T HE U NIVERSE B EYOND By; Amber Self

S TARS o An Astronomer studies starlight. o Stars are classified by 3 colors and temperature. o Blue (Rigel) is hot, yellow is medium, and red (Betelgeuse) is cool.

C OMPOSITION OF STARS The rainbow colors that are produced when white light passes through a prism spectrograph. A spectrograph is a prism shaped object that helps to show spectrum. A continuous spectrum is when the spectrum shows off all of the colors. The surface of a star gives off a continuous spectrum but the light we se passes through the stars atmosphere.

C LASSIFYING STARS Stars were once classified by letters such as type A, stars that had very noticeable hydrogen patterns, and the rest of the stars were classified as type B stars. Stars are now classified by temperature. Class Color surface temp.( C) elements ex. Of stars OBlue above 30,000 helium 10 lacerate BBlue-white 10,000-30,000 helium & hydrogen Rigel, Spica A blue white 7,000-10,000 hydrogen Vega, Sirius F yellow-white 6,000-7,500 hydrogen canopus G yellow 5,000-6,000 calcium the sun K orange 3,000-5,000 calcium arcturus M Red less than 3,500 molecules Betelgeuse

H OW B RIGHT IS THAT STAR ? How bright a star looks or appears is called apparent magnitude. Astronomers use a star’s apparent magnitude and it’s distance from Earth to calculate its absolute magnitude. Absolute magnitude is the actual brightness of a star.

D ISTANCE TO THE STARS Astronomers use light years to find the distance a star is from Earth. A light year is the distance that light travels in one year. Light travels about 9.5 trillion kilometers a year. Using parallax and simple trigonometry astronomers can find the actual distance to the stars that are close to earth. Parallax is an apparent shift in the position of an object when viewed from different locations

T HE H-R D IAGRAM The H-R diagram is a graph showing the relationship between a star’s surface temperature and it’s absolute magnitude. The main sequence is a diagonal pattern of stars on the H-R diagram. The red giant is a star that expands and cools once it runs out of hydrogen fuel. The white dwarf is a small, hot star near the end of its life otherwise known as the leftover center of an old star.

W HEN STARS GET OLD Supernova is basically the death of a large star by explosion. A neutron star is a star in which all the particles have become neutrons; the collapsed remains of a supernova. If a neutron star is spinning it’s called a pulsar. A black hole is an object with move than three solar masses squeezed into a ball only 10 km across whose gravity is so strong that not even light can escape.

G ALAXIES o Galaxies are large groupings of stars in space. o Spiral Galaxies have a bulge at the center and very distinctive spiral arms. o Elliptical Galaxies have very bright centers and very little dust and gas. o Irregular Galaxies are galaxies that don’t fit into any other class.  To the right is an example of a spiral galaxy.

C ONTENTS OF GALAXIES o Nebulas are giant clouds of dust and gas. o Nebula is also the Latin word for ‘cloud’. o Globular Clusters are groups of older stars. o There may be 20, ,000 stars in average in a globular cluster. o Open Clusters are groups of stars that are usually located along the spiral disk of a galaxy. o A Quasar is a star-like source of light that is extremely far away. o A Quasar is also one of the most powerful energy sources in the universe.