Galaxies and Stars 8.E.4A.1 Obtain and communicate information to model the position of the Sun in the universe, the shapes and composition of galaxies, and the measurement unit needed to identify star and galaxy locations

Galaxies Galaxies are made up of gas, dust, and billions of stars Galaxies have different shapes Elliptical Spherical or flattened disks Spiral A nucleus of bright stars and 2 or more spiral arms Irregular No definite shape Shapes of Galaxies can change over time as a result of collisions with other galaxies and evolution of galaxies themselves

The Sun and the Milky Way The Sun is a star in the Milky Way galaxy Milky Way is a spiral galaxy The Sun is located approximately 2/3 of the way from the center of the Milky Way

Galileo Galilei Born on February 15, 1564 in Pisa, Italy “Father of Modern Science” Modernized physics and astronomy Discovered all objects fall at the same rate Created a hydrostatic balance for measuring tiny objects Supported the Heliocentric Theory Developed a telescope of his own, used it to observe the moon’s surface features, Venus revolved around the Sun, and Jupiter’s moons revolved around Jupiter not the Earth providing evidence against the Geocentric Theory

Tycho Brahe Born December 14, 1546 Danish astronomer and alchemist Precise and comprehensive astronomical and planetary observations which influenced future discoveries (Planetary Laws of Motion) Did not use a telescope for his astronomical observations Discovered the variation of the Moon’s longitude for the lunar theory

Johannes Kepler Born December, 27, 1571 From the Holy Roman Empire (modern day Germany) 1596, a math teacher Worked with Tycho Brahe and seceded him upon Brahe’s death Founded the 3 Laws of Planetary Motion Using Brahe’s data, Kepler discovered that the orbit of Mars was an ellipse Defended the Heliocentric Theory

3 Laws of Planetary Motion The Orbits of the Planets are Ellipses, with the Sun at one focus of the ellipse The line joining the planet to the Sun sweeps out equal areas in equal times as the planet travels around the ellipse The Ratio of the squares of the revolutionary periods for 2 planets is equal to the ratio of the cubes of their semimajor axes

Light Light travels 9.46 x 1012 Km (5.88 x 1012 miles) in a year Light from the Sun travels 8 minutes before reaching us Light from the Andromeda galaxy (closest galaxy to the Milky Way) was emitted 2.5 million years ago (before the first humans) The further away a light is, the older the light is when we see it.

Parallax Method astronomers use to determine how far away stars are Stars seem to shift in position when viewed from Earth because of Earth’s revolution around the Sun Parallax shift Astronomers use the diameter of Earth’s orbit to determine the parallax angle across the sky

Expanding Universe 8.E.4A.2 Construct and analyze scientific arguments to support claims that the universe began with a period of extreme and rapid expansion using evidence from the composition of stars and gases and the motion of galaxies in the universe

The Universe The Universe is composed of matter and energy All of the matter in the universe now was in the universe when it formed

Evidence Evidence to Support Scientist Claims Looking for the oldest star Nebula (gas and dust) exist in space and are remnants from the formation of the universe Stars undergo a life cycle, amount of hydrogen gas in the star changes therefore affecting the brightness and color of the star https://www.youtube.com/watch?v=8FPVIV-LzYM

Measuring the rate of expansion of the universe Astronomers determined the galaxy is expanding based on the color of light emitted from galaxies and stars As the Universe expands and galaxies move apart, the wavelength of light emitted from those galaxies is stretched which shifts the light toward the red end of the spectrum (red-shift). More distances or faint a galaxy, the more rapidly it is moving away from Earth https://www.youtube.com/watch?v=o3G_eaSaLck https://www.youtube.com/watch?v=y5tKC3nEx2I