Hat jemals ein Komet die Sonne verfinstert? Heute ist der Komet sehr nahe gekommen, und das hat mich verwundert

I meant if it had ever happend *in recorded history*, sorry

tldr; yes but no but yes, kinda.

The answer is certainly „yes“, but with caveats. Usually when we talk of something „eclipsing“ something else, the ‚eclipser‘ is larger (or at least roughly the same apparent size) as the ‚eclipsee‘. With respect to comets, that’ll never* happen because even the largest comet nucleii are a few tens of kilometers diameter, and the Sun is substantially larger than that!
(*OK, an e.g. 10km comet nucleus inside Earth’s atmosphere could indeed eclipse the Sun entirely, but we’d have a different set of concerns beyond „ooh pretty!“)

But have comet nuclei passed between the Sun and the Earth? Sure! SOHO has discovered over 5,000 tiny sungrazing comets, many of which have passed in front of the Sun as they vaporize. [Here’s a good example.](https://earthsky.org/space/first-ever-movie-of-comets-death-plunge-into-sun/) But that’s only visible from space.

Another way to look at OPs question – and probably the spirit in which it was meant – is to ask whether a comet just like the one in the SOHO images today has ever crossed in front of the Sun (in reliably recorded history). Because for sure, the apparent size of that thing’s tail is WAY larger than the apparent size of the Sun (the white circle in the middle).

From SOHO’s perspective the answer is „no“, but with yet another a caveat. Just last October, a different Comet ATLAS (Tsuchinshan-ATLAS) passed through this camera, and its extended dust trail did indeed „eclipse“ the Sun. [NASA put together a really nice video about it here.](https://svs.gsfc.nasa.gov/14706/#media_group_376570) That was particularly cool because we got to look right along the dust plane of the comet trail (go watch that video). But the dust was far too diffuse for us to notice any dimming or whatever from the Sun.

Also, you shouldn’t confuse the apparent size of a comet nucleus (e.g. as shown in OP’s SOHO image) with the *actual* size of the comet viewed with the solar disk as a backdrop. There’s just no comparison. [This image [JAXA Hinode mission]](https://www.nasa.gov/wp-content/uploads/2016/09/hinode_sot_comet_20111216_000542-864×512-1.jpg) of a sungrazing comet (lower-left corner) in 2011 puts some context on this, and even then the comet size is somewhat exaggerated.

They would either have to be very very large, or very very close to earth to actually eclipse the sun.

Let’s put it this way. If a comet is fully eclipsing the sun (given the average size of comets) as opposed to just passing in front of it, it’s probably going to be an extinction event 🙂 Running won’t help at that point.