the Sun, 3) 5000 light years from the Sun, 4) 50,000 light years from the Sun, 5) 500,000 light years from the Sun, 6) 5 million light years from the Sun, 7) 100 million light years from the Sun, 8) 1 billion light years from the Sun, and 9) 14 billion light years from the Sun.

To access this site, go to http://www.atlasoftheuniverse.com/


3. Parallax and Distances to the Sun and Stars

The information at these sites helps to explain how scientists are able to determine the distance to stars and galaxies.  The Parallax site includes a graphic which shows how the measurement is made, while the Distances to the Sun and Stars site includes a historical perspective along with information on current technology used in determining stellar distances.

To access the site that explains parallax, go to
http://hyperphysics.phy-astr.gsu.edu/Hbase/astro/para.html#c1

To access the site on the Distance of the Sun and Stars, go to http://www.uwgb.edu/dutchs/CosmosNotes/distance.htm


4. The 3-D Sky

This site provide the user with a VRML 3-D model of the Sun (in yellow) surrounded by the 375 brightest stars within 600 light years of the Sun.  As the model is rotated, it helps give a feel for the Sun’s position with regards to its neighbors.  Links are provided for VRML 3-D models of Stars and of Galaxies

To access this site, go to http://www.honeylocust.com/Stars/


5. Mysteries of Deep Space

Many space-related activities are available at this site.  The two activities which are particularly useful for this benchmark would be Time Travel to the Edge of the Universe and Back! and Demonstrating the Distances of Stars.  Both of these activities involve working toward an understanding of the vast distances between stars.

To access this site, go to http://www.pbs.org/deepspace/classroom/


6. The Cosmic Distance Scale

This site is similar to a “powers of ten” presentation.  The user is able to zoom in or zoom out of the universe, first starting with Earth.  At each zoom, it is possible to click on an information link which provides further detail.

To access this site, go to http://heasarc.gsfc.nasa.gov/docs/cosmic/

To access an activity on cosmic scale, visit
http://www.dlese.org/library/catalog_DLESE-000-000-006-009.htm

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Benchmark Related Vocabulary

Astronomy
Earth
Galaxy
Star
Sun