Comment on Non-Rotating Early Galaxy Is a Surprise to Astronomers
heydo@lemmy.world 3 days ago
I watched Anton Petrov’s video on this and found out that distant objects literally move in slow motion for us. Like the further away an object is the slower it appears to move to us. It’s an effect of the light being stretched or red-shifted. Since space and time are intertwined, stretching space stretches the time interval between light waves, so the expansion of the universe causes distant objects to move in slow motion ( from our perspective).
If we look at an object that existed 1 Billion years after the Big Bang, a second from the epoch appears to last five seconds for us.
kichae@wanderingadventure.party 2 days ago
Heydo That’s true, but we also don’t measure galaxy rotation by watching things move. The rotation rate of galaxies is incredibly slow on human timescales. Like, the Milky Way rotates once every 100,000 - 150,000 years.
Instead, we’re looking at differences in redshift from one side of the galaxy compared to the other. A rotating object – assuming it’s axis of rotation isn’t perfectly facing you (i.e. you’re looking straight down its north/south pole) – always has one side that’s moving toward you, and another that is moving away from you. The side that is moving toward you will be slightly blueshifted compared to the average, while the side that is moving away will be slightly redshifted. Finding a galaxy that isn’t rotating means finding a galaxy that doesn’t have this red/blue shift pattern.