Relative Sizes of Astronomical Bodies

What is astronomy? astronomy (ə ˈ str ɒ nəm ɪ )n1. (Astronomy) the scientific study of the in dividual celestial bodies (excluding the earth) and of the universe as a whole. Branches include astrometry, astrodynamics, cosmology, and astrophysics

Where Are We in the Great Scheme of Things? The Earth is a planet that revolves around a star that we have named, the Sun whose gravitational pull keeps the Earth and 7 other planets revolving around it. "My Very Educated Mother Just Served Us Nine Pizzas" According to the new definition, a full-fledged planet is an object that orbits the sun and is large enough to have become round due to the force of its own gravity. In addition, a planet has to dominate the neighborhood around its orbit. Pluto has been demoted because it does not dominate its neighborhood. Our solar system is a little less than a light year across—what is a light year?

Light year A light year is the distance that you would travel if ‘riding’ on a light beam for a year. Light travels at an incredible 300,000 kilometers (186,000 miles) per second. If you could travel at the speed of light, you would be able to circle the Earth’s equator about 7.5 times in just one second! At that speed, you could go, round trip, from NYC to LA, 38 times in 1 second. One light-year = 9.5 trillion kilometers (5.88 trillion miles). We do not know of anything faster in the universe.

gal·ax·y (g l k-s ) Any of numerous large- scale aggregates of stars, gas,and dust that constitute the universe, containing an avg of 100 billion solar masses ranging in diameter from 1,500 to 300,000 light-years. Also called nebula. Any of a vast number of star syste ms held together by gravitational a ttraction in an asymmetric shape, an irregular galaxy or, more usually, in a symmetrical shape, a regular galaxy, which is either a spiral or an ellipse. Former names : island universe, extragalactic nebula

The Milky Way Galaxy The Milky Way galaxy is a barred, spiral galaxy which we only figured out we lived in a bit over 100 yrs ago The Milky Way is 100,000 light years across * There are around 200 BILLION stars in our galaxy We are on one edge of one an outer spiral arms * If we said that light travels at 186k miles per second, how many miles does our galaxy width represent?

100,000 years x days/year x 24 hours/day x 60 min/hr x 60 sec/min x miles/sec…….= e+17 miles

The Milky Way is in a cluster of gravitationally attracted galaxies that we call the “Local Group” The Local Group is in an irregular group of clusters of galaxies that we call the “Virgo Supercluster” that is 100 to 200 million light years in diameter. We think that superclusters may be arranged into larger structures called “Walls” which are over one billion light years long To wrap it all up….the UNIVERSE, all things that we can SEE in space contains over 10 billion trillion stars arranged in about 100 billion galaxies and is estimated at 156 billion light years in diameter We think that we are at the center but we really have no clue.

We Will….. There are many different phenomena to discuss ‘out there’ but we must start small lest we get overwhelmed by the huge amount that we both know and don’t know. We will begin with an overview of the History of Astronomy….why it was considered a spiritual matter by many cultures….why it was so important for day to day living …what were some of the landmark events and important figures along the way…and where we are now We will move from there to explore our solar system and of our movement within it. These, of course have much to do with our weather, seasons, tides …. We will be able to view the night sky and identify our immediate neighbors We will learn how to map the night sky and locate constellations and members in them We will learn about many objects in the heavens as pulsars, neutron stars, anti- matter, black holes, nebula, comets, meteors…. And how they act. We will look at the birth and death of stars We will look at theories of the space-time continuum and the idea of time travel/’worm holes’….. We will look at the amazing work being done with space travel/International space station and all of the cutting edge work on Mars—I hope to bring in friends/scientists from Nasa who can share