Stars

Nebulae A nebula is a cloud of dust, hydrogen gas and plasma. The material clumps together to form a protostar. This is the first stage in the star life cycle. Nebulae often create star-forming regions, such as the Eagle Nebula, also called the Pillars of Creation.

Cat’s Eye NebulaAnt Nebula

Protostar – a newborn star

Main Sequence Star (our Sun) 90% of all stars, including our Sun, are main sequence stars (average stars) range from very hot and bright to cool and dim

Red Giant When a middle aged star begins to die, the temperature near the core rises. The star expands. This will happen to our Sun in about 5 billion years.

A red giant runs out of energy and collapses. It becomes a white dwarf, a small and dense star. A white dwarf is the core of the original star. It is very hot and takes a billion years to cool off. White Dwarf

Black Dwarf - a white dwarf that cooled, lost its energy and no longer gives off light. It is a black object in space.

Our Sun’s Life Cycle Our Sun is an average star. Protostar Main Sequence Star Red Giant White Dwarf Black Dwarf

Giant Stars are 10 to 100 times larger in diameter than our Sun are therefore more luminous (brighter).

Supergiant Stars are more than 100 times the diameter of our Sun. They are more luminous than giant stars. They are relatively cool stars but they are bright because they are so large. Betelgeuse is a supergiant star.

Supernova – collapse of the core of a red giant that produces a shock wave that blasts the star’s outer layers into space. ALL stars become Red Giants but ONLY Giant Stars and Supergiant Stars go Supernova. This is what remains after a supernova explosion.

Neutron Star – the core left behind after a supernova may be only a few dozen miles across but a sugar-cubed-size piece would weigh 1 billion tons on Earth. They have so much gravity that if you dropped a marshmallow on a neutron star, the impact would generate as much energy as an atom bomb!

Pulsar – a neutron star that spins very fast and emits bursts of radio waves. A supernova can result in either a neutron star OR a pulsar. The just discovered blue pulsar here is a “dead” star beaming out more energy than 10 million suns!

ONLY the most massive stars become black holes when they die. Quasars are galaxies with black holes at their center. The Milky Way Galaxy has a black hole at its center named Sagittarius A*. Black Hole Here is a picture of a black hole.

Black Hole To escape Earth’s gravity you need to accelerate at 7 miles per second (12 times faster than a bullet). We have been able to do this with rockets since The gravity of a black hole is so strong that even light can’t escape. The speed of light (186,282 miles per second) is too low!

Life Cycle of a Giant StarSupergiant Star Protostar ▪ Protostar Giant Star ▪ Supergiant Red Giant ▪ Super Red Supernova Giant Neutron Star ▪ Supernova or Pulsar ▪ Black Hole

What determines what a new star will become when it dies?

Hertzsprung- Russell Diagram Classifies stars based on their absolute magnitude and surface temperature. Absolute magnitude is how bright a star would be if all of the stars were the same distance from Earth. Surface temperature is related to a star’s color.