3. MACHOs
3. MACHOs
MACHO stands for MAssive Compact Halo Objects. It is a type of dark matter which is made up from baryonic matter, the stuff that you and me are made out of. Baryonic Dark Matter consists of brown dwarfs, neutron stars, and black holes. Most MACHOs are believed to exist in the halos of the galaxies. The halos are the outermost parts of the galaxy. There are very few stars here, however those that do exist seem to be moving faster than the observed matter will allow it, there must be more matter than can be seen. This is how we know that dark matter exists.
Baryonic Dark Matter can only exist somewhere in a galaxy (halo is considered part of a galaxy). This is because baryonic dark matter is or was a type of star. A neutron star, is a dead star which is believed to be formed in a supernovae. A neutron star is very massive and forms from a star about 15 to 30 times the mass of our sun! The unique property of the neutron star is that made up of mostly neutrons.
http://www.astro.umd.edu/~miller/nstar.html
To learn more about neutron stars go to: http://www.astro.umd.edu/~miller/nstar.html
Brown dwarfs are another type of baryonic dark matter. They are a type of star that is not massive enough to emit light, also known as a dead star. Brown dwarfs are really hard to discover because they are so dim. The first brown dwarf was discovered in 1995 and called Gliese 299B, more have since been discovered, however there still aren’t many known brown dwarfs. A type of brown dwarf is a giant planet, for example our very own Jupiter; Jupiter is a smaller version of a brown dwarf.
http://chandra.harvard.edu/resources/illustrations/dwarf_schematic.html
To learn more about brown dwarfs go to: http://www.bahnhof.se/~davidgr/browndwf/bd_home.html
Black holes are another candidate for baryonic dark matter. Black holes form from huge explosions of stars called superanovae. Either a star, star cluster, or galaxy core then becomes unstable and collapses in on itselt creating a structure of very high density. This structure is a black hole. A black hole is very dense, so dense that its gravitational field will not allow anything to escape, not even light. But don’t worry you will not get sucked into a black hole unless you cross the event horizon. The event horizon is the boundary where once you have crossed into it you will never be able to escape, because in order to escape one must travel faster than the speed of light and that is impossible.
http://www.inspi.net/best-of-hubble-telescope/images/2002-30.jpg
Although scientist don’t understand what exactly goes on inside of a black hole there are many hypothesis. Some think that time travel is possible inside a black hole. Others think that if you went into a black hole you would be transported either to another part of the universe or another universe altogether. Many things about dark matter are still unclear but only time will tell.
For more information on black holes or MACHOs go to: www.nasa.gov
Posted by bsalmon on March 26, 2005 at 07:52 PM