Blog #3, Worksheet #1.2, Milky Way Map

Create a map of the Milky Way

Our sun is located about 8.5 kiloparsecs or 27,000 light years away from the galactic center. The sun lies on the inner edge of the Orion Arm of the galaxy. Our galaxy is constantly rotating and the sun has an orbit of approximately 240 million years around the Milky Way.

The side view of the galaxy shows that there are a few distinct areas. Two of these are the thin and thick disks of the Milky Way. The disks are defined by their contents. The thin disk, located closer to the galactic center, is mostly made up of gas, dust, and newly formed stars and holds most of the star forming regions of the galaxy. The thin disk is only about 400 light years in height. As you move further away from the center, towards the thick disk, there are better-established stars. The further you move from the center, the older the stars become. Most stars in the thick disk are more than 10 billion years old. The thick disk is about 1,000 light years in height.

The halo is a roughly spherical region surrounding the galactic disks. It contains very little gas or dust and is mostly comprised of older stars, some extending back to 15 billion years old. The halo is home to many star clusters or loose groupings of stars the gravitationally attract one another. Much of the halo is not visible and is approximated based on the positions of various star clusters.

At the center of the galaxy is the nucleus or bulge. The bulge is nearly 10,000 light years across and made up of almost completely very old stars. The stars are most densely packed in the bulge.

Globular clusters are very dense, roughly spherical star formations. Clusters contain stars that formed around the same time and are thus often used to categorize stars and make presumptions about different characteristics of star groupings. Clusters often contain hundreds of thousands to millions of stars. Most of the stars in globular clusters are 10-15 billion years old.

The Small Magellanic Cloud (SMC) is a very small dwarf galaxy located very close to our Milky Way (only about 200,000 light years). It is only 7,000 light years in diameter and thus much smaller than the Milky Way. Some researchers believe the SMC used to be a regular spiral galaxy but was disrupted by the gravitational pull of the Milky Way and formed its current irregular shape.

The Large Magellanic Cloud is another galaxy very close to the Milky Way. The LMC is closer (153,000 light years) and larger (14,000 light years in diameter) than its partner the SMC. There is a bridge of gases across the sky that links the SMC and LMC. Like the SMC, the LMC is part of the local group of galaxies that are within observational distance of the Milky Way allowing us to study it very closely.

Sagittarius A*, abbreviated Sgr A*, is an incredible bright and dense light and radio source at the center of the Milky Way. Because of its properties, researchers believe it is the sight of a super massive black hole. Although the black hole is not visible, by observing the rotation of stars around the center of the Milky Way, there is now strong evidence that large black holes exist at the center of many spiral galaxies like the Milky Way.

The Orion Star Forming Region is a nebula about 1,300 light years away from Earth. It is made up of gas and various gasses that allow it to be a breeding ground for new stars in the galaxy.  The Orion Nebula is one of the closest and brightest nebulae and can be seen with the naked eye from Earth’s surface. The region is one of the most observed and studied entities in the galaxy.

An open cluster is a grouping of stars much more loosely joined the globular clusters. Nevertheless, open clusters are made up of thousands of stars formed from the same region around the same time and thus usually have very similar properties. The closest open cluster to the Sun is Hyades at only 153 light years away. The furthest discovered light cluster from our solar system (as of 2005) is the Berkeley 29 cluster, at over 48,000 light years away.

Work Used

http://www.astro.umass.edu/~myun/teaching/a100_old/images/MWmodelb.jpg

http://www.nasa.gov/mission_pages/sunearth/news/gallery/galaxy-location.html

http://www.universetoday.com/18256/where-is-the-sun/

http://csep10.phys.utk.edu/astr162/lect/milkyway/components.html

http://hubblesite.org/reference_desk/faq/answer.php.id=39&cat=galaxies

http://astronomy.swin.edu.au/cosmos/T/thick+disk

http://earthsky.org/clusters-nebulae-galaxies/the-small-magellanic-cloud

http://imagine.gsfc.nasa.gov/features/cosmic/nearest_galaxy_info.html

http://www.nasa.gov/mission_pages/chandra/multimedia/black-hole-SagittariusA.html

http://www.astronomynotes.com/chapter1/s2.htm

http://www.univie.ac.at/webda/recent_data.html