Astronomy A Closer Look: Nebulas, Dark and Diffuse

Discussion in 'Astronomy' started by Mizar, Dec 8, 2004.

  1. Mizar

    Mizar Premium Member

    The word Nebula is actually derived from a latin word that means Cloud. A nebula is a large cloud of interstelar dust or gas. Nebula can extend hundreds of light years or just be about 1/4 of a light year long. Most nebula are made up of hydrogen which is the most abundant element in the universe. Nebula are generally created when a star dies and releases all of its contents into space. Some nebula however are giant clouds of gas remnant from the big bang that never colassed into stars. Stars are generally formed in nebula due to their high content of the raw materials needed for a star. A shock wave from a near by supernova can cause a nebula to begin to colapse and turn into a star. Most of the time when stars begin to form in a nebula the light from the star allows the nebula to become visible.

    The Nebula "Dust"- You have heard me say gas and dust and you will hear it again. What is this interstelar dust? the dust is any particle in space that is larger than an average molecule. So the clouds of nebula can contain rocks and minerals. This is the dust.

    Diffuse nebula-
    Diffuse nebula can actualy be seprated into two groups of their own. A diffuse nebula is any cloud of gas that some way emmits visible light and can be seen.

    Diffuse nebula A- Emmission nebulas
    Emmission nebulas are generaly nublas of high tempature gas. A star forms inside of the gas cloud and emmits ultra violet light. The light acts upon the atoms and Ionizes the atom causeing it to light up. For the most part Emmission nebulas are RED becasues of the large ammout of hydrogen gas in them. Emmission nebula emmit their own light becasue of the ionized particles and atoms. A example of an Emmission Nebula is M42 the Orion Nebula.
    (the orion nebula is eaisly visible to the naked eye in the constelation of orion. It is in a chain of what appears to be 3 "stars" right below the belt of orion. THe middle "star" is the nebula. Binosulars will reveal a hazy patch of light that you can not focus. On larger binoculas you may be able to see a grop of stars in the center called the Trapizerium)
    the orion nebula-

    Diffuse Nebula B- Reflection Nebula
    Reflection Nebula are exactly what their name implys. They are nebula of dust and gas the reflect light from stars inside and around the nebula. It is believed that reflection nebula contain large ammounts of dust instead of gas and that this dust is thought to be graphite coverd in ice. Becasue the nebula reflect light their light is the same as that of the star giving it light. Most Reflection nebula re blue because they are generally around Blue hot young stars because these types of nebula are the frequent star factories. A good example of a reflection nebula is the Trifid nebula M20 in Sagitarius

    Dark nebula-
    Dark nebula are somposed of the same things as emmission and reflection nebula. Dark nebula however do not have any nearby stars to heat them up or ionize them. Nor do they have a star to allow them to reflect light. What we get is a large group of gas that has no light being emited and blocks all light behind it. The most famous dark nebula is most likely the Horse Head nebula-

    Planetary Nebulas- see the other closer look thread-
  2. drlau

    drlau Premium Member

    Excellent post, Mizar!

    Nebulas are some of the most fascinating things to study in astronomy.

    I had no idea that there was a nebula in Orion's Belt. Ignorance Denied again!
  3. Mizar

    Mizar Premium Member

    Actually it is not in the belt of Orion it is just right below it.