Stars & Galaxies

Life Cycle of a Star

NEBULA _____________: A dense cloud of gas and dust

The nebula begins to contract due to __________ and the pressure and temperature increase and becomes a ________________. gravity PROTOSTAR

When the temperature gets hot enough, _______________ begins and a _______ ____________ star is born. fusion MAIN SEQUENCE

A star loses ____________during fusion as energy is released A star loses ____________during fusion as energy is released. This decreases the star’s gravity. A star will expand, becoming a ___________ ____________, when the outward force of ________________ is greater than the inward force of ______________. mass RED GIANT fusion gravity

As the fuel runs out in a star, _________ slows down As the fuel runs out in a star, _________ slows down. When the ______________ force of fusion is less than the ____________ force of gravity, the star will shrink in size, becoming a _________ ____________. fusion outward inward WHITE DWARF White Dwarf

SUPERNOVA explosion A ___________________ is an _________________ that marks the end of a very massive star’s life. When it occurs, the exploding star can outshine all of the other stars in the galaxy in total for several days and may leave behind only a crushed core.

The life cycle of stars depends on their mass. Small and medium stars become __________________ once they die. Larger stars become novae and die as: ____________ BLACK DWARVES NEUTRON STARS A neutron star is an imploded core of an exploded star made up almost entirely of neutrons. A teaspoon of their material would weigh more than all of automobiles in the U.S. together The most massive stars become supernovae and die as: ______________________ BLACK HOLES A black hole is an extremely massive remnant from which light can not escape http://chandra.harvard.edu/photo/2004/rxj1242/index.html

Why do larger/hotter stars burn their fuel faster and live shorter lives than the Sun? Large, more massive stars have much more _____________ than the sun. This greater internal pressure causes fusion reactions to occur __________. This causes the largest stars to burn their fuel, and eventually run out, much more ______________. Larger stars live shorter _____________. Bigger stars are brighter and hotter due to the rapid rate of __________. gravity quickly quickly lives fusion

Where do we get the elements? All stars spend the majority of their lives fusing __________ into ________________: the main sequence. hydrogen helium When all of the __________ in the central regions is converted to helium, the star will begin to “burn” helium into _______________. hydrogen carbon sun Stars heavier than about 5 times the mass of the ______ can do this with no problem: they burn _____________, and then _______________, and then _____________, _______________, silicon, and so on…until Iron. hydrogen helium carbon oxygen

energy Iron is the lightest element that doesn’t release __________ when you attempt to fuse it together. You actually end up with less energy than you started with! So instead of generating pressure to hold up the outer layers, the iron fusion actually takes it out of the core. Thus, there is nothing left to combat ________________ from the outer layers. The result: ___________! gravity collapse This implosion (___________) happens very, very quickly: about 15 seconds. During the collapse, the nuclei in the outer parts of the star are pushed together, so close that elements heavier than __________ are formed. supernova iron

Measuring Distances in Space Parallax Astronomical Unit Light Year

Galaxies Galaxy: A large group of stars, gas, and dust that is held together by gravity 3 types of galaxies Spiral, Elliptical, and Irregular

Galaxies Have spiral arms that wind outward from the center, resembling a pinwheel. Why can astronomers see the spiral arms of the Andromeda Galaxy more clearly than the spiral arms of the Milky Way Galaxy? Spiral Galaxy

Galaxies Have billions of stars but little gas and dust Typically filled with old stars because without gas and dust, new stars are no longer forming Elliptical Galaxy

Galaxies Elliptical Galaxy

Galaxies Have an irregular shape Typically smaller than elliptical and spiral galaxies Have bright, young stars and lots of dust and gas to form new stars Irregular Galaxy

Galaxies Irregular Galaxy

Have your ever looked up into the night sky and scanned the stars for the Greek hunter Orion? Orion is a ___________ -- a pattern of stars that represents mythological characters. What appears as groups of stars that are close together are actually great distances apart. Each star has a specific brightness and a location that can be calculated from Earth constellation

Optical Telescopes A ____________ uses a lens to collect and focus light. Light enters through a lens. The light is bent toward a single point called the focal point. Because the light is bent, the image forms upside down. An eyepiece lens magnifies the upside-down image for viewing. The telescope can be focused by changing the distance between the two lenses. Refracting telescope

Optical Telescopes A ____________ uses a curved mirror instead of a lens to collect and focus light. N some models, one end of the main tube is open. At the other end of the tube is a large, curved mirror. The large mirror collects, reflects, an focuses light to a small, flat mirror near the open end. The small mirror reflects the light to an eyepiece lens Reflecting telescope