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Because the html format does not always appear the same to each viewer unlike in a normal TOEFL reading passage the words will not be referred to by line, instead they will be in bold and italisicized type with the number of the question inside parentheses.

Astrobiology 101

Red dwarfs are smaller, (Q.2)dimmer, and cooler than our sun. There are more than a dozen of these stars within a few light years of our Earth, yet not one of them is visible to the naked eye. For years it was thought that they were a poor place to look for alien lifeforms. However, recent computer models contradict this supposition. This is excellent news for xenobiologists since four out of every five stars is a red dwarf.

The argument against life being present on the planets orbiting around red dwarfs was twofold. First, these stars are so faint because they begin with ten to sixty percent less mass than the sun. They are frugal: their nuclear reactions are far slower than in other types of stars. This (Q.5) stinginess could be a point in their favor since the average lifetime of a red dwarf is one hundred times that of the Sun, which would allow life a much longer time to evolve. Although with so little energy available how could there be life? Living organisms as we know them depend on a range of temperatures where water is liquid. A planet orbiting a red dwarf at the same distance as our planet orbits the Sun would be a frozen ball of ice. Of course, you could simply place the planet closer to the red star, hence it should be warmer and habitable.

But that is the second problem; a closer orbit comes with a cost. A planet that is (Q.6) nestled next to the star would always present one face towards the star, very much like our moon does to the Earth. So one side would be a blast oven and the other an icy circle of hell. Not so, according to and Manoj Joshi at NASA's Ames Research Center. When they ran a computer simulation of such a planet they found out that if the planet had an atmosphere only about 15 percent thicker than ours the results implied that it could shelter life. Venus already has an atmosphere ninety times that of Earth's so a slightly denser atmosphere is well within the realms of possibility. A more abundant atmosphere would transfer enough heat from the eternal sunny side to endless night. The temperature range was inside acceptable norms: from 50 degrees to minus 50 degrees Celsius.

Another difficulty presents itself with this scenario since water would tend to migrate from the hot side to the frigid dark side. However, Martin Heath of Greenwich Community College, London thinks he might have the solution to this dilemma. He postulates that if the oceans are deep enough, water will circulate back from the nether regions over to the hot side. Under a deep ice cap, sea water would be insulated from the intense cold and remain liquid and thus be able to freely disperse.

While this type of planet might be able to bear life, the conditions would be (Q.9) strikingly dissimilar to what we find on Earth. One important fact to remember is red dwarfs emit a great deal of their energy in the infrared. Which could offer some problems to the process of photosynthesis.  In addition, red dwarfs exhibit more massive starspots than Sol which could reduce incoming light by up to two fifths. Starflares also pose a problem since they can brighten a red dwarf by as much as one hundred percent. Besides these global changes, life would have to deal with the variety of fixed temperatures on this planet. Ground zero in the hot zone would be centered on the equator where the star would be directly overhead. The rim of eternal shade would be somewhere around zero degrees and cooler the deeper you went until you reached temperatures of minus fifty degrees centigrade. Since the sun would be stationary in the sky, the backside of a hill would be in perpetual shadow, as well. This continuous light vs constant shade would certainly produce intriguing ecosystems.


1. Choose the another title for this article:
A. The Search for Life in the Universe  B. Red Dwarfs: a New Place to Look for Life  C. The Physics of Planets Orbiting Red Dwarf Stars
D. The Stationary Planet

2. The word dimmer as used in this article is closest in meaning to:
A. less intelligent  B. darker  C. deader  D. denser

3. According to the first paragraph why is the possiblity of life around red dwarfs an auspicious bulletin?
A. Because they were a poor place to look for aliens. B. Considering that they are invisible to the naked eye
C. Inasmuch as they are cooler and smaller  D. Because they are the most numerous of stars

4. According to the passage what benefit would deep bodies of salt water bring?
A. An abundant atmosphere  B. Circulating wind patterns  C. Indispensable temperature redistribution
D. Essential seasonal changes

5. The word stinginess as used in this passage is closest in meaning to:
A. discounting  B. harmful  C. miserly  D. generous

6. The word nestled could best be replaced by
A. petted roughly  B. subsequent  C. settled comfortably  D. humped

7. Why does the author mention a blast oven and an icy circle of hell?

A. To illustrate the drastic differences in conditions that were originally postulated for the two opposing faces on this type of planet.
B. To chart out the temperatures from 50 degrees to minus 50 Celsius.
C. To explain that naked eyes would be severely damaged on these worlds.
D. To point out that red dwarfs with their immense starspots and flares would produce similar if not identical situations on these planet's surfaces.

8.Which of the following is not mentioned as NOT being a problem for the prospect of life on these worlds.
A. A feeble allotment of light  B. An everlasting relocation of water  C. A dearth of tides needed for evolution
D. Extreme temperatures

9.   The word strikingly is closest in meaning to:
A. Exhaustingly  B. Expertly  C. Ingloriously  D. Impressively

10.What do you suppose the next topic discussed would be?
A. How animals and plants might differ on these planets.  B. Searching for life around white dwarfs.
C. Droughts and Flooding on these planets.  D. Photosynthesis on the dark side of these planets.


 
Sugestions for additonal reading:
Why red dwarves may harbour alien life at http://www.newscientist.com
WOLF 424 AB  Read about a pair of red dwarfs, and then explore the astronomical site of solstation.com
The Search for the Extrasolar Planets: Written and Compiled by George H. Bell
Habitable Moons: What does it take for a  moon to support life?  By Andrew J. LePage Adapted from Sky & Telescope, December 1998
Mars' First Colonists: Roaches?  from WIRED
The Planet Whimsy   by yours truly (better viewed with Firefox) 

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Ce texte © 2001-2009 Christopher Yukna - tous droits réservés



 
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