Posted on 09/29/2018 4:50:31 AM PDT by LibWhacker
The earth orbits the center of the galaxy once every 225 to 250 million years. Presumably the black hole at the center rotates much faster and spiral arms further out go somewhat slower.
We've been observing galactic rotation for about 90 years. I'm not sure we have enough data to say for sure how fast any galaxy rotates. But ask me again in about 30 million years. :o)
The Milky Way is only in 2nd gear.
Good to know...now I have another way to set my watch ;-)
Nice to know that at this age, the universe is still regular.
They’re talking about disk galaxies. The Milky Way is believed to be a barred spiral galaxy, not a disk. Lacking the ability to see the whole thing from a distance of course, it’s somewhat of an educated guess.
(This is not helped by the fact that their picture is of a spiral galaxy, not a disk.)
Everything in a spiral galaxy rotates around the center of the galaxy at the same rate. It’s as if every disk-like galaxy were a giant phonograph record, everything rotating in lock-step. It’s one of the great discoveries in astronomy, made by Vera Rubin. She probably should’ve gotten the Nobel Prize for it, but never did. She made it by studying stellar red shifts (fortunately, they don’t have to watch the galaxy rotating for tens of millions of years before getting a fix on the rotation rate!)
Disk galaxies come in two flavors: Spiral and lenticular. So spirals are included in the discovery.
Short of a miracle of science or God, my lifespan is less than a hundred years, so a BILLION years means what to me again?!!! @.@
I believe that all galaxies are essentilly discs. The disagreement would be argument over the thivkness of the accretion.
The rotational period is a function of the gravitational friction of the black hole
I remember seeing that. Gravitational waves, no?
BTW, beautiful galaxy. Looks very similar to NGC 1232, the one pictured in this article. Someone been busy playing with Photoshop? Not criticizing... It’s a beautiful galaxy any way you look at it.
Come to think of it, a watch spring looks just like a spiral galaxy. That’s your deep thought for the day.
These galaxies differed in both size and rotational velocity by up to a factor of 30. With these 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.
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The key to this study is they are only looking at the outer rims. FReepers who only read the headlines won’t know this.
You are correct. Thank you for the correction.
pedophile stars? Just like Hollywood
Actually, the flatness that Rubin discovered only applies to the outer bands. The inner and middle bands vary quite a bit in velocity. Some outer bands are nearly flat and some trend up as pictured above. Essentially, she discovered one of the important effects of dark matter.
They rotate faster than that toward their centers, and slower than that toward their periphery. Somewhere between they ALL rotate at THAT rate. They call this the “selection fallacy”.
I’m sure there are Federal grants involved.
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