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It can't. The galaxy is assumed to be roughly symmetrical, and they fill in the missing data with what we can see on our side of the galaxy. It's "best" in the
by sbierwagen 2y ago
It can't. The galaxy is assumed to be roughly symmetrical, and they fill in the missing data with what we can see on our side of the galaxy. It's "best" in the sense that it's the most accurate fiction, I suppose.
Gaia is good to about 13,000 light years: https://en.wikipedia.org/wiki/File:Galaxymap.com,_map_12000_parsecs_(2022).png https://en.wikipedia.org/wiki/File:Galaxymap.com,_map_12000_...
The Milky Way is maybe 100,000 light years in diameter. So we're only getting good distance readings on a small fraction, and nothing behind the central bulge of our galaxy. The first won't improve until we send an astrometry telescope way outside the orbit of the Earth, for better baselines, and the second is going to need a telescope sent 10,000 light years out of the galactic ecliptic.
- thrance 2y agoWe can infer the general distribution of mass on the other side of the galaxy from observing the trajectory of stars, can't we?
- sbierwagen 2y agoIt takes 230 million years for the Sun to make one full orbit around the Milky Way.
- gunian 2y agohuh? how can sun orbit the milky way if it is within the milky way
- dylan604 2y agoAround the center of the Milky Way. The sun orbits the center just like the planets orbit the sun.
- gunian 2y agois there some sort of gravitational body in the middle that makes everything orbit in galaxies? it must be massive right
- sbierwagen 2y agoOne of today's lucky ten thousand. Most galaxies have a black hole at the center that mass at least a hundred thousand times more than our sun: https://en.wikipedia.org/wiki/Supermassive_black_hole https://en.wikipedia.org/wiki/Supermassive_black_hole
- gunian 2y agodoes that mean all galaxies will eventually be consumed by the black holes at their center?
- NKosmatos 2y agoThat’s one of the theories, called Big Crunch: https://en.wikipedia.org/wiki/Big_Crunch https://en.wikipedia.org/wiki/Big_Crunch There are other (more probable) theories about the end of the universe, and if you’re up to it you can read more here: https://en.wikipedia.org/wiki/Ultimate_fate_of_the_universe https://en.wikipedia.org/wiki/Ultimate_fate_of_the_universe I’m in favor of the Big Chill, since I like the concept of entropy as introduced by the second law of thermodynamics: https://en.wikipedia.org/wiki/Heat_death_of_the_universe https://en.wikipedia.org/wiki/Heat_death_of_the_universe
- ziofill 2y agoOrbit around the center. It’s like saying the Earth orbits around the solar system.
- dylan604 2y agoBut the earth doesn't orbit around the solar system. it orbits around the sun as part of the solar system. the solar system as a unit orbits around the center of the galaxy. if you've ever seen the concept images of the Oort cloud, you could visualize that snowball looking roundish object as a visual for the solar system traveling through the galaxy.
- SideburnsOfDoom 2y agoThe same way that the Earth can orbit the centre of mass of the solar system and also be within the solar system. We say that the Earth orbits the Sun because that's where 99.86% of the mass of the solar system is located. The Sun in turn orbits the the centre of mass of the Milky Way. But I don't think that the mass of the Milky way's central supermassive black hole dominates in the same way.