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Milky Way Lot Bigger Scientists Thought
Also: study offers evidence one or more comets responsible sudden cooling period Earth 13,000 years ago. Transcript radio broadcast: 20 January 2009
This SCIENCE NEWS VOA Special English. I'm Steve Ember.
And I'm Barbara Klein. This week, we will tell you about new measurements our own Milky Way galaxy.
We will tell about study linking diamonds climate change nearly thirteen thousand years ago.
We also will tell about efforts grow crops with less water.
An image Milky Way from NASA's Chandra X-ray Observatory
The biggest structures universe galaxies.
These huge groups stars, gas and dust can be thousands light years across.
They also home an untold number planets.
Until recently, space scientists have thought our galaxy not very special.
It considered smaller member group galaxies.
Now, new measurements show our Milky Way galaxy bigger scientists once thought.
measurements reported meeting American Astronomical Society Long Beach, California.
Mark Reid astronomer with Harvard-Smithsonian Center Astrophysics.
He led international team studied Milky Way.
He said new measurements mean our galaxy fifty percent larger.
makes it least equal size largest galaxy our local group, Andromeda Galaxy.
Andromeda Galaxy big enough and near enough be seen unaided eye star group Andromeda dark night.
Mister Reid said: "No longer will we think Milky Way as little sister of Andromeda Galaxy our Local Group family."
The team made discovery measuring speed which our galaxy moving through space.
It found we traveling about two hundred seventy kilometers second. about fifteen percent faster scientists had believed.
The difference speed also means difference mass fifty percent.
Astronomers have always thought Andromeda Galaxy more massive the Milk Way because it believed have more stars.
Now, they will have rethink model.
The team measured number areas Milky Way where stars forming.
These areas, called cosmic masers, rich gas molecules have effect strengthening radio waves. radio waves measured when earth is two points opposite one another its orbit.
difference apparent position cosmic masers lets astronomers measure their distance from Earth.
The team used most powerful telescope world -- National Science Foundation's Very Long Baseline Array.
It really ten telescopes as distant from one another as Hawaii and United States Virgin Islands.
Instead of collecting light, twenty-five meter wide telescopes collect radio waves.
Their combined observing power gives Very Long Baseline Array ability see finest details any telescope world.
The new information also adds astronomers' understanding our galaxy's spiral arms.
Mister Reid noted that: "Our galaxy probably has four, not two, spiral arms gas and dust forming stars."
Recent observations had suggested two four spiral arms hold most the older stars Milky Way galaxy.
information gathered American space agency's Spitzer Space Telescope.
scientists believe huge object from space hit Earth about sixty-five million years ago.
They believe object crashed about time dinosaurs disappeared.
Some experts believe crash led death dinosaurs and other ancient creatures.
Now, group research scientists says it has found evidence similar event happened about thirteen thousand years ago.
It says explosion or explosions comets could explain disappearance animals and human beings who lived North America time.
Douglas Kennett University Oregon led team researchers. Their findings reported this month Sciencemagazine.
The researchers say report offers evidence one or more comets responsible sudden cooling period Earth's surface.
They say this ice age lasted about thirteen centuries. It called Younger Dryas. During this period, large North American animal species like mammoths and saber-toothed cats disappeared.
The researchers reported finding nanodiamonds several areas across North America.
These extremely small particles believed be linked comets.
Nanodiamonds produced under only very high temperature and high pressure event, such as comet striking Earth.
The researchers say nanodiamonds all found level soil thought to be about thirteen thousand years old.
Under this layer nanodiamonds, they found remains ancient animals, including those disappeared after Younger Dryas.
researchers also found tools used Clovis culture, group human beings who lived time.
tools also found under, but not above diamonds.
The researchers say their findings support idea huge explosion or explosions caused fire and pressure powerful enough kill off life Earth.
They say event this size could have resulted climate change.
They say it would have caused huge clouds dust block sunlight.
scientists dismiss comet theory.
They say there other reasons why the large animals and people from period disappeared.
Some scientists believe Clovis people died off because they killed too native animals.
Others say climate change caused Clovis people and animals die.
One argument against comet theory comet would have left large hole Earth's surface.
Others say evidence important, but more evidence needed confirm theory.
Scientists working develop crops can reduce amount water used for agriculture.
Almost sixty percent world's freshwater withdrawals from rivers, lakes and other water resources go toward irrigating fields.
Thomas "Tommy" Carter plant scientist North Carolina.
He works Agricultural Research Service United States Department Agriculture.
He leads Team Drought, group researchers five universities. They have been using traditional breeding methods develop soybeans can grow well under dry conditions.
Tommy Carter started working drought-resistant soybeans nineteen eighty-one.
His research has taken him as far as China, where soybeans have been grown thousands years.
Farmers United States, however, have grown soybeans only about century.
Tommy Carter says soybeans they grow most part genetically similar.
More differences could better protect crops against climate changes can reduce production.
Those changes include water shortages which could increase from rising temperatures Earth's atmosphere.
The Agriculture Department has soybean germplasm collection, collection genetic material passed from one generation next.
Members Team Drought studied more two thousand five hundred examples from collection.
They looked ones from Asia.
They searched germplasms that could keep plants from weakening and wilting during hot, dry summers United States.
Tommy Carter says they found only five. But these slow-wilting lines, he says, produce four eight bushels more normal soybeans under drought conditions.
yield depends location and environment.
The team now doing field tests. first breeding line expected be released this year use private seed companies and public soybean breeders.
Scientists also working other plants either use less water or use it better, or both. example, companies like Monsanto, DuPont and Syngenta developing corn with reduced water needs.
Monsanto expects be ready four years market its first corn seeds genetically engineered resist drought.
This SCIENCE NEWS program written Mario Ritter, Jerilyn Watson and Brianna Blake, who also our producer. I'm Barbara Klein.
And I'm Steve Ember. Join us again next week more news about science Special English Voice America.
English grammar test conversion by Akin Tosyali, ingilizce.com ogretmen2@ingilizce.com
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Comprehension Section.
Do NOT CHEAT No looking up! You would be only cheating yourself!
A study offers evidence that one or more comets were responsible for a sudden cooling period on Earth years ago.
This week, we will tell you about new measurements of our own galaxy.
The biggest structures in the universe are .
The measurements were reported at a meeting of the American Astronomical Society in Long Beach, .
Mark Reid is an astronomer with the Harvard-Smithsonian Center for .
He said the new measurements mean that our galaxy is percent larger.
The team used the most powerful in the world -- the National Science Foundation's Very Long Baseline Array.
Mister Reid noted that: "Our galaxy probably has , not two, spiral arms of gas and dust that are forming stars."
Many scientists believe that a huge object from space hit about sixty-five million years ago.
They believe the object crashed about the time disappeared.
It says an explosion or explosions by could explain the disappearance of many animals and human beings who lived in North America at that time.
They say this ice age lasted about centuries. It is called Younger Dryas.
They say it would have caused huge clouds of dust to block .
Many scientists dismiss the theory.
Almost percent of the world's freshwater withdrawals from rivers, lakes and other water resources go toward irrigating fields.
Farmers in the United States, however, have grown for only about a century.
For example, companies like Monsanto, DuPont and Syngenta are developing with reduced water needs.
English grammar test conversion by Akin Tosyali, ingilizce.com ogretmen2@ingilizce.com