Can you hear me now?
Posted on 06/02/2012 11:45:49 AM PDT by Ernest_at_the_Beach
A re-analysis of radio telescope observations from three countries has yielded a surprising result: nearby galaxies harbour one-third more hydrogen than had previously been estimated.
While nothing like enough matter to solve physics’ “dark matter” problem, the work by CSIRO astronomer Dr Robert Braun (chief scientist at the agency’s Astronomy and Space Science division in Sydney) also helps explain why the rate of star formation has slowed down. While there’s more hydrogen than astronomers had thought, its distribution makes star formation more difficult.
Andromeda – the galaxy headed for a catastrophic collision with our own in about four billion years – provided the clue for Dr Braun. SpaceRef says he was piqued by “gaps” in the 21-cm radio signal that suggested absorption of the radiation neutral hydrogen gas (tagged HI in astronomy) would normally have emitted.
This, he says, suggests self-absorption of the radiation – glowing gases emit a 21-cm signal, but it’s absorbed by cooler gas in front of it (from our point of view). Researchers have tended to ignore self-absorption in formulating their estimates of hydrogen mass, Dr Braun said.
By taking self-absorption into account, Dr Braun says, his measurements reveal small but massive clouds of HI in all of the galaxies he analyzed – M31, M33 and the Large Magellanic Cloud – sufficient to add between 30 percent and 36 percent to the galactic mass estimates.
The research also shows there’s less HI available in galactic haloes than there was 12 billion years ago – which helps explain why the rate of star formation is so much slower in the modern universe; the haloes act as the reservoirs that re-fuel star formation.
Dr Braun notes that “Although there’s more atomic hydrogen than we thought, it’s not big enough to solve the Dark Matter problem. If what we are missing had the weight of a large kangaroo, what we have found would have the weight of a small echidna.”
As new instruments like the Square Kilometer Array are brought into service, Dr Braun says similar measurements can be made of more distant galaxies. The 50-light-year resolution that Australia’s Parkes Radio Telescope provided for the Large Magellanic Cloud isn’t sufficient for distant galaxies, he said.
However, the current study will feed into a sky survey to be undertaken by Australia’s Square Kilometer Array Pathfinder telescope in Western Australia. The FLASH (first Large Absorption Survey in HI) survey will use background radio continuum sources to identify and characterize neutral hydrogen in the foreground, and increase the accuracy of our measurement of HI absorption lines. ®
fyi
>>Andromeda – the galaxy headed for a catastrophic collision with our own in about four billion years –
It’s funny how hysterical science (that is, science looking for grant money) has changed Andromeda from the friendly neighbor galaxy next door to the evil galaxy coming over to destroy us.
That’s because four billion and twenty years ago, it wasn’t a threat.
Now, with just four billion years left, it’s a major threat.
so haloes happen when glowing and cooling gases collide.. Coool. Quite the celestial laboratory the ‘Old Man’ created.
That’s ‘Ancient of Days’ to you, grasshopper.
>>Now, with just four billion years left, it’s a major threat.
...and we need a couple million taxpayer dollars to study it. NOW!
I was thinking much the same thing; then, I concluded that there’s no reason to panic for at least another ten years. Maybe fifteen.
I thought that this was attributed to coal-fired power plants, SUVs, and cow flatulence...
You realize, don't you, that you know too much for your own good...
CA....
You realize, don't you, that you know too much for your own good...
CA....
I always suspected kangaroos were involved with the dark matter scenario!
I will, however, keep my aardvark/dark energy correlations to myself, for the time being.
Can you hear me now?
What am I looking at?
HI gas? Stay away from the beans at the luaus.
Theories abound...
There must be a Federal government program/department/agency that can be created to help save the Earth and indeed the entire galaxy from this horrible collision. And of course the needed tax increases on all all of those rich (middle class) Americans that will be needed to fund this noble effort -- a tax on everybody until the end of time. Perhaps a high speed train line can be built to take everybody to another galaxy?
Don’t worry, in a billion years or so our sun will be so hot the Earth’s water and atmosphere will be burned away. I hope we have warp drive by then or we’ll be in serious trouble!!
Thanks Ernest, here’s an “extra, extra” topic for the APoD ping list members, and a multi-list topic, btw. :’)
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