SPACE

Binary star defined:
A binary star is a pair of stars revolving around a common center of gravity. About 50% of all stars are members of either binary star systems or multiple star systems which contain more than two stars.

Pulsar defined:
A pulsar is a rotating neutron star that gives off sharp regular pulses of radio waves at rates ranging from 0.0001 to 4 seconds. A pulsar is formed by the collapse of a star with 1.4 times the mass of the sun.

Black hole defined:
When a star with a mass greater than about four times that of the sun collapses even the neutrons cannot stop the force of gravity, there is nothing to stop the contraction and the star collapses forever. The material is so dense that nothing – not even light – can escape.

The Milky Way defined:
The Milky Way is a hazy band of light that can be seen encircling the night sky. This light comes from the stars that make up the Milky Way galaxy, the galaxy to which the Sun and the Earth belong. Galaxies are huge systems of stars separated from one another by largely empty space. Astronomers estimate that the Milky Way galaxy contains at least 100 billion stars and is about 100,000 light years in diameter.

The Big Dipper defined:
The Big Dipper is a group of seven stars which are part of the constellation Ursa Major. The Big Dipper is almost always visible in the Northern Hemisphere. It serves as a convenient reference point when locating other stars; for example, an imaginary line drawn from the two end stars of the Dipper leads to Polaris, the North Star.

The North Star defined:
If an imaginary line is drawn from the North Pole in space, there is a star called Polaris, or the North Star, less than one degree away from the line. As the Earth rotates on its axis, Polaris acts as a pivot-point around which all the stars visible in the Northern Hemisphere appear to move, while Polaris itself remains motionless.

The star closest to the Earth:
The sun, at a distance of 93 million miles (150 million kilometers), is the closest star to the Earth.

How hot is the Sun?
The center of the sun is about 27,000,000°F (15,000,000°C). The surface, or photosphere, of the sun is about 10,000°F (5,500°C).

Light from the Sun to Earth takes how long?
Sunlight takes about 8 minutes and 20 seconds to reach the Earth, traveling at 186,282 miles (299,792 kilometers) per second.