Introduction to Astronomy

The Solar System This diagram shows the orbits of the planets around the Sun; the planets themselves are microscopic on this scale. Our solar system consists of the Sun and all the objects that orbit it, including the planets and their moons, and countless smaller objects such as asteroids and comets. s ations of nearby stars; stars would be atom-sized on this been greatly exaggerated for visibility. Zooming in on a tiny s us to the nearby stars of our local solar neighborhood . While now that many (perhaps most) stars are orbited by planets. On the 1-to-10 billion scale, you’d have to cross the United States to reach the nearest stars. One light-year becomes 1000 kilometers on the Voyage scale, so even the nearest stars are more than 4000 kilometers away, equivalent to the distance across the United States. Sun  Centauri Sun Procyon A, B Sirius A, B  Centauri A, B  Ceti  Eridani Proxima Centauri zoom factor ≈ 20,000 zoom factor ≈ 10,000 24 light-years ≈ 2 x 10 14 km 60 AU ≈ 10 10 km Even the Moon’s orbit around Earth is far too small to see on this scale. U r a n u s ’ s o r b i t N e p t u n e ’ s o r b i t 1 2 l i g h t - y e a r s 6 l y The Earth–Moon System This diagram shows Earth, the Moon, and the Moon’s orbit to scale. We must magnify the image of our solar system another 10,000 times to get a clear view of our home planet and its constant companion, our Moon. Earth You are here. The physical sizes of human beings and even the planet on which we live are almost unimaginably small compared to the vastness of space. Yet in spite of this fact, we have managed to measure the size of the observable universe and to discover how our lives are related to the stars. A water molecule is a million times smaller than a grain of sand. On the 1-to-10 billion scale, you would be slightly smaller than a water molecule. This photo of the Hubble Ultra Deep Field shows galaxies visible in a patch of sky that you could cover with a grain of sand held at arm’s length. These comparisons show how tiny we are compared to the solar system in which we live, but we’ve only just begun to cover the range of scales in the universe. • To appreciate the size of our galaxy, consider that the stars on this scale are like grapefruits thousands of kilometers apart, yet there are so many that it would take you thousands of years to count them one-by-one. • And with more than 100 billion galaxies, the observable universe contains a total number of stars comparable to the number of grains of dry sand on all the beaches on Earth combined. Moon Earth zoom factor ≈ 40 800,000 km 13,000 km The Moon is the only world besides Earth upon which humans have ever stepped.

Courses in PHYS

Popular Documents from Concordia University

Concordia University