Chapter 21 Section 4 Star Systems and Galaxies

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Chapter 21, Section 4 Star Systems and Galaxies Based on Prentice Hall Textbook by

Chapter 21, Section 4 Star Systems and Galaxies Based on Prentice Hall Textbook by Rusty Sturken May, 2009 Background imaghttp: //mayda. com/astro/Img/M 31_LRGB-03 C-1 k. jpge from http: //mayda. c

Star Systems • More than half of all stars are members of groups of

Star Systems • More than half of all stars are members of groups of two or more stars. Our sun is not. • Star systems with two stars are called double stars or binary stars. • Star systems with three stars are called triple stars.

Binary Systems • Often astronomers can detect the presence of a star in a

Binary Systems • Often astronomers can detect the presence of a star in a binary system without seeing it, they can tell it is there by observing the effect of its gravity on the second star • Sometimes with binary stars, one star blocks the light from the other star and the system is called an eclipsing binary

Eclipsing Binary http: //calgary. rasc. ca/images/Algol_Eclipsing. gif

Eclipsing Binary http: //calgary. rasc. ca/images/Algol_Eclipsing. gif

Planets around other stars • Scientists have discovered planets around stars by observing how

Planets around other stars • Scientists have discovered planets around stars by observing how a star “wobbles” very slightly back and forth • Over 300 “extrasolar” planets have been found according to Space. com • Most of the extrasolar planets found so far are massive gas giants with large influence on their star’s gravity.

Saturday, April 2 nd, 2005 Astronomers Photograph Extrasolar Planet “First ever photo of an

Saturday, April 2 nd, 2005 Astronomers Photograph Extrasolar Planet “First ever photo of an extrasolar planet, a Jupiter-sized gas giant. ” http: //www. utahskies. org/image_library/deepsky/misc/top. extrasolar. planet. photo. jpg

Where to look for Earthlike planets • The so-called "habitable zone" around a star

Where to look for Earthlike planets • The so-called "habitable zone" around a star is a belt in which liquid water could exist on the surface in lakes, rivers or oceans. Too close to its stellar parent and a planet would be too hot, while an orbit too far out would yield only a frozen world, NASA scientists have said. Quote from http: //www. space. com/scienceastronomy/090416 -kepler-first-images. html

Galaxies • Galaxies are giant structures that contain hundreds of billions of stars, Oh,

Galaxies • Galaxies are giant structures that contain hundreds of billions of stars, Oh, by the way…There are billions of galaxies in the universe • Galaxies contain single stars, double stars, star systems and lots of gas and dust between the stars. • Astronomers classify most galaxies into three main categories: – spiral galaxies, – elliptical galaxies, – irregular galaxies

Spiral Galaxies • Spiral galaxies have arms that spiral outward, like pinwheels http: //zoo

Spiral Galaxies • Spiral galaxies have arms that spiral outward, like pinwheels http: //zoo 1. galaxyzoo. org/images/ tutorial/example_face_on_spiral. jpg http: //www. spacetoday. org/images/Hubble/ Hubble. Beauty/NGC 1512 Barred. Spiral. Galaxy. jpg

The Milky Way • Our solar system exists in the Milky Way galaxy, and

The Milky Way • Our solar system exists in the Milky Way galaxy, and is about 25, 000 lightyears away from the center of the Milky Way • Our solar system is about two-thirds of the way out on one of the spiral arms of the Milky Way • We can’t see the center of the Milky Way due to the massive cloud of gas and dust between the sun and the center

The Milky Way http: //abyss. uoregon. edu/%7 Ejs/images/milky_way_large. jpg

The Milky Way http: //abyss. uoregon. edu/%7 Ejs/images/milky_way_large. jpg

The Milky Way http: //www. crystalinks. com/galaxymilkyway. jpg

The Milky Way http: //www. crystalinks. com/galaxymilkyway. jpg

Elliptical Galaxies • Elliptical galaxies look like flattened balls • Have little gas and

Elliptical Galaxies • Elliptical galaxies look like flattened balls • Have little gas and dust between the stars so new stars can not form – Ellliptical galaxies only contain old stars http: //photojournal. jpl. nasa. gov/ jpeg. Mod/PIA 08696_modest. jpg

Elliptical Galaxy http: //zuserver 2. star. ucl. ac. uk/%7 Eidh/apod/image/0406/m 87_cfht. jpg

Elliptical Galaxy http: //zuserver 2. star. ucl. ac. uk/%7 Eidh/apod/image/0406/m 87_cfht. jpg

Irregular Galaxies • Some galaxies don’t have a regular shape, they are called irregular

Irregular Galaxies • Some galaxies don’t have a regular shape, they are called irregular galaxies • The Large Magellanic Cloud is an irregular galaxy http: //www. nasa. gov/images/content/ 159426 main_image_feature_666_ys_4. jpg

Irregular Galaxy http: //starchild. gsfc. nasa. gov/Images/Star. Child/universe_level 2/ngc 6822. gif

Irregular Galaxy http: //starchild. gsfc. nasa. gov/Images/Star. Child/universe_level 2/ngc 6822. gif

Irregular Galaxy http: //www. astro. utu. fi/news/img/RGB_bird_idl 600. jpeg

Irregular Galaxy http: //www. astro. utu. fi/news/img/RGB_bird_idl 600. jpeg