The distribution of Matter in Space The formation of a star, Life and Death video To Infinity and beyond!! To Boldly go where no man has gone before !

A star is a hot, glowing ball of gas (mainly hydrogen) that gives of tremendous light energy.  Vary greatly in their characteristics  Colour of stars depend on its surface temperature  Very hot stars look blue  Cooler stars look red

The Birth of a Star A star has a life cycle as well Form in regions of space where there are huge accumulation of gas and dust called nebulae  Each nebula is composed of about 75% hydrogen and 23% helium The attraction of gravity acting between the atoms of gas and grains of dust causes the nebula to start collapsing into a smaller, rotating cloud of gas and dust As more material is drawn into the spinning ball  Mass of the core increases  Temperature climbs

If the core gets hot enough, it will start to glow. Called a Protostar As the process of “star-building” continues, the interior gets hotter and hotter When the core reaches degrees celcius – fusion takes place and a star is born.

Life and Death of Stars Most stars spend most of their lives in this main sequence, converting hydrogen to helium When the hydrogen has been used up, the stable-state star shrinks in size,  helium starts fusing to carbon Gravity causes the star to contract, further nuclear reactions occur, leading to expansion of the outer layers

Star becomes larger,  turning into a red giant (if it is a sun – like star)  or turning into a red super- giant (if it is a massive star) The final stage in a star’s life occurs when the fusion reaction stops

Sun-like star, temperature is no longer hot enough to keep the reaction going it shrinks gradually becoming a white dwarf  Eventually fading completely until it evolves in to a cold, dark black dwarf

Massive star, lack of heat input into the core, gravity causes the star’s core to collapse rapidly The collapse causes the outer part of the star to explode, in an event known as a supernova  If the star is not destroyed entirely by the explosion, the core is left as a neutron star or a black hole Neutron star = rapidly spinning objects about 30 km in diameter Black hole = highly dense remnant of a star in which gravity is so strong that not even light can escape

Star Groupings Constellations are the groupings of stars we see as patterns in the night sky.  Officially there are 88 constellations recognized by the International Astronomical Union Asterisms are unofficial star groupings  One of the most famous “the big dipper”

Galaxies Is a grouping of millions or billions of stars, gas, and dust. Held together by gravity Three types Spiral galaxy: (milky way) we live in Elliptical Irregular Travel the Universe (15 min) Crash Course on Galaxies (12 min)