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