By: Mike Malatesta Introduction to Open Clusters

goals  Study the formation of open clusters  Find the chemical make-up of certain open clusters view on the techmaun telescopes  Study rotation of open clusters?

Formation - Dust and gas clouds (giant molecular cloud many thousands times the mass of the Sun) -Cloud too big to collapse into one star -same chemical composition -approximately the same age - Many different sizes from solar masses - Can collapse because of shock waves from supernovae. - Approx. 1 every 1000 years forms in the MW

Characteristics  All stars in the cluster are the same distance from Earth because their distances from each other are small when compared.  Usually dense core surrounded by smaller stars.  Core typically 3-4 light years across  Stars can extend to 20 light years from the center  1.5 stars per cubic light year

Classification  Tumpler scheme  3 part designation  I-IV (strong or weak concentration)  Aribic numeral 1-3 (from small to large range in brightness of members)  p,m,r (poor, medium, or rich in stars)

The H II Region  Cloud of excess molecular hydrogen gas surrounding recently formed stars  K  Stars massive enough heat and ionize the H II  Creates ionization front radial outward from center  Front begin supersonic but slow to subsonic as distance increases  Pressure from ionized gas causes ionized volume to expand  It is eventually overcome by the outer shock from the nebula expansion  Radiation pressure from young stars drives gas and dust away

Full color

H-Alpha Filter

NGC 637 color 2x2

NGC 637 color 1x1 zoom

distribution  H II regions are mostly found in spiral and irregular galaxies  In spirals they are located primarily in the spiral arms  Density waves cause slowing and condensing of matter  Shockwaves

H-alpha filter 10 min. 10/10/2010 Fsq 106 New Mexico 10/10/2010

IC 5146 Cocoon Nebula 10 min. Clear Barnard 168 Fsq 106 New Mexico 10/10/2010

Dark Nebulae  Clumps or clouds of dust grains that absorb light and create dark patches on brighter background of the milky way  Irregular formation  No outer boundary  Sometimes convoluted shapes  Neutral H2 in outer layer  Darker and colder towards center  C+ to neutral carbon and then to CO  Stability of CO outweighs the rest and is major component of dark areas

Structure collapse  HCN to HNC  HNC preferred for chemical equilibrium  Less than 1/1000 the light than the space surrounding  Heating by cosmic rays  Cooling by transitions of internal CO  Gravitation works against collisions and magnetic field  Gravitational energy released through contraction  Gas temperature increases  Pressure increases preventing further collapse  Dust grains emit infrared radiation which cools the nebula  ½ gravitational energy towards cooling  ½ gravitational energy towards contraction

Star formation  Small jumbles of dust and gas are attracted by gravity “protostar”  Each protostar is one stellar system  Most < 1 solar mass  Very few up to 100 solar masses. Large role in formation of nebula  Collapse very rapidly  Initial protostar is 30 times diameter of sun  Surrounding dust becomes “protoplanet”  Star contracts until heat is produced by converting H to He  If hot enough ionizes dark nebula into a bright nebula

Sources  Frommert, Hartmut. "Open Cluster Stars." SEDS. SEDS, Web. 6 Oct  "H II Region." Wikipedia, the Free Encyclopedia. Web. 06 Oct  "Chandra :: Educational Materials :: Stellar Evolution - Cycles of Formation and Destruction." The Chandra X-ray Observatory Center :: Gateway to the Universe of X-ray Astronomy! Web. 06 Oct  Stecker, Michael A. "Barnard-168 and Cocoon Nebula." Michael A. Stecker. Web. 13 Oct  Davis, Tom V. "The Cosmic Cocoon: IC 5146 by Tom V. Davis." Universe Today. 07 July Web. 13 Oct  Schombert, James. "Dark Nebula." University of Oregon Department of Physics. Web. 13 Oct