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In a study published March 9 [PDF] in The Monthly Notices of the Royal Astronomical Society, astronomers announced the discovery that all disk galaxies rotate about once every billion years, no matter their size or mass.
“It’s not Swiss watch precision,” said Gerhardt Meurer, an astronomer from the International Centre for Radio Astronomy Research (ICRAR), in a press release. “But regardless of whether a galaxy is very big or very small, if you could sit on the extreme edge of its disk as it spins, it would take you about a billion years to go all the way round.”
To carry out the study, the researchers measured the radial velocities of neutral hydrogen in the outer disks of a plethora of galaxies — ranging from small dwarf irregulars to massive spirals. These galaxies differed in both size and rotational velocity by up to a factor of 30. With these radial velocity measurements, the researchers were able to calculate the rotational period of their sample galaxies, which led them to conclude that the outer rims of all disk galaxies take roughly a billion years to complete one rotation. However, the researchers note that further research is required to confirm the clock-like spin rate is a universal trait of disk galaxies and not just a result of selection bias.
http://blogs.discovermagazine.com/d-brief/2018/03/14/galaxies-rotate-billion-years/
[Source]: Astronomy.Com
[Also Covered By]: ZME Science
(Score: 2) by c0lo on Thursday March 15 2018, @08:28AM (9 children)
"the discovery that all disk galaxies rotate about once every billion years, no matter their size or mass.". Really? You really mean all?
" the researchers measured [...] in the outer disks of a plethora of galaxies" - so actually is not quite all, only a plethora of them. Is a plethora larger or smaller than a kilo-bunch?
"the researchers note that further research is required to confirm the clock-like spin rate is a universal trait of disk galaxies and not just a result of selection bias." - so that plethora leaves enough room for a selection bias, which means it's less than a "statistically representative set".
Mmmmm... I see.
https://www.youtube.com/watch?v=aoFiw2jMy-0 https://soylentnews.org/~MichaelDavidCrawford
(Score: 3, Funny) by cocaine overdose on Thursday March 15 2018, @08:39AM
(Score: 4, Informative) by takyon on Thursday March 15 2018, @08:47AM (1 child)
The abstract pretty much agrees:
Gyr = gigayear = 1 billion years.
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 2) by DannyB on Thursday March 15 2018, @05:54PM
So my standard answer still works:
I'll get back to you on that in one quarter of a galactic turn, or right after I upgrade to Windows XP.
The lower I set my standards the more accomplishments I have.
(Score: 0) by Anonymous Coward on Thursday March 15 2018, @09:23AM (3 children)
How did they manage to fail to remove the selection bias?
1. Take sufficient large sample size
2. Have a computer randomly select galaxies based on the number in 1
Measure ALL those galaxies.
(Score: 3, Insightful) by PiMuNu on Thursday March 15 2018, @10:56AM (2 children)
> 1. Take sufficient large sample size
You can only measure what you can see. The galaxies need to be side on to do the measurement, need to be visible, etc.
(Score: 0) by Anonymous Coward on Thursday March 15 2018, @11:19AM (1 child)
That would suggest that the authors think that there is a correlation between orientation, visibility and other selection criteria (compared to our galaxy) and the rotational speed. I doubt that such correlation would exists.
(Score: 2) by PiMuNu on Friday March 16 2018, @10:58AM
> the authors think that there is a correlation between orientation, visibility and other selection criteria
No, it means the authors cannot exclude such a correlation. They can't exclude such a correlation because they can't measure the galaxies that they can't measure.
(Score: 0) by Anonymous Coward on Thursday March 15 2018, @09:51AM (1 child)
Lando broke the hyper drive. Thats why
(Score: 0) by Anonymous Coward on Thursday March 15 2018, @11:19AM
It's not my fault!