Missing Matter

[blobrana]

"In the May 20 issue of The Astrophysical Journal, Charles Danforth and Mike Shull (University of Colorado, Boulder) report on NASA's Hubble Space Telescope and NASA's Far Ultraviolet Spectroscopic Explorer (FUSE) observations taken along sight-lines to 28 quasars. Their analysis represents the most detailed observations to date of how the intergalactic medium looks within about four billion light-years of Earth. The astronomers say they have definitively found about half of the missing normal matter, called baryons, in the space between the galaxies."

Read more (http://hubblesite.org/newscenter/archive/releases/2008/20/full/)

[synthesizer-patel]

For a long period of time there was much speculation and controversy about where the so-called "missing matter" of the Universe had got to. All over the Galaxy the science departments of all the major universities were acquiring more and more elaborate equipment to probe and search the hearts of distant galaxies, and then the very centre and the very edges of the whole Universe, but when eventually it was tracked down it turned out in fact to be all the stuff which the equipment had been packed in.

(WTT Douglas Adams )

[EndLightEnd]

Well that is interesting, but Im confused by what it means when it says "about half the missing normal matter".

So if baryons are only about 4-5% of everything in the universe, what portion of this was "missing" previous to this study?

[blobrana]

I seem to remember it was about half of the baryonic matter that was unaccounted for.
The stars and galaxies accounts for less than 10% of the total baryonic matter, with detected gas around galaxy clusters and intergalactic hydrogen adding about 40%.

This discovery brings up the total to 75% or more.

[Reiku]

This often confuses me.

I reported that they have recently found the axion, which is a dark matter candidate. Then Ben states that there was also another experiement which ''might'' have found their existence.

Now, we have found half the mass needed to account for gravitational influences. Does this now mean there is less dark matter, OR no dark matter at all?

[blobrana]

This often confuses me.

Hum,
imagine a party cake sliced up into 25 pieces.
And you get one piece. The rest is handed out to other guests hiding some where in the house.

Except, you notice that half of your slice is missing.
So naturally you look around for your missing half of your portion.

This new search has found half that missing bit lying on the floor; the rest is probably stuck to the knife.


Does this now mean there is less dark matter?

Generally, no.
(in my example the 24 guests slices represent the dark component we still can`t see)

[Reiku]

Are you being... patronising?

[blobrana]

Is my answer offensive?

[Reiku]

Well, i wasn't sure. The way you worded it... i don't know... sounded like you where talking to a child, that's all... sorry...

[blobrana]

Well, i wasn't sure.

Sry,
no insult was meant.

Just my writing style.
(ie i also reply to Joe Blogs)

[Reiku]

;)
ok

[kaneda]

I thought it was obvious that when galaxies formed, they would only take what matter was in easy reach. The rest has continued to fill the spaces between galaxies but it is surprising just how much of it there is.

If the universe is expanding, then it must have been a dense fog billions of years ago. Essentially, as we look further back in time, the medium should become ever denser. Is there evidence of this which would be firm evidence of an expanding universe?

[krokah]

I thought the early universe was just a mixture of hot gas that was part of the fog. As the universe expands to does the void, of course comes the question: "What came first, the universe or the void?"