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The exact form of the Milky Way was figured out the in early fifties of the 20-th century. The exact form of the Milky Way was not figured out in the early 1950s. It remains a matter of debate. Astronomers agree that the Milky Way is a barred spiral galaxy. How many arms? That's still debated. Stars in the Andromeda Galaxy were not visible to humans until ...

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This is not really an answer, as I don't know, but was too long for a comment, and some of the references might be useful for you: Active galactic nuclei (AGN) require not only a supermassive black hole, but also quite a lot of gas. In order to reach the central parts of the galaxy, gas must either cool, or it must be "forced" in more violent ...

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There is no galactic magnetic field inside the (inner) solar system. The solar wind is a near-perfect plasma and according to the frozen-in theorem it carries the magnetic field of the Sun with it extremely well. At some stage in the outer solar system this assumption will break down, especially at the transition region from the solar wind to the ...

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The motion of the Sun in the direction perpendicular to the Galactic plane is deduced from a mixture of measurement and theoretical calculation. The measurements are (i) deducing the Solar System's current position and speed with respect to the galactic plane (see How far is the Earth/Sun above/below the galactic plane, and is it heading toward/away from it? ...

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Milky way obviously is an English word with that literal meaning a way (path) covered in milk. So it's not exactly derived. But it is a literal translation from Latin 'via lactia' and the Greek γαλακτικός κύκλος (milky circle - galaktikos kýklos, hence the word Galaxy). It resembles our own Galaxy's appearance on the night sky as a diffuse, slightly milky ...

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I think the short answer is "You can't observe $z=0$ LyC leakers, but you can observe $z\sim0$ LyC leakers." No z = 0 leakers… Measuring the Lyman continuum (LyC) — i.e. photons capable of ionizing neutral hydrogen (HI) — is indeed very hard. The HI cross section to LyC is  \sigma_\mathrm{LyC} = \sigma_\mathrm{LL} \times \left( \frac{\lambda}{912\...

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