StarsStarsPresented by: Diana Presented by: Diana

SforzaSforza

What is a star?What is a star?

A star is a ball of gas A star is a ball of gas held together by its own held together by its own

gravity.gravity.

• Stars are made up of huge clouds of dust and gas collapse under gravitational forces, forming protostars. These young stars undergo further collapse, forming main sequence stars.

• Stars expand as they grow old. As the core runs out of hydrogen and then helium, the core contacts and the outer layers expand, cool, and become less bright

When a star reaches When a star reaches 27,000,000°F, Nuclear 27,000,000°F, Nuclear

Fusion beginsFusion begins

Nuclear Fusion is an Nuclear Fusion is an atomic reaction in atomic reaction in

which many nuclei (the which many nuclei (the centers of atoms) centers of atoms)

combine together to combine together to make a larger onemake a larger one

A star goes through a phase A star goes through a phase called the Main Sequence.called the Main Sequence.

In there, there is a central In there, there is a central band of stars which are band of stars which are formed after the stars formed after the stars

energy is converted from energy is converted from Hydrogen to Helium.Hydrogen to Helium.

The sun…The sun…

…is a star

Other stars and their distance from Other stars and their distance from the earth in light yearsthe earth in light years

Sirius 8.6Canopus 74Capella 41Rigel 900Vega 25Deneb 1,500Proxima Centauri 4.3

Life span of a starLife span of a star

•A star stays in main sequence for about 10 billion years.

• After that, the hydrogen fuel is depleted and the star begins to die.

A star is part of a galaxyA star is part of a galaxy

What is a galaxy???

A galaxy is a huge group of stars, dust, gas, and other celestial bodies bound together by gravitational forces.

• They can be spiral.

• They can be elliptical.

• They can be irregularly shaped.

Milky Way GalaxyMilky Way Galaxy

Stars also make Stars also make CONSTELLATIONSCONSTELLATIONS

• A constellation is a group of stars that, when seen from Earth, form a pattern.

•The stars in the sky are divided into 88 constellations.

WHY DO STARS TWINKLE?WHY DO STARS TWINKLE?

• Stars twinkle when we see them from the Earth's surface because we are viewing them through thick layers of turbulent (moving) air in the Earth's atmosphere.

• For more information visit…Star Classification - Zoom Astronomy