Tampilkan postingan dengan label space. Tampilkan semua postingan
Tampilkan postingan dengan label space. Tampilkan semua postingan

Jumat, 02 April 2010

Who gets to be an Astronaut?


“That’s one small step for man, one giant leap for mankind.” Astronaut Neil Armstrong spoke these words on July 20, 1969, as he became the first person ever to step onto the Moon.
An astronaut is a space traveler. Astronauts fly into space on spaceships. They go where there is no air, higher than any airplane can fly. While they orbit (go around) Earth, they are weightless—they float and feel no gravity.

In Neil Armstrong’s day, all astronauts were military test pilots. Today, they’re as likely to be medical doctors, scientists, or engineers. Astronauts are still pretty unusual, however. Only a few hundred people have ever traveled into space.
Astronauts receive intense training. Then they may prepare a year or more for a specific mission. Pilots must be able to control all spacecraft systems and deal with emergencies. They may need to make course changes or dock with a space station. They must be able to land the spacecraft. Mission specialists are experts on particular experiments. Any astronaut may have to perform duties in a space suit outside the craft.

WHAT DO ASTRONAUTS DO IN SPACE?
Most space missions do not require human passengers. Robots and computers can do many jobs without needing people. But astronauts can perform some experiments in space that machines cannot. They can examine, for example, how flames burn or how crystals grow without gravity. Some experiments test the effects of spaceflight on human beings. Astronauts also launch and repair satellites, machines that orbit Earth. They also retrieve objects in space for return to Earth.
Astronauts may spend weeks or even months in space. Russian cosmonaut Valeriy Polyakov holds the record for the most consecutive days in space. He spent 438 days aboard the Mir Space Station in 1994 and 1995.

THE FIRST ASTRONAUTS
Russian astronauts are called cosmonauts. The first person in space was cosmonaut Yuri Gagarin. He made the trip in April 1961. The first American, a month later, was astronaut Alan Shepard. The first capsules that carried astronauts into space were barely large enough to hold their single passenger.

FLYING TO THE MOON
The Apollo program began during the 1960s. Apollo was an American project to send people to the Moon and back. There were three astronauts in each Apollo crew. Two of them explored the Moon while the third stayed aboard the main spacecraft.
Neil Armstrong, Buzz Aldrin, and Michael Collins were the crew of Apollo 11. This was the first mission to land on the Moon. Altogether, 12 astronauts walked on the Moon as part of the Apollo program. They performed experiments and brought back moon rocks for study. No one else has ever been to the Moon.

THE SPACE SHUTTLE
During the 1980s, the United States began to use space shuttles to send astronauts into space. Previously, spaceships could only fly once. Each trip required a new spaceship. Now, space shuttles can fly into space many times. They are launched from the top of a rocket, but they land like an airplane. Up to seven crew members can live aboard a shuttle.
The United States has begun research on a new type of reusable spaceship to replace the space shuttle. This new spaceship will use newer technology and will be cheaper to operate than the space shuttle. Someday astronauts may walk on the Moon again, or even travel to other planets!

Senin, 29 Maret 2010

What is the Milky Way?


WHAT IS THE MILKY WAY?
The Milky Way is a huge group of stars called a galaxy. There are billions of stars in the Milky Way. The Sun and all nearby stars are part of the Milky Way Galaxy. There are also huge clouds of gas and dust in between the stars. New stars form in the clouds of gas and dust.
The Milky Way Galaxy is shaped like a thick disk turning in outer space. There is a big bulge at the center of the disk. Curved arms spiral into the central bulge. The whole thing looks like an enormous whirlpool or pinwheel. Our Sun and solar system are in one of the whirlpool’s arms out toward the edge of the disk. That’s why the Milky Way looks like a band of light in the night sky. We’re looking at the edge of the disk instead of the round face.
The Milky Way turns slowly. Everything in the Milky Way orbits (circles) the center of the galaxy. It takes about 250 million years for our solar system to go once around the center of the Milky Way.
Astronomers think there might be an enormous black hole at the center of the Milky Way. A black hole sucks in everything around it. A black hole is invisible. Not even light can escape from a black hole.
The Milky Way is not the only galaxy in the universe. With powerful telescopes, we can see billions of other galaxies. Many of them are shaped like our own Milky Way, but some look like giant balls or strands of trailing stars.

HOW BIG IS THE MILKY WAY?
The Milky Way is huge. The entire Milky Way is about 100,000 light-years across. Astronomers measure great distances in light-years. One light-year is how far light travels in one year. Light travels extremely fast. A flash of light goes almost 6 trillion miles (10 trillion kilometers) in one year. That’s a 6 with twelve zeroes after it: 6,000,000,000,000! Even at that blazing speed, it would take a flash of light 100,000 years to cross the Milky Way.
The bulge at the center of the Milky Way is about 10,000 light-years thick. Our solar system is about 25,000 light-years from the center of the galaxy.