Uhh? jsOrrery, SOHO, and Mercury

[Christopher S.]

Am I crazy? Is this the FOV on the camera or is orbit data not quite right somewhere? https://mgvez.github.io/jsorrery/ Check Mercury's position here.

In other words, according to js0rrery the Zenith isn't for another few days.

Edited April 11, 2023 by Christopher S.

[Philalethes]

That's Jupiter, not Mercury.

Also, I believe you mean "conjunction" rather than "zenith", if I'm interpreting what you're thinking of here.

You can see it line up pretty well in that orrery:

[Christopher S.]

Ah, I was not visualizing the motion on SOHO properly. I had just woke up and ruled Jupiter out due to being on the S side of the imagery, thinking it was above and not possible for the speed of motion, but then I realized Earth's motion is why this spot has moved in this way. Please forgive me lol.

Yes, conjunction is correct. I said Zenith knowing it's applicable in a way, but it has many possible meanings here, so best to be concise.

Edited April 12, 2023 by Christopher S.

[Philalethes]

1 hour ago, Christopher S. said:

then I realized Earth's motion is why this spot has moved in this way

Yeah, the superior planets are some real slowpokes; at least beyond Mars.

1 hour ago, Christopher S. said:

I said Zenith knowing it's applicable in a way, but it has many possible meanings here

I would guess that being the sense of how it's commonly used to denote the highest altitude reached by a celestial body as it transits the meridian each day, i.e. the upper culmination; I can certainly see the parallel with respect to how it's similar to the closest point of approach of a celestial object to another, even if culmination is the phenomenon it more closely resembles and is used in place of, since it is a culmination of sorts. The Wikipedia article on zenith even has a paragraph dealing with just this terminology, directing to culmination:

Quote

The term zenith sometimes means the highest point, way, or level reached by a celestial body on its daily apparent path around a given point of observation. This sense of the word is often used to describe the position of the Sun ("The sun reached its zenith..."), but to an astronomer, the Sun does not have its own zenith and is at the zenith only if it is directly overhead.

In a scientific context, the zenith is the direction of reference for measuring the zenith angle (or zenith angular distance), the angle between a direction of interest (e.g. a star) and the local zenith - that is, the complement of the altitude angle (or elevation angle).

At the bottom there's also a curious tidbit about how it's used on the ISS where there's no immediate reference from gravity to what's up and down:

Quote

On the International Space Station, zenith and nadir are used instead of up and down, referring to directions within and around the station, relative to the earth.

Interestingly, due to how the orbits of the planets will rarely be lined up exactly with the ecliptic or the celestial equator, this actually means that the closest approach between the two bodies won't be precisely at the conjunction in neither right ascension nor ecliptic longitude, but it will typically be close enough not to make a big difference for observers like us who are just watching over days and weeks and longer. The actual closest approach is referred to as appulse.

Edited April 12, 2023 by Philalethes Bythos