Parsec astronomy in au7/24/2023 Or, in other words, an arcseconds spans a larger and larger physical size (as described by James K) out to ~15 Gly (where it spans roughly 28,000 lightyears), after which it spans a smaller and smaller size. A parsec is equivalent to 3.26 light years, and since a light year is the distance light travels in. A parsec is a unit of distance that is often used by astronomers as an alternative to the light-year, just as kilometers can be used as an alternative to miles. The result - which is obtained by integrating the Friedmann equation - is that galaxies become smaller and smaller out to a certain distance (roughly 15 billion lightyears), after which the second effect starts to dominate and they start to grow in size. One parsec is the distance at which one astronomical unit subtends an angle of one arcsecond. But tan (2) isn't 2tan (1) so 2 Parsec can't be simply 2 1 Parsec or 23. On the other hand, we look further and further into the past, and hence see galaxies at a time when they looked larger and larger. 11 years ago Wait if 1 Parsec tan (90deg-1arcs)1AU then 2 Parsec tan (90deg-2arcs)1AU. Thus, we have two competing effects: On the one hand, galaxies become smaller and smaller with distance, as expected and as decribed in James K's answer. And because the Universe expands, everything was closer together in the past, so we see distant galaxies as they were when they were closer and hence spanned a larger angle on the sky. We assume you are converting between parsec and astronomical unit. I just wanted to mention an effect which comes into play if you look really, really far away:īecause light moves at a finite speed, we see galaxies (and other things) as they were in the past. How many parsec in 1 AU The answer is 4.8481367817234E-6. James K's answer is right on, and probably what you're after.
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