Thread: our galaxy

what's outside of the milkyway

stuff

other galaxies, interstellar clouds + lots of empty space

mostly dark matter though

"The contents of the Universe include 4% atoms (ordinary matter), 23% of an unknown type of dark matter, and 73% of a mysterious dark energy."

Originally Posted by lavender

what's outside of the milkyway

Our galaxy is just one of 100,000,000,000 galaxies. Between them, there is often millions of light years of "space". Our galaxy does have two tiny satellite galaxies.

Our neighbourhood:


http://en.wikipedia.org/wiki/Local_Group

what's outside of the milkyway ?
life.

Originally Posted by Arch2008

"The contents of the Universe include 4% atoms (ordinary matter), 23% of an unknown type of dark matter, and 73% of a mysterious dark energy."

Do they call it dark because it is not observable yet? Just mathmatically placed?

The Wilkinson Microwave Anisotropy Probe (WMAP) shed some light on dark matter. Apparently it was here right from the beginning of the universe. Some candidates for DM are MACHOS (MAssive Compact HalO objectS) and WIMPS (Weakly Interactive Massive ParticleS). MACHOS are described as brown dwarf stars or minor black holes in the halo of a galaxy, whereas WIMPS are simply nuclear particles that interact weakly with the electromagnetic force, so they can essentially float right through your molecules and do not reflect light, etc. Since there were no stars at the beginning of the universe, I think that WIMPS are the most likely candidate.

Scientists added up an approximate mass of the universe and measured the increase in acceleration in the expansion of the universe since the Big Bang. They then calculated how much energy it would take to give the mass of the universe this acceleration. The result is called Dark Energy. We really know very little about it.

Can someone prove to me that there is such a thing as dark matter?