Stellar Evolution

Solar Composition Most stars in space have this composition: 74% hydrogen, 26% helium Fusion is the energy maker of the sun

Star Formation All stars begin as a stellar/solar nebula (cloud of gas and Dust) it is theorized the gas and dust formed as a result of another star’s collapse. A Protostar (new star) is formed from a nebula that collapses due to the force of gravity. After the nebula collapses fusion reactions begin and a new star is formed The life cycle of this star has already been determined due to the amount of mass it began with.

Star Life Cycle: You need to memorize! DRAW & LABEL

Life Cycle of a Star Protostar turns into a medium size star Medium sized star becomes a red giant with all of its matter squeezed together. It could do two things depending on its original mass Red Giant with low mass becomes a white dwarf (shines with a white hot light) it then becomes a black dwarf (dead star) OR If the Red Giant was very massive it can become a supernova and blow up, its core can become a neutron star (gives off pulses of energy) or a Black hole

Black Holes Begin as stars with mass 10x greater than our sun and have a short life span due to this mass After the supernova explosion the core that remains is so massive that (without fusion to support it) the core is swallowed by its own gravity.. It literally gets sucked inward on itself. Not even light can escape it, it swallows energy and matter like a vacuum cleaner Most are found due to their companion star, gases from the companion are pulled into the black hole and they give off a burst of x-rays before the matter falls into the black hole. There are new theories on black holes: hole to new universe, they form new stars, different dimension…

Hertzsprung-Russell diagram Don’t copy any of this… watch the video for an explanation The properties of mass, luminosity, temperature, color and diameter are closely related Each star has specific characteristics related to each of the properties 90% of all stars fall along main sequence

Basic Properties of Stars 1. Apparent Magnitude: Brightness as it appears on Earth 2. Absolute Magnitude: Amount of light a star actually gives off 3. Luminosity: is the actual energy output on the surface of a star per second, measured in watts

Positions and Distances of Stars Distance is measured in light years (distance light travels in 1 year = 6 trillion miles) To account for the motion of the Earth when viewing the stars, the apparent shift in position of the star is called parallax

Telescopes Refracting: first type, lenses brought visible light top a focus Reflecting: mirrors bring visible light to a focus All telescope goals are to bring radiation (wavelengths human eye can not detect) to a focus There are x-ray, infrared, ultraviolet, and gamma ray telescopes that only detect those parts of the electromagnetic spectrum Interferometry: process of linking separate telescopes together so they act as one. Very detailed! Space based telescopes: Hubble, Ultraviolet Spectroscopic Explorer, Chandra X-Ray Observatory, Compton Gamma Ray Observatory

Spectra: Draw a picture of each Spectrum: Visible light arranged according to wavelength. Used to find out the elements stars are composed of. Continuous: can be caused by a glowing gas or liquid, color band lengths indicate amount of element present Emission: bright lines at certain wavelengths indicate the element present Absorption: caused by different chemical elements being absorbed, dark lines indicate element present

Groups of Stars There are 88 constellations that were named by ancient people They appear to move around the poles They can be seen only during certain times of the year. They are not gravitationally bound together

Binaries Two stars that are gravitationally bound together Orbit a common center of mass Most appear as a single star Novas Nova is a star that increases in brightness in a few hours