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Milky Way Is Twice the Size We Thought
Peter writes to tell us about a research group at the University of Sydney in Australia, who in the middle of some calculation wanted to check the numbers everybody uses for the thickness of our galaxy at the core. Using data available freely on the Internet and analyzing it in a spreadsheet, they discovered in a matter of hours that the Milky Way is 12,000 light years thick, vs. the 6,000 that had been the consensus number for some time.
Yeah, it comes with "%30 MORE!" now.
Obesity is everywhere.
Wikipedia says it's only 1000 light years thick.
So until now everyone was just measuring the radius of the Milky Way?
This is a good reminder how you're supposed to dig down to the raw data and validate that. I remember reading in one of Richard Feynman's books about a similar case, some conclusion or data appeared well supported, because a lot of the research papers were supportive of the idea, but it turned out that they derived what they said based on a single source.
The case here is similar, it's a good reminder how science is about data, validation and facts not about authority. You're supposed to check your data, check your facts and try to avoid making implicit assumptions.
It takes a man to suffer ignorance and smile
Be yourself no matter what they say
So I read the article (yeah, yeah - I know...I was bored) and I hope the spreadsheet software used wasn't Excel - we all know how well that counts.
The Mothership
They're measuring the sea of electrons between the stars, which they assume stops at the 'edge' of the galaxy.
... If you know the distance to the pulsar accurately, then you can work out how dense the WIM is and where it stops - in other words where the Galaxy's edge is.
FTA:
"As light from these pulsars travels to us, it interacts with electrons scattered between the stars (the Warm Ionised Medium, or WIM), which slows the light down.
There are some who call me
What we're seeing now is middle age spread.
"Nine times out of ten, starting a fire is not the best way to solve the problem." - my wife
That famous scientist may have allowed himself to get carried away a bit. What it means is that there was no clean breakthrough article. Rather, evidence gradually accumulated. What it does not mean is that the connexion is "perhaps true", certainly not in the current stage where effective medicines exist.
On the other hand it's good practice to have roundup articles that go over the evidence.
[1] Now known to consist of dark matter and dark energy, which is why you can't see them.
1 light-year = 4 * (cost of war in Iraq so far) * (mile/$)
;)
I hope that brings it into perspective for you
For the perfect anti-Unix, write an OS that thinks it knows what you're doing better than you do and let it be wrong.
What I find disturbing is the fact that a number is this widely off and no one discovered it for such a long time! I can imagine deviation by x % or less where x
The split of Humans from the Apes pushed back by another 6 to 7 million years earlier than previously thought based on molecular genetics. The difference from the earlier estimate of around 5 to 6 million years is therefore over 100%
http://www.news24.com/News24/Technology/News/0,,2-13-1443_2169361,00.html
Whenever life gets you down, Mrs. Brown,
And things seem hard or tough,
And people are stupid, obnoxious or daft,
And you feel that you've had quite eno-o-o-o-o-ough...
Just remember that you're standing on a planet that's evolving
And revolving at nine hundred miles an hour,
That's orbiting at nineteen miles a second, so it's reckoned,
A sun that is the source of all our power.
The sun and you and me and all the stars that we can see
Are moving at a million miles a day
In an outer spiral arm, at forty thousand miles an hour,
Of the galaxy we call the "Milky Way".
Our galaxy itself contains a hundred billion stars.
It's a hundred thousand light years side to side.
It bulges in the middle, sixteen thousand light years thick,
But out by us, it's just three thousand light years wide.
We're thirty thousand light years from galactic central point.
We go 'round every two hundred million years,
And our galaxy is only one of millions of billions
In this amazing and expanding universe.
(Animated calliope interlude)
The universe itself keeps on expanding and expanding
In all of the directions it can whizz
As fast as it can go, at the speed of light, you know,
Twelve million miles a minute, and that's the fastest speed there is.
So remember, when you're feeling very small and insecure,
How amazingly unlikely is your birth,
And pray that there's intelligent life somewhere up in space,
'Cause there's bugger all down here on Earth.
If you violate copyright, do it right.
From TFA with commentary:
Proving not all science requires big, expensive apparatus, Professor Gaensler and colleagues...downloaded data from the internet
No, this actually proves that you can reuse data gathered with large expensive apparatus. There's a difference. They couldn't have done this without expensive infrastructure that just happened to cost them nothing (or close to nothing) - ie. The original instruments and the Internet.
The University of Sydney team's analysis differs from previous calculations because they were more discerning with their data selection. "We used data from pulsars: stars that flash with a regular pulse," Professor Gaensler explains. "As light from these pulsars travels to us, it interacts with electrons scattered between the stars (the Warm Ionised Medium, or WIM), which slows the light down.
Well now wouldn't you want to explore why the data differs so much, before declaring your answer to be the correct one just because you verified your calculations are correct?
My first thought is: Did they use some standard or average value for the density of the WIM? Could the discrepancy be because the WIM itself is not uniform through the thickness of the galaxy/
This is definitely an interesting result and worth following up but rather than declare victory the real question is why is there such a large discrepancy with other data?
These posts express my own personal views, not those of my employer
Perhaps the differences in quoted thicknesses are the result of different definitions of the edge?
It's pretty hard to measure the size and shape of the Milky Way simply because we are stuck in the middle of it. Measuring the size and shape of far away galaxies is a lot easier because we have a better view. Our galaxy is a flat disk with spiral arms where we are in one of those arms - the overall structure is very hard to measure from that perspective. To complicate things further there is quite a lot if interstellar dust that messes up our view in certain directions.
As an analogy - imagine being stuck in a traffic jam. Figuring out the extent of it is very hard from the view you get from your car. A helicopter in the sky has no problems though.
siener's youtube channel
TFA says: "The team's results were presented in January this year at the 211th meeting of the American Astronomical Society in Austin, Texas." but there's no indication of where the results have actually been published in a peer-reviewed journal so that one could read the paper for oneself. I looked on the AAS site and couldn't find anything there either. So, pending access to a detailed published per-reviewed account of their work, I'm reserving judgement as to how valid the claim is.
I am an astronomer, so first some background: The Milky way has several components: young stars, old stars, dust and various components of gas. They all have different thicknesses. There is no single "thickness". One of these components (warm ionized gas) has been measured to have a thickness larger than expected. This measurement has not been confirmed by others, nor (I think) published yet.
Despite this complexity, this discussion thread is awash with arguments, confusion, wild speculation, suggestions that dark matter might be wrong etc. etc. OK, fine, this is slashdot, that's what slashdot is for.
But the same people (presumably) have also rushed off to edit Wikipedia! (I see a half dozen edits this morning, to add in the "new" thickness.) That's the part that I find incredible. And people really take Wikipedia seriously?
***GUARANTEED increase your galaxy by 6,000 light years***
thick and sturdy clusters. ladies love dark matter. hawking beautiful einstein copernicus keppler cassini
jplab buzz lightyear wormhole
[sorry--I couldn't resist]
I might know what I'm talkin' about, but then again, this is Slashdot...