ASTR 100 Ball State Spring 2016 MWF
ASTR 100 Ball State Spring 2016 MWF ASTR 100
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This 4 page Class Notes was uploaded by Sarah Gardner on Saturday January 23, 2016. The Class Notes belongs to ASTR 100 at Ball State University taught by Dr. Bob Berrington in Fall 2016. Since its upload, it has received 39 views. For similar materials see Introduction to Astronomy: Solar System and Beyond in Astronomy at Ball State University.
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Date Created: 01/23/16
ASTR 100 Section 2, Spring 2016, MWF Section 1 The Cycles of the Sky Continued 1/18/16 MLKJ day, no school 1/20/16 Wednesday Placement of our Solar System in the Milky Way We are found in the Orion “arm’ of the spiral of the Milky Way When you are looking at the constellation Sagittarius, you are looking toward the center of the Galaxy Center of the Galaxy The center of the Galaxy is an extremely dense stellar region It has a massive black hole which all of the stars in the region orbit The black hole is 10 light days across, which would be 4 million times the mass of the sun Scale of the Universe Cont. Our galaxy is in a cluster of other galaxies, known as a local group o 50 known members in our local group (which is 45 light years across) o There is one other similar sized galaxy in our local group Andromeda Nebula (also known as Andromeda Galaxy) Andromeda Galaxy o Furthest celestial object that can be seen with the naked eye (2.0x10^6 ly distant) o Viewed from Earth, it can be found in the Andromeda constellation o It is the nearest big galaxy in the local group; about the same mass as Milky Way o Has many satellite galaxies Galaxies are commonly in clusters o Some of the galaxies’ structures are spiral, others look like “fuzzy patches” o Clusters can have thousands of members with different sizes and masses Coma Cluster of Galaxies o Most of the mass in this cluster is not visible (much like ours) We can use other wavelengths (Xrays) to see the distribution of intracluster gas [Side note: light is only produced by nondark matter] We can see with the xrays the mass that need to be there in order to hold the cluster together Outskirts of the Virgo Cluster The Virgo Cluster is 2.0x10^7 pc (parsecs) away. We are on the very edge of this cluster There is a very large central galaxy in the Virgo cluster, orbited by other galaxies The cluster contains M87 o M stands for “Meziay” The man who discovered it He dedicated much research to objects in the sky that were “not comets” or “not planets” He wasn’t sure what they were, but we later discovered that many of them were galaxies th o 87 stands for “87 entry” in Meziay’s log 1/22/16 Friday Scale of the Universe Cont. The universe is expanding gradually o Cause: dark energy Dark energy is an antigravity (opposes gravity) Gravity is what holds the universe together The pressure of antigravity is always increasing o Dark Matter The total matter in the universe that is not dark is 4% Can’t be seen because it doesn’t interact with the electromagnetic spectrum We don’t know exactly what it is It has mass, but is not luminous Matter that is not luminous= a Macho Superclusters o Several clusters grouped together o Organized into “veins” in the universe via gravity (pulling toward each other to form these paths). Units A number is meaningless without a unit o “I’ll give you five” 5 what? Dollars? Pennies? Cats? o They are often used in shorthand (abbreviations) m=meters g=gram s=second in=inches; ft=feet (rarely used) o Unit Systems MKS = meters, kilograms, seconds Favored by physicists CGS = centimeters, grams, seconds Favored by astronomers Luminosity is always measured in CGS o Prefixes (don’t need to know all – be familiar up to the 9 power of ten) Angular Units Degrees 1 rotation = 360 degrees (abbrev º) 1º = 60 minutes (abbrev. ‘) 1 minute = 60 seconds (“) (3600”= 1º) Radians 1 rotation = 2 π radians = 360 º 1 radian = 57.3 º Right Angle = 90 º = π/2 radians 3.1415…= π